Tails Through Time

The Bell L-39 Swept-Wing Demonstrator

2011-12-19T23:11:00.001-06:00

The Bell L-39 making a simulated carrier approach.

Following the end of the Second World War, captured German aerodynamic research had indicated the high-speed benefits of swept wings and many designs under development in the mid to late 1940s were revised to incorporate swept wings- two such examples being the North American F-86 Sabre and the Boeing B-47 Stratojet. While the USAF might have been enthusiastic about the benefits of swept wings, the US Navy still had its reservations- the Bureau of Aeronautics (BuAer), the Navy organization tasked with the development and support of naval aircraft, had concerns about the low-speed handling characteristics of swept wings as it was this particular flight regime that was critical in flight operations aboard aircraft carriers. While there was no questioning the high-speed benefits, the Navy didn't have the luxury of long runways to land at high speeds. To determine the scope of the problem, BuAer solicited bids from industry for a swept-wing flying demonstrator to explore the low-speed handling qualities of swept wings. Grumman tendered two proposals, one based on a modified F4F Wildcat as well as an all new aircraft that would have allowed wings of differing sweep to attached to the fuselage. Bell submitted a modification of its P-63 Kingcobra which won the contract as it offered lower development costs using two P-63 aircraft. The aircraft would be designated L-39. In those days, the Navy designated its research aircraft with a letter denoting the manufacturer followed by the manufacturer's model number- as exemplified by the more well-known D-558 Skystreak and later Skyrocket- "D" for Douglas, Model 558. In the case of the L-39, "L" was Bell Aircraft's letter designation and the swept wing demonstrator had the company designation Model 39. The design had really only a tangential relationship to the P-39 Airacobra (more on this in a bit).

The wings were basically P-63 Kingcobra outer wing panels that were modified to be swept to 35 degrees and attached to an unswept center stub section. This was done for aerodynamic balance purposes. The wings were further modified with slats which could be positioned before flight either open or closed. Because of the wing modifications, the landing gear was non-retractable, but since BuAer was more interested in low speed landing, this was of no consequence. Two L-39s were built, differing only in the size of the slats.

The swept outer panels attached to an unswept center section.

The first L-39 was ready to fly only 10 weeks after the go-ahead from the Navy and made its first flight on 23 April 1946. The initial set of flight tests showed some handling issues that were easily resolved with further modification to the first aircraft- namely a fuselage extension aft of the wing to increase the moment arm of the tailplane to provide more pitch authority, a ventral fin for stability, and to shift the center of gravity rearward more, the original four-bladed P-63 propeller was replaced with a lighter three-bladed unit from a P-39 Airacobra (and thus the only real link between the P-39 and the L-39). The second L-39 demonstrator was completed with the additional modifications and joined the flight test program.

It was quickly determined that the swept wing with the slats closed possessed entirely unacceptable stall characteristics- namely it was abrupt and caused the aircraft to roll to one side. However, if the wing were slatted, then the stall characteristics become acceptable. Simulated carrier approaches and landings were made by both BuAer test pilots and even Corky Meyer, Grumman's chief test pilot (as Grumman was in the process of designing swept wing aircraft for the Navy). Handling and stall characteristics in the low speed regime around the carrier were quickly determined to not be an issue as long as the swept wing were slatted and the L-39 flight test program concluded in August 1946.

Close up of the L-39's wing slats.

One issue that did come up during the L-39 test program was that swept wings needed a responsive power source in the carrier landing pattern. On aircraft there is a relationship between power required for flight and airspeed. As the airspeed decreases, the power needed also decreases, but it then reaches a point due to drag that the power needed starts to go up even as the airspeed decreases. This is called the "back side" of the curve. In carrier aircraft, they are flown on this backside because the approach to the deck must be at as low as a speed is possible. On a propeller-driven aircraft, power can be immediately applied to halt the aircraft from settling in the approach and striking the ramp. But swept wings had a steeper "back side" and early jet engines took time to spool up. And it would be jet engine development that would later dog the Navy's aircraft programs in the 1950s. But more on that in a later post!

Source: U.S. Naval Air Superiority- Development of Shipborne Jet Fighters 1943-1962 by Tommy H. Thompson. Specialty Press, 2008, p69-73.

The Massive Curtiss XP-71 Fighter

2011-12-16T23:11:00.002-06:00

Early windtunnel model of the XP-71 with its wider twin-seat cockpit.

Before the entry of the United States into the Second World War, news stories were splashing headlines about the massed bomber attacks the Luftwaffe was conducting against British cities during the Blitz and in the run up to 1941, a concern about the potential of bomber attacks on the United States took root (despite the obvious shortcomings of any enemy bomber attack on US targets protected on each side by large oceans). A number of designs and studies were undertaken to evaluate the problem of intercepting enemy bombers and one of these resulted in a design specification for a large high-altitude fighter to carry a heavy cannon armament to attack bomber formations from ranges that would place it beyond a bomber's defensive guns. In April 1941, the Curtiss Aeroplane Company submitted six proposals with two, more refined, proposals the following November. One configuration met the proscribed needs of the military for a bomber destroyer and this aircraft was assigned the designation XP-71 with a $3.2 million contract for two prototypes which was signed on 28 October 1941.

The Curtiss design had the internal company designation CW-29 and had it been built, it would have been the largest fighter aircraft ever developed in the United States- with a wingspan of 82.3 feet, a gross weight of 39,950 lbs and a fuel load up to 1,940 gallons, it was to be able to climb to 25,000 feet in just 12.5 minutes with a cruising speed of 428 mph. With an operating ceiling of 40,000 feet and a range of 3,000 miles, the XP-71 would attack enemy bomber formations well before they reached their targets. A heavy armament of two 37mm cannons with 60 rounds each and a 75mm cannon with 20 rounds was located in the nose and equipped with automatic feed systems so the aircraft only needed a minimal crew of just two. Two large Pratt & Whitney R-4360 Wasp Major 28-cylinder radial engines drove a total of nearly 7,000 horsepower to wing-mounted contra-rotating pusher props with a total of eight blades each and a diameter of 13.5 feet. General Electric turbosuperchargers would give the XP-71 the necessary high altitude performance along with a pressurized cockpit.

To put the massive size of the XP-71 into context, let's compare it with one of the larger production American fighters of the war, the Republic P-47 Thunderbolt. The XP-71 would have twice the wingspan, four times the gross weight, nearly four times the combat range, and nearly three times the engine horsepower of the Thunderbolt. In fact, the XP-71 had it been built would have been larger, heavier, faster, and longer ranged than even a late-model North American B-25 Mitchell medium bomber.

This schematic hints at the immense complexity of the XP-71.

The mockup was inspected at Curtiss' St. Louis facility on 16 November 1942, at which time the design was revised from having two crew to just a single pilot. The original proposal had the two pilots sitting side-by-side. Following the mockup review, detailed design work took place well into 1943, by which time it was becoming clear to both the US Army Air Forces and Curtiss that the XP-71 might well be the most complex aircraft yet built. During ground firing trials of the nose cannon installation in February 1943, the nose structure failed in spectacular fashion, necessitating a redesign. Curtiss also had problems finding a suitable rangefinder for the fire control system and eventually settled on a radio-based model. Cooling of the R-4360 engines in the wing nacelles also required considerable attention with an annular intake with a gearbox-driven cooling fan being developed to insure adequate cooling airflow to the massive radial engines.

By the latter half of 1943 it was becoming apparent that the XP-71 was a plane without a mission as the strategic bombing campaign of Germany got underway. The likelihood of German bomber formations, let alone Japanese bomber formations, approaching US cities was almost nil. The USAAF considered re-roling the XP-71 as a photorecon aircraft, but no solid commitments were forthcoming. On 23 October 1943, the XP-71 program was terminated after the expenditure of $2.3 million with the first flight planned for June 1944. Curtiss attempted to salvage the program by pitching the XP-71 as an antishipping aircraft with its heavy nose cannons, but this role was already being filled by the proven B-25 Mitchell in the Pacific and Curtiss's engineering resources were needed on other projects.

Source: U.S. Experimental and Prototype Aircraft Projects: Fighters 1939-1945 by Bill Norton. Specialty Press, 2008, p138-139. Photos: National Museum of the United States Air Force.

Violet Club: Quite Possibly the Worst Nuclear Bomb Ever Fielded

2011-12-13T13:43:00.002-06:00

The warhead, or physics package, of the Violet Club bomb

When taking a look at the development of British nuclear weapons following the Second World War, it has to be viewed in the context of a piece of legislation in the United States that was passed in 1946- the McMahon Act or the Atomic Energy Act. Sponsored by Senator Brien McMahon of Connecticut who chaired the Senate Special Committee on Atomic Energy, this legislation is better known for its creation of the Atomic Energy Commission and the placement of nuclear weapons development and nuclear applications under civilian rather than military control. However, one consequence of the McMahon Act was the stipulation that nuclear weapons development be restricted from US allies- this affect the United Kingdom and Canada who had provided scientists and support to the wartime Manhattan Project. As a result of being shut out of American nuclear weapons development, the British set about to create their own air-dropped weapon which would be fielded in 1953 at RAF Witttering- though somewhat amusingly the first aircraft that could carry the bomb, designated Blue Danube, the Vickers Valiant, didn't become operational until a year later. The purpose of this wasn't just a message to the Soviets, but also to the United States that Britain was more than capable of fielding its own nuclear deterrent despite the McMahon Act.

On 1 November 1952 the United States detonated its first fusion bomb (H-bomb) in the Ivy Mike test at Eniwetok Atoll in the Pacific. Given that the British were still shut out of US nuclear development by the McMahon Act, despite the fact that the Blue Danube fission bomb (A-bomb) was still a year out from being operational, strategic imperatives meant that Britain had to develop it's own H-bomb and the program was launched in 1954. In the UK, many military systems were assigned code names under the Ministry of Supply's "rainbow codes"- hence, "Blue Danube". In the development of an H-bomb, the casing had its own code name and the actual warhead, called the physics package, had another code name. The casing of the H-bomb was based on the Blue Danube casing and was designated Violet Club while the physics package was designated Green Grass.

But before the code names had been settled upon, the British H-bomb had a different name- "Interim Megaton Weapon"- implying that it was a high-yield weapon but not a true thermonuclear or H-bomb/fusion weapon. And this is really at the heart of the history of the Violet Club and its historical legacy. First, it indicates that Violet Club was intended to be a temporary weapon and secondly, it wasn't a fusion bomb as was commonly believed by *both* the Soviet Union and the United States.

The warhead or physics package of the bomb was based on earlier warhead designs that were named Orange Herald and Green Bamboo. Orange Herald was a lighter version of Green Bamboo and the designs were projected to be the new fusion warheads for the Royal Air Force's V-force, the Blue Steel stand-off missile, and the planned Blue Streak intermediate-range ballistic missile. Testing of Orange Herald showed that it had failed to boost the fission reaction to create a fusion reaction. The failure of the warhead designs left the British scrambling for a high-yield weapon and this became the Green Grass warhead of the Interim Megaton Weapon that was based on design elements of the earlier Green Bamboo and Orange Herald designs. As was the case in the United States, interservice rivalries in Great Britain meant that the Army wanted highly enriched uranium (HEU) for nuclear landmines in Europe and the Royal Navy wanted HEU for the reactors for its planned nuclear-powered submarine fleet. The Royal Air Force was of the feeling that the HEU that had so far been produced in British reactors had to be used or it would be lost to rival services, so that was one of several motivations to rush the Interim Megaton Weapon into service as it would use a significant amount of HEU.

Schematic of the Green Grass warhead showing how the ball bearings were used.

It was the design of the Green Grass warhead that went into the Violet Club that made it for all practical purposes a useless weapon. A hollow sphere of HEU was surrounded by a system of 72 explosive lenses that compressed the HEU to critical mass and detonation. But here was the problem. In the Green Grass warhead, the mass of HEU was in *excess* of the critical mass once compressed by the explosive lenses. That meant if the warhead were crushed or damaged during handling, it could partially detonate. American designs avoided this by having an HEU core that was inserted into the physics package usually by the bombardier once the bomber was in flight, thereby "arming" the bomb once the core was inserted. Without the core inserted, the HEU mass in the American designs was below the critical mass. The solution by British designers was to fill the center of the HEU sphere with 20,000 steel ball bearings to prevent the sphere from being crushed and reaching critical mass. To arm the bomb, a plastic plug was removed from the bottom of the warhead (accessible via a hatch on the underside of the Violet Club casing) that allowed the bearings to flow out, thereby arming the bomb.

While it may sound like a creative solution, there were several issues:

The weight of the ball-bearings increased the bomb's weight to 11,250 lbs which was greater than the capacity of not only the bomb release mechanisms of the V-bombers but also the ground-transport equipment of the bomb.
The outflow of bearings took at least half an hour under ideal conditions- in cold weather, the bearings could freeze together, making arming the weapon near-impossible.
Once the bomb was armed by allowing the ball-bearings to flow out of the center of the warhead, there was on way of making the weapon safe again. In fact, engine running was prohibited even with Violet Club "safed" as it was feared vibration would cause the plastic plug to fall out and inadvertantly arm the weapon.
Because the bomb was armed irreversibly, airborne alerts were impossible because take off and landing were too hazardous to attempt with an armed Violet Club.
Dispersal of the V-force to outlying fields was impossible as the bomb couldn't be flown to the dispersal airfield and the bomb transport equipment couldn't handle the Violet Club when it had its ball-bearings in place.

The Blue Danube- the Violet Club looked similar externally.

While the Air Staff of the RAF ordered twelve Violet Club bombs, only five were made and as British author Chris Gibson put it in his book Vulcan's Hammer "From the RAF's point of view, that was five too many." With such an unwieldly weapon, why was it even fielded? First of all, remember that the British were classifying the Violet Club as megaton-class weapon by calling it the Interim Megaton Weapon. It definitely wasn't a megaton weapon, perhaps more 400 kilotons at best, but certainly the Operation Grapple tests at Christmas Island in 1957 did indicate to the Americans the British were succeeding at fielding their own H-bombs- even if those test detonations failed to created the desired thermonuclear reaction. So who was the target of the Violet Club? While serving notice to the Soviet Union that Britain was still a force to be reckoned with, it seems that perhaps the Americans were the target, so to speak- with a weapon in their inventory called Interim Megaton Weapon implying that newer designs forthcoming and the Grapple series of tests in 1957 making a good show of things despite failing to work as planned, in 1958 the United States repealed the McMahon Act and resumed full nuclear cooperation with the United Kingdom. The Green Grass warhead used in Violet Club would be the last all-British nuclear weapon as a new Mutual Defense Agreement signed as part of the repeal of the McMahon Act meant British designers now had access to more advanced and compact American designs. In fact, the successor to the much-despised Violet Club, the Yellow Sun Mk.2, used an Anglicized American Mk.28 thermonuclear warhead. But no other fission weapon ever fielded by any other nation approached the explosive yield of the Violet Club.

Source: Vulcan's Hammer: V-Force Projects and Weapons Since 1945 by Chris Gibson. Hikoki Publications, 2011, p47-51. http://www.nuclear-weapons.info/vw.htm, by Brian Burnell.

How the US Coast Guard Ended up with the Dassault Falcon

2011-12-10T23:23:00.001-06:00

HU-25 Guardian on short final into KDAL.

When the United States Coast Guard announced in January 1977 that a maritime patrol version of the Dassault Falcon 20 business jet was selected to replace the Grumman HU-16 Albatross and Convair HC-131As in the medium-range search and rescue role, it was the first time in the Coast Guard's 65-year history at that point that it had selected a non-American aircraft for its purposes. The road that led up to this landbreaking decision actually began in 1971 when the Coast Guard issued it's Medium Range Surveillance (MRS) requirement. At the time, the Coast Guard had selected what would have been a specially-developed version of the North American Rockwell Sabreliner 75 that would have been powered by Avco Lycoming ALF-502 turbofan engines- at the time, production standard Sabreliner 75s were powered by General Electric CF700 engines. However, the USCG came under intense criticism for the first incarnation of the MRS contract as it had not held an open competition for other aircraft manufacturers to submit proposals. Yielding to Congressional pressure, the Coast Guard canceled the contract with North American Rockwell and re-opened the MRS requirement as an open competition in 1975.

The new MRS requirements stipulated that the aircraft be turbofan-powered to allow a high dash speed and high-altitude performance to fly over weather when enroute to a search area. The cabin had to be at least 600 cubic feet to allow all the equipment needed for fly several missions without having to return to base for a changeout of mission-specific equipment. Basic mission parameters were set at a 700 nm loiter at 2,000 feet at a distance of 150 nm from the base. A speed of at least 350 knots was required during the transit to and from search areas and the aircraft had to be capable of an airspeed of no more than 220 knots at 2,000 feet when in the search area. In March 1976, the USCG had received several submissions for consideration:

North American Rockwell submitted it's previous proposed Sabreliner 75 development;
Gulfstream submitted two versions of the GII business jet, one powered by Rolls-Royce Spey turbofans and one powered by GE CF34 turbofans;
A highly unconventional submission came from ICX Aviation which had plans to license build the Yakovlev Yak-40 jetliner in Youngstown, Ohio. Their proposal was based on a Yak-40 powered by three Garrett AiResearch TFE731 turbofans;
Lockheed proposed a version of the Jetstar powered by two GE CF34 engines;
VFW-Fokker submitted two versions of the VFW 614 jetliner, one with Bendix cockpit avionics and one with Collins cockpit avionics- both versions would have used GE CF34 engines;
And finally Dassault through the Falcon Jet Corporation (a joint venture between Dassault and Pan Am to market the Falcon 20 in the United States) submitted a version powered by Garrett ATF3 engines called the Falcon HX-XX.

The HU-25s are being replaced and serve at only 3 air stations.

By the fall of 1976, the field of submissions had been narrowed down to just three- Lockheed's CF34-powered Jetstar, VFW-Fokker's VFW 614 jetliner, and the Falcon HX-XX. Contractor bids were submitted to the Coast Guard on 28 October 1976 based on a 41-aircraft purchase and the Falcon HX-XX came out the cheapest at $4.9 million per aircraft. The VFW 614 was nearly 20% higher in unit price to the Falcon proposal and the Lockheed Jetstar proposal was a surprising 25% higher than the Falcon, coming in as the most expensive option. At the time, the Buy American Act of 1933 was applied to the bids which meant that the VFW-Fokker proposal was increased by an additional 12% in accordance with provisions of the act as it lacked significant American parts. The Falcon HX-XX, however, was exempted from this provision of the Buy American Act as the Falcon Jet Corporation in their proposal would import green airframes from Dassault and finish them out in the United States with American parts to equal 68.1% of the aircraft's value being sourced from US contractors- by the provisions of the law at the time, 50% was considered the minimum to qualify as a domestic product. Knowing the political winds in Washington when it came to a "foreign" aircraft purchase, the Falcon Jet Corporation even showed how over a 10 year service lift the value of American parts in the HX-XX increased to nearly 75%.

As a result, on 5 January 1977, Secretary of Transportation William T. Coleman, Jr, announced that the Falcon HX-XX was the winning submission and the aircraft would be designated the HU-25 Guardian in Coast Guard service. It set a precedent for the Coast Guard and two years later the service selected the Aerospatiale (today American Eurocopter) Dauphin helicopter to become the HH-65 Dolphin in the short-range recovery role. History repeated itself again several years ago when the EADS/CASA CN235MP was selected to replace the HU-25 Guardian in the medium range surveillance role- designated HC-144 Ocean Sentry, the first ones were delivered to the USCG in 2006.

Source: Air International, Volume 20, Number 4. "Uncle Sam's Gallic Guardian", p173-179.
Photos: JPSantiago, United States Coast Guard

The Ad Hoc Lashup That Resulted in Japan's Best Fighter of WW2

2011-10-17T23:15:00.000-05:00

Japan's finest fighter of World War 2.

Unlike Germany and the Allies during the Second World War, the vast majority of Japanese fighter aircraft were powered by radial engines while other nations had a mix of both radial and inline engines for their fighter units. Only one production-standard Japanese fighter entered service with an inline engine, the Kawasaki Ki-61 "Hien" (Allied code name Tony). Over 2,500 Ki-61s were produced and saw service with the Imperial Japanese Army Air Force (IJAAF) from 1943 to the end of hostilities in 1945. The Hien was designed by Kawasaki's chief designer, Takeo Doi and his deputy, Shin Owada (Doi would later go on to design the postwar YS-11 airliner) in response to an IJAAF requirement for a multirole fighter that would use a license-produced version of the German Daimler-Benz DB601 liquid-cooled inline engine that also powered the Messerschmitt Bf 109. Proving itself to be a promising design, the Ki-61 turned out to have a major Achilles heel in its Kawasaki-built engine which was designated the Ha-140. Though the DB601 would be one of the Second World War's finest engines, by the time the Ki-61 entered service it was an old design that was already being outclassed by more powerful engines of both radial and inline design. Worse yet, the DB601 had very tight manufacturing tolerances and in Japanese license production, getting Ha-140 engines built as well as the DB601 proved elusive given the increasing toll being taken on Japanese industry which found itself constantly short of quality metals and lubricants given the tightening US Navy submarine blockade of the home islands.

Ki-61 to Ki-100.

Worse would come as the war progressed into 1944 with Kawasaki's Akashi factory constantly being plagued by supplier shortages and properly manufactured crankcases and cylinder blocks. By the spring of 1944, more than half of the Ha-140 engines produced at Akashi that did leave the assembly line failed to pass acceptance testing! As a result, at Kawasaki's facility in Kagamigahara that produced the Ki-61 fighter found itself with increasing numbers of finished fighters sitting in open storage waiting for their Ha-140 engines. Matters worsened on 19 January 1945 when B-29 Superfortresses completely destroyed the Akashi engine plant, leaving 275 Ki-61 fighters without any engines. With the B-29s ranging with near impunity over the home islands, the IJAAF headquarters, the Koko Hombu, suggested that the engineless Ki-61s be adapted to take the most readily available and reliable engine- IJAAF engineers suggested that Kawasaki find a way to fit the engineless fighters with the Mitsubishi Ha-112 radial engine, a 14-cylinder twin row radial engine comparable in power to the Pratt & Whitney R-1830 radial used on the Consolidated B-24 Liberator and the Douglas C-47 Skytrain/Dakota.

Takeo Doi was initially not pleased with the Koku Hombu's directive to fit the Ha-112 to the Ki-61. The radial engine was 48 inches in diameter and the fuselage of the Ki-61 was only 36 inches in diameter. But seeing as to how there was little alternatives and the need for fighters great, Doi had his engineering staff work around the clock to make the Ha-112 work with the Ki-61 Hien. Fortunately Kawasaki was in possession of a Focke Wulf Fw 190 which had been delivered to the Japanese several years earlier for engineering study. Using the cowl and engine mount of the Fw 190 as a starting point, Doi and his team even replicated the horizontal alignment and collection of the exhaust pipes of the Fw 190 which in the Kawasaki design actually added between 6 to 9 mph of thrust augmentation to the aircraft's speed. Designated the Ki-100, the prototype aircraft made its first flight a mere three months after start of design work- a figure all the more incredible in light of the tremendous toll the B-29 attacks were taking on Japanese industry. By the time the third Ki-100 prototype took flight, the Koko Hombu was sufficiently impressed that all the engineless Ki-61s were ordered to be converted to Ki-100 standard.

On many occasions, Ki-100s bested Hellcats and Corsairs.

"Sufficiently impressed" would be an understatement- the Ha-112 radial engine actually made the Ki-100 superior in every performance parameter to the Ki-61, much to the surprise of Takeo Doi. Although just slightly slower in cruise than the Hien, the Ki-100 was more maneuverable and had a faster climb rate. The IJAAF even took the Ki-100 prototypes into mock air combat against a captured P-51C Mustang. With the flight test program only lasting three weeks, the first Ki-100s went into combat with the 18th Sentai in Chiba on the same night in March that B-29s had laid waste to sixteen square miles of Tokyo in a firebombing attack. Less than six weeks elapsed since first flight to first combat! Production of the Ki-61 was terminated immediately and in less than three months all 275 engineless Ki-61s were rebuilt as Ki-100s AND the Kagamigahara factory also managed to build nearly 75 new-build Ki-100s that featured a cut back rear fuselage to improve aft vision for the pilot. As fast as Ki-100s could be built they were funneled straight to home defense units who found the Ki-100 a formidable fighter. Numerous large dogfights against Grumman F6F Hellcats and Vought F4U Corsairs found the Ki-100 on the winning side with more American fighters shot down than Ki-100s. By May 1945 the Ki-100 finally had met its match as long range P-51D Mustangs from Iwo Jima were now escorting the B-29s all the way to Japan and back. Dogfights with P-51Ds ended up swinging in favor of pilot skill and numerical advantage rather than any deficiency on the part of either aircraft.

The one weakness of the Ki-100 was its high altitude performance as it lacked a turbocharger and as a result, few B-29s fell to the Ki-100. Work was underway for a supercharged high altitude Ki-100 when the war came to an abrupt end with the atomic bombing of Hiroshima and Nagasaki. Unfortunately for Japan, only about 500 Ki-100s were built before the war ended, but compared to other Japanese fighter designs, the Ki-100 proved to be Japan's finest fighter aircraft as a swansong for the once-feared IJAAF. From inception to the end of the war, the lifespan of the Ki-100 was barely ten months with an ad hoc marriage of engine and airframe out of necessity! The only surviving Ki-100 can be seen today at the RAF Museum.

Source: Air International, October 1976, Volume 11, Number 4. "The Last Swallow of Summer: The Extraordinary Story of the Ki-100", p185-191.

Rivet Haste: Rebirth of the USAF at the end of Vietnam

2011-10-01T05:08:00.000-05:00

Heritage Flight F-4E Phantom painted in Vietnam-era colors.

In several prior postings I had talked about how the United States set about improving the performance of its fighter pilots over the skies of Vietnam. The first one dealt with the testing and analysis of MiG fighters that had been obtained secretly by the United States and the second posting covered the origins of Red Flag, the exercises in Nevada that gave pilots valuable experience under simulated combat conditions. The Navy also instituted measures to improve its fighter pilots' performance after the Ault Report was commissioned by the Chief of Naval Operations to review naval air-to-air tactics. One thing to keep in mind is that there were numerous parallel measures being undertaken in the late 1960s and early 1970s to improve the dogfighting skills of American pilots. The main American fighter of the day that was in service with both the US Navy and USAF was the McDonnell Douglas F-4 Phantom II. The Air Force in particular, also looked at ways of improving the performance of the Phantom, a design that was originally intended for fleet air defense but found itself in swirling low speed dogfights over Vietnam for which it was never designed.

The Phantom had two idiosyncrasies that proved to be a liability in a dogfight. Being a big hulking fighter with two J79 engines that left a nice smoke trail for the enemy to spot were one of just many faults of the aircraft. As the engines of the Phantom were optimized for high speed, so to were the aircraft's aerodynamics. In the low-speed regime during a dogfight, the F-4 was prone to what was called adverse yaw- normally when the pilot wanted to turn one direction, he only had to move the stick in that direction. At low speeds and high angles of attack that were commonplace in a dogfight, however, if a pilot pushed the stick to the left, the downward-deflected aileron on the right wing would produce more drag than lift, causing the Phantom to yaw back to the right even though the pilot wanted to turn left. As the yaw increases, the effective sweep on the left wing decreases and it starts to produce more left and the F-4 snaps to the right and then into a spin. All this happened nearly instantly and pilots had to compensate for the adverse yaw when rolling left or right by using the rudder aggressively during close air combat- instead of moving the stick into the direction of the turn, the rudder was deflected. So a left turn meant keeping the stick centered and pushing the left rudder pedal down. This causes the Phantom to yaw to the left and this decreases the effective sweep on the right wing- it therefore creates more lift and the plane now snap rolls into the direction of the turn. This took a lot of practice and it was suspected that a significant number of Phantom combat losses were due to adverse yaw conditions.

The ergonomics of the Phantom cockpit weren't exactly great, either, with a mass of switches and dials that most Phantom drivers felt were scattered randomly over the instrument panel and side consoles. Most derided by the pilots were the switches on the panel by the pilot's left knee that controlled the Sidewinder and Sparrow missiles- one of the switches was a three-position switch that cycled through the Sidewinders and Sparrows. It felt identical to the other control switches on the missile panel and the last thing pilots wanted to do was look at the switch to make sure they flipped the right one in the middle of a dogfight. Resourceful pilots in Vietnam got hold a piece of plastic tubing that was used to sample oil from the engines. Cutting it into a two-inch length, it was slipped over the end of the switch so it stuck out from other switches. All a pilot had to do during combat was swat the tubing by his left knee to cycle through his missiles.

South Korean F-4E shows off its leading edge slats.

When the F-4E entered service, its most obvious advantage was that it had an internal cannon in the nose, rectifying a situation often encountered in Vietnam when the MiGs were inside of the minimum launch parameters for either the Sidewinder or the Sparrow missiles. But the F-4Es had another advantage and that was what was called a "soft wing"- the wing now had leading edge slats that were controlled automatically by the flight control system whenever the angle of attack would reach a certain level. When the AoA hit this preset level, the slats would automatically pop out and it increased the lift across the wing- this had a dual effect on the Phantom- it eliminated the adverse yaw condition, even at high angles of attack. And secondly, the Phantom became practically spin proof as adverse yaw got eliminated- accidents from spins dropped dramatically and pilots could now haul around the beast in the sky without worrying about loss of control. In fact, some pilots felt that the soft wing F-4E flew just like the Northrop T-38 Talons used in advanced flight training.

When the USAF brass got word of the improvised plastic tubing modification used in Vietnam, it became apparent after some analysis that many MiG kills were missed due to the missile switches being configured incorrectly. And truth be told, it was pretty embarrassing to know that to make a multimillion dollar fighter more effective in combat needed a cheap piece of tubing. The Air Force came out with a modification to the F-4E that was numbered 556. Pilots called it the "five-five-six mod" and what it did was add a switch on the outside of the left throttle. Operated by the pilot's left pinkie finger (hence it was called the "pinkie switch"), it if was pushed forward, the Sparrow missile was selected. If it was in the middle setting, a Sidewinder was selected. And if it was pulled all the way back, the F-4E's gun was selected. Since the pilot's hand was always on the throttles, the switch was readily accessible. The second part of the 556 mod was another switch added to the front of the left throttle that allowed the pilot to instantly reconfigure the weapons systems from air-to-ground to air-to-air. No longer was there a switch sequence to follow. Push one button, that was it. Other changes consolidated the bomb dropping switches into a single small panel.

TISEO unit on the F-4E.

While the soft wing and the pinkie switch did much to ease the pilot's workload in air combat, there was still the issue of the rules of engagement requiring visual identification of a MiG before shooting. This restriction pretty much rendered the Sparrow useless as a beyond-visual range (BVR) weapon that could swat MiGs down from unseen distances. The biggest problem with the Sparrow with the RoE in use over Vietnam was that most engagements began head-on. At that distance, the Sparrow could be fired at a maximum of ten miles and a minimum of three miles. But head-on, the MiGs were much smaller and harder to see even if with a radar lock. With closure rates approaching one mile every three seconds, by the time the Phantom crew had a positive visual on the MiG, it was already too late to fire a Sparrow. The solution was called TISEO- Target Identification System Electro-Optical. Some F-4Es had an electro-optical telescope mounted on the leading edge of the left wing above the inboard pylon. The telescope had 4x and 10x magnification and displayed the image on the WSO's radar display. Now when the backseater had a radar lock, he could command the TISEO to track the target and then switch to 10x magnification for visual identification while the MiG was still in the firing envelope of the Sparrow missile.

With the soft wing, the pinkie switch, and the TISEO, the USAF realized it had the tools to make its fighter pilots more lethal. In the late summer of 1972, the Rivet Haste program was established. Rivet Haste would be the Air Force's acknowledgement that years of substandard training and poor doctrine had to be reversed. Rivet Haste combined the slatted wing, TISEO, and 556 mod of the F-4E and teamed them up with handpicked crews with combat experience over Vietnam. They were assembled at Nellis AFB and here the key of Rivet Haste would take place- intensive training with the new F-4Es against the secret MiG force that Air Force flew out of Tonopah north of Las Vegas. Each Rivet Haste crew were paired up to stay together through training to deployment for combat- this allowed the pilot and his WSO to develop their own system of coordination in the cockpit and carry that to combat. Six pilots and six WSOs were in each Rivet Haste group and each pilot/WSO would fly at least three missions against the MiGs at Tonopah. Each month, a new group of six pilots and six WSOs were assigned to Rivet Haste. Crews assigned to Rivet Haste saw it as a quantum leap in air combat training that the USAF had never had before, but the war in Vietnam ended less than two weeks after the first Rivet Haste crews arrived in Southeast Asia.

It wasn't all for naught, though. The 556 mod spawned a cockpit design philosophy called HOTAS- Hands On Throttle And Stick- this meant that every function that a pilot needed in air combat (and even in air to ground combat) would be instantly accessible either on the throttle or stick. Many of the crews that were part of Rivet Haste would go on into important leadership positions in the post-Vietnam USAF that would result in a greater emphasis on realistic training. The realistic training provided to Rivet Haste crews would be one of several foundations that would result in the Red Flag exercises.

As the saying today goes "Fight like you train, train like you fight".

Source: Sierra Hotel: Flying Air Force Fighters in the Decade After Vietnam by C.R. Anderegg. Air Force History and Museums Program, 2001, p11-13, 32-35.

The First Steps to a Turboprop Transport, Part Two

2011-09-19T12:13:00.001-05:00

A week and a half ago I had blogged about how the USAF was getting turboprop transport experience by setting up a test squadron at Kelly AFB to operated transport aircraft that had been converted to turbine power:

52-2693 and 52-2672 in flight together.

Back in January 2010 I had written a short posting about the second of the demonstrator aircraft that were operated by the 1700th Test Squadron and operated in the second flight of the unit- the Boeing YC-97J, a Pratt & Whitney T34-powered version of the C-97 Stratofreighter. I had recently picked up Cal Taylor's voluminous tome on the Douglas C-133 Cargomaster and he devotes considerable space to the YC-97J and its operational use by the 1700th TS. The YC-97J made its first flight at Edwards AFB on 19 April 1955 and given that it used the same T34 engines as the upcoming C-133, the USAF was keenly interested in flight testing the engine in an operational environment with the YC-97J. From my previous posting about the YC-97J:

Boeing converted two aircraft (52-2693 and 52-2672, both KC-97Gs) to turboprop power. Pratt & Whitney YT34 turoprop engines (which would later be used on the Douglas C-133 Cargomaster) delivering 5,700 horsepower were substituted for the four R-4360 radial engines. For a brief time the USAF considered redesignating these two Stratofreighters as C-137, but ended up assigning them the designation YC-97J (ironically the C-137 got used for the Boeing 707s used by the military, itself a development of the Model 367-80 prototype).

The conversion to turboprop power shaved nearly 5,0000 lbs off the aircraft's weight as the YT34s were much lighter but more powerful. The first flight was made on 19 April 1955 and the YC-97J demonstrated significant improvements in overall performance. The top speed was 417 mph compared to 375 mph for a regular Stratofreighter and the YC-97J took only 14 minutes to reach 20,000 feet whereas the regular Stratofreighter took 50 minutes!

Inflight study of the YC-97J during its Edwards flight test program.

In addition to using the same T34 engines as the C-133, the YC-97Js also used an early version of the same Curtiss turboelectric three-bladed propellers planned for the C-133. The first YC-97J completed its flight testing at Edwards and was delivered to Kelly AFB on 14 September 1955, nine months after the YC-131Cs had arrived. The second YC-97J arrived at the end of the month. After a short series of flights operating within the continental United States, the USAF authorized the aircraft to begin overwater missions with the first overwater flight being to Kindley Field in Bermuda- the aircraft covered the 1,700 mile route from San Antonio to Bermuda in 4 hours 42 minutes, the fastest time at that point by a prop-driven aircraft. On 26 January 1956, the YC-97J departed for Rhein-Main AB in West Germany staging through Dover AFB in Delaware, then Newfoundland and Scotland. Despite record breaking cold weather on the trip, the YC-97J performed flawlessly without any of the usual maintenance headaches that were commonplace for the piston-driven C-97s. On the leg between Newfoundland and Scotland, four hours were shaved off the usual flight time when using C-124s or C-118s, the run being made in only 6 hours 30 minutes. It was clear that the time savings was tremendous on long distance missions. The international aviation press covered the flight with interest. On an outbound stop in London, the YC-97J was climbing out of Heathrow at 2,500 feet per minute and London ATC asked the pilots to slow the rate of climb as the radar dish was too slow to keep up! The return flight from Frankfurt stopped in Paris, London, the Scotland (Prestwick), Newfoundland (Goose Bay) then Selfridge AFB in Michigan before returning to Kelly AFB. It was the first round-trip trans-Atlantic crossing by an American turboprop aircraft. During the mission to West Germany and back, no engine or prop maintenance was needed and the aircraft's four engines used a mere four quarts of oil for the entire trip. Needless to say, the USAF was very enthusiastic about the aircraft!

In March 1956 the two YC-97Js were put on a scheduled cargo run between Kelly AFB to Ramey AFB in Puerto Rico via Charleston AFB in South Carolina and the return routing stopped over at Brookley AFB in Alabama (now Mobile Downtown Airport). Average flying time between San Antonio and Puerto Rico was 16 hours and despite the stopovers, it was still nine hours faster than what piston-driven USAF transports took to cover the distance. But it didn't stop there- that same month the first YC-97J made the first trans-Pacific crossing by a turboprop aircraft, averaging 360 mph over the 18,000 mile round trip. The longest leg of the route to Tokyo was between Midway Island and Yokota AB outside of Tokyo- on this leg the YC-97J flew at 30,000 feet and averaged 400 mph.

In preparation for the arrival of the Douglas C-133 Cargomaster, the first group of air crew and mechanics arrived at Kelly AFB from Dover AFB for familiarization training with the T34 engine and its Curtiss propellers. The three-week course had pilots flying an average of 38 hours on the YC-97Js to build turbine experience while the Dover mechanics worked side by side with the Kelly AFB maintenance team to keep the YC-97Js flying. The reliability of the turboprop over the piston engine was now unquestionable and in the summer of 1956, both YC-97Js would fly a total of 46 hours 35 minutes together in a single calendar day as proof of the reliability of the turboprop. The engine overhaul time (TBO) over the course of the test program with the 1700th started out at 150 hours and ended up at 1,000 hours.

The YC-97J departs San Diego Lindbergh Field.

In addition to its scheduled cargo flights, the YC-97Js were also flown on demonstration flights for interested groups ranging form the US Navy to other defense contractors like Pratt & Whitney and North American Aviation. On a three day demonstration in Connecticut for Pratt & Whitney, the YC-97J made 78 engine starts, 19 takeoffs and landings, 7 air starts and 15 flights without any malfunctions of the engine or propellers. By October, one of the T34 engines became the first American turboprop engine to reach 1,000 flight hours since its last overhaul. It was removed from the YC-97J with 1,001 hours and 20 minutes flight time and in that time, it only needed 44 hours of unscheduled maintenance and used a miserly 392 quarts of oil in that time frame, a fraction of what the regular C-97's piston engines would have used in 1,000 flight hours. The propellers also proved to be extremely reliable and when the first C-133 Cargomasters were delivered to Dover AFB, the engines and propellers were already rated at 1,000 hours TBO, a significant feat in that day.

The 1700th TS's flight test program with the YC-97Js concluded on 15 November 1956, six weeks ahead of schedule. However, the aircraft were kept operational until 17 January 1957 as they were used in Operation Safe Haven to fly refugees from the 1956 Hungarian Revolution from Europe to new homes in the United States. The first YC-97J, would go on to create more aviation history, though- it was modified to become a Super Guppy transport. Aero Spacelines president Jack Conroy had already flown a piston driven Super Guppy, and aware of the pending retirement of the YC-97Js, acquired one as the turboprop engines made his conversion not only faster, but more efficient. The new turbine Super Guppy used a swing nose instead of a tail break as was the case with the original design and it was put into service with NASA in 1966, its first job transporting the second stage of the Saturn IB rocket from Huntsville, Alabama, where it was built to the Kennedy Space Center in Florida. It was subsequently retired to the Pima Air and Space Museum in Tucson, Arizona.

Stay tuned for the final installment in this series which will look at the turboprop-powered YC-121F Super Constellation!

Source: Remembering an Unsung Giant: The Douglas C-133 Cargomaster and Its People by Cal Taylor. Firstfleet Publishers, 2005, p29-43. Photos: Smithsonian Institution, SDASM.

How a Tax Issue Launched the Boeing 707

2011-09-13T10:41:00.001-05:00

Boeing chairman Bill Allen

In a past blog post I had mentioned that while most of aviation history is a study in technological progress, it as much shaped by the individuals and their personality traits as it is any development in aeronautics. That past posting back in March 2010 dealt with C. Edward Acker's personality and how it shaped Air Florida and impacted the newly-deregulated market in the United States in the 1980s. While someone like Acker brimmed with swagger and bravado, there as many individuals in the history of aviation who, by nature of their quiet reserve, are often overlooked as movers and shakers. I recently have been reading Sam Howe Verhovek's book Jet Age: The Comet, the 707, and the Race to Shrink the World and he places Boeing's chairman at the time of the launch of the 707, Bill Allen, as one of the true visionaries and business leaders in the industry. I have to admit my own understanding of Bill Allen up to this point was that while he shaped Boeing tremendously into what it is today in the commercial airliner market, he hardly filled the role of visionary, looking very much like many of the management types that you could have pulled from central casting for a 1950s-era movie. But what was it about Bill Allen that makes him a central figure in Verhovek's book? When he assumed the leadership role in Boeing in 1950, Boeing held less than 1% of the commercial airliner business that was dominated by Douglas and Lockheed. Though stunningly successful in the Second World War with its bomber designs, Bill Allen rightly saw that the growing air travel market represented a bigger prize than any military contract. But with a fraction of the commercial market, Boeing was already seen as a three-time loser in the race- the Boeing 247 was too small compared to the Douglas DC-3, the Boeing 314s were only built in small numbers primarily for Pan Am, and the landmark Boeing 307 Stratoliner was a flop that hardly made a dent in the marketplace.

Bill Allen wasn't a pilot and he wasn't even an engineer. He would have readily admitted to not knowing much about either when it came to aviation. But he had his start as the company lawyer who handled the legal paperwork for Bill Boeing's timber business and then his aircraft company. Before long, Allen was one of those quiet in-the-background individuals that everyone saw Boeing himself often sought out for advice. When Boeing quit the company in 1934, Philip Johnson took his place and led the company through a dramatic expansion during the Second World War- and again, Johnson came to rely on Allen for advice and counsel on company decisions. When Johnson died of a stroke in his fifties, there was only one person the rank and file at Boeing would trust- and that was Bill Allen. But he found himself a single parent to two young girls after losing his wife to cancer when the offer from the board came to him.

Maybe it was loyalty and maybe it was that he was part of Boeing since its early days as a timber company, but he took the job- but at the time, the airline industry was content with its Douglas and Lockheed piston propliners and Allen had a tough time selling the airlines on the idea of a jet. For many airlines, the jet was an unknown. Well, it was- until the De Havilland Comet took flight and electrified the world with its speed and grace. By 1952 the British aeronautical industry was the talk of the world with Eastern's Eddie Rickenbacker and Pan Am's Juan Trippe openly discussing orders of the Comet. It was an about face by the world's airlines and the US airline industry in particular that just a year earlier thought jet technology too immature for the traveling public.

Bill Allen on the right shows the Dash 80 to Bill Boeing.

Many companies wanted government subsidy to develop a jet airliner- Boeing's own engineers had been applying their experience in developing the B-47 Stratojet and the B-52 Stratofortress towards the company's own project which was designated Model 367-80 (the Model 367 was the C-97 Stratofreighter- the Dash 80 was designated such for secrecy, leading competitors to think it was just an improved version of the C-97). The costs of developing the Dash 80 amounted to a quarter of the company's value and to go it alone without government development aid represented a tremendous financial risk. There was many pros as there were cons in Allen's mind when it came to launching a jetliner.

But, Allen's own legal background was in tax law. During the Korean War, the Congress put what was called an "excess profits" tax in place to prevent companies from profiteering from the war effort. A company's baseline was set at its profilts made during the peacetime period of 1946 to 1949. Anything above that level in profits was subject to the tax. That period was a hard time on Boeing with the cancellation of numerous wartime contracts and profits during those years were slim at best. But with the ramp up in defense spending during the Korean War, Boeing's fortunes improved dramatically and that meant that the company was fully exposed to the excess profits tax while Douglas and Lockheed's profits during that time were higher thanks to their own commercial airliner production. That meant that Boeing would owe 82 cents on every dollar of profit while Douglas only would owe 68 cents and Lockheed only 48 cents on each dollar of profit.

Having a flying prototype gave Boeing an advantage.

Under most circumstances, Bill Allen might have gone to the state of Washington Congressional delegation for a political fix. But being the tax lawyer, he saw an opportunity- Take Boeing's profits and invest them heavily into the Boeing 707 project- that amount would be deducted from the profits and written off as a business expense. Boeing wouldn't need government aid to develop a new jetliner and it reduced the company's tax exposure. Allen pitched the idea to the Boeing board as an investment in the company's future that would put it at the forefront of jetliner development. In addition, company funding of a demonstrator aircraft would not only give the airlines something to see and ride as a flying design, it would also put Boeing in the lead for the USAF's plans for a new jet tanker to support its growing B-52 Stratofortress fleet. In a stroke of what some might call genius, Bill Allen could kill three birds with one stone- reduce Boeing's tax exposure, get a flying jetliner demonstrator, and use that demonstrator to get the jet tanker contract. That was the engineering genius of the Dash 80- it appealed to both airlines and the USAF for disparate roles. Boeing's competition for the jet tanker hadn't optimized their designs as transports as fully as Boeing had with the Dash 80.

It only took a month to get the go-ahead from the board of directors. In the summer of 1952, Bill Allen issued short statement to the press:

"The Boeing Company has for some time been engaged in a company-financed project which will enable it to demonstrate a prototype jet airplane of a new design to the armed services and the commercial airlines in the summer of 1954."

The rest, as they say, is history!

Source: Jet Age: The Comet, the 707, and the Race to Shrink the World by Sam Howe Verhovek. Penguin Group, 2010, p84-110. Photos: Smithsonian, Boeing.

The First Steps to a Turboprop Transport, Part One

2011-09-10T23:07:00.000-05:00

The YC-131C in flight. Note the 3-bladed propellers.

By the time of the Korean Armistice in 1953, the US Air Force was busy absorbing the lessons of airlift accrued over a less-than-ten-year span from the logistics flights to support World War II to the Berlin Airlift to the strategic airlift partnership forged with the commercial airlines in the Korean War. In pace with advances in aerodynamics and propulsion, the USAF began a four-step process in exploring the possibilities of turboprop propulsion given that pure jet engines of the day were still incredibly fuel-thirsty. The first steps were taken in 1945 with the test program of the Convair XP-81 turboprop fighter that also had an Allison J33 jet engine for additional power. The next steps were the testing of turboprop engines on existing high-speed jet designs that would result in the XF-84H "Thunderscreech and test versions of the Boeing B-47 Stratojet and the McDonnell XF-88 that flew with turboprop engines. The third step was the installation of turboprops on existing transport designs to evaluate their performance on large transports. And the final step was the introduction of production-standard turboprop transports which would result in the Lockheed C-130 Hercules and the Douglas C-133 Cargomaster.

On 15 June 1954, the headquarters of the Military Air Transport Service (MATS) activated the 1700th Test Squadron (Turboprop) at Kelly AFB, Texas, with the task of developing maintenance procedures and techniques for the employment of turboprop transport aircraft pending the arrival of the C-130 and C-133 into the USAF service. The squadron had three flights with each flight dedicated to a single type for the testing of standard transport aircraft that had been converted to turboprop power. The first of the three flights to be activated would operate the Convair YC-131C. Two aircraft were converted from standard C-131 Samaritan transports (the USAF version of the CV-340 airliner) to use early test versions of the venerable Allison T56 turboprop. The YT56 turboprops replaced the piston engines of the C-131 and drove three-bladed Aeroproducts propellers. As this was the combination planned for the Lockheed C-130A, Allison was, needless to say, keen on being involved in getting flight time for the new engine. Tail numbers 53-7886 and 53-7887 were pulled from USAF service and modified by Convair at their Fort Worth facility at Carswell AFB. After initial flight testing at Edwards AFB, the first YC-131C was flown to Kelly AFB on 20 January 1955 with the second aircraft arriving three days later.

Ground run of the YT56 engines at Convair Fort Worth.

As the goal of the test program set up by the 1700th TS was to fly the turboprop aircraft assigned to it as much as possible, the YC-131Cs were assigned to a scheduled military passenger service that operated between Kelly AFB in San Antonio and Andrews AFB outside of Washington, DC. The first services began on 14 March 1955 as the first scheduled turboprop passenger services in the United States. Covering a distance of just over 1,200 miles, the YC-131Cs took 4 hours 20 minutes on the first flight, approximately 20 minutes faster than a piston C-131 on the same route. By May of that year a regular flying schedule was established that would have the 1700th TS flying the two YC-131Cs 3,000 flight hours in nine months. As maintenance at destination stations was not expected to be adequate, each scheduled route flown by the YC-131C always returned back to Kelly AFB where the squadron had proper maintenance facilities. By July the Civil Aeronautics Administration (the CAA, the predecessor agency to the FAA) assigned four pilots to the 1700th TS to gain knowledge and experience in scheduled turboprop transport operations. That particular month, the second YC-131C became the first American-built turboprop aircraft to exceed 1,000 flight hours.

The second YC-131C being handed over the USAF.

In the first six months the YC-131Cs were flown intensively, sometimes over 30 hours per day between the two aircraft. The initial time between overhaul (TBO) on the Allison YT56 engines was set at 100 flight hours at the start of the program but the engine proved to be highly reliable and as the program progressed, the TBO was increased progressively up to 200 flight hours. Though the engines could have safely flown with a longer TBO than 200 hours, Allison engineers were anxious to teardown and study the engines to improve the planned production T56 that would be used on not just the Lockheed C-130 but also on the same company's L-188 Electra airliner. During the nine month test program, 55 engines were changed out and sent back to Allison for analysis. The three-bladed Aeroproducts propellers also had TBO limits, starting at 300 hours and then extended out to 1,000 hours by the end of the test program. With a reliability well in excess of what was possible with piston engines, the two YC-131Cs also became the first USAF turboprops to exceed 1,000 flight hours with one day a record being set with an astounding 46 hours and 20 minutes flown in a 24-hour period, evenly split between the two aircraft.

On 15 December 1955 the test program with the YC-131C ended, 45 days early thanks to the reliability of the YT56 engine. The USAF gained important data on fuel planning for turboprops, ATC procedures, holding patterns and ground operations that was also shared with the airline industry. In addition, the first squadrons that would be receiving the first C-130A Hercules aircraft at Sewart AFB, Tennessee, Ardmore AFB in Oklahoma, and Eglin AFB in Florida, sent their initial cadre of maintenance personnel to the 1700th TS in San Antonio for familiarization with the T56 engine. Both aircraft were eventually declared surplus and passed on to civilian owners before being scrapped.

The next blog post will look at the second of the three turboprop conversions operated by the 1700th TS. Stay tuned!

Source: Remembering an Unsung Giant: The Douglas C-133 Cargomaster and Its People by Cal Taylor. Firstfleet Publishers, 2005, p29-43. Photos: Smithsonian Institution, SDASM.

The Fighter That Shot Itself Down

2011-09-06T11:35:00.001-05:00

The F11F-1, the first production Tiger version

In the mid-1950s the US Navy was hard at work with Grumman in getting the new F11F Tiger into service. Originally developed as a supersonic development of the F9F-6/7 Cougar, the program eventually resulted in an all-new aircraft for the day fighter role powered by the Wright J65 turbojet, a license-built version of the British Sapphire engine that also powered the Hawker Hunter and Gloster Javelin. Part of the flight test program to get the Tiger operational involved clearing the performance envelope for the firing of its four 20-millimeter Colt cannons which were mounted under and aft of the air intakes. As the Tiger was designed to be as light as possible so to attain the highest performance with its J65 engine, the expended cases and links from the Colt cannons were ejected overboard rather than be retained onboard the aircraft. During the cannon firing portion of the flight test program, it was immediately found that the airflow patterns around the aircraft allowed the spent cases and links to hug the fuselage, causing multiple dents and scratches. At one point in the program the Tiger test aircraft had to be fitted with an armored leading edge to the horizontal stabilizer as the damage from the links in particular could be significant.

The solution was to change the ejection mechnism and associated chutes so that the shells were forcibly ejected out longer chutes that projected out into the airstream and away from the turbulent air along the sides of the Tiger. A complex internal mechanism recycled the links to a special compartment just ahead of the cannon ammunition boxes as the links tended to cause more surface damage than the spent casings.

On 21 September 1956, Grumman test pilot Tom Attridge sortied out of the company airfield at Calverton, Long Island in aircraft BuNo 138620 to conduct high speed firing tests of the cannons. It was the 41st flight for this particular F11F-1 Tiger and it was Attridge's second test flight of the day. His flight profile for this test was to start out at 22,000 feet and accelerate in afterburner at a 20 degree angle past Mach 1. Passing through 13,000 feet he would fire a four second burst of the cannon, wait three seconds to allow the guns to cool, and then fire a second burst, ending the profile at 7,000 feet when the ammunition load would be expended.

How to shoot yourself down....

Attridge flew the prescribed profile and upon expending the ammunition, was suddenly confronted by the shattering of the forward armored windscreen caused by some sort of object. He immediately throttle back and pulled up to reduce speed to prevent the windscreen from caving in and at 13,000 and 200 KIAS he turned back towards Calverton. The only damage he could ascertain was a gash to the right intake lip and that everytime he took the engine up above 78% power, it began to run rough. Two miles from the end of the Calverton runway and at 1,200 feet with his wheels down and flaps lowered, Attridge found that 78% engine power was insufficient to maintain his glide path as the sink rate began to increase. He advanced to full throttle only to be greeted by what he described as "the engine sounded as if it was tearing up" and he immediately lost power. Three-quarters of a mile short of the runway, the Tiger settled into the trees and the aircraft traveled for 300 feet before coming to a stop. Though the aircraft was on fire, Attridge managed to escape quickly without injury and the Grumman crash crew and rescue helicopter were on scene in less than three minutes. Eleven minutes after landing, the company helicopter landed a local hospital to have Attridge evaluated.

Examination of the aircraft showed it had been hit by at least three 20-millimeter rounds- one in the windshield, one in the right intake lip and one in the nose cone. In addition, projectile fragments were found in the first compressor stage of the engine along with fan blade damage- engineers suspected that perhaps the round that hit the right intake ricocheted into the engine. It was determined that Attridge had inadvertently shot himself down. At the first cannon burst, he was in 0.5G supersonic descent and had actually flown underneath the trajectory of the cannon projectiles from the first cannon burst. Eleven second later, as he began to pull out of the descent, he flew into the stream of projectiles from the first burst.

Subsequent examination of the aircraft showed that Attridge had flown the same test profile earlier that day and what was thought to be large ding from an ejected casing on the vertical fin actually turned out to be a projectile hit- apparently Attridge had grazed himself on the first test flight of the day and gotten away with not shooting himself down!

Source: Aero Album, Spring 1968, Volume One. "The Tiger That Clawed Itself" by Robert Munro, p12-14.

Oliver Rasmussen Evades the Japanese for Ten Weeks- in Japan

2011-08-17T11:05:00.000-05:00

Oliver Rasmussen in the back seat of the Helldiver

The run up for the Allied invasion of the Japanese home islands began on 1 July 1945 when Task Force 38, a powerful US Navy fast carrier armada, weighed anchor and headed out from its forward anchorage in the Philippines. Under the command of Vice Admiral John McCain aboard the Essex-class carrier USS Shangri-La, TF38 was tasked with Phase One of Operation Olympic, the preparatory phase of the invasion of Kyushu planned for November 1945. The aircraft of the task force would establish air superiority by mid-August over Kyushu which would in turn set the stage for Operation Coronet, the invasion of Honshu in 1946. The first strikes would begin on northern Japan on 13 July before moving south to Kyushu. In poor weather than grounded most of the Japanese fighter forces, the aircraft of TF38 struck coastal targets and shipping on Hokkaido, the northernmost of the home islands. Despite the weather, the Japanese managed to put up a spirited defense in the two-day strikes, with the Navy losing 44 aircraft and 26 pilots in crew.

On the first day over Hokkaido, the Shangri-La's air wing would lose eight Curtiss SB2C Helldivers. One of the Helldivers lost was flown by Lt.(jg) Howard Eagleston, who descended too low under the overcast and struck a mountain in rural Hokkaido. He was killed on impact, but his gunner, 23-year old radioman Oliver Rasmussen, survived. With only the clothes he wore and an empty backpack, Rasmussen knew all too well what the Japanese did to their prisoners and decided he'd chance it in the Hokkaido wilderness. Being part Chippewa Indian from Minnesota, Rasmussen had come from an impoverished family (he referred to them as "the second generation right out of the teepee") but had spent his youth in the great outdoors. Having only a vague idea of his general location, Rasmussen spent seventeen days trekking to the coast, living off the land and avoiding any Japanese residents he came across. On 31 July upon reaching the coast, Rasmussen found his first source of significant food- a farmer's cow near his hideout would provide the sailor fresh milk for nine straight nights- each night he'd creep out to the cow and help himself to the milk and return to his hideout. The farmer never figured out what was going on, eventually turning to cow lose figuring she was longer able to produce any milk.

Rasmussen then built a small boat and tried to head out to sea, but the breakers on that particular stretch of coastline proved hazardous. He retreated back up into the mountains of Hokkaido and set up quarters in an abandoned railroad shack where he kept himself fed with raw onions, birds' eggs, uncooked rice and frog legs. On 16 August, the day after the Japanese surrender, he was spotting by a Japanese civilian, but not aware the Japan had surrendered, Rasmussen abandoned his hideout and sought new refuge. After several days of exploring, he found a site well-hidden that was within easy reach of five farms. He scavenged some scrap lumber to build a small shelter and helped himself to the produce and milk from the five farms each night. As he hadn't bathed in weeks, one of the farms' dogs got his scent on 5 September and the owners went to investigate. He managed to knock over some of the farmers as he made a narrow escape back into the wilderness. Each day he noted more and more American aircraft flying overhead, but he was unable to get their attention. He did find it odd, though, that they attracted no defensive fire and it didn't appear that they were conducting any offensive strikes.

Frustrated that he wasn't able to attract any passing aircraft and growing weary of being in the wilderness, he opted for the direct approach on 19 September and walked into the port city of Tomakomai and presented himself to the local police station to surrender. To Rasmussen's surprise, the police chief treated him as a guest with his first real meal in ten weeks and a bath. It was then that he found out about Japan's unconditional surrender on 15 August. Rather amusingly, the police chief asked Rasmussen if he knew anything about the rash of milk and produce thefts from local farms over the past several weeks- to which Rasmussen denied any knowledge. After an astonishing sixty-eight days in the Japanese wilderness, he was returned to the USS Shangri-La to a hero's welcome. While the end of the war dominated news headlines in the United States, upon his return stateside some news articles did cover his story and regrettably most were condescending about Rasmussen's experience given his native American heritage. As a result, he told no one else about his story despite remaining with the Navy.

Donald Norton's book on Oliver Rasmussen's experiences

Postwar, he made a career in the Navy working the Berlin Airlift and flying combat missions over Korea. He retired a chief petty officer in 1962 and settled in California where he got a technical job at the Lawrence Livermore National Lab. He passed away in his sleep in 1980 after a year-long battle with cancer with only a few people aware of his story. In the 1960s, though, a family friend made numerous recordings of Rasmussen's ten-week experience in Japan for a planned book. That family friend, however, died a year after interviewing Rasmussen and Rasmussen's wife put the tapes into storage. There they remained until nearly 20 years later, when one of Rasmussen's subordinates in the Navy from the 1950s, Donald Norton, set out to document Rasmussen's story for his own book project. Finding out that Rasmussen had died in 1980, his widow passed on the recordings to Norton, which became the basis for the book Chippewa Chief in World War II: The Survival Story of Oliver Rasmussen in Japan which was published in 2001.

Source: Whirlwind: The Air War Against Japan, 1942-1945 by Barrett Tilman. Simon and Schuster, 2011, p199-204.

RNZAF Squadron Leader Leonard H. Trent and his Victoria Cross Mission

2011-08-07T21:22:00.000-05:00

Sqn Ldr Leonard H. Trent

With the drums of war building in Europe in 1939, the Royal Air Force asked Lockheed for a twin-engine bomber to be used for anti-submarine and coastal patrols. Based on the RAF's own experience with the Hudson which was based on the Lockheed 14 Electra airliner, Lockheed offered a bomber version of the Model 18 Lodestar transport as the Ventura. First flying on 31 July 1941, the British were suitably impressed with the Ventura's performance to order 650 of the Ventura I and 487 of the upgraded Ventura II aircraft. Though the bulk of the Venturas were diverted to US forces following Pearl Harbor, a significant number did reach the RAF who needed the Ventura as a replacement for the Bristol Blenheim as a fast, low-level, bomber. Though there were more suitable aircraft for the role, at the time, only the Ventura was available in the numbers needed. In Norfolk, the RAF equipped No. 21 Squadron with the Venturas and co-located were two Commonwealth squadrons also assigned the Ventura- Australian-manned No. 464 Squadron and New Zealander-manned No. 487 Squadron. The three units were tasked with coastal targets in occupied Europe. Despite a high number of accidents and technical issues, the three units pressed ahead in committing the Ventura to combat, being assigned industrial targets primarily in Holland. As the war progressed, the RAF would team up the Ventura units with squadrons flying the faster Mosquito and Douglas Boston (RAF version of the A-20 Havoc) bombers.

The pilots of No. 487 Sqn and one of their Venturas

On 3 May 1943 the Kiwis of No. 487 Squadron were assigned a diversionary raid against a power station in Amsterdam while an RAF squadron flying Bostons would attack the Royal Dutch Steel Works at low level. Opposition was expected to be heavy but the Venturas despite their poor reliability could absorb a considerable amount of damage and still fly home. The pilots of No. 487 Squadron were encouraged to do what they could to hit the target and complete the mission as a means of boosting the morale of the Dutch population and resistance. Leading the twelve Venturas would be Sqn Ldr Leonard H. Trent.

As poor luck would have it, that same day the German military governor of Holland would be visiting the area and the Luftwaffe had placed a large number of its fighters on alert. To make matters worse, a squadron of RAF Spitfires assigned to escort No. 487 Squadron arrived at the rendezvous point off the coast half an hour too soon. Not only did this trigger the Luftwaffe alert, but when the Venturas arrived at the rendezvous point, the Spitfires were low on fuel and had to return to base, leaving the Kiwis to hit the power station unescorted in broad daylight. Crossing the Dutch coast at 12,000 feet, the twelve Venturas were in two formations of six and were bounced by seventy Luftwaffe fighters. Trent's second-in-command took hits and had to turn back to return to England- his aircraft would be the only one of the twelve to make it home. As the Venturas fought off the Germans, the fighters savaged the formation, leaving only three aircraft led by Sqn Ldr Trent to complete the mission. Six Venturas were shot down in less than four minutes. As they neared the target, another two Venturas were shot down, leaving Trent and his crew as the only remaining aircraft. Approaching the target and his gunner managing to shoot down a Messerschmitt Bf 109, Trent pressed home his attack and just as his bombs hit the power station, accurate flak destroyed his aircraft with Trent and his navigator being thrown clear of the shattered aircraft. The rest of his crew failed to escape and Trent and his navigator parachuted down and were captured.

RAF Ventura over its target

After his capture, Trent was sent to the Stalag Luft III POW camp where he participated in the "Great Escape" in March 1944. He avoided getting shot by surrendering right outside of the camp gates. The Gestapo executed fifty escaped prisoners, but Trent only got solitary confinement because of his early capture. On his repatriation did the circumstances of the disastrous Amsterdam raid become known and on 1 March 1946 he was awarded the Victoria Cross, Britain's highest military honor, for his leadership on the raid that claimed 11 of the 12 Venturas sent to hit the power plant. The squadron was virtually wiped out after that raid and the RAF questioned the continued use of the Ventura as a daylight attack bomber. King George VI himself and his daughter, the future Queen Elizabeth II, visited No. 487 Squadron at their base only days later to offer their condolences.

After the war, Trent remained with the Royal Air Force and in January 1956 he became the first commanding officer of No. 214 Squadron at RAF Marham which was the first to become operational with the Vickers Valiant, the first of the RAF V-bombers that formed Britain's nuclear deterrent until the arrival of the Polaris SLBM with the Royal Navy. He retired in 1965 when the Valiant fleet was retired due to wing spar structural failures and returned to New Zealand where he passed away in 1986. His biography, Venturer Courageous, was published in 1984 and authored by James Sanders and Laddie Lucas.

Source: PV Ventura/Harpoon Units of World War 2 (Osprey Combat Aircraft No. 34) by Alan C. Carey. Osprey Publishing, 2002, p17-19. Photos: Royal Air Force, United States Navy.

Master Sgt Red Erwin, One of Many Heroes

2011-05-30T20:57:00.000-05:00

In coming up with a suitable blog post for Memorial Day, I had scoured my aviation library for a historical event- given that I've long been interested in military aviation history, there's no shortage of material in that department, believe me. However, I'm currently reading Barrett Tillman's outstanding book Whirlwind: The Air War Against Japan 1942-1945 and came across the story of a red-headed Alabaman, Master Sgt. Henry "Red" Erwin. In April 1945, the massive arsenal of democracy that was American industry had already started the systematic destruction of the Japanese war machine the previous month as Boeing B-29 Superfortresses of the XXI Bomber Command based in the Marianas Islands under the command of General Curtis LeMay began to deliver destruction to the cities of Japan. The first fire-bombing raids had already visited untold disaster on Tokyo and other urban areas of the Home Islands. Superfortress attacks on the kamikaze bases on Kyushu had helped ensure victory on Okinawa. And by this month, the XXI Bomber Command finally had enough Superfortresses to wage a round-the-clock strategic bombing campaign on the Japanese homeland. On 12 April 1945 news reached the bases in the Marianas about the death of President Franklin D. Roosevelt- for many of the fighting men in the Pacific, Roosevelt was the only leader they had known. But there was war to fight, and every bomb dropped meant getting home sooner.

Erwin is 2nd from the right, front row, with his B-29 crewmates

On that day, 250 Superfortresses set out in three airborne task forces to attack industrial centers near Tokyo. Half of the force belonged to the 29th Bomb Group and were tasked to hit the Koriyama chemical complex north of Tokyo. Off the coast of Japan, the lead pilot of the Koriyama-bound force was Captain George Simeral flying The City of Los Angeles. His crew excelled at their jobs and earned The City of Los Angeles the lead position of the task force. His crew had been together since June 1944 and had already flown ten missions over Japan. As Simeral neared the coast. he ordered his radioman, Master Sgt. Red Erwin, to drop a phosphorous flare to mark the assembly point for his own squadron. Erwin left his station in the forward compartment, picked up the large flare canister and pulled the arming pin before dropping it as was the standard procedure- only this time the flare prematurely fired and a 1,300-degree Fahrenheit blast hit him in the face, blinding him and instantly burning off his nose and one ear. The forward compartment of the B-29 filled with white smoke and Simeral and his co-pilot quickly lost view of their instruments and the outside world.

Erwin realized that the hot burning flare could burn through the compartment like a big blowtorch into the bomb bay and set off the bomb load. Griping around the compartment, he somehow managed to find the flare and pick it up. He stumbled his way forward, planning to throw it out the co-pilot's window but found his way obstructed by the navigator's table- the navigator at the time was in the astrodome taking a sighting when the flare fired. As the table could be unlocked and hinged downward, Erwin tucked the hot flare between one arm and his side and managed to fold the table so he could continue his way forward through the compartment. Though blinded, he somehow managed to get to the co-pilot's window, open it, and throw the burning flare overboard. He immediately collapsed on the bomber's throttle console.

In the short time it took for Red Erwin to throw the flare overboard, the crew had lost control of the B-29 and Simeral managed to regain control with the bomber only 300 feet above the sea as the crew opened every hatch and window possible to vent the forward compartment. Everyone else did what they could to easy Erwin's suffering and Captain Simeral set course for Iwo Jima. The doctors there could do little for him and he was flown to Guam where a fleet hospital was located. General LeMay had been informed of the situation and when doctors advised him that Erwin would likely die from his burns, LeMay was determined to get him the Medal of Honor irrespective of the regulations.

To understand what happened next, you have to realize that LeMay was already well-known in the USAAF as being very results-oriented. When he was tapped by the head of the USAAF, General Henry "Hap" Arnold, to head the XXI Bomber Command, the B-29 was not performing well as a combat machine, being constantly plagued by rushed training and poor maintenance practices. Arnold wanted results as he was one of the most staunch defenders of the B-29 program and the massive funding it required- not to mention a successful air campaign over Japan strengthened his case for an independent United States Air Force. LeMay was given his orders- and unusually for a combat command, the XXI Bomber Command was run right out of Arnold's office at the Pentagon so theater commanders couldn't appropriate the prized Superfortress for tactical missions. It was LeMay who had to deliver and the way Arnold entrusted LeMay, so did LeMay entrust his subordinates- "Get me the results I want and I won't ask questions." As a result, his subordinates became well-known in the Pacific Theater for circumventing rules and red tape to get their boss results.

It usually took several months to get a Medal of Honor awarded as it passed via several levels of review. That didn't suit LeMay. His first act was to order an aircraft and its crew to Hawaii to get a Medal of Honor that could be presented to Erwin before he died. The crew took this task to heart and having found one in a display case, were unable to locate who had the keys to open the case. So they broke into the case and returned to Guam with the medal in hand. With the medal secured, LeMay then cabled General Arnold at the Pentagon and insisted that Erwin's award be approved immediately as he was on his deathbed. Luckily for LeMay, Arnold agreed with him and quickly got the orders and citation approved and the papers were on President Harry S Truman's desk in just days. In fact, one of Truman's first acts as President after FDR died was to sign the papers for the awarding of the Medal of Honor to Red Erwin!

Red Erwin's widow with the painting of him at Maxwell AFB

At a hastily arranged ceremony at Erwin's bedside at the fleet hospital in Guam, LeMay presented him with the Medal of Honor six days after the mission took place. The general order that announced the award took three months to be processed and formally announced! But the tough Alabaman surprised everyone by surviving his wounds. Over the next two and a half years he underwent over 40 reconstructive surgeries and managed to regain his vision. Discharged from the now-independent United States Air Force in 1947, he went to work for the Veterans' Administration hospital in Birmingham, Alabama, working closely with burn patients for the next forty years. Master Sgt. Henry "Red" Erwin passed away in 2002 at the age of eighty.

After his death, the U.S. Air Force established the Red Erwin award for the outstanding enlisted airman of the year in the Air National Guard and Reserves. More recently, the library at the Air University at Maxwell AFB in Alabama was named the Red Erwin Library in his honor with a specially-commissioned painting of him and the B-29 Superfortress. Always the modest man, Erwin told everyone that he didn't wear the Medal of Honor for what he did on that fateful mission in 1945- he wore the medal for everyone who served.

Source: Whirlwind: The Air War Against Japan, 1942-1945 by Barrett Tillman. Simon and Schuster, 2010, p164-167. Photos: United States Air Force.

General Giulio Douhet, the First Air Power Visionary

2011-05-16T11:02:00.000-05:00

Giulio Douhet, air power visionary

Those of us interested in aviation take it almost for granted the unyielding pace of technological development that has driven aviation forward through time. But even less heralded are those in aviation history who have shaped the thinking of aviation- it's easy for us to lay eyes on an aircraft or even to put our hands on one. They're very tactile and sensory experiences in aviation- to see one, hear one, feel one, even ride an aircraft. But how do you experience aviation doctrine? How do you grasp the thought processes that have shaped aeronautical progress? They're very abstract and not prone to enjoyment and appreciation by most of us. However, technological progress is a rudderless boat in chaotic waters without visionaries and thinkers to provide steering and direction. Of course we can name designers like Jack Northrop or Andrei Tupolev. Or pilots like Charles Lindbergh or Chuck Yeager. But the subject of today's blog posting is none of those- he didn't design any aircraft, he didn't even fly aircraft. But his writings on air power have left an indelible mark on aviation, if not history itself.

Born in 1869, Giulio Douhet was a rare breed of Italian army officer who was both an infantry and artillery officer and what we might call a technocrat, having studied science and engineering as well. His earliest writings as part of the General Staff of the Italian Army covered mechanization and the incorporation of what would be come tanks in military doctrine. But with the arrival of lighter-than-air aircraft like dirigibles and the first practical biplanes prior to the First World War, Douhet quickly appreciated the advantages of aviation in war- aircraft could move in three dimensions and operate above and out of the reach of ground and naval forces with relative impunity. In 1912 when the Italians first used aircraft in combat in Libya, he wrote Rules for the Use of Airplanes in War, one of the first efforts to create a doctrine for military aviation- despite his own background as an artillery and infantry officer, Douhet felt that the current military leadership lacked an understanding of the inherent advantages of air power and an almost zealous desire to educate the establishment on air power would be Douhet's mission in his life.

When the First World War broke out in Europe in August of 1914, Douhet was forty-five years old and no less energetic than officers half his age. With a near-insatiable appetite for the latest developments in aviation, he advocated the building of a force of 500 bombers that could bomb enemy forces from above without having to engage in prolonged combat. He worked closely with the Italian engineer Gianni Caproni in advising him on his own Caproni line of bomber aircraft. But Douhet would find the Italian military leadership incompetent as defeat after defeat was suffered by Italian forces. Convinced that aviation technology could reverse the lagging fortunes of the Italian military, Douhet wrote and spoke frequently to anyone and everyone in the military and government establishment. By 1916 his superiors had had enough when he had ordered construction of Caproni bombers without authorization. He was stripped of his rank and imprisoned on charges of "issuing false news" and "disturbing the public tranquility". It didn't stop him, though. He continued to write and refine his theories from his cell.

In the fall of 1917, the Italian Second Army was completely routed at the Battle of Caporetto (in modern day Slovenia), suffering over 300,000 casualties. The Italian government in desperation released Douhet from prison and commissioned him as a general in charge of coordinating the nation's aviation strategy and doctrine. It would be too little too late as the entrenched Italian bureaucracy was unwilling to enact his plans and he resigned in protest in June 1918. With the Armistice in November of that year ending the First World War, Douhet's trial verdict was reversed and he was promoted, but by this point in his life he had lost faith in the Italian government and refused to return to duty. During the interwar period he traveled Europe visiting other nation's air arms, consulting with air officers and meeting with aircraft designers. In 1921 he wrote his landmark work Command of the Air which advocated an relentless air campaign of bombing an enemy's population and production centers, reducing their moral and material means of resistance. Properly conducted, he reasoned, such an air assault could force a quick decision and save millions of lives in the long run by avoiding a costly ground war. Douhet also pointed out that the efficient and proper means of carrying out such an air campaign would require an independent air arm led by an aviation-minded general staff. At the time, this was a revolutionary concept and only in Great Britain was the nascent Royal Air Force an independent air arm. For other industrialized nations of the 1920s, their air arms were subordinated to the army.

Billy Mitchell, USAAC

Reception of Douhet's work outside of Italy was mixed. It wasn't even required reading at the RAF Staff College. But his work would find converts primarily in the United States- at the time the Air Force was part of the Army as the US Army Air Corps. One officer in particular would even meet with Douhet- Brigadier General Billy Mitchell. It was the year after Mitchell had demonstrated the vulnerability of warships to bombers by sinking several captured German warships off the Virginia coast. Mitchell had copies of Command of the Air sent to his superiors and he got banished to Hawaii and then Asia as a result. In 1925 Mitchell wrote a book of his own, Winged Defense, in which he refined Douhet's ideas of a strategic air campaign further and even declared the battleship obsolete as aviation technology matured. As a result, Mitchell was demoted in rank back to colonel. He would later be court-martialed for publicly criticizing the US military following the crash of the airship USS Shenendoah in a storm. But his six week court martial provided Mitchell the perfect forum for advocating views shaped by his mentor, Giulio Douhet.

Sir Hugh Trenchard, RAF

Douhet died of a heart attack in 1930 and Mitchell himself would die in 1936, neither man living to see how their views of air power would come to fruition in the Second World War. While Command of the Air got little attention in the Royal Air Force, the most influential individual in the RAF at the time fortunately was a proponent of Douhet's theories- Sir Hugh Trenchard, Chief of Staff of the RAF and the man known as the "Father of the RAF". Trenchard, like Mitchell, would refine Douhet's ideas. By the time of the Second World War, Trenchard was every bit the irritant to the establishment as Douhet and Mitchell were, but had enough influence to avoid their fate. Following the disastrous loss of Norway to the Germans in 1940, Trenchard used his position in the House of Lords to criticize Prime Minster Neville Chamberlain's prosecution of the war which contributed to his replacement by Winston Churchill. Trenchard used in influence to put like minded officers in key positions in the Royal Air Force. After the war, Trenchard advised General Henry "Hap" Arnold in his own push for an independent United States Air Force.

The same year Mitchell died in 1936, contracts were issued to both Boeing and Douglas for a large four-engined bomber- while both companies' designs, the XB-15 and the XB-19, respectively, remained experimental, the engineering and design work on such a unprecedentedly large bomber would shape aviation technology throughout the Second World War.

Source: Whirlwind: The Air War Against Japan, 1942-1945 by Barrett Tillman. Simon and Schuster, 2010, p9-16.

The Fairchild XNQ-1/T-31 Trainer

2011-05-12T11:32:00.000-05:00

In USAF markings as the T-31

As the Second World War began to wind down with victory in Europe established and the end of the Pacific War on the horizon, the US Navy set out to issue specifications for a replacement for the basic and primary aircraft trainers that were used during the war (like the PT-19 or the BT-13, PT standing for "Primary Trainer" and BT standing for "Basic Trainer in the Navy lexicon) as well as the North American SNJ/T-6 Texan. These specifications were released to the industry on 26 April 1945 by the Bureau of Aeronautics (BuAer). Three companies entered designs- Temco entered the T-35 Buckaroo which was adapted from the Globe Swift general aviation aircraft, Beechcraft entered the T-34 Mentor which was a tandem seat adaptation of the Bonanza and Fairchild entered a custom-designed aircraft that had the Navy designation XNQ and the later USAF designation T-31. History, of course, shows that the Beech Mentor won the competition and one of it's strong points was its tricycle undercarriage layout compared to the taildragger layout of both the Buckaroo and the XNQ. For the forward thinking armed services, taildragging aircraft were obsolete.

Fairchild's chief engineer, Armand Thiebolt, had already established a name for himself having designed a number of training aircraft during the war, from the PT-19 Cornell to the AT-21 Gunner. His work on the XNQ was based on his own experiences and what he felt was a balance between state of the art and simplicity. Registered with a civilian tail number N5726, the first XNQ, built at Fairchild's Hagerstown, Maryland, plant, made its first flight there on 10 February 1947 with Fairchild's chief test pilot, Richard Hansen, at the controls. The 20-minute maiden flight was uneventful and showed only some simple rework of the aileron tabs were necessary. After a series of company test flights, the XNQ was delivered to the US Navy at Anacostia, Washington for formal evaluation. After an initial series of flights in the Washington DC area, the flight test program continued at NAS Patuxent River after which the aircraft returned to Fairchild to prepare it for evaluation by the USAF as the T-31.

By this point the second aircraft had been completed and both XNQs as T-31s were flown to Randolph AFB outside of San Antonio, Texas, for their formal USAF evaluation in a fly-off with both the Beech and Temco candidates. At the time the USAF also considered the De Havilland Canada DHC-1 Chipmunk as well as the British Boulton Paul Balliol, but both were quickly eliminated from consideration, leaving Fairchild, Beech, and Temco remaining in the USAF evaluation. Like the US Navy, the USAF selected the Beech T-34 Mentor, again, its tricycle landing gear layout being one of its strong points. It was the second rejection of the Fairchild design. The aircraft was passed on to the US Navy where it was flown by student test pilots at the US Navy's Test Pilot School at NAS Patuxent River and after a gear up landing that resulted in only minor damage in 1953, the Navy declared the unique aircraft surplus to its needs after it had only amassed just over 1,000 flight hours.

The wing commander for the National Capital Wing of the Civil Air Patrol arranged to take ownership of the XNQ and in October 1953 the aircraft was repaired at NAS Patuxent River before being flown to a small airfield south of Alexandria, Virginia where it was stationed for the next 2 years, only clocking 12 flight hours in that time period. Part of the problem with the XNQ wasn't its performance or handling, but that its wingspan was just over a foot too wide for the standard 40-foot hangar at the airfield and it ended up spending most of its time outdoors which adversely affected its condition. In 1955 the aircraft was ferried to Rockville, Maryland, but again, was stored outdoors which resulted in further deterioration. When that small airfield was closed, the Fairchild was abandoned in situ.

In her original US Navy markings

John St. Clair, the operations officer of the Congressional Squadron of the Civil Air Patrol, trucked aircraft to his home 8 miles away to try and save it given its unique history. He later assumed formal ownership of the aircraft to keep it from going to the junkyard. Fast forward to 1978, the aircraft is still on the St. Clair farm in rural Maryland and Armand Thiebolt's son visited John St. Clair and asked about purchasing the aircraft, the deal of which fell through. Later, Robert Taylor, the founder of the Antique Airplane Association, asked St. Clair if he would done the XNQ to a museum, which he agreed to and a crew from the association trucked what was left of the aircraft to Waco, Texas with plans of restoring her to flight status. The history of the XNQ took a new turn after its arrival in Waco when general aviation pilot Don Pellegrino and his wife were weathered in at the airport and he found the XNQ in storage in a hangar and approached Taylor about purchasing the aircraft.

While negotiations proceeded, the aircraft was moved to Oklahoma City in 1982 but still no restoration work had started. At a fly-in in Iowa, Taylor approached Pellegrino and told him "Make me an offer I can't refuse" and with that, Pellegrino become the XNQ's new owner for $800. In September that year Pellegrino trucked the aircraft to his farm in Iowa and began restoration work in earnest. After ten years of working on it in his free time, the XNQ made its second maiden flight on 1 June 1992, the first time the aircraft had flown since 1955! Pellegrino flew the 25 FAA-required hours of flight testing himself and since then he has since moved to Rhome, Texas, just outside of the Dallas-Fort Worth area and has flown the XNQ to airshows around the country. And yes, she still has her same tail number of N5726 after all these years!

Bill Spidle has three pages of detailed photographs of a walk around of the XNQ.

Source: Air Enthusiast, No. 117, May/June 2005. "Their Loss, My Gain: Fairchild's XNQ-1- Twice Rejected for Service" by Gilles Auliard, p78-79. Photos: US Naval Test Pilot School Alumni.

Sukhoi's First Jet Bomber

2011-04-19T22:30:00.000-05:00

The Sukhoi Su-10 in its final configuration

Following the end of the Second World War, both the Soviet Union and the West aggressively pursued jet bomber designs after the Luftwaffe had successfully introduced the Arado Ar 234 to combat in the waning months of the war. In the West, many early designs were based on layouts of high-mounted wings with wing-mounted nacelles to allow for a reasonably-sized bomb bay. Similar approaches were taken in the Soviet Union with the design bureaus (called OKBs) of Illyushin, Tupolev, and Sukhoi tapped to develop jet bomber designs to succeed the Soviet Air Force's standard bomber, the piston-powered Tupolev Tu-2. Last summer I had posted about an early Tupolev design that actually did fly, the Tu-12, that was based on the Tu-2 as a matter of expediency pending the arrival of the Tu-14 bomber. While Illyushin and Tupolev both had large aircraft design experience from their own work on twin-engine bombers during the war, Pavel Sukhoi's experience was limited to his prewar tenure at OKB Tupolev. But, given the pace of technological progress and the urgency of rearmament in competition with the West, Sukhoi was ordered on 26 February 1946 to develop a jet bomber powered by four Junkers Jumo 004B turbojets, the same jet engines that powered the Arado Ar 234. Work on Sukhoi's first bomber design began in earnest in April of that year and the aircraft received the official designation of Su-10.

Several powerplant arrangements were considered along with the use of six engines instead of the four as originally specified. In the Soviet Union, the Central Aerohydrodynamic Institute in Moscow, or TsAGI by its Russian name, did a lot of wind tunnel and theoretical research work to support design efforts at each of the OKBs. At the time that OKB Sukhoi was working on the Su-10, TsAGI had lagged behind Germany and the West in high speed research and as a result, they lacked a significant amount of information on evaluating jet aircraft designs. As a result, much of what laid the basis of TsAGI's high speed aircraft research came about during their work in support of the development of the Su-10 in addition to what had been obtained of German design work following the end of the war. Two leading design variants were evaluated in TsAGI's wind tunnels- one design had four of the jet engines clustered in the mid fuselage and exhausting out the rear with two jet engines under the nose- this was felt to be advantageous design as it left the wings clean. The other leading variant had wing mounted nacelles with a high unswept wing with three engines mounted in clusters on each wing.

To meet the specified target speed of 528 mph at 26,000 feet, Pavel Sukhoi decided that four engines were insufficient and that six were necessary. Since the Junkers Jumo 004 engine was the only jet engine available to the Soviet Union at the time that had reached production status, the Soviet Politburo placed high priority in reverse-engineering the engine for production- Vladimir Klimov and his OKB were already known for their piston engine designs during the war and he was put in charge of getting the German engine into production as the Klimov RD-10. Klimov's closest aide, Nikolay Kuznetsov, headed the actual reverse-engineering effort- Kuznetsov would go on to form his own engine OKB several years later.

Inboard layout of the Su-10

With approval from the state authorities to use six engines, design work had settled on a cluster of three engines on each wing as the most efficient layout- the nacelle had two engines side by side with the third RD-10 engine below and slightly ahead of the pair. On 6 May of that year, a full scale mockup was built that was tested in TsAGI's largest wind tunnel with real RD-10 jet engines. Within two months, refinements to the design based on TsAGI's evaluation were in place as full-scale engineering began on the prototype. While two months sounds rapid, development of the Su-10 hit repeated technical hurdles, the biggest of which was that TsAGI lacked a significant portfolio of well-studied high speed airfoils. As a result, while supporting development work on the Su-10, assimilating German design work, TsAGI was also hurriedly developing its on portfolio of high speed airfoils. As a result, Sukhoi's team was constantly having to revise the Su-10 design based on developments from TsAGI.

By October the full scale mockup had been approved by Soviet Air Force authorities and metal was finally cut for the prototype on 14 October 1946. In the first week of December, the Soviet government commission in charge of aircraft production decreed that the Su-10 would no longer use the Klimov RD-10 engine but instead use the TR-1 engine from the Lyulka OKB, the first indigenous Soviet jet engine design. Since the TR-1 was more powerful than the RD-10, the Su-10 could revert back to a four-engined design and once again Sukhoi and his team had to revise the bomber's design to accommodate the new Lyulka engines. Working at a frantic pace to meet state-decreed deadlines, Sukhoi managed to have a full set of production drawings ready by 23 December 1946 and three days later the OKB's own workshops had completed a static test airframe and production jigs and tooling for the prototype. If things weren't frantic enough as it was, the Minister of Aircraft Industry wanted the Su-10 flying for participation in the air show at Moscow on 18 August 1947! Common sense prevailed and that was one deadline Sukhoi was allowed to ignore.

Three-view showing the layout of the Su-10 medium bomber

By 15 December 1947 the hydraulic system had been fully tested on a special ground rig (similar to today's "iron bird"), but construction of the prototype was hampered by slow progress from the various subcontractors that were responsible for some of the Su-10's systems. For example, the defensive armament system (which consisted of a manned tail turret, a remotely-operated dorsal turret and forward-firing cannon), the autopilot, the navigation suite and even the Lyulka TR-1 engines were to have all been delivered to Sukhoi's workshops for the prototype but by the end of 1947 none of those items were ready yet. During the delay, studies looked at alternative powerplant options and it was decided that the initial flight tests of the Su-10 would use the TR-1 engine but as soon as the more powerful TR-2 engine developed from the TR-1 became available, the Su-10 prototype would have its engines swapped out and then continue with the flight test program.

These persistent delays led to the Su-10 prototype to sit in the OKB workshops missing various components- by 4 June 1948 the Soviet Council of Ministers ordered that spending had to be reduced on aircraft development programs that year and one of the unlucky programs to get canceled was the Su-10. By that summer OKB Ilyushin had already made the first flight of its Il-28 medium bomber and its performance outstripped what was projected for the Su-10. Not even rolled out, the Su-10 prototype was donated to the Moscow Aviation Institute where it was slowly reduced to parts over time as an instructional airframe. Sukhoi in the years to come devoted its efforts at interceptor, fighter, and ground attack aircraft and it wasn't until the arrival of the Su-24 Fencer in the late 1970s that Sukhoi finally had a production jet bomber.

Source/Images: OKB Sukhoi: A History of the Design Bureau and Its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2010, p93-101.

The Last Operational B-17 Flying Fortresses

2011-04-03T22:14:00.000-05:00

The Israeli B-17s originally flew without any defensive armament

On the day prior to the expiration of the British Mandate over Plestine on 15 May 1948, David Ben-Gurion declared the independence of the new State of Israel and within hours, Arab forces from Egypt, Jordan, Syria, and Lebanon invaded, starting the 1948 Arab-Israeli War, or the War of Independence in Israel. At the time of the declaration, the hastily-organized aviation assets of the fledgling state became the nascent Israeli Air Force, which in turn became part of the IDF, Israeli Defense Forces, on 26 May 1948. Initially outclassed by the Arab air forces with only a modest light plane fleet, the air war began to swing in favor of the Israelis on 20 May with the arrival of the first Avia S-199s from Czechoslovakia- the Junkers Jumo-powered version of the Messerschmitt Bf109 leveled the playing field against the Egyptian Spitfires. Despite a UN arms embargo on the participant parties on the 1948 war, resourceful Israelis and supporters worldwide (who were called "machal") insured a supply of arms through rather creative means, often involving subterfuge. Al Schwimmer was a long time flight engineer for Trans World Airlines who organized the transfer of arms to Israeli in 1948. At first Schwimmer got surplus C-47 transports transferred via Panama to form the nucleus of the IDF's air transport arm, but he soon recruited a former government purchasing agent, Charlie Winters, who at the time was based in Miami and was using three civilianized Boeing B-17 Flying Fortresses to transport produce between Puerto Rico and Florida. Winters sold the B-17s to the Israelis for $15,000 a piece and organized a team of former USAAF mechanics and engineers to make the aircraft combat ready.

Aircraft 1602 had a Mickey Mouse cartoon on its tail

The three B-17s (44-83811, 44-83753, and 44-83851) were covertly flown from the United States to an airfield in Czechoslovakia that was acting as the European terminus for the aerial supply line to Israel. Bogus flight plans to Brazil were filed to cover their tracks. Winters himself flew one of the B-17s across the Atlantic. He had arranged for a fourth B-17 as well, but this aircraft after eluding authorities in Canada managed to reach the Azores only to be impounded by the Portuguese government. At the Czech airfield of Zatek, the B-17s were further upgraded with improved instrumentation. They were loaded with bombs for the flight to Israel on 15 July 1948, but with the military situation becoming tenuous for the Israelis that summer, during their delivery flight they were diverted to hit Egyptian targets since they were carrying bombs anyway. One B-17 was to hit Gaza City, the second B-17 was assigned the Egyptian air base at El-Arish, and the third B-17 was assigned King Farouk's Royal Palace in Cairo. The first two B-17s had problems finding their assigned targets but the third B-17 did manage to bomb Cairo, which, like the Doolittle Raid's psychological effect on the Japanese in 1942, caused significant anxiety in Egypt as Cairo was felt to be immune from attacks by Israel's rag-tag air force of what was thought to be just light aircraft. The first two aircraft ended up bombing an Egyptian target in Rafiah instead but the overall effect of the raids not only damaged Egyptian morale, it served to boost Israeli morale as well. Since all three aircraft had been hurriedly made combat ready, numerous technical problems beset them on their delivery flight/first combat mission- one of the more notable issues was that the oxygen system kept quitting, which on several occasions during the flight from Czechoslovakia to Israel by way of Egypt had caused some of the crew members to pass out.

The three Israeli B-17s at various points in their careers

All three B-17s landed safely at Ekron airfield in Israel following their highly eventful delivery flight- the leader of the flight, a former USAAF pilot named Bill Katz, was named commander of a new squadron based at the former RAF base of Ramat David that would operate the B-17s- 69 Squadron "Patishim" or "The Hammers". The three aircraft were camouflaged and serialed 1601, 1602, and 1603. At the time the IDF had been relying on converted transports as bombers, so the arrival of the B-17s represented a significant leap in offensive capability for the Israelis. The following day on 16 July the three bombers flew three combat missions together, the first one to bomb the El-Arish air base that was missed the previous day, the second mission later in the day to bomb advancing Egyptian forces in the south and that night the third mission was against advancing Syrian forces in the north. Over the next several days multiple bombing missions were flown each day against Egyptian, Jordanian, and Syrian forces. Several attacks were mounted against Arab air bases in the belligerent countries and even several missions were flown against targets in the Syrian capital of Damascus. At first the missions were flown with fighter escort by Israeli Spitfires and Avia S-199s, but as the Arab air forces' losses mounted, soon the B-17s were able to operate without fighter escort. By the time of the armistice in February and March of 1949, over 200 combat missions had been flown by 69 Squadron. With the end of the war, the squadron eventually moved to the new air base at Hazor.

One of the B-17s, aircraft 1602, was modified to carry a search radar under the nose where the chin turret was located. This aircraft through the first half of the 1950s was stripped of its desert camouflage and operated as a maritime patrol aircraft in bare metal colors in the Mediterranean. By this time, enough spares had been acquired to allow all three B-17s to be retrofitted with gun turrets and at least two of the B-17s were kept operational at any given time. By July 1956 the long serving bombers were placed in storage.

During the 1956 War, Israeli B-17s wore yellow/black identification bands

The Suez Crisis of 1956 brought the three B-17s back out of storage that October. Israeli involvement in the 1956 war began on 29 October with Operation Kadesh, the Israeli invasion of the Sinai Peninsula. On 31 October 1956 the three B-17s attacked Egyptian positions in the Gaza Strip, but a series of mounting technical problems over the course of the war spelled the end of B-17 operations for the IDF. The bombers were finally retired in November 1958 as the last operational B-17 Flying Fortresses in action. 69 Squadron was disbanded as well, but would be reformed in 1969 as the second Israeli Air Force squadron to operated the F-4E Phantom II. Today 69 Squadron operates the F-15I Ra'am, the Israeli variant of the F-15E Strike Eagle. Al Schwimmer, the TWA flight engineer who was instrumental in organizing Israel's air force, would go on after the 1948 War to establish Israeli Aircraft Industries. His activities were called by David Ben-Gurion as the "single biggest contribution by the Diaspora towards the survival of the State of Israel". Charlie Winters was an Irish Protestant who helped the Israelis as a favor to his Jewish friends in Miami. As a result, he was charged by the US District Attorney in Miami for violating US laws and was fined $5,000 and sent to prison for 18 months. Two other Americans were also charged who aided Israel- one was Al Schwimmer, who never served prison time as he was convicted in absentia and was pardoned by President Bill Clinton in 2000. The other American in the operation was Hank Greenspun, who also never served an prison time and was pardoned in 1961 by President John F. Kennedy.

Charlie Winters passed away in 1984 having never told his children of his role in the creation of the State of Israel. It was only after the Israeli government sent an arrangement of blue and white flowers did his family learn of his activities in 1948. His ashes were interred in the ancient Templars' Cemetery in Jerusalem. In 2008, Winters was pardoned by President George W. Bush as only the second posthumous pardon in history.

Sources/Images: Aviation Classics, Issue 8. "The Israeli Air Force and the B-17" by Tim Callaway, p118-119. B-17G Flying Fortress in Israeli Air Force Service 1948-1957 by Alex Yofe. White Crow Publications, 2010.

Operation Teaball: Network-Centric Real-Time Intelligence During Vietnam

2011-03-31T22:31:00.000-05:00

In 1972, US fighters had an added resource in the fight against MiGs

In past blog posts I've discussed some of the measures taken by the military to reverse the decline in air combat proficiency in the skies over Vietnam. This past November I had blogged about the origins of Red Flag as well as the top secret USAF program to obtain and fly MiGs. Back in March I wrote about the US Navy's own efforts that began with the Ault Report. While these were all steps that would benefit fighter pilots in the skies over Vietnam, there was another effort that took place that has received scant attention in the history books and presaged today's military buzzword of "network-centric" warfare. Between the bombing halt of 1968 and the start of the North Vietnamese Easter Offensive in 1972, air combat over North Vietnam was nearly non-existent. With the start of the NVA offensive in 1972, though, President Nixon reversed the gradual drawdown of US forces in Southeast Asia with a massive buildup and bombing offensive under Operation Linebacker I and Linebacker II. With the ramp up of offensive air strikes on North Vietnam, US aircrews found themselves embroiled in multiplane dogfights that were resulting in growing US losses. In the three months following the start of Linebacker in May 1972, the US lost 48 aircraft, 21 to VNAF MiGs and 27 to improved ground defenses. In the same period, only 31 MiGs were shot down by US aircraft and things worsened in the summer with 13 US aircraft lost to MiGs and only 11 MiGs shot down.

At the same time, the policy of rotation of air crews meant that experienced personnel were rotated out of combat and replaced with novice air crews on their first combat tour. In the days before Red Flag and dissimilar air combat training, the loss rate of first tour air crews was staggering enough the General John Vogt, commander of the Seventh Air Force which oversaw combat air operations in Southeast Asia, ordered the minutes of mission critique conferences to be disseminated to all units in theater, not just the units involved. But it wasn't enough for General Vogt. He reported to the USAF Chief of Staff, General John Ryan, that the US was losing the air war over Vietnam in 1972. As a result, General Ryan ordered his staff to create a plan to assist US pilots in the skies over Vietnam- no studies, no plans, but what General Ryan wanted was something in place that could offset the fact that the VNAF MiG pilots were battle-experienced and had excellent GCI controllers who could relay the MiG air crews detailed descriptions of the tactical situation.

General John Vogt, commander USAF Seventh Air Force

Ryan tasked a three-man "action group" with setting something up- USAF officers Lt. Col. William Kirk and Maj. Ernie Short teamed up with Delmar Lang, an intelligence specialist with the National Security Agency. Lang was brought in as he had several times in the years prior repeated offered to set up an eavesdropping facility that could listen in on the communications between the VNAF MiG pilots and their GCI controllers to provide real time information to US pilots. Lang's idea had historical precedence- during the Korean War, the USAF had a listening post on the island of Cho-do off the coast of Korea that was staffed with linguists and air control specialists that would listen in on North Korean, Chinese, and Russian communications to give US pilots a real-time picture of what was going on in "MiG Alley". Since the Korean War, the pace of technological progress in electronic and signals intelligence (ELINT and SIGINT) improved by leaps and bounds, but national security and a variety of compartmentalized secret programs kept many of these new methods out of sight to those on the front line. Delmar Lang's NSA position, however, coupled with the access given Lt. Col. Kirk and Maj. Short, intended to cut through the institutional resistance to using those technological resources to win the war in the skies of over Vietnam.

On 26 July 1972, literally in just one month, General Ryan's "action group" set up the Operation Teaball Weapons Control Center at the Thai air base of Nakhon Phanom (nicknamed "Naked Fanny" by US pilots). Working with the intelligence specialists of the USAF's 6908th Security Squadron, the Teaball control room had map displays where data from a variety of intelligence sources already in place was collected and synthesized to form a single tactical picture that could be disseminated to US pilots in real time by specialist ground controllers. Orbiting high over the Gulf of Tonkin and Laos, specialist ELINT/SIGINT RC-135s listened in on communications between MiG pilots and their GCI controllers- this data was then relayed to a Lockheed U-2 orbiting high overhead that then relayed the information direct to the Teaball control center at Nakhon Phanom. Ground and ship-based (like "Red Crown" in the Gulf of Tonkin) radar pictures were added to refine the tactical picture. Finally, radar and SIGINT data from specialist EC-121s- such as the famous radar early warning EC-121 that used the call sign "Disco"- was also relayed to the Teaball specialists as well. Also little known was a US capability to trigger the IFF systems of the MiGs so they could be easily tracked. The stream of data from all these sources made use of a top-secret NSA computer system called "Ironhorse" that was designed to analyze and synthesize all the data to create a cohesive tactical picture that was then displayed on the map screens for the Teaball controllers to relay via another radio relay RC-135 to US pilots over North Vietnam. Once the system was up and running, the delay was as little as 45 to 60 seconds before the Teaball controllers were issuing advisories to US pilots!

"Combat Lightning" was one many specialist KC-135 variants used

Each combat air crew, regardless of service branch, were notified of a discrete UHF channel to monitor that advisories from the Teaball control center were broadcast. Teaball controllers also knew the call signs of each and every combat mission for that day going into North Vietnam. Positions of VNAF MiGs were given in relation to a notional point called the "Bull's Eye" which was Hanoi. Distance and bearing from the Bull's Eye was given and air crews often programmed the Bull's Eye into their aircraft's own navigational equipment. "Blue Bandits" were MiG-21s, "White Bandits" were MiG-19s, and "Red Bandits" were MiG-17s. The code word "Green Bandit" indicated an exceptionally experienced VNAF MiG pilot was airborne. "Heads up" meant MiGs were nearby. Teaball controllers and analysts noted that certain combat flights were targeted especially heavily by the MiGs at times, and these US air crews were designated "Queen for a Day". A Teaball controller might inform a flight of F-4s about "Red Bandits, 25 miles SE of Bull's Eye, heading NE 300 knots" over a designated UHF channel. In effect, the Teaball controller acted as a GCI controller for the US pilots, constantly feeding them information on the position and action of any MiGs nearby to allow the US pilots to exploit the situation.

Lt. Col. Kirk briefed every unit that was flying combat missions over Vietnam and warned them explicitly "Pay attention when I call you on that channel!" Within the first month of Operation Teaball's operation, American fighters had moved from a 1:1 kill ratio to a 3:1 ratio and by the end of the Linebacker operations, the ratio had risen to 4:1 in favor of US air crews. The system saved many an air crew's life in the skies over North Vietnam, to the point that inbound flights often checked in with the Teaball control center once they had taken off to be sure they had their call signs!

Operation Teaball was one of the earliest and most successful uses of data fusion and what today we would call "network-centric" warfare- to use diverse data collection sources fused together to give situational awareness to our men and women in combat. It was the first time that such diverse sources of intelligence that were once the sole realm of distant analysts in the United States were used to deliver real-time actionable information to win battles.

Sources: The Linebacker Raids: The Bombing of North Vietnam, 1972 by John T. Smith. Arms and Armour, 1998, p95-97. Air Force Magazine, July 2008, Volume 91, Number 7. "The Teaball Tactic" by Walter Boyne.

The Bell 207 Sioux Scout- Grand Daddy of the Gunship

2011-03-17T23:10:00.000-05:00

The Bell D-245 Warrior set the pattern for gunship designs

With the turbine-powered Bell UH-1 Iroquois "Huey" utility helicopter offering a quantum leap in capability for the US Army over previous, cumbersome, piston-driven rotorcraft, it was a natural progression that the UH-1s would be armed for aerial fires support for the growing conflict in Vietnam. But Bell's engineers in Fort Worth were steps ahead of the military with studies as early as 1958 for a tandem-seat purpose-built helicopter gunship that used the transmission and engine systems of what would become the UH-1. Bell's first offering had the in-house designation D-245 and was named "Warrior" which laid down the standard layout of gunships that followed- a slim fuselage with tandem seating for a pilot and gunner, stub wings for weapons, and nose-mounted gun turret. But despite its potential, the Army had yet to determine operational doctrines for the use of attack helicopters and the D-245 Warrior was quietly shelved.

Despite official disinterest from the US Army, Bell decided to embark on internally-funded development to further refine the D-245 Warrior design. In June 1962 Bell unveiled the D-255 Iroquois Warrior to the Army at its Fort Worth facility. The D-255 was a bit larger than the earlier D-245 but retained the tandem seating for pilot and gunner in stepped layout with the pilot sitting behind and higher than the gunner in the forward seat. Again, the tail boom, rotor transmission and engines were adapted from the UH-1. While the mixed reaction from the US Army was an improvement over the official disinterest that the earlier D-245 design elicited, it still wasn't enough to get a production contract from the Army. Again the D-255 was quietly shelved, but this still wasn't going to discourage the Bell team from staying ahead of the game. In December 1962 a brainstorming session of the engineering team resulted in a decision to build a flying demonstrator to prove the US Army what Bell's gunship concept could accomplish.

The Sioux Scout was quite small for a two-seat gunship

Designated the Model 207 and named the Sioux Scout, the demonstrator combined the engine, rotor, and drive systems of the proven Bell OH-13 Sioux (the bubble-cockpit helicopter made famous in the introduction to the TV series M*A*S*H) with its civilian counterpart, the Bell 47. The six-cylinder Lycoming 435 engine of the OH-13/Bell 47 was supercharged to deliver 220 horsepower driving the main rotor system from the OH-13 and the tail rotor/tail boom of the Bell 47. An all-new slim fuselage was created that used box beams to create a rigid structure to which were attached the stub wings that could carry external stores on six hardpoints on each side as well as house an additional 43 gallons of fuel which gave the Sioux Scout a range of 200 miles. At high speeds, the stub wings helped offload the main rotor as well. An Emerson Electric TAT-101 gun turret was installed under the nose (the rigid fuselage structure dampened recoil) housing twin 7.62mm machine guns that were adaptations of the M60 gun. With 1,100 rounds of ammunition, the gunner in the forward seat used a pioneering hand controller to operate the gun turret 100 degrees side to side, 15 degress upward, and 45 degrees downward. Under each stub wing were six round, 2.75 inch rocket launchers on each hardpoint.

The gunner had an outstanding field of view from the front seat

The Sioux Scout made its first flight from Bell's Fort Worth facility in Hurst on 27 June 1963, in the process becoming the first pure gunship in the world to take flight. Since the demonstrator program was somewhat secret, the helicopter was painted red and white to not so blatantly give away its military purpose. After several weeks of testing with Bell that added up to 65 flight hours, the Sioux Scout was repainted in more Army-like olive drab and began a series of weapons tests at Fort Sill, Oklahoma, northwest of Fort Worth. In November of that year, the Sioux Scout was taken on the road, touring Army bases and being flown by both Army and even NASA test pilots with over 300 flight hours that included firing over 83,000 rounds of ammunition from the chin turret. Finally, in 1964, B Troop, 3rd Squadron, 17th Cavalry of the 11th Air Assault Division spent a month flying the Sioux Scout in operational conditions and in field exercises. At the time, the 11th Air Assault Division was tasked by the Army commanders with experimenting and creating operational doctrines in helicopter assault at Fort Benning, Georgia.

The Model 209 prototype had retractable landing skids

Other than the Sioux Scout being underpowered and the reliability of the experimental gun turret being less than ideal, Army evaluators were overwhelmingly pleased with the outcome of the 11th Air Assault Division's operational evaluation of the demonstrator. The recommendation was issued that a turbine-powered, more capable version be developed as quickly as possible for operational use. In late 1964 the Secretary of the Army created the Advanced Aerial Fire Support System (AAFSS) with invitations to industry to submit designs. With the quick realization that the AAFSS design would take time to field, the Army decided that an interim design was needed that would field the gap until the AAFSS became operational. Bell dusted off its D-255 Iroquois Warrior design and with further refinements based on the Sioux Scout evaluation, designated it the D-262. However, in 1965 the Army rejected the D-262 design. But, as Bell had done before, they quietly went about refining the design further on company funds- within several months of the rejection of the D-262, the situation in Vietnam worsened and the US commander in Vietnam, General William Westmoreland, advised the Pentagon that either the AAFSS needed to fielded quickly or some interim design was needed as soon as possible. In March 1965 Bell just happened to finish the full-scale mockup of its refined gunship designated the Model 209 and "leaked" to Army commanders what it was up to. Before long, the Army issued a formal requirement for an interim design. Beating out submissions from Sikorsky, Kaman, Piasecki and Boeing Vertol, the Model 209 was selected on 11 March 1966 for production as the AH-1 Cobra.

And the AAFSS? That became the Lockheed AH-56 Cheyenne and was a classic case of wanting too much out of a design. It ended up getting cancelled in August 1972. That same month, the Army created the Advanced Attack Helicopter program (AAH) which became the AH-64 Apache. And what become of the Sioux Scout? The grand daddy of gunships can be seen today in the Army Aviation Museum in Fort Rucker, Alabama. And of course, Bell's interim design is still in production today for the US Marine Corps as the AH-1Z Viper.

Source: Helicopter Gunships: Deadly Combat Weapon Systems by Wayne Mutza. Specialty Press, 2010, p56-60. Images from aviatstar.org

The "Wings of Russia" Sukhoi Super Jumbo

2011-03-12T22:55:00.000-06:00

The Sukhoi KR-860 was conventional in its layout

At the 2001 Paris Air Show, the Russian delegation created quite a stir by unveiling a four-engine, double-deck, long-haul airliner christened "Kryl'ya Rossii", or "Wings of Russia". The ambitious project had the Sukhoi OKB designation "KR-860"- KR for "Kryl'ya Rossii" and 860 indicating the passenger load. Design work on the KR-860 began in 1997 under the General Designer, Mikhail P. Simonov who had headed the design bureau since 1983. Already under his direction the Su-27 Flanker family of fighter aircraft had been upgraded and new variants had taken flight. By the time that design work began on the KR-860 project, Sukhoi had already been making its first steps into the civil aviation market with the start of work on the Su-80 utility transport and the Su-38 agricultural aircraft. But an aircraft in the class of the KR-860 was nothing short of a bold leap by Sukhoi. The "Wings of Russia" would rival the Airbus A380 and would be larger than the Boeing 747. The design team had looked at advanced technologies and unconventional layouts such as a flying wing, but eventually settled on a blend of advanced technologies (fly-by-wire, composites) combined with a conventional layout with a double deck fuselage and four turbofans. At each step of the KR-860's design evolution, tradeoffs were made between high technology and innovation and low-risk approaches.

Note the twin nose gear and unusual cockpit fairing

Although the layout of the KR-860 was conventional in appearance, the Sukhoi team succeeded in achieving a predicted lift/drag ratio of 19.5 (compared to the L/D ratio of the Boeing 747 of 17) via aerodynamic refinements. Large winglets were a part of the design and the smooth lines of the double deck fuselage were unusually broken by a blister-like fairing that housed the flight deck. One of the more unusual features of the KR-860 was its use of folding outer wings to reduced the footprint of the aircraft. Boeing had looked at a similar system during the design of the Boeing 777 and had even built a test article, but eventually dropped the idea as the gain in space at the gate wasn't enough to offset the increased weight and complexity. For the KR-860, though, the folding outer wings meant that the aircraft could use any gate position that could accommodate a Boeing 747. While the main landing gear was very similar to that of the 747 and A380 with two inward-retracting wing units and two fuselage mounted units, the nose landing gear was more like that of the Antonov An-124 Condor transport with twin units. The third unique feature of the KR-860 was its three integral airstairs that were on the centerline of the underfuselage- the forward airstair was ahead of the nose gears, the second one was mid-way down the fuselage where the wings were located, and the third and aft unit was under the tail. Like the integral airstairs on the Ilyushin Il-86, these were meant to reduce the ground support needs for the KR-860.

Note the folding outer wings and the boarding airstairs under the nose

A variety of powerplant options were evaluated for the aircraft- the most serious contender was the General Electric CF6-80E1 used on the Airbus A330 family of aircraft- Sukhoi was reportedly in negotiations with GE at the time of the KR-860's unveiling at the 2001 Paris Air Show. License production of the engine in Russia was even discussed. In addition, consideration was also given to the Rolls-Royce Trent 800 used on the Boeing 777 and the Pratt & Whitney PW4168 used on the A330. In addition, Russian solutions were evaluated from the Kuznetsov NK-93 ducted fan to the unusual suggestion of using eight Soloviev PS-90 turbofan engines in paired nacelles. This would have been the cheapest solution, but the pair nacelles and eight engines would have been significantly heavier and cost more in fuel consumption.

The aft boarding airstairs under the tail

The eight-engined variant was considered more appropriate for a cargo variant which had an upward-hinged nose visor like that of the An-124 Condor and the Boeing 747-400F. Sukhoi even pitched this version as a successor to the An-124s operated by the Russian Air Force. The cargo version was capable of carrying up to thirty of the 40-foot rail/road cargo containers. Using four turbofan engines, such a version was claimed to have a cost per mile only slightly higher than that of rail transit. In addition, combi versions were suggested and one of the more unusual variants was that of a flying liquified natural gas (LNG) tanker to connect outlying regions in Siberia planned for oil/gas exploration that lacked suitable infrastructure for conventional transport methods.

Sukhoi estimated the costs for the development of the KR-860 would be more than offset with its use in cargo transport. Costs depending upon the authority consulted ranged from 3-4 billion US dollars to as high as 5.5 billion US dollars. As ambitious as the KR-860 was, there was simply not enough passenger traffic in Russia to justify an aircraft its size. Sukhoi turned to both India and China which had booming passenger markets to explore risk-sharing partnerships. At the end of the day, though, an aerospace project the size and scope of the KR-860 was simply more than both Sukhoi and the Russian government could handle and with more pressing financial needs, the Kremlin was reluctant to invest in the development of Sukhoi's super jumbo. Russian aviation authorities were highly skeptical of the need for the KR-860 given that most of what might get built would be exported to more robust and booming aviation markets. As a result, the KR-860 "Wings of Russia" program died quietly as Sukhoi shifted its resources to a much smaller aircraft that was needed in Russia to replace the aging fleets of Tupolev Tu-134 and Tu-154 fleets. Though development of the Sukhoi SuperJet 100 had started in 1999, the shift of OKB resources from the KR-860 to the SuperJet program which was formally launched in 2002.

Source: OKB Sukhoi: A History of the Design Bureau and its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2010, p501-503.

Genesis of the Predator UAV

2011-02-26T22:26:00.001-06:00

Leading Systems' Amber UAV, grandfather of the Predator

In the mid-1970s, Abraham Karem, a designer of high-tech weaponry for the Israeli Defense Forces, emigrated to the United States but despite his credentials working with the Israeli military, found himself unable to get employment with any of the major American defense contractors. Karem had some innovative ideas for unmanned aerial vehicles (UAVs), so ended up starting his own company, Leading Systems, in the garage of his home in Irvine, California, to pursue his UAV concepts. In 1982, the Defense Advanced Research Projects Agency, DARPA, was providing seed money to small companies that offered innovative solutions to problems outlined by the US military. One such problem was a need for an advanced UAV that could provide reconnaissance imagery while having a long endurance but be both inexpensive and reliable. The classified DARPA program TEAL RAIN was established to study the technology for long-endurance UAVs. The problem at the time was that previous long endurance UAVs exemplified by the Boeing Condor as well as the Compass Cope program were large and prohibitively expensive. Two years after he founded Leading Systems, Abraham Karem secured seed money from DARPA to develop his concepts and in 1984, he received a contract to develop a classified reconnaissance UAV code-named Amber. While most competing companies adapted existing piston engines from snowmobiles and motorcycles for their designs, Karem used the DARPA seed money to hire engineers willing to design and build engines custom tailored for the Amber program.

The first Amber UAV flew in 1986 (just two years after Karem got the DARPA contract!). Karem designed Amber to fold up and be fired from a standard torpedo tube- the US Navy was one of the backers of the Amber project- as a result, it had a slender fuselage with a parasol wing and an inverted-V tail with a pusher prop. Two types of Amber UAVs were planned- the "A" version had a pointed nose section carrying a warhead and was to be a low-cost cruise missile- approaching its target, the wing was to be jettisoned, hence the need for a parasol-type wing. The "B" version replaced the warhead section of the "A" version with a slightly bulged nose compartment that housed imaging sensors and datalinks to act as a reconnaissance UAV. The "B" version had a stalky retractable landing gear as well. The use of an inverted-V tail was to protect the pusher prop during landing and takeoff. By 1988, Amber had demonstrated a flight endurance of nearly 40 hours when competing companies were barely getting 12 hours out of their designs. Not only was Karem's design outflying its competitors, it was also proving to be immensely reliable as well. Thirteen Amber UAVs were built by 1990.

In the same year that Amber was breaking records in 1988, Congress began to get impatient with the Pentagon's slow pace of UAV development. By 1990 the Pentagon was forced by Congressional mandate to consolidate the UAV research efforts of the different armed services into a single Joint Program Office (JPO). The JPO, however, wasn't budgeted any funds for research, which meant that only big defense contractors could stay in the running where internal corporate funding was plentiful. At the same time, and in its infinite wisdom, Congress banned DARPA from supporting UAV projects outside of the jurisdiction of the Pentagon JPO and as a result, Leading Systems' funding dried up overnight and Amber had to be canceled despite its achievements.

Leading Systems/General Atomics Gnat 750

To try and stay afloat, Abraham Karem and his small team at Leading Systems developed a UAV based on Amber that was less-complex and used a standard Rotax piston engine for propulsion. This UAV was named the Gnat 750. Since the Gnat was planned for the export market, it was larger and didn't have as many of the advanced features of Amber, but it retained the overall layout with the difference that the wing was now directly attached to the fuselage instead of high-mounted on a pylon. The inverted-V tail was still there as well as a pusher prop and the stalky retractable undercarriage. The Gnat 750 first flew in 1989 and despite being "less high-tech" than Amber, boasted a significant number of design improvements. However, the loss of DARPA funding was too much for Leading Systems and Karem was looking at shutting down the company. However, San Diego-based defense contractor General Atomics was looking in 1990 to diversify its holdings outside of its core business of nuclear reactor technologies. One of its corporate directors was a former US Navy rear admiral, Thomas Cassidy, who joined General Atomics in 1987. He thought Karem's operation would be a good fit for what General Atomics was looking for and in 1990, General Atomics acquired Leading Systems and set up Abraham Karem and his team in a subsidiary General Atomics Aeronautical Systems to continue the development of the Gnat 750 UAV.

In 1993, the Pentagon issued a requirement to rapidly field a surveillance UAV to support UN peacekeeping forces in the former Yugoslavia. The Gnat 750 was selected, but because the need was immediate and existing military acquisition procedures were too slow, the program was transferred to the CIA under the code name LOFTY VIEW. Since the CIA would be operating the Gnat 750 in secret, it fell outside of the purview of the Congressional mandate the created the UAV JPO that inadvertently killed off the Amber program. By 1994 the first Gnat 750s were deployed to a CIA operating base in Albania for operations throughout the Balkans. The UAVs provided overhead surveillance for UN convoys as well as spotting artillery emplacements and the operating locations of the various belligerents in the wars that wracked the region through the latter half of the 1990s. The bad weather of the Balkans and the limited range of the Gnat's datalink proved to be the main issues that affected operations.

While the CIA was getting the Gnat 750 operational over the Balkans, General Atomics Aeronautical Systems had secured funding under an advanced concept technology program. At the time, UAV development had been stratified into "Tier" levels based on endurance and performance. I had reviewed these Tiers a year ago in a previous blog posting that covered the development of top-secret stealthy Quartz UAV:

In the 1990s, there were three "tiers" of UAV development based on operational capability. "Tier I" was for a low-altitude system that became the Gnat-750 UAV. "Tier II" was for a more capable medium altitude system based on the Tier I craft and that became the current Predator UAV family. The specification for "Tier III" would have been filled by the Quartz project, but with its cancellation, Tier III was split into two- Tier II+ was for the Quartz's performance without stealth and this became the RQ-4 Global Hawk UAV. Tier III- ("Tier III Minus") was stealthy but without the performance and payload of Tier II+. This design became the RQ-3 DarkStar. DarkStar, a joint effort between Boeing and Lockheed, had little in common with Quartz and itself would be canceled in 1999 in favor of further development of the Global Hawk.

General Atomics RQ-1/MQ-1 Predator

The Pentagon was issuing contracts for UAVs at each Tier. General Atomics's funding was for development of a Tier II UAV. The new design took the Gnat 750 and stretched the fuselage and lengthened the wings. The inverted-V tail, stalky retractable undercarriage, and pusher prop were retained (though with a more powerful Rotax piston engine). Since one of the weaknesses of the Gnat 750 was the limited range of its datalink, the new UAV had an enlarged nose section that had the imaging payload on the underside of the nose similar to what the Gnat 750's layout, but incorporated a satellite communications dish in a bulged radome as the new datalink. Use of a satcom datalink now meant that the UAV operators and pilots didn't even have to be in the same region as the UAV's area of operations. It was now possible for the crews to fly the UAVs from stateside bases using the satcom datalinks to fly the Tier II UAV anywhere in the world it was needed.

Named Predator, the new Tier II UAV made its first flight in June 1994. Less than a year later during the Roving Sands 95 exercise at Fort Bliss, Texas, the Predators were used for the first time in an operational demonstration. They were so successful at Roving Sands that year that the USAF established its first UAV squadron, the 11th Reconnaissance Squadron at Indian Springs Auxillary Airfield in Nevada (later renamed Creech AFB in 2005) shortly after the exercise in Texas and just one month after Roving Sands, the first Predators were deployed to the Balkans under Operation Nomad Vigil. From July to November that year the 11th RS operated its Predators out of Gjader in Albania in support of Operation Deliberate Force, the NATO air campaign against Bosnian Serb forces. While more capable than the Gnat 750s operated by the CIA, the need for overhead surveillance was so great in the Balkans that both the Predator and the Gnat 750s operated simultaneously in theater.

By 2001, the USAF had taken delivery of 68 Predator UAVs. Due to the steep learning curve in operating such a radically different type of aircraft, 19 were lost, but only 4 were confirmed to have been shot down over the Balkans. But it was only the beginning of how the Predator began to change the way air campaigns were fought. And that is subject matter for a future posting on this blog!

Sources: Birds of Prey: Predators, Reapers and America's Newest UAVs in Combat by Bill Yenne. Specialty Press, 2010, p37-40.

Popular Science, September 1994. "Drones: Invented and Forgotten" by Bill Sweetman, p34.

Designation-Systems.net by Andreas Parsch. "Leading Systems Amber" and "General Atomics Gnat".

Photos: Federation of American Scientists, United States Air Force.

Aviation Trivia of the Day is now Tails Through Time

2011-02-23T22:44:00.002-06:00

I suppose this was a long time in coming. When I started out this blog nearly two years ago (it will be two years in March), the daily posts were fairly short and took me no more than five to ten minutes to put together. But as time went on, I wasn't satisfied with just some short aviation factoid or bit of trivia and each post became a bit longer and pretty soon I was adding a picture or two...or three...maybe four...and pretty soon each post became a bit more involved and required more of my time than when I first started this blog. Time constraints and real world obligations prevent me from devoting a full daily post of the depth and quality that I can only dream of doing on a daily basis in the spirit of "Aviation Trivia of the Day".

After taking a week to mull things over, I decided to reorient this blog more along the lines of what I had once done for Airlinebuzz as well as my own aviation art blog, The Chicken Works. Back then I used to put together more involved posts for both the forum that started out under the heading "Aviation Postcards" and with the advice of some good friends on Airlinebuzz, soon evolved into "Tails Through Time" for my aviation art blog. I had also thrown in some daily aviation trivia on that blog, but found that many folks were finding that my own artwork was getting buried under my aviation trivia. So I started this blog as a spin off but found that over the last two years I've more or less migrated to the format that resembled my more in-depth posts "Tails Through Time". The picture above is the original header I made for those posts and it inspired the newer version that's at the top of each page of this blog.

I'm still a consumptive reader of aviation books and have every intent of sharing what I come across here in this blog- just not on a daily format as I'd been struggling to maintain since the birth of my fourth child this past August. Rest assured to the regular readers that there will be regular postings here and I will guarantee you at least some of what shows up here will resonate with your inner avgeek child! The web address will stay the same, though.

Stay tuned !

The Ground-Breaking Boeing Condor UAV

2011-02-16T22:39:00.002-06:00

The Condor in flight

In the 1960s as the technology for unmanned aerial vehicles (UAVs) progressed, the USAF initiated two programs that would provide unmanned analogues to the premier airborne reconnaissance aircraft of the day, the Lockheed SR-71 Blackbird and the U-2. Both aircraft had their strengths and weaknesses and the USAF hoped to expand upon their capabilities with adjunct UAV reconnaissance aircraft. The companion program to the SR-71 Blackbird originated from the Lockheed Skunk Works as the D-21/Tagboard reconnaissance drone for the CIA. Possessing the same Mach 3 performance as the Blackbird, the D-21 was originally launched from the back of a modified A-12 Cygnus. However, after a disastrous fourth airborne launch that cost the launching aircraft and one of its crew, the D-21/Tagboard was moved over to the Boeing B-52 Stratofortress as the launching aircraft. After four failed operational missions in which the D-21 was lost, the program was canceled in 1971, at which time the second program which would have been a companion to the Lockheed U-2 was getting under way. Being a large jet-powered glider-like aircraft not too dissimilar in performance to the U-2, in 1971 the USAF initiated the Compass Cope program with Boeing and Teledyne Ryan producing prototypes- Boeing's design being the YQM-94 Gull (Compass Cope B) and Ryan's competing design being the YQM-98 Tern (Compass Cope R). After a competitive evaluation, Boeing's Gull was chosen in August 1976, to which Ryan lodged a protest. It was pointless at that juncture as the USAF canceled Compass Cope in 1977 before any production Gulls were built.

But it wasn't the end of the story for Boeing's work for a high-altitude, long-endurance (HALE) UAV. The Defense Advanced Research Projects Agency (DARPA) was still interested in the idea of a HALE UAV for strategic reconnaissance. DARPA wanted to go one step further than the Compass Cope program, though. A contract was issued to Boeing for a HALE UAV that could operate for days at high altitudes carrying reconnaissance payloads that ranged for optical camera systems to electronic intelligence collection arrays to even an airborne synthetic aperture radar for all-weather/day-night surveillance. Boeing contracted with Burt Rutan who was using an all-composite structure in his record-breaking long-distance aircraft, Voyager. Boeing's design, aptly named Condor, used a predominantly composite structure with a wingspan of 200 feet, the same as that of the Boeing 747. The fuselage was only 68 feet long but was slab sided to facilitate the mounting of either an ELINT or SAR antenna array. Designed to be disassembled into sections and transported by a Lockheed C-5 Galaxy, the Condor's fully loaded weight was 60% fuel.

Comparing the Condor and the 747

The wing's airfoil section was extremely efficient and provided natural laminar flow at altitudes in excess of 50,000 feet. Since the Condor was to be autonomously controlled, the wing had to have benign stall characteristics to simplify the control of the UAV. The wing was so efficient that it had twice the lift-drag ratio of the U-2- 40:1 compared to 20:1 for the spyplane. Since the wing would be highly flexible, a fuel transfer system was used to move fuel between wing tanks to reduce flexing in flight. The use of composites resulted in a wing that weighed only 2 lbs/square foot- an impressive feat considering that a commercial jetliner's wing comes in at approximately 30 lbs/square foot.

The Condor was powered by two Teledyne Continental 175-horsepower six-cylinder piston engines that were superturbocharged for operation at very high altitudes. Each wing-mounted engine drove a three-bladed propeller 16 feet in diameter. Since the propellers were optimized for high-altitude cruise, at lower altitudes they would cause a significant amount of fuel burn and drag- as a result, a two-speed gearbox was used- one gear ratio for low-altitude flight and a different gearing for high altitude cruise.

The flight control computer of the Condor was groundbreaking in that the Condor was the first UAV designed and flown autonomously without external control input from a remote pilot. Two Delco Magic 3 series computers were used as the brains of the Condor- the Magic 3 series computers were also used in the guidance systems for the Titan II ballistic missiles and the Delta family of rocket launchers. One computer acts as the primary computer with the second one operating in standby and ready to takeover should the primary computer fail. The control software consisted of only 60,000 lines of Fortran code- minuscule when one considers that today's RQ-4 Global Hawk reconnaissance UAV uses several million lines of software code! The Condor's computers were responsible for vehicle functions, flight control, and navigation using inputs from an inertial navigation system (this was in the days before GPS). The computer system was even designed to not only handle inflight emergencies but also prevent an enemy from taking electronic control of the UAV. Should that happen, the system was designed to recognize it was being taken over and immediately direct the Condor back to friendly territory.

A microwave landing system was adopted to provide control of the Condor during takeoff as well as landing. Using a dolly, once the Condor reached 65 knots, it lifted off the ground and left its takeoff dolly behind. It would take anywhere from two to three hours for the Condor to reach its cruising altitude of over 50,000 feet. At cruise altitude, the Condor cruised at 200 kts, but its all composite construction made it a very small radar target and its piston engines had a very low infra-red signature- so despite its size and apparent leisurely cruise speed, it was a difficult target to track on most radars of the day. Descent for landing took two to three hours as well, and an extendable nosewheel and landing skids were used for landing. To save weight, instead of doors covering the skids and wheel, a replaceable Mylar sheet was used that the skids and nosewheel broke through on landing.

The Boeing Condor today at the Hiller Aviation Museum

The Condor was developed in secret and its rollout in March 1986 was its unveiling to the world. It made its first flight on 9 October 1988 from Boeing's test facility at Moses Lake, Washington (the former Larson AFB). Since the rules on UAV operations in controlled airspace had yet to be fully written, a manned chase plane had to accompany the Condor during its transit through any controlled airspace. Only eight test flights were made with the last one on 28 November 1989, but the Condor set two world records- one for record altitude for a piston-engined aircraft at 67,028 feet on the fourth test flight and one for unmanned aircraft endurance at an impressive 58 hours, 11 minutes on the final test flight. Given that the test flights occurred over eastern Washington state, it's unlikely any operational reconnaissance payloads were carried, but to this day the exact nature of the payloads to have been carried- or even if they were carried- on the Condor remain classified. With a cost of $300 million, the Condor program did prove the viability of autonomous UAV flight as well as advanced composite construction and ultra-lightweight structures, but it lacking in military flexibility as well as its slow speed resulted in its cancellation after the final test flight. Only one Condor was built and flown, and in 1998 it was acquired by the Hiller Aviation Museum in the Bay Area where it can be seen on display today. It's the largest aircraft to be suspended in an interior museum display in the world. Not bad, even just sitting in the museum it still sets a record!

Sources: Birds of Prey: Predators, Reapers and America's Newest UAVs in Combat by Bill Yenne. Specialty Press, 2010, p20-32.
Condor photo in the Hiller Museum by Joe May @ Travel for Aircraft- "Photo Funday- Boeing's Condor"

Operation MARHUK: The Combat Debut of the Marine's AH-1J SeaCobra

2011-02-14T14:18:00.001-06:00

Marine SeaCobras took a beating operating at sea

The first US Marine Corps AH-1 Cobra gunships in action were actually AH-1Gs which were ordered by the Marines in 1967- having closely watched the Army development of the Cobra gunship, 72 helicopters were requested for one helicopter attack squadron in each of its three Marine Air Wings. Despite having the approval of the Secretary of the Navy, Defense Secretary McNamara overruled the decision and only allowed the Marines to order 38 of the single-engined AH-1G variant. With the first Marine AH-1Gs going into action in Vietnam in April 1969, reports from the field couldn't have been more salutatory in the effectiveness of the Cobra gunship. Based on that initial experience, the Marines wanted a more powerful Cobra- one with twin engines, Marine avionics, a rotor brake for shipboard operations and a harder-hitting gun in the undernose turret. After overcoming the resistance of an obstinate Secretary McNamara, the AH-1J SeaCobra went into production with the first examples undergoing combat evaluation in South Vietnam in February 1971. With the onset of the Easter invasion by North Vietnam of the south and the American response, Operation Linebacker, the first Marine helicopter attack squadron, HMA-369 based in Okinawa, was called upon shortly after its establishment to conduct offensive operations against North Vietnam.

The USMC had the AH-1J built from the start to operate from ships

At the time, Army Cobra gunship were operating in South Vietnam against the invasion thrusts of the North Vietnamese Army. Despite having just received its new AH-1J SeaCobras, Admiral John McCain, Jr, head of the US Pacific Command, wanted to make sure that the blockade of North Vietnam was complete. Even though carrier aircraft had sown mines closing Haiphong Harbor, the North's main port, the North Vietnamese had resorted to having Chinese and Soviet cargo ships anchor offshore various locations and cargo would be offloaded into smaller sampans for transfer to the shore. This way the mined sea lanes could be avoided. Because fixed wing carrier aircraft were urgently needed for Operation Linebacker attacks on North Vietnam, it was decided that the AH-1J SeaCobra would be ideal for the role of maritime interdiction off the coast of North Vietnam. In the entire Pacific theatre, only HMA-369 in Okinawa had suitable helicopters for the job and Operation MARHUK (Marine Hunter-Killer) was born. It would be the Bell AH-1J SeaCobra's baptism of fire and off the coast of the heavily defended North Vietnamese coast, no less.


HMA-369's "Marhuker" patch

HMA-369 originally wanted a helicopter carrier to be based on for Operation MARHUK, but the Navy's LPHs were heavily committed else where and the 18 officers, 99 men and seven AH-1J SeaCobras of HMA-369 that were ready to deploy in June 1972 were shoehorned into the amphibious transport ship USS Denver (LPD-9). Marine brass give the squadron officers a blank check to do what ever was necessary to get HMA-369 to the war zone and the nickname "Marhukers" was given to the officers who improvised and bent and possibly broke many rules to make their SeaCobras combat ready. Even 5-inch Zuni rockets were procured, a weapon that had not yet been cleared for use from the AH-1J. The ship and its escorts would be positioned near the Hong La anchorage further south down the coast from Haiphong. Here Chinese and Soviet merchant ships anchored offshore and North Vietnamese sampans offloaded cargo offshore to bring into Hong La. Since the rules of engagement forbade hitting the merchant ships, the SeaCobras stayed at least 500 yards away from the ships and remained overwater the whole time as the North Vietnamese had heavy AAA guns on the shoreline. The SeaCobras operated in pairs and would sink the sampans with their Zuni rockets and 20mm undernose cannon. The pilots were also trained to call in naval gunfire and air strikes while the gunners in front seats of the AH-1Js focused on the sampans. After several weeks, the shore-based heavy AAA guns learned not to fire on the SeaCobras thanks to the naval fire support and air strikes the pilots would call in.

In August 1972 HMA-369 moved to the USS Cleveland (LPD 7) and then again to the USS Dubuque (LPD 8). Over the course of Operation MARHUK, the AH-1J SeaCobras were called on to provide air cover for downed aviators in the North as well as functioning as forward air controllers for Navy strike aircraft. Missions ranged from 80 miles north of the DMZ to as far north as 80 miles south of Hanoi inland! When Operation MARHUK ended on 26 January 1973 with the end of Operation Linebacker II, nearly 1,000 sorties had been flown with 123 sampans sunk, further straining the logistics of North Vietnam that eventually drove them to the bargaining table. It was quite a stunning debut for the AH-1J SeaCobra.

Source: Helicopter Gunships: Deadly Combat Weapon Systems by Wayne Mutza. Specialty Press, 2010, p72-76.

How the USS Wasp Defeated Rommel's Afrika Corps on Just Two Operations

2011-02-08T22:10:00.000-06:00

Spitfire Mk.V makes its takeoff run on the USS Wasp

From 1940 to 1942 the Italian Regia Aeronautica and the Luftwaffe mounted over 3,000 sorties against the British fortress island of Malta in the Mediterranean in an effort to secure their supply lines to Field Marshall Erwin Rommel's Afrika Korps in North Africa. Despite repeated attacks, the Allies managed to keep Malta supplied, even with Axis airfields only sixty miles to the north in Sicily. With the coming of the harsh Russian winter in 1941, poor flying conditions put a temporary hold on most air operations over the Eastern Front and Hitler decided once and for all to deal with Malta. Aircraft idled on the Eastern Front were temporarily moved to airfields in Sicily and southern Italy to begin an intensive aerial bombardment as a prelude to an invasion of the outpost. By the end of January 1942, Malta's defenses had been reduced only a few dozen Hawker Hurricanes which were far outclassed by the Messerschmitt Bf 109s that routinely prowled the skies around the British garrisons. The Hurricanes were delivered to Malta by a Royal Navy aircraft carrier- launching from a point 600 miles west of Malta off the coast of Algeria for the long flight to Malta. Now the British planned to send Supermarine Spitfires the same way to bolster the defenses of the island. Supermarine's engineers devised a 90 gallon external belly tank to extend the range of the Spitfire as well as the addition of a dust filter under the nose to keep the carburetor air relatively grit-free.

On 7 March 1942 the HMS Eagle delivered fifteen Spitfire Mk.Vs to the island and by the end of the month, the Eagle made two more deliveries. But the Luftwaffe and the Regia Aeronautica stepped up the pace of their attacks on the beleaguered island fortress and the bombers and torpedo bombers that were based on the island to harass Axis shipping had to be withdrawn, providing a much needed respite for the Afrika Korps who could now be supplied unmolested. The small Spitfire force suffered heavy attrition both in combat and due to air attacks on the island airfields and by the end of the month, the only carrier available to deliver Spitfires to the island, the HMS Eagle, had developed steering problems that would lay her up for four weeks in the dockyard at Gibraltar. As a result, on 1 April 2942 Prime Minster Winston Churchill contacted President Franklin D. Roosevelt for assistance in getting more Spitfires to Malta. No Spitfires were available in Egypt to be spared, and the other two available Royal Navy carriers weren't suitable- the HMS Argus was too small and the HMS Victorious' lifts were too small for Spitfires. The Luftwaffe hoped to knock Malta out before the late spring thaw in on the Eastern Front.

Spitfires being craned aboard the USS Wasp

On 10 April 1942 President Roosevelt ordered Operation Calendar- on that day the USS Wasp docked in Glasgow and loaded forty-seven Spitfires while retaining twelve Grumman F4F Wildcats for self-defense. Nine days later the Wasp and her escorting force of British warships entered the Mediterranean. On 20 April 1942 at sunrise off the coast of Algeria, the Wasp launched her Wildcat combat air patrol first followed by the twelve Spitfires on the deck and then the thirty-five Spitfires that were brought up from the hangar deck. Alll but one of the Spitfires made it to Malta, greatly bolstering the defenses. Unfortunately the following day the Luftwaffe struck back at the island's airfields and by the end of the day, only seventeen Spitfires were left operational. RAF repair crews labored under constant air attack to cannibalize battle damaged Spitfires that were beyond repair to get the others operational to fight off the next attack. Once again, Churchill contacted Roosevelt and on 29 April the USS Wasp arrived back in Glasgow for Operation Bowery. This time not only did the Wasp take aboard forty-seven Spitfires, but she was joined by the newly-repaired HMS Eagle which took seventeen Spitfires. At dawn on 9 May 1942 a force of sixty-four Spitfires departed; one crashed on takeoff, killing its pilot and a second Spitfire flown by Royal Canadian Air Force pilot Jerry Smith found once airborne that he couldn't draw fuel from the 90-gallon drop tank. Once the deck of the Wasp was clear, he managed to land safely back aboard the carrier despite never having landed on a carrier and his Spitfire not having an arresting hook! No barriers were engaged either, and as result, the US Navy pilots aboard the Wasp "unofficially" awarded him a set of gold Navy pilot's wings.

Spitfires share the deck with Wildcats with the HMS Eagle following

Of the sixty-two Spitfires that set out for Malta that day, two were lost along the way. As each Spitfire landed, it was immediately refueled and rearmed while a Malta-based pilot replaced the ferry pilot, all while the engine remained running. RAF ground crews had each Spitfire airborne and ready to meet the next Luftwaffe attack in only 15 minutes! Over the next two days, the Spitfires and remaining Hurricanes on Malta exacted a harsh price from the Luftwaffe attackers, but by this point, the weather was improving over the Eastern Front and Hitler ordered the aircraft transferred to the Mediterranean for the Malta operation moved back to Russia. The Regia Aeronautica was given responsibility for knocking out Malta's defenses but never came close to achieving the near-defeat of the fighter defenses of April and May of that year. Between 18 May and 8 June another seventy-six Spitfires were delivered to Malta, this time by Royal Navy carriers, but it never matched the effect of the USS Wasp making just two deliveries, leading Churchill to quip "Who says a wasp can't sting twice?"

The overall effect of having Malta as a base of operations against Axis shipping in the Mediterranean cannot be understated- of the Axis merchant ships that provided the lifeline to Erwin Rommel's Afrika Korps, 70% of Italian merchant shipping was sunk by Malta-based aircraft and 23% of German merchant shipping was sent to the bottom of the Mediterranean by the RAF on Malta. Had the British lost Malta, the outcome of the war in North Africa might have been very different.

Source: Military Aircraft Monthly International, Volume 10, Issue 1. "Air Wars: Spitfires to Malta" by Dr. Alfred Price, p4-11.

One Powerful Helicopter Gunship- the ACH-47A "Guns A-Go-Go"

2011-02-05T21:45:00.000-06:00

The weapons loadout of the ACH-47A Chinook gunship

After years of experimentation with armed helicopters, the US Army finally sent armed Bell UH-1B Huey gunships into combat in October 1962 with the rocket/gun armed Hueys acting as escort for Piasecki CH-21 Shawnee transports out of Tan Son Nhut Air Base in Saigon. Despite the growing success of the armed Hueys in the growing conflict in Vietnam, the Army sought a helicopter that offered even more firepower to replace the Huey gunships. Initial evaluations began in 1964 and even despite the selection of the Bell AH-1 Cobra (the world's first dedicated helicopter gunship design) in 1966, the general staff wanted something with even more firepower than the Cobra gunship as it was felt to only be an interim design pending what the Army felt was the ultimate gunship, the Lockheed AH-56 Cheyenne. While the Army pushed for a large gunship based on experiences in Vietnam, it found itself running into opposition from the USAF which felt its traditional domain of fixed wing close-air support being infringed upon by more capable helicopter gunships. Regardless, combat experience proved to be a powerful argument and the existing Hueys were felt in certain situations lacking in firepower. With the Army due to deploy the Boeing Vertol CH-47 Chinook transport helicopter to Southeast Asia in November 1965, Boeing Vertol submitted a formal proposal to the Army to modify eleven Chinooks into heavy gunships and on 2 July 1965 the first test Chinook was diverted from the production line in Philadelphia for conversion into the prototype ACH-47A.

The heavy lift capability offered by the twin turbine-powered Chinook allowed for many choices of possible armament systems, weapons loads, and self-protection. No concept was considered too outlandish as even manned turrets and stub wings for mounting weapons were considered. The eventual weapons fit of the ACH-47A became the XM5 40mm grenade launcher in a turret in the nose fed by a flexible belt that ran through the cockpit to the forward cabin where a container holding 500 rounds was located; a 30-inch stub wing on each side of the forward sponsons that at the end mounted an M24A1 20mm cannon, each fed by an 800-round container in the middle cabin; under each stub wing was a pylon that could mount either a 19-round 2.75-inch rocket launcher or a pod-mounted 7.62mm rotary Minigun. In addition to these permanently mounted systems, there were five crew-operated 50-caliber gun stations- forward right side, forward left side, right and left waist, and cargo ramp. The waist and forward stations had enlarged openings to allow a wider field of fire and the top half of the cargo ramp was removed to expand the rearward field of fire. Each 50-caliber gun had its own 1,000 round supply. With the five gunner stations, the ACH-47A would be the only helicopter gunship to fly into combat with a full 360-degree field of fire.

Two ACH-47As during the flight test program. Note the gloss paint scheme.

Despite the removal of items not needed for the gunship mission (items like the troop seats, cargo handling gear, even soundproofing), over 2,500 lbs went back into the ACH-47A for armor plating for the crew, rotor pylons, and vital systems. The standard Lycoming T55 turboshaft engines were uprated to 2,850 hp each compared to 2,200 hp for the standard CH-47A transport. This meant that a fully-loaded ACH-47A had the same performance as a operationally-loaded CH-47A. The first ACH-47A made its maiden flight at the Boeing Vertol plant in Philadelphia on 6 November 1965, only four months after the work began! After flight testing, the first ACH-47A was delivered to the Army for weapons trials at Aberdeen Proving Ground in Maryland and then to Fort Benning, Georgia for operational training in March 1966. At Fort Benning, the 53rd Aviation Detachment, Field Evaluation (Provisional) was formed for the training and operation of the ACH-47A and in April 1966 three more ACH-47As arrived, but due to budgetary constraints, only four ACH-47As could be built and delivered. The first one, 64-13145, was initially named "Crazy 8" but was renamed "Cost of Living". 64-12149 became "Easy Money", 64-13151 was named "Stump Jumper" and the last one, 64-13154, was named "Birth Control". The last three shipped out to Vietnam in May 1966 while "Cost of Living" remained at Edwards AFB for more testing.

"Easy Money" resting between missions at An Khe

The six-month period of operational testing would be split between Vung Tau in the southern coast one hour downriver from Saigon and at An Khe in the centeral highlands of South Vietnam. At Vung Tau the ACH-47As would operate not just with American units fighting the Viet Cong but also the Royal Australian Task Force. At An Khe, the ACH-47As operated with the 1st Cavalry Division. At both locations the 53rd Aviation Detachment remained the operator and acquired the nickname "Guns A-Go-Go" as a result of the heavy firepower of the Chinook gunships. Troops in contact with enemy forces favored the ACH-47As for their firepower and 360-degree field of fire. On 5 August 1966, "Stump Jumper" was destroyed in a freak accident at Vung Tau when it collided while taxiing with a transport CH-47A. The ACH-47A that was still at Edwards AFB "Cost of Living" conducting advanced testing was then prepared for deployment to replace the destroyed "Stump Jumper". One of the missions assigned exclusively to the ACH-47As was to go into an area that had just been carpet bombed by a B-52 Arc Light strike and finish off any enemy positions that survived the bombing. It was considered heavily armed enough and heavily protected enough to be able to finish off the job left by an Arc Light strike!

At the end of the test period in December 1966, "Cost of Living" arrived in Vietnam and the 53rd was redesignated the 1st Aviation Detachment (Provisional) attached to the 1st Cavalry Division at An Khe. Enemy forces became reluctant to fire upon any Chinook after a while because at a distance, the ACH-47A was hard to distinguish from a standard CH-47A transport Chinook. On 5 May 1967 while on an attack run, a retention pin on the stub wing of "Cost of Living" came loose and allowed the gun to elevate and fire into the forward rotors, causing the gunship to crash with the loss of all onboard. The two remaining ACH-47As, "Easy Money" and "Birth Control", however, kept flying as the need for their firepower was highly desired by troops in contact. The end of the Chinook gunship program came during the 1968 Tet Offensive at the Battle of Hue. On 22 February 1968, "Birth Control" was forced down due to multiple hits after an attack run in low ceiling conditions. Autorotating into a rice paddy near the walls of the Citadel in the ancient city of Hue, the crew started taking heavy fire from the Citadel area. "Easy Money" made several attempts to land and rescue the crew of "Birth Control", but the ground fire was too intense. "Easy Money" finally landed, but overshot and found itself between the Citadel and "Birth Control". Two UH-1 Huey gunships unleashed 76 2.75-inch rockets into the source of the enemy fire, allowing "Easy Money" to struggle airborne with the crew from "Birth Control". Before the downed ACH-47A could be recovered, it was destroyed by enemy mortars. Since the tactics called for the ACH-47As to operate in pairs, "Easy Money" never flew into combat again as no Chinooks were available for conversion as every one was needed for transport duties in Vietnam. With the number of Bell AH-1 Cobra gunships increasing in Vietnam, "Easy Money" sat out the rest of the war as a maintenance trainer at Vung Tau.

The logo of "Guns A-Go-Go

"Easy Money" ended up in the boneyard at Savannah Army Depot. Boeing had evaluated the airframe for possible conversion to the prototype CH-47D, but it was found to be too corroded to be of any use. It was moved to Fort Eustis where it was used as a sheet metal trainer before it was moved to the base scrapyard. It's historical identity was discovered in 1997 when the "Easy Money" name was uncovered under layers of paint. The aircraft was duly restored and is now on display at Redstone Arsenal, in Alabama. In 2006, the 160th Special Operations Aviation Regiment "Nightstalkers" at Fort Campbell, Kentucky, set up a new battalion at Fort Lewis, Washington, to serve special operations units based on the West Coast for operations in the Pacific. Equipped with the advanced MH-47G Chinook, the unit approached the veterans of the 53rd "Guns A-Go-Go" for permission to resurrect the unit designation, patch, and "Guns A-Go-Go" call sign- which of course was agreed to with enthusiasm!

I highly recommend you visit a tribute website to the ACH-47A and "Guns A-Go-Go"!

Source: Helicopter Gunships: Deadly Combat Weapon Systems by Wayne Mutza. Specialty Press, 2010, p41-55.

Dr. Hans Multhopp's Raven and Its Legacy

2011-02-04T22:45:00.000-06:00

Dr. Hans Multhopp and a model of his Ta 183 fighter

By 1942 both Messerschmitt and Heinkel had flown jet fighter prototypes but other great fighter aircraft manufacturer of Germany at the time, Focke-Wulf, was lagging behind in jet aircraft development with the technical director of the company, Kurt Tank, still working on preliminary ideas for a jet fighter aircraft. Tank's first designs resembled the Heinkel He 162 with a single, dorsal-mounted engine. As Tank refined the design further, the engine moved into the fuselage with a nose intake, then it got lateral intakes, twin fins and finally ended up as a single-engine twin-boom fighter that resembled the De Havilland Vampire and was named the "Flitzer" (Dasher). However, Tank's protege in the company, Hans Multhopp, had been working on something even more spectacular than the Flitzer. Multhopp joined Focke-Wulf in 1938, having been recruited by Tank himself from the University of Gottingen where he worked under the famed aerodynamicist Ludwig Prandtl. By 1940 Multhopp was second-in-charge of the company's aerodynamics department and by 1943 Tank had promoted him to head the company's advanced design bureau. It was here that Multhopp developed what was called Project V. Multhopp had christened his design "Huckebein" after a mischievous raven in a children's cartoon of the day. The Huckebein had sharply swept wings and a raked back T-tail that gave it an appearance that was nothing like any design in the works anywhere at the time.

Kurt Tank's Flitzer design

Tank was dubious about the features of the Huckebein and had scale models of both the Flitzer and the Huckebein built and tested. Despite the tests not uncovering any flaws with the Huckebein, Tank continued work on his own Flitzer but by 1944 it was quite apparent that it couldn't deliver the performance the Luftwaffe desired, which was for a jet fighter aircraft that could outperform the Messerschmitt Me 262. Even though the Me 262 was quite capable in many respects, the German air ministry, the RLM, had overstated the progress of the Allies in jet fighter aircraft development. In addition, by 1944 it was apparent that the Boeing B-29 Superfortress could outperform the B-17 and B-24 bombers that were hitting the Reich regularly. The main drawback of the Me 262 was that in using two engines, it used up per aircraft twice the scarce materials than a single-engined aircraft. Because of this, the RLM and the Luftwaffe exercised even tighter control over fighter aircraft development that in hindsight, were excessively bureaucratic.

In 1944 with Tank having to accept that the company would have to focus its development resources on the Huckebein, the RLM issued a specification for a high performance fighter powered by a single Heinkel HeS 011 jet engine. Messerschmitt submitted what was to become the P.1011 fighter. Focke Wulf submitted Multhopp's Huckebein and even seaplane builder Blohm und Voss submitted a fighter design. Through the winter of 1944-1945 RLM officials and Luftwaffe staff endlessly deliberated the merits of each design and even discussed revamping the specification- as Allied armies were approaching the Rhine in the West and the Soviet Red Army was continuing its relentless push on the Eastern Front. Junkers was then invited to submit their design as well. With no progress being made, the Luftwaffe High Command called an emergency meeting in February 1945 to resolve the matter and the Focke Wulf Huckebein was selected as the Ta 183 ("Ta" in reference to Kurt Tank) to be the interim design while the Messerschmitt design was regarded as the optimal design for further development to supplant the Ta 183 in service. Plans were drawn up sixteen test Ta 183 aircraft with a maiden flight planned for May or June 1945 with the first production fighters being delivered to the Luftwaffe in October 1945.

Ta 183 Design III, this influenced the Saab J29 Tunnan

The Ta 183 was aerodynamically very advanced with a 40 degree, thin, swept wing that had low wing loading for high altitude performance and maneuverability. The sharply raked back vertical fin mounted a T-tail unit that was used only for trimming purposes with pitch and roll to be handled only by the wing surfaces. The cockpit was pressurized and aircraft was armed with hard-hitting 30mm cannon. An alternate variation of the Ta 183 was also envisioned with a less sharply swept wing, a conventional tail unit and longer fuselage- this was the Design III which Tank worked on while Multhopp refined the original Ta 183 which was designated Design II.

The Ta 183 is a popular subject of "What-If" modeling

Work proceeded quickly after that February meeting, but the following month the Allies crossed the Rhine into Germany and work on the Ta 183 under Hans Multhopp and Kurt Tank ground to a halt when the British Army captured Bad Eilsen, the location of Focke-Wulf's design department. The fall of Nazi Germany left the Allies an impressive treasure trove of aeronautical progress. The British initially failed to realize the technological leap the Ta 183 represented when they sifted through the captured material at Bad Eilsen. The Soviets, however, were quick to realize the Ta 183's potential, having found a complete set of plans on microfilm when they captured the RLM headquarters in Berlin. While the plans were examined by Artyom Mikoyan and Mikhail Gurevich of the MiG design bureau, it would be fallacy to say that the MiG-15 is a copy of the Ta 183 as Mikoyan and Gurevich were talented designers in the their own right. Perhaps their examination of the Ta 183 plans confirmed their own intuitions on how best to proceed with the MiG-15. There is no doubt, though, that Sweden managed to get a hold of the Ta 183 plans and data and that it is believed to have influenced their own design work on the Saab J 29 Tunnan fighter.

Following the end of the Second World War, Kurt Tank and Hans Multhopp parted ways, with Tank moving on to work on projects in Argentina and India (subject for future blog posts, stay tuned!). Multhopp and a team of his assistants went to work at Farnborough in the UK and developed plans for a transonic research aircraft powered by an Rolls-Royce Avon turbojet with 60-degree swept wings and a T-tail with the pilot sitting prone in the shock cone of the nose intake. However, Britain was economically spent after the war and Multhopp's design never got built. In 1949 he moved to the United States and went to work with the Glenn L. Martin Company where he worked on two designs that also had T-tails- the XB-51 tactical bomber and the P6M Seamaster jet flying boat. He would later become the chief scientist for Martin Aircraft and his career would culminate with Martin's pioneering work on lifting body spaceplane designs like the X-23/PRIME and the X-24 which provided much data for the NASA Space Shuttle program.

While the Ta 183 was only one of many advanced designs being worked on in Germany during the Second World War, it is probably the most emblematic of Germany's influence on postwar aircraft design. Many designs that were considered ground breaking in the 1940s like the Boeing B-47 Stratojet and the North American F-86 Sabre, originally began as less-than-spectacular straight wing designs that were reworked to incorporate what was being learned from the analysis of captured German aeronautical research.

Source: Aircraft, January 2011, Volume 44, Number 1. "The Luftwaffe's Last Hope" by Bruce Hales-Dutton, p46-50.

The Messerschmitt Me 163 Komet Takes to the Air Again

2011-02-01T22:33:00.000-06:00

The all-red scheme is striking on the Me 163 replica glider

Towards the end of the Second World War, Luftwaffe pilot Jozef Kurz went through pilot training for the Messerschmitt Me 163 Komet rocket interceptor but the war ended before he was able to make a powered flight in the aircraft. Years after the end of the war, Kurz had become an avid glider pilot and decided to build an airworthy replica of the Komet. Using hundreds of original microfilm drawings to create the needed building plans, Kurz had to make certain compromises in the design but remained as faithful as possible as he wanted his replica Komet to be as externally accurate as possible. The biggest difference was the use of wood in the replica instead of metal as was used on the original design. This resulted in some changes in the internal structure which also had the vertical fin as integrated structure instead of a separate structure on the original aircraft. But Kurz was able to keep the external appearance nearly faithful to the original, even using the Gottingen 765 wing profile. Like the original, Kurz's replica glider had two wing spars and the wings were removable reduce its hangar footprint and facilitate road transport. Because the replica was made of wood, it had a weight of 868 pounds compared to the empty weight of the original Me 163 Komet of nearly 4,200 lbs.

The control surface arrangement of the replica glider was also faithful to the original, with fabric-covered coupled elevator/ailerons on the outboard wings and large trim tabs on the inner wings. Fixed slats were also built into the outer wings similarly to the original. Aside from using wood in the construction (and the obvious lack of the Walter HWK 109 rocket motor), the other main change from the original was using a single central wheel integrated into the central landing skid instead of using the jettisonable twin-wheel dolly.

Kurz painted his replica Komet in the markings of the most famous Me 163- the Me 163B flown by Erprobungskommando 16 (EK16- an operational test unit) commander Wolfgang Späte on the Komet's first operational combat mission in 1944. Though no pictures exist of the red Komet, Späte had written two books about his experiences in the Komet and described the plane he flew on the first operational mission- he had no knowledge beforehand that his ground crew painted the Komet in homage to the Red Baron- his accounts indicate the paint added about 40 pounds to the Komet and while it was audacious move and reflected confidence in the rocket interceptor's performance, Späte ordered the aircraft repainted in standard camouflage on his return. Kurz first flew his own Komet replica on 18 June 1996 with the registration D-ESJK. Designating his glider the Me 163BS, Kurz made numerous short test flights before unveiling it at a vintage aircraft fly-in in September 1997. Its last flight in Kurz's hands was at the Berlin ILA 2000 air show. With only five flight hours logged, Kurz sold the replica to EADS (which then had just been formed as the parent to Airbus Industrie and Eurocopter) for display in the Flugmuseum Messerschmitt at Manching, Bavaria.

Note the EADS logo under the cockpit

German aircraft historian Werner Blasel, who had been the main driving force behind the establishment of a heritage flight at Manching as part of the museum, felt that it would have been a waste for the replica glider to remain as a museum display given that it had already proven its airworthiness. Work to return the glider to flying status began in 2004 and was completed in 2006. The most apparent changes were the addition of triangular side windows behind the cockpit, a new canopy, and external aerials that more closely resembled the original Komet. Since there were no longer plans to fit any sort of engine in the fuselage, structural rework was carried out to better integrate the wings with the fuselage structure to allow the aircraft to take the stresses of higher forces. Modifications were made to the undercarriage to facilitate ground handling and the slats were reprofiled to improve the glider's handling characteristics. Lead ballast was also added to better balance the aircraft in flight. The aircraft was re-registered as a one-off glider with the civilian registration of D-1636. Historical markings were added (sans Swastika, which is prohibited from display in Germany) and it made its second maiden flight on 20 June 2006 after which it joined the EADS Heritage Flight fleet at the Flugmuseum Messerschmitt.

At the end of 2010 the replica Komet had flown forty hours. Two pilots with the EADS Heritage Flight are rated in the glider, using a Dornier Do 27 tow plane to get to altitude. Taking 10 minutes to reach 4,000 feet, the Komet is said to be most demanding on the tow line and is much easier to handle in free flight. As the aircraft was optimized for high speed flight, its gliding performance wasn't on par of purpose-built sport gliders but has nonetheless been a hit at air shows in Europe.

Source: Aircraft, January 2011, Volume 44, Number 1. "Red Alert" by Marc Frattini and Dr. Andreas Zeitler, p38-45.

The First Operational Helicopter UAV: DASH and the Gyrodyne QH-50

2011-01-29T23:12:00.000-06:00

The Kaman HTK-1, forerunner of the DASH

In the years following the end of the Second World War, the Soviet Navy expanded its submarine force considerably to offset the powerful surface fleet of the United States Navy. In response to this growing threat, the Chief of Naval Operations at the time, Admiral Arleigh Burke, envisioned a two-layer stand-off system to knock out Soviet subs. The innermost layer of defense consisted of the ASROC weapons system. ASROC (Anti-Submarine ROCket) consisted of a solid rocket motor booster that lofted a Mk 44 torpedo on a ballistic trajectory to the suspected location of the enemy submarine. Later versions of ASROC could deliver a nuclear depth charge or the Mk 46 torpedo. However, ASROC only had a range of five miles and the launch and control system couldn't be readily added to the existing fleet of World War II-era destroyers. As a result, the second outer layer of defense became the DASH system- Drone Anti-Submarine Helicopter. At the time, funding was hard to come by given the limits of the technology of the day until aeronautical engineer Charles Kaman proved that a remotely-controlled drone helicopter could be stably operated with his own HTK-1 test drone, based on the HTK helicopter trainer. The transition to turbine power improved the capability of Kaman's tests when a QH-43G Huskie was successfully tested from the USS Wright (CVL-49) and the USS Mitscher (DL-2), proving that a drone helicopter could be operated from warships. Secret tests at the time with the QH-43G showed that not only could a warload be carried and delivered, but dunking sonar could be used as well as communication to friendly subs. Kaman's tests proved that DASH would work as the outer defense layer against the Soviet threat. As a result, in 1958, the Navy invited submissions from industry for the DASH contract.

The final round in the competition left Bell, Kaman, and Gyrodyne standing- and to the surprise of many who expected Kaman to win, Gyrodyne was selected the winner in December 1958. Gyrodyne already had a contract with the Navy dating from 1951 to study the co-axial rotor arrangement which the Navy felt offered promise as it was compact compared to conventional helicopter designs (the same reason that the Russians went with Kamov co-axial designs for their shipboard helicopters). The founder of Gyrodyne, Peter Papadakos, started the company in 1946 when he acquired the assets of the Bendix Helicopter Company which included an unfinished design for a one-man helicopter which he finished and perfected as the Rotorcycle. At one point, the US Marine Corps was considering acquiring the Rotorcycle as a one-man reconnaissance vehicle- and this undoubtedly won Gyrodyne the DASH competition as the company's design was based on the Rotorcycle- and having flying hardware that was more compact that Kaman's designs won the contest for Papadakos and Gyrodyne.

DASH QH-50 recovering aboard the USS Allen M. Sumner

To make the Gyrodyne design as compact and light as possible, many safety and redundancy systems used on manned helicopters were dispensed with and the first versions of what would become the QH-50 weighed only 1,200 lbs and used a Volkswagen automobile engine. The initial plans were for the QH-50 to be essentially disposable in delivering a nuclear depth charge to the target. However, the need for extensive security and safety measures made storing nuclear depth charges on the modernized destroyers impractical, so a single Mk 44 torpedo became the DASH weapons load. The first shipboard landing was made on 1 July 1960 aboard the USS Mitscher with a safety pilot cumbersomely strapped to a bicycle seat behind the rotors! The first unmanned landing was made in 7 December 1960 aboard the USS Hazelwood (DD-531). Following development testing off the coast of Key West, Florida, the QH-50 was upgraded in 1962 to use a more powerful Boeing T50 turbine engine which increased the warload to two Mk 44 torpedoes. After having been impressed by a DASH demonstration, in 1963 President John F. Kennedy authorized deployment of the system to provide two helicopters and associated equipment (hangar, control center, transmitting/receiving antennas) for the 240 destroyers upgraded to FRAM I and FRAM II standards (Fleet Rehabilitation And Modernization).

Project Snoopy QH-50 showing the underslung tray of equipment

The simplicity of the QH-50 and the DASH system (lack of redundancy) proved to be its weakness- without feedback from the QH-50, the ship's radar had to be used to track its location. If there was an equipment failure in any of the electronics, the drone would be lost. As a result, of the 746 QH-50s produced for the US Navy, fully 80% were lost due to electronics failures! By 1966, Secretary of Defense Robert McNamara pushed for a reduction in DASH funding as the growing conflict in Vietnam was consuming a significant portion of the US defense budget. Given that the submarine threat was nil during Vietnam, the Navy and Gyrodyne were eager to show that the QH-50 could perform other roles. Under Project Snoopy in 1967, QH-50s were modified with telemetry and transmission systems in a tray underslung where the torpedoes were usually carried. A television camera was also mounted in the tray and the Project Snoopy drone were used in Vietnam operationally to spot the fall of naval gunfire on enemy targets. Under a series of DARPA programs code named "Blow Low", "Night Panther", and "Night Gazelle", armed QH-50s were flown operationally in Vietnam. Some of the helicopters carried bombs to attack enemy river shipping and some QH-50s also flew with a TV-camera-aimed 40mm grenade launcher. Another operational test program fielded in Vietnam had QH-50s carrying underslung cargo loads to resupply Special Forces units deep in enemy territory. Of all the QH-50s produced for the US Navy, 5% were lost in combat action in Vietnam.

The last QH-50 was delivered to the US Navy in August 1969 and the only foreign operator of the DASH system was Japan, which took delivery of 18 helicopter drones for service from seven destroyers in their fleet. The last Project Snoopy missions in Vietnam were flown in 1970, after which most DASH systems had been phased out from the fleet with the introduction of Kaman SH-2 Seasprite as LAMPS- Light Airborne Multi Purpose System- that offered greater manned capability from ships too small to operate the larger Sikorsky SH-3 Sea King. The US Army at White Sands Missile Range and the US Navy at the Naval Air Weapons Station at China Lake gave the QH-50 a new lease on life flying test and research missions and ending their days as targets in anti-helicopter trials. The last QH-50 mission was flown in 2006 by the US Army at White Sands, New Mexico. As a result, Gyrodyne has claim to first and so far only production and operationally-deployed helicopter UAV until the deployment of the Northrop Grumman MQ-8 Firescout in 2009.

Source: Helicopter Gunships: Deadly Combat Weapon Systems by Wayne Mutza. Specialty Press, 2010, p97-101.

The First Successful Combat Drops of Laser-Guided Bombs

2011-01-27T22:28:00.000-06:00

Capt. Thomas Messett led the first combat LGB drop

By 1972 President Richard Nixon's policy of "Vietnamization" was underway as the bulk of responsibility for the defense of South Vietnam transferred from US forces to the South Vietnamese military. Nearly the bulk of US forces in Vietnam had already departed and the Seventh Air Force had already sent half of its combat aircraft back stateside. Only two aircraft carriers remained in the Gulf of Tonkin. The North Vietnamese saw the opportunity to win the war via a conventional attack and on 29 March 1972, twelve of North Vietnam's fifteen divisions made a three-pronged invasion into South Vietnam, leaving only one division in North Vietnam and two divisions in Laos in reserve. Within three days of the Easter invasion, South Vietnamese forces were on the brink of collapse. Over the course of the month of April, a massive influx of US combat aircraft striking the advancing NVA was all that prevented the collapse of the Saigon regime. On 8 May 1972 US Navy aircraft mined the approaches to Haiphong harbor and that evening President Nixon addressed the nation to announce Operation Linebacker, the intensive bombing of North Vietnam, to commence on 10 May 1972. With the North Vietnamese having exposed their logistical tail in their multi-pronged invasion of the South, they left themselves open to air attack on their rear.

On the first day of Linebacker, sixteen McDonnell Douglas F-4 Phantoms of the 8th Tactical Fighter Wing "Wolfpack" based at RTAFB Ubon in Thailand armed with 2,000 lb electro-optically guided bombs attacked the Paul Doumer Bridge that linked the port city of Haiphong with the capital of Hanoi over the Red River. The weapon systems officers (WSOs) in the back seat of the Phantoms used a TV screen to display the image from the TV camera in the nose of the bomb. Picking out a sharp contrast point between light and dark, the WSOs selected the aim points on the bridge and the bombs were on their way after the dropping aircraft turned for safety. Every electro-optical bomb missed, with the bombs locking on the shadow of the bridge on the water below or suffering a guidance unit failure. Some other supporting aircraft scored hits with conventional bombs, but none of the spans had been dropped.

The AN/AVQ-10 Pave Knife, showing the camera/laser aperture

While the first laser-guided bombs were under development prior to the 1968 bombing halt, continued work by Texas Instruments had improved the method from the hand-held "Zot Box" that was used by the WSO while the Phantom flew a pylon turn around the target to podded systems in the form of the AN/AVQ-10 Pave Knife that allowed more flexible attack approaches to be made. The WSO used the laser in the Pave Knife pod to designate the target point for the laser-guided bombs. The 8th TFW at Ubon had six Pave Knife pods and it was decided to use them on the next day to revisit the Paul Doumer Bridge. Compared to the sixteen aircraft from the previous day, on 11 May 1972 only four F-4D Phantoms led by Captain Thomas Messett (who flew in the previous day's raid) would attack the bridge. One Phantom carried two 3,000 lb LGBs and the other three Phantoms carried two 2,000 lb LGBs. Only Captain Messett's F-4 carried a Pave Knife pod. The defenders of the bridge didn't think the four Phantoms were the main strike force and as they dived on the bridge, Messett and his WSO designated target points on the bridge and all eight bombs scored direct hits on the bridge, dropping the entire span on the Hanoi side of the bridge into the Red River. It would be a year before the Paul Doumer Bridge was usable again.

The 3,000 lb GBU-11 added fins and laser guidance to the M118 bomb

The other bridge that was crucial to hitting at the North Vietnamese logistical support of the Easter invasion was the Thanh Hoa Bridge, an immensely tough rail bridge nicknamed "Dragon's Jaw" that crossed the Song Ma River and connected the rail shipment points from China to Hanoi. During Operation Rolling Thunder from 1965 to 1968 over 1,000 missions flew against the Dragon's Jaw, not one mission succeeding in bringing its spans down. The USAF even resorted to dropping floating bombs upstream of the bridge to try and bring it down in Operation Carolina Moon. Nothing worked, it was known as the toughest target in North Vietnam. On 13 May 1972, two days after the Paul Doumer Bridge was dropped, the 8th TFW set out to drop the Thanh Hoa Bridge for good with fourteen Phantoms carrying nine 3,000 lb LGBs, fifteen 2,000 lb LGBs, and forty-eight 500 lb conventional bombs (due to a shortage of laser-guided bombs). Attacking through an intense flak barrage, direct hits by the LGBs put the entire western span of the Dragon's Jaw into the Song Ma River below. Before the end of Linebacker I in October, the Navy flew an additional eleven missions against the bridge and the USAF another two to insure the bridge was out for good.

Post-strike recon photo of the Paul Doumer Bridge

It was a stunning debut for a new age of precision munitions. When the Pave Knife was used against the Paul Doumer and Thanh Hoa Bridges by the 8th TFW, it was technically still a developmental program and was rushed forward in response to Nixon's order to blunt the North Vietnamese invasion. Twelve pods were built for the testing program. When the preparations for Operation Linebacker started, three pods stayed stateside to continue the testing program. Three pods went to the US Navy for use on specially-wired Grumman A-6A Intruders and six pods went to the 8th TFW at Ubon for use on specially-wired F-4D Phantoms. Two pods were lost over North Vietnam during Linebacker I- the remaining four pods became quite valuable and after Paul Doumer and Thanh Hoa, were used only on the most critical and important targets. The commander of the Seventh Air Force, General John Vogt, reportedly told the pilots of the 8th TFW "Don't come back if you don't have that pod with you when you return!"

Source: The Linebacker Raids: The Bombing of North Vietnam, 1972 by John T. Smith. Arms and Armour Press, 1998, p61-75.

The 747 Shuttle Carrier Aircraft (SCA)

2011-01-24T11:59:00.000-06:00

The Boeing 747 was one of two choices for the SCA

During the design and development of the Shuttle Orbiter, air breathing jet engines were a part of the design for some time until cost and technical considerations in early 1974 led to their deletion from the concept. No longer able to "self-ferry", NASA now faced the problem of how to get the Orbiter from the remote landing sites to the launch locations. At the time NASA Langley had a study ongoing on a large aircraft design called VIRTUS that would have carried the Orbiter under the center wing flanked by twin fuselages and a twin boom tail with power coming from four Pratt & Whitney JT9D turbofans. Design work had proceeded on VIRTUS as far as wind tunnel tests with a 1/34 scale model, but sheer size, long development time and costs involved for an aircraft that would be built in very small numbers resulted in end of the VIRTUS project. At the time, Jack Conroy, the developer of the Super Guppy concept that NASA was using to transport rocket stages, had suggested using a jumbo-class aircraft to carry the Orbiter on its back. Proposals were issued to the industry and Lockheed offered up a twin-fuselage aircraft based on the C-5 Galaxy with the Orbiter suspended underneath a new center wing section- but, like the earlier VIRTUS program, it was eliminated from consideration due to cost, development time and that the design was so wide, no runway available could accommodate the design. Boeing offered a modified version of the 747 that carried the Orbiter on its back that presented a much lower risk approach. Boeing at the time even suggested that the large external tanks could be carried on the back of a 747, but wind tunnel studies showed the idea to be less practical than initially thought. Lockheed had subsequently reworked its design to a simple modification of a C-5 Galaxy to carry the Orbiter on its back much like Boeing's proposal.

By mid-1974 Boeing's 747-based proposal and Lockheed's simpler C-5 Galaxy-based proposal were the only serious contenders to become the new Shuttle Carrier Aircraft (SCA). On 24 April 1974 NASA selected the C-5 Galaxy proposal from Lockheed based on it having the least acquisition expense and a C-5 Galaxy would need less structural modification than a Boeing 747. Accordingly, NASA approached the United States Air Force with the proposal and a request to make three to five C-5s available. The USAF was very receptive to the idea and the Lockheed proposal only added 400 to 600 pounds of modifications to the Galaxy without adversely affecting its cargo carrying capacity when not being used to transport the Orbiter. An arrangement was set up whereby NASA would pay for the modifications and then lease the modified C-5s as needed from the Military Airlift Command. One Galaxy was agreed to be bailed to NASA full-time for development into the SCA and for use in the atmospheric flight tests with the planned first Orbiter (which would become the Shuttle Enterprise). Despite some lingering concerns about the effects of the Orbiter's wake on the C-5's T-tail, both NASA and the USAF had worked out an acceptable arrangement for both parties.

N905NA conducted the atmospheric landing tests with Enterprise

The downturn in the American economy in the early 1970s led numerous US airlines to release their 747 aircraft which were too large for the market at the time. As a result, the acquisition cost of the Boeing 747 as the SCA dropped much lower than that of the Lockheed proposal. With the ready availability of low-time 747s on the market, NASA abandoned plans for using the Galaxy as it was decided it was much easier in the end to have complete control of the SCA than to have to compromise with military priorities for use of the C-5 Galaxy. On 18 July 1974 NASA purchased a used Boeing 747-123 (N9668, msn 20107) from American Airlines. It was the 86th 747 off the production line at Everett and was delivered to American on 29 October 1970. By the time of the NASA purchase, it had only logged 8,999 flight hours and 2,985 cycles flying primarily transcontinental services between New York JFK and LAX. NASA re-registered the aircraft as N905NA. Before modification into the SCA configuration, N905NA was used for in-house studies with NASA Ames on wake vortices. Following conclusion of the wake vortex research program, Boeing initiated the $30 million conversion program on N905NA on 2 August 1976.

Not often seen is the sense of humor NASA has with the SCA

Boeing installed new bulkheads to strengthen the fuselage with skin reinforcement at critical stress areas. The horizontal stabilizer structure was also beefed up along with the addition of telemetry and transponder test equipment, fittings for the Orbiter support struts, and the installation of a 747-200 rudder actuator system. Boeing also developed a set of removable modifications for the SCA- the first one was a telescopic forward support assembly that was used only during the atmospheric flight tests with the Shuttle Enterprise. This support would hold the Enterprise at a six-degree angle of attack to facilitate release during the flight tests. A fixed assembly was also developed for use during SCA ferry missions that held the Orbiter at a three-degree angle of attack, which induced less drag during the ferry flights. The aft support assemblies (there were two) were common to both the atmospheric flight tests and ferry flights and finally 10 foot by 20 foot vertical endplates were added to the end of the horizontal stabilizer to provide additional stability when carrying the Orbiter- in practice, though, NASA never removed the endplates.

The 747's trim system was also modified to allow a greater range of trim in pitch to counteract the downwash off the Orbiter's wing on to the horizontal stabilizer. Most of the main deck interior was stripped out, but some seats were retained for support personnel during the ferry flights. The JT9D engines were also converted to allow a thrust increase from 43,500 pounds to 46,950 pounds of thrust. The current JT9D engines on the current incarnation of the 747 SCA are rated at 50,000 pounds of thrust. Since each Orbiter has a different empty weight, an adjustable ballast system using standard cargo containers in the forward underfuselage cargo compartment had to be developed to maintain the center of gravity. On 14 January 1977 Boeing finished the modification work and after a period of flight testing, it was delivered to NASA.

Concerns about flight crew safety during the atmospheric flight tests with the Shuttle Enterprise led NASA to incorporate an escape system on N905NA since the flight crew of the Enterprise had ejection seats. The escape system was based on what was used on the 747 prototype during Boeing's 1969 flight tests- in the event of an emergency, a handle was pulled that blew out thirty fuselage windows to facilitate rapid decompression of the aircraft. Three seconds later an emergency egress hatch on the lower forward fuselage was blown out with extendable spoiler being deployed. The crew would make their way back from the flight deck to the middle of the upper deck lounge area where a hole leading to a 16 foot escape slide would lead them out the blown hatch and clear of the aircraft. Testing showed the flight crew could bail out of the 747 within 11 seconds. The atmospheric flight tests will be the subject of a future blog post, so stay tuned.

N905NA has three upper deck windows, N911NA has five

In 1988 NASA acquired a second 747 to act as a back up to N905NA. Part of this was driven by the recommendations following the Challenger accident that a significant portion of Shuttle flights would still be landing at Edwards AFB. The first 747-100SR was purchased from Japan Air Lines where it had flown as JA8117, msn 20781. Boeing purchased the aircraft from JAL on behalf of NASA and conducted the necessary modification work to bring it up to SCA standards with the new tail number N911NA. On 20 November 1990 it was delivered to NASA and in 1995-1996 both of the 747 SCAs were repainted in NASA's new colors.

During a ferry mission the SCA' smaximum speed it 250 KIAS (Mach 0.6) at an altitude of 13,000-15,000 feet with a range of approximately 1,150 miles. Without the Orbiter, the SCA cruises at 24,000-26,000 feet with a range of 6,300 miles. During ferry flights the usual crew is two pilots and two flight engineers, but only one flight engineer is needed on non-ferry flights. At one point NASA looked at inflight refueling of the SCA as the equipment was readily available as it was installed on a handful of the USAF's 747s- the E-4 airborne command posts and the two VC-25A presidential transport aircraft. Proximity flight tests were even carried out with N905NA and a KC-135 tanker minus the Orbiter, but the discovery of cracks at the base of N905NA led to the termination of the studies as it was feared that wake turbulence from the tanker may have been possible. Plans were in motion to fly the proximity tests with an Orbiter, but the costs involved and wake turbulence concerns led to the quiet abandonment of the idea.

Source: Space Shuttle: The History of the National Space Transportation System- The First 100 Missions by Dennis R. Jenkins. Specialty Press, 2001, p195-202.

Operational Improvisation: Over-the-Shoulder Nuclear Bombing

2011-01-23T21:51:00.000-06:00

F-84Gs of the 20th FBW had lightning markings, each squadron had its own color

In 1952 the Republic F-84Gs of the 20th Fighter-Bomber Wing crossed the Atlantic supported by aerial refueling to set up shop at their new base, RAF Wethersfield, in order to provide tactical nuclear strike capability for the first time to NATO forces in Europe. Just a year earlier, scientists and engineers at Sandia, one of the development centers in the United States for nuclear weapons, had developed the Mark 7 nuclear bomb, the first tactical nuclear weapon with an explosive yield of 20 kilotons. While the Mark 7 weapon would be carried operationally by many USAF and US Navy tactical attack aircraft, the first aircraft to carry the Mark 7 operationally also happened to be the first production tactical fighter to have not just nuclear capability, but also air-refueling capability. That was specifically the G variant of the Republic F-84 Thunderjet, which had an air refueling receptacle for a flying boom in the left wing root, a more powerful jet engine, and provisions for the Mark 7's special pylon that had the necessary circuitry for nuclear weapons delivery.

The Mark 7 was the first American tactical nuclear weapon

The 20th FBW had been given six months to prepare for the move to Great Britain as well as to become the first tactical nuclear fighter-bomber unit in military history. At the time of the deployment, the F-84Gs and pilots of the 20th FBW were only versed in clear-weather weapons delivery more suited to the bombing ranges in the predominantly sunny southwestern United States, drops being made starting at 20,000 feet in altitude. The weather in Europe, however, was far from ideal for this sort of weapons delivery mode, with a predominantly cloudy maritime climate in the areas that the 20th FBW was expected to operate. I had posted this past September about the nuclear delivery role assigned to the McDonnell F-101 Voodoos of the 81st Tactical Fighter Wing based in RAF Bentwaters/Woodbridge in the late-1950s and early 1960s. Not unlike the conditions facing the pilots several years later that flew the Voodoo, the pilots of the 20th FBW were expected to navigate visually and by dead reckoning to their targets with only the most basic of navigational aids. By the time the 20th FBW had set up shop at RAF Wethersfield, a different form of nuclear delivery was needed and the wing commander, Colonel John Dunning, had sent some of his best pilots to Kirtland AFB in Albuquerque, New Mexico near Sandia, to find out more about a new weapons delivery tactic called LABS- Low Altitude Bombing System. Developed at Kirtland by Major Jack Ryan, it hadn't yet received much attention as most nuclear delivery tactics of the day concerned use by strategic bombers. Col. Dunning wanted his pilots in Europe to have every advantage possible and LABS offered that prospect.

In a LABS run, an IP (initial point) is chosen that is a known distance and direction from the target and was most ideally located three miles away. The LABS equipment was quite basic- it was a timer with a gyro that was free to move about the pitch axis of the delivery aircraft. Having previously set the time from the IP to the pull up point near the target and the calculated angle of release beforehand, an aircraft on a LABS run headed towards the target at 500 mph at low level with the IP in between the aircraft and the target. Once the IP was reached. the pilot pushed the "pickle" button on the control stick which started the timer and a flashing red light on the gunsight was connected to both the timer and the LABS gyro. The pilot pulled into a steady 4G climb and at a precise point and angle (usually 25 to 30 degrees), LABS released the nuclear weapon which continued onward on a precalculated ballistic trajectory towards the target while the pilot pulled his aircraft into an Immelman loop and exited the area as fast as possible. In effect, LABS "tossed" the bomb towards the target.

Diagram showing the over-the-shoulder bomb toss

On return to Europe, the pilots that trained in the LABS technique for the 20th FBW found that finding an IP near the target was challenging. It was noted that as the distance between the IP and target decreased, the ideal release angle of the Mark 7 bomb increased. If the IP was very close to the target itself, then the optimum release angle was 90 degrees. Pushing the idea further, the pilots of the 20th FBW worked out that if the IP was the target itself, then the optimum LABS release angle was 110 degrees and the bomb would impact right at the point where the pull-up maneuver was initiated. No IP was needed- the target itself was the IP. The bomb was released "over the shoulder" and would arc upward to 10,000 feet and more than a minute elapsed before it detonated, allowing time for the F-84G to rollout and accelerate out of the area in a dive. The USAF and the specialists at Kirtland AFB doubted if the average USAF pilot could carry out such a complex maneuver as the wings had to be absolutely level in the pull up or the bomb's impact point would stray away from the target. The operations officer of one of the 20th FBW's constituent squadrons had noted that the F-84G didn't even need a LABS gyro- the aircraft's own gyro started to "tumble" right past vertical and by complete coincidence, right at 110 degrees! Major John J, Kropenick, the ops officer who made this observation, came up with his own solution, the "Kropenick Autopilot" that was taught to all the pilots of the 20th FBW- two large rubber bands were hooked to the control stick on the run in, each one then looped over a cockpit light on the sidewall on each side. The tension of the rubber bands kept the stick precisely centered during the pull up and once the Thunderjet's own gyro tumbled, the bomb would be released. Pilots taught the method with the "Kropenick Autopilot" had bomb scores acceptable to the USAF given the 20-kiloton yield of the Mark 7 bomb.

By the time the LABS equipment had been fitted to the 20th FBW's Thunderjets, the pilots of the wing had gotten quite proficient at using the "Kropenick Autopilot" and made the transition to using the LABS equipment for "over the shoulder" toss bombing with a minimum of delay and fuss.

Source: Aviation History, March 2011, Volume 21, Number 4. "Over-the-Shoulder A-Bombing; Cold War F-84G pilots improvised a surprising twist on bomb delivery" by David Rust, p54-57.

The Achilles Heel of the Douglas B-66 Destroyer

2011-01-19T10:21:00.000-06:00

The B-66 Destroyer ended up only resembling the A-3 Skywarrior

In January 1952 when the US Air Force issued its official General Operational Requirement (GOR) for a tactical bomber and reconnaissance jet aircraft to replace the Douglas B-26 Invader and the "interim" Martin B-57 Canberra, the selection of a minimum change version of the Douglas A3D Skywarrior as the B-66 Destroyer made sense. Douglas's proposed changes weren't all that major- deletion of the folding wings, catapult gear and arresting gear, addition of ejection seats and anti-icing, strengthening the airframe for the stresses of low altitude flight and an enlarged search radar antenna. Since the aircraft was "off the shelf", no prototypes were ordered. Eventually the USAF's GOR evolved to cover four distinct versions- the B-66B, a nuclear capable bomber version to replace the North American B-45 Tornado, the RB-66B, an all-weather day/night reconnaissance version, the RB-66C, a tactical electronic reconnaissance aircraft, and the WB-66D weather reconnaissance aircraft. Douglas agreed to an ambitious timetable to get the B-66 in production and operational, but the USAF kept requesting changes that ended up making the B-66 Destroyer a totally different aircraft that literally shared nothing in common with the Skywarrior. It's a testament to Douglas's abilities that the schedule slipped only two years as a result of constant changes being requested by the USAF! The B-66 ended up weighing just over 10,000 lbs more than the A3D Skywarrior as a result of all the changes.

Had it gotten the J57 engine, the B-66 might have had a longer career

But being overweight wasn't the biggest flaw in the B-66 design. Ed Heinemann and his Douglas team recommended the Pratt & Whitney J57 turbojet for the B-66 after the A3D was switched from the anemic Westinghouse J40 turbojet to the more powerful J57 (the first production turbojet in the world to exceed 10,000 lbs of thrust). However, the Air Force held a competition for the engine to power the B-66- in addition to the recommended J57 engine, the Allison J71, General Electric J73 and surprisingly the Westinghouse J40 were submitted. Not surprisingly the J40 was dropped early on and the J73 soon followed for technical reasons. To the surprise of Douglas, the USAF then selected the J71 for the Destroyer, not only an engine that had yet to fly but it was also less powerful than the J57 by nearly 2,000 lbs of thrust! The official reasoning was that the Allison J71 was readily available (a bit of a stretch here on the part of the USAF) and the B-66 had lower priority than other USAF programs that used J57 engines- namely, the Boeing B-52 Stratofortress, the Boeing KC-135 Stratotanker, the North American F-100 Super Sabre, the McDonnell F-101 Voodoo, and the Convair F-102 Delta Dagger. At the time the Voodoo was under development as a long range penetration fighter for SAC, so it became obvious to many that SAC dominated the USAF budget and would receive any and all J57 engines possible. The main reason the F-100 got any J57s at all was that the F-100 was central to the Tactical Air Command's desire to have its own tactical nuclear attack force built around the F-100.

Ordinarily those assigned to the B-66 Program Office at Wright Patterson AFB would have pushed for the J57, but politically the B-66 was seen as primarily a reconnaissance aircraft and only in interim bomber. Those with fighter experience in TAC wanted the F-100, those with tactical bomber experience in TAC wanted the Martin XB-51. And SAC was determined to preserve its budgetary allocation at all costs. In the end, no one really fought for the B-66 Destroyer when it was given the clearly less-powerful Allison J71 engine. Allison had trouble getting the J71 prototypes bench tested to at least 50 hours without any problems and only barely made the cut which exacerbated the schedule slippage of the first operational Destroyers. And even at that, the test pilots at Edwards AFB flying the first B-66s hated the J71- it was slow to spool up for more power, it surged often, and even would flame out and stall while taxiing. On 8 October 1955 the pilots of the AFTC (Air Force Flight Test Center) filed an extremely unsatisfactory report on the J71. The test force concluded that the J71 engine was accepted by the USAF only partially developed and a replacement engine was needed, the preference being for the J57 used by the Skywarrior. It was alleged that on a hot summer day in Denver with a typical combat load, the B-66 Destroyer couldn't even get airborne!

The tail guns were soon removed and replaced with ECM tailcone

Unfortunately for the B-66 program, the Secretary of Defense at the time, Charles Wilson, came to the Defense Department as the CEO of General Motors, of which Allison was one of its divisions. Wilson's 1953 confirmation hearings before the Senate were highly controversial because of his reluctance to sell his GM holdings and comments that alluded to him possibly favoring GM as Secretary of Defense. The loss of the J71 contract would have been a severe blow to Allison at the time. As a result, the Destroyer kept the J71 engines and Allison tweaked the engine further to bring the engine up to 9,700 lbs of thrust. While this satisfied the USAF given the mission profiles of the Destroyer in the 1950s, the addition of heavy electronic warfare equipment to the Destroyer to created the EB-66, the only tactical electronic warfare aircraft available in Vietnam, strained the limits of the J71 in the hot tropical environment of Vietnam. Destroyer crews nicknamed the aircraft "The Airplane with One-Way Engines" in reference to the fact that outside of the lackluster McDonnell F3H Demon, the other design to use the J71 was the Northrop Snark cruise missile. However, in 1956, Northrop switched the Snark's engine from the J71 to the- you guessed it- J57.

Source: Glory Days: The Untold Story of the Men Who Flew the B-66 Destroyer into the Face of Fear by Wolfgang W.E. Samuel. Schiffer Military History, 2008, p24-38.

Flight Testing on the Cheap: The Ground-Breaking M2F1 Lifting Body

2011-01-18T21:16:00.000-06:00

In the early 1960s NASA's research work into lifting body designs was in full swing with the X-23/PRIME program testing lifting bodies in the re-entry regime from orbit. I had previously blogged about the PRIME program and the data that it provided the aerospace industry. But while the unmanned X-23 program answered the question of a lifting body's flight characteristics at the high speeds encountered during re-entry, questions still remained about the suitability of a lifting body in subsonic flight- would a lifting body design be controllable and stable in the low speed flight regime upon return to Earth of a reusable space vehicle? At the time, Dale Reed, an engineer at NASA's Flight Research Center (FRC) at Edwards AFB, had been following the lifting body research in his free time. Being an avid remote-control aircraft model builder, Reed built a 24-inch flying model of what was designated the M2 shape- the M1 shape was the product of research at NASA Ames which started out as a 13-degree half cone with a rounded nose. The M1 shape was refined into the M2 shape which added twin vertical fins, a canopy for a pilot, and horizontal control surfaces. This M2 shape was what Dale Reed modeled in his free time and dropped it from a 60-inch remote control "mothership" while his wife Donna would film the M2 model flight with an 8mm camera. He later showed the films to the director of the FRC, Paul Bikle, and Alfred Eggers, one of the pioneering researchers on lifting body work. They were suitably impressed with Reed's work that in November 1962 Bikle authorized a six-month program paid out of the FRC's discretionary fund to build a manned glider version of Reed's M2 model.

The M2 glider had a steel tubular frame to which was attached the pilot's seat and landing gear (taken from a Cessna 150)- the exterior would be a light wooden shell this way different shapes could be tested. As it was, work on the lifting bodies within NASA would eventually settle on the M2 shape as the most ideal and the glider was designated the M2-F1. Space was set aside in the main hangar at the FRC which was cordoned off and nicknamed "Wright's Bicycle Shop". A local glider builder was contracted to help construct the outer shell while NASA engineers and technicians, many of whom were members of the Experimental Aircraft Association (EAA), lent their time and talents to the construction of the M2-F1. As many of them did it in the free time, it ended up costing NASA only $30,000 to build the M2-F1 when it was finished in early 1963! One of the reasons Paul Bikle funded the program out of FRC's discretionary fund was that he feared NASA headquarters in Washington would disapprove, or worse, take control of the project and make it excessively complex and expensive.

The finished M2-F1 was 20 feet long, 10 feet high, and 14 feet wide. At the aft ends of the blunt half cone it had twin fins that mounted horizontal control surfaces nicknamed "elephant ears". The main body itself had two flaps at the end that were for trimming the glider in flight. Complete with the pilot, the M2-F1 weighed only 1,138 pounds. Later in the flight test program a Weber zero-zero ejection seat was fitted, but for the first set of flights, no ejection seat was used. By March 1963 the full scale wind tunnel tests at NASA Ames were completed with encouraging results and back at Edwards AFB tow runs were made with various vehicles pulling the M2-F1, the first captive flight taking place 5 April 1963. For these initial flights, the M2-F1 was suspended below a Rogallo wing as the vehicles weren't fast enough to pull the M2-F1 to its rotation speed.

The engineers wanted to a faster vehicle to get the M2-F1 airborne before pulling it aloft behind a tow aircraft to higher altitudes. A 1963 Pontiac Catalina convertible was procured and stripped down. It had a 455-cubic inch engine, four barrel carburetor, and was a five speed stick shift. The engineers enlisted the help of famed California hot-rodder Bill Straup in Long Beach to replace the street tires with racing tires and to tune and tweak the engine for maximum performance. Rollbars and radio equipment were installed and the right hand front passenger seat was turned around to face aft. Adorned with the suitable high visibility markings and NASA logos, the FRC's hot rod pulled the M2-F1 for the first time airborne in June 1963. Satisfied with the near-ground/low altitude peformance, a Douglas R4D (Navy version of the DC-3/C-47) pulled the M2-F1 glider aloft for the world's first piloted lifting body free flight on 16 August 1963 when NASA test pilot Milt Thompson cast off from the tow plane at 10,000 feet and landed smoothly onto Rogers Dry Lake below. Six other test pilots flew the M2-F1 glider after casting off from the R4D towplane- Bill Dana, Capt. Jerauld Gentry, Don Mallick, Bruce Peterson, Donald Sorlie, and Col. Chuck Yeager. Bruce Peterson and Milt Thompson flew the majority of the M2-F1 flights. The M2-F1 eventually got a proper ejection seat and a small rocket was added which was fired before landing to assist with the pre-landing flare. Eventually modifications and test equipment required the M2-F1 to trade in its Cessna 150 landing gear for the gear of a Cessna 180.

The last M2-F1 flight took place on 16 August 1966 after just over 100 flights and 400 ground tows. It was donated to the Smithsonian Institution and was restored years later and returned to NASA Dryden (what the FRC is today known as) for display. Proving that a lifting body shape could be safely flown at subsonic speeds, NASA proceeded to develop the M2-F2, a heavier, alumimum, rocket powered version that was dropped from the NB-52A and was capable of supersonic flight. Plans were to build two M2-F2s, but eventually one M2-F2 was built to supersede the M2-F1 and a competing lifting body design was built by Northrop as the HL-10. As an interesting bit of television trivia, the crash depicted in the opening of the "Six Million Dollar Man" is Bruce Peterson crashing in the M2-F2 on 10 May 1967, which he did survive.

Source: Space Shuttle: The History of the National Space Transportation System- The First 100 Missions by Dennis R. Jenkins. Specialty Press, 2008, p36-38.

The Short and Deadly Career of the De Havilland Swallow

2011-01-16T21:37:00.000-06:00

Evolution of the Comet from mailplane to jetliner

The Allies reaped a technological windfall with the unconditional surrender of Nazi Germany in May 1945. Both the United States and Great Britain in particular found that their wartime studies of future jet aircraft experienced quantum leaps in performance with the incorporation of the aeronautical knowledge of the personnel technical documents, and aircraft of the Third Reich. During the final half of the Second World War, Britain grappled with the future of passenger flight with the Brabazon Committee's deliberations on the future of commercial aviation. Of the five designs put forth by the Committee, the most advanced was the Type IV design for a jet-powered 100-passenger design. This aircraft would become the De Havilland DH.106 Comet- but the DH.106 started out as a very small, modest adaptation of the Vampire jet fighter as jet-powered mailplane with a six-seat passenger compartment. But with the input of the Brabazon Committee, the DH.106 evolved into a substantially larger aircraft that at one point was a tailless design before taking on the shape now familiar as the Comet.

TG283, the low-speed DH.108 aircraft

The British were particularly interested in the Messerschmitt Me 163 Komet rocket-powered point interceptor- it was fast, had modestly swept wings, was tailless and was known to have good flying characteristics. As a result of their evaluation of the Komet, the government issued the E.18/45 requirement which was awarded to De Havilland for the construction of two small jet-powered research aircraft to study swept wings and the tailless configuration. Designed by De Havilland engineer Ronald Bishop, what was designated the DH.108 used the fuselage of the De Havilland Vampire jet fighter which was stretched and streamlined combined with a new swept vertical fin and new swept wings. This served to save time and effort and like the Vampire jet fighter, the DH.108 had wing root intakes. Unofficially named "Swallow", the two prototypes received the RAF serials TG283 and TG306. TG283 had a 43-degree swept wing and was intended for low speed testing while TG306 had a 45-degree wing and was assigned to high-speed transonic testing. Initial wind tunnel studies suggested that the Swallow would have lousy stall characteristics, so the first of the two to fly, the low-speed assigned TG283, had fixed wing slats and anti-spin parachutes in fairings on the wingtips. It made its first flight on 15 May 1946 and TG306, the high-speed Swallow, made its first flight a month later and had automatic wing slats but no anti-spin parachutes.

VW120, the third DH.108 Swallow that broke the sound barrier in 1948

The test pilot for the DH.108 was the chief test pilot for the company, Geoffrey De Havilland, Jr, the son of the company's founder. After several problem-free test flights it was found that both aircraft lacked the predicted poor stall characteristics and the high speed aircraft, TG306, joined the formal research program on 23 August 1946. By the time De Havilland had safely taken it to 630 mph at altitude with no problems, it was decided he would take TG306 to break the world speed record. On a practice run over the Thames Estuary on 27 September 1946, the aircraft exceeded its structural limits at high speed and broke up, killing Geoffrey De Havilland, Jr, as the aircraft had no ejection seat. John Cunningham succeeded De Havilland as chief test pilot and took over flying the DH.108. To replace the lost aircraft, a third DH.108 was ordered and received the RAF serial VW120. It featured a more pointed nose, revised canopy and cockpit including a Martin-Baker ejection seat, and a higher thrust Goblin engine than what had powered the first two aircraft. Cunningham took VW120 up on its maiden flight on 24 July 1947. With Cunningham and fellow test pilot John Derry flying VW120, a series of new speed records were set in 1948 and on 9 September of that year, Derry took VW120 past Mach 1 in a dive from 40,000 feet, making the DH.108 Swallow the first British aircraft to break the sound barrier- though it must be pointed out that Derry had for the most part lost control of VW120 during the supersonic portion of the flight but had safely recovered and landed.

After flying demonstrations at the 1948 Farnborough SBAC air show, VW120 was handed over to the Royal Aircraft Establishment to join TG283 (the first Swallow) in the research program. On 15 February 1950 RAE test pilot Stuart Muller-Rowland was killed when VW120 broke up due to structural failure during a high speed test run. Three months later TG283 was lost and killed its test pilot, RAF Squadron Leader G.E. Genders, when it stalled at low speed and low altitude.

Despite the loss of all three DH.108s with the loss of life, the data from the Swallow flight test program and the research program at the Royal Aircraft Establishment benefited not just the design of the DH.106 Comet jetliner, but also that of the DH.110 Sea Vixen naval fighter as well.

Source: Military Aircraft Monthly International, Volume 9, Issue 12. "A Deadly Swallow: The short sharp story of De Havilland's DH.108" by Nico Braas, p28-32.

The British Knock Out the Italian Fleet with Biplanes

2011-01-12T22:27:00.000-06:00

The Fairey Swordfish as marked/painted for the Taranto attack

The planning for the attack on the Italian fleet at the harbor of Taranto began in earnest in 1938 during the Munich Crisis when it seemed that Europe was headed for war. Though boasting a force of six battleships, five cruisers and twenty destroyers at the start of the conflict that could have caused significant headaches for the Royal Navy in the Mediterranean, Mussolini rarely ordered the fleet to sail far from the home port of Taranto and they would return at the earliest opportunity, failing to engage the British Mediterranean fleet. With the threat of war looming, captain of the HMS Glorious, Capt. Lumley Lyster, was asked to draw up an attack plan to knock out the Italian fleet while it sat in harbor. Essential to any attack given the strength of the defenses of the harbor would be surprise, necessitating a night attack. By the time 1940 had come around and maintaining the sea links with the British forces in North Africa took added importance, the need to proceed with the attack, codenamed "Operation Judgement", the trained Fairey Swordfish aircrews that trained aboard the HMS Glorious were now serving aboard the HMS Illustrious and under strict secrecy, the attack was planned for 12 October 1940 on Trafalgar Day. Unfortunately, a fire in the hangar deck of the Illustrious resulted in the Swordfish aircraft being drenched in saltwater, necessitating their clean up and repair. Also, the original attack plan called for the HMS Eagle to accompany the Illustrious on the attack, but Eagle had suffered damage from an accidental bomb explosion earlier in the year. As a result, some of Eagle's Swordfish and aircrew were transferred to the Illustrious. The attack was rescheduled for the night of 11/12 November 1940.

Given the nature of the defenses based on the latest British reconnaissance, the first wave to attack Taranto would consist of twelve Swordfish, only six of which would carry torpedoes while the balance of aircraft carried bombs and flares. At the time, the conventional naval wisdom was that torpedoes were only usable in deep water, but the Royal Navy had modified their torpedoes to run in the shallow water of Taranto Harbor. The photos showed that the battleships were protected by torpedo nets, but they were standard keel-depth nets. The torpedoes used were configured to magnetically detonate below the ships' keels.

Diagram of the attack on the Italian fleet

At 8:30pm the first wave took off from the HMS Illustrious. The gunners weren't carried, their place being taken by a supplemental fuel tank to allow a two-man crew to fly the 340-mile roundtrip mission. By 9:00pm the twelve aircraft were all airborne and they set off for Taranto. Several of the Swordfish became separated from the main formation and had to make their own way to the target- one pilot arrived at Taranto ahead of the main force and had to await the rest of the aircraft- some references indicate that this may have alerted the Italians. Arriving over the harbor at 11:00pm, the strike force immediately came under fire. One of the Swordfish peeled off from the group and dropped a series of flares at 7,500 feet along the eastern perimeter of Mar Grande, the outer harbor. A second Swordfish followed suit, illuminating the area for the rest of the strike force. Lt. Commander K. Williamson, the CO of No. 815 Squadron, made the first torpedo run against the battleship Conte di Cavour, blowing a hole in the side of the ship but getting shot down in the process. Two more Swordfish that accompanied Williamson then pressed their attack against the battleship Andrea Doria, which was unsuccessful. The last group of the first wave attacked two cruisers and four destroyers as well in Mar Piccolo, the inner harbor. The Swordfish's agility paid dividends as the seemingly archaic aircraft managed to weave around the barrage balloons and jink hard to throw off the anti-aircraft fire.

HMS Illustrious with a Swordfish on the deck

With the first wave turning back for the Illustrious, the only aircraft shot down was that of their CO, Lt. Commander Williamson, who was taken prisoner along with his crewman. The second wave, under the lead of Lt. Commander J.W. Hale, the CO of No. 819 Squadron, had left the Illustrious thirty minutes after the first wave took off. Of the twelve Swordfish in the second wave, only eleven arrived at Taranto due to technical problem with the twelfth aircraft that forced it to return to the carrier. Arriving over the harbor at midnight, again the flare-dropping Swordfish lit up the area while the bomb and torpedo-armed aircraft set to work on the rest of the Italian battle fleet. Two aircraft attacked the battleship Littorio, but only one scored a hit. Another aircraft despite taking damage pressed an unsuccessful attack against the battleship Vittorio Veneto. The battleship Caio Duilio was also hit, and only one aircraft from the second wave was shot down, the two aircrew being killed. By 240am, the last of the Swordfish landed on the Illustrious. A third wave was planned the following night, but bad weather prevented a final blow to the Italian fleet.

The attack was a stunning success by an aircraft that was older and slower than many of its contemporaries. Just 11 torpedoes and 48 bombs managed to knock out half of the Italian battle fleet at Taranto and while the defenders fired off over 22,000 rounds, only two aircraft were shot down, quite an impressive feat! The attack followed by the Battle of Cape Spartivento two weeks later and the Battle of Cape Matapan in March 1941 consolidated the Royal Navy's control of the Mediterranean, hastening the defeat of the Axis. The planning staff of the Imperial Japanese Navy, at the time putting together the plans for the attack on Pearl Harbor, studied the British attack at Taranto carefully and managed on 7 December 1941 to knock out more battleships in the process, but unlike the Mediterranean, the attack failed to shift the balance of power in the Pacific as the US Navy had shifted its fleet emphasis to the aircraft carrier as the new capital ship.

Source: International Air Power Review, Volume 27, Winter 2010/11. "Warplane Classic- Fairey Swordfish- the Fleet Air Arm's enigmatic warrior" by Allan Laws, p125-129.

British Defenses Against the Summer 1944 V-1 Bombardment

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Cutaway view of the Fiesler Fi 103, or V-1 "Buzz Bomb"

Within a week of the Allied landings on Normandy on 6 June 1944, the Germans initiated a new form of bombardment against London, launching ten of Hitler's "Revenge Weapon No.1" or Vergeltungswaffe 1- V-1 for short. Of the V-1s launched in the early morning darkness of 13 June, six suffered failures that prevented them from even reaching the English coast from launch sites at Pas de Calais. Four bombs made it into British airspace, three of them hit in open land causing no casualties. One of those four V-1s, though, hit Bethnal Green, 2 miles from the famous Tower Bridge (which was used as the nominal aiming point) where it killed six people and injured nine more. British intelligence had predicted history's first cruise missile bombardment for a year, but the opening salvoes were far smaller than what was feared. It took three days to resume the launches and by 16 June 244 V-1s had been fired at the British capital. Of those missiles, 153 crossed into British airspace and of those V-1s, 73 hit the London area causing widespread damage and civilian casualties.

German launcher crew prepare a V-1 on its firing ramp in France

In the three day lull following the first attack, the Royal Air Force and British Army swiftly deployed its defenses to southeast England. The first line of defense consisted of nine squadrons of Supermarine Spitfire and Hawker Tempest fighters as well as two squadrons of De Havilland Mosquito night fighters. The aircraft three lines of standing patrols, the first line 20 miles off the coast, the second line at the coast, and the third line 15 miles inland. Behind the fighter patrols came the gun zone made up of 192 heavy caliber AA guns and nearly 200 light-caliber guns in an area 20 miles deep. If a fighter pursued a V-1 into the gun zone, gunners were ordered to hold their fire to allow the fighter to complete its pursuit. Behind the gun zone on the southeast suburbs of London was the balloon zone made up of 480 barrage balloons. Over a quarter million mothers and children were evacuated out of London itself during the bombardment. Up to the end of June 1944, an average of 153 V-1s were fired at London. One-third failed or were shot down before crossing the English coast. Another one-third crashed or were shot down over southeastern England before reaching London. But that left a significant amount that managed to hit the London area.

By mid-July, the defenses were revised based on the experience so far. This time each defensive measure was given a predefined zone for unrestricted engagement of any flying targets. The British Army's AA gun batteries were increased to 412 heavy guns and nearly 600 light guns in a 65-mile long strip along the coast that allowed the gun-laying radars of the batteries a clear view over the English Channel. Fighter pilots were prohibited from crossing the new gun zone, knowing that the gun batteries had unrestricted rules of engagement. The fighter zones were now split into two, with an outer zone over the English Channel that stopped five miles from the coast where the gun zone began. The inner zone began at the rear of the gun zone along the coast and extended back to the barrage balloon zone in London. In less than a month the number of barrage balloons increased to over 2,000. With the new defensive layout, over one-half of incoming V-1s were stopped from reaching the capital. 2 August would be the heaviest bombardment day, with 316 V-1s launched from 38 launchers in Pas de Calais. Of that number, 107 would impact in London. On that day, the nominal aiming point for the V-1 batteries in France, the Tower Bridge, took a direct hit from a V-1.

A Spitfire pursues a V-1 at treetop height

By early August, the first Gloster Meteor jet fighter units were becoming operational and were tasked with V-1 interception. However, there were three developments that would vastly improve the British defenses, all technological wizardry courtesy of the United States. First was the SCR-584 gun laying radar that was the state of the art in 1940s radar technology and could lock onto targets instead of having to be manually directed by operators. A new device called the the Number 10 Predictor was the second device, it could exploit the improved fidelity from the SCR-584 to direct the AA fire more accurately. And the third bit of wizardry would also save many US Navy carriers and warships in the Pacific- proximity-fuzed AA shells that no longer needed a direct hit to bring down a target. With these three advances, the average V-1 engagement by a British Army gun battery only used a mere 156 rounds to bring down a V-1.

The last V-1 launched from Pas de Calais came on 1 September, by which point the launch sites were all overrun by British Army units on the breakout from the Normandy beaches. From that point on, the V-1s that hit London were delivered by air-launching which was less effective and more prone to interception. During the first phase of the bombardment from June to September 1944, until the British defenses received new radars and proximity-fuzed AA shells, the most effective defense was actually the Allied air attacks on the French rail system. V-1 launch sites often had to wait days before receiving new missiles to fire due to attacks on supply trains and the rail network itself. Throughout this first V-1 bombardment phase, the launchers at Pas de Calais never launched V-1s at their intended capacity.

The V-1's magnetic compass in the nose was enclosed in a wooden sphere

By far the most interesting defense that nearly got fielded in the summer of 1944 also came from the United States. Dr. Don Hare and his team at the Airborne Instruments Laboratory in New York were working on radio countermeasures systems when they were asked by the US government to assist in developing a counter to the V-1 attacks on London. Since the V-1 required no outside cues, it was invulnerable to jamming. Its direction guidance came via a magnetic compass in the nose that cued the master gyroscope that controlled the rudder. As the V-1 had to be simple to produce, it lacked any ailerons and its straight wing lacked any dihedral to provide stability. RAF pilots had already discovered a V-1 could be thrown off course and downed by forcing the bomb into a steep bank by tipping one wing. Dr. Hare's team reasoned that if a suitably strong magnetic field could be created, the magnetic compass could be tricked into cueing the master gyroscope to put the V-1 into a tight turn, thereby downing it. The American team's idea was to use existing railway lines that formed a loop around London 60 miles in circumference as a giant magnetic loop. By connecting specific rail lines in a giant circuit, it would take 1,000 amps of DC power to create a magnetic field over London that could confuse the V-1's autopilot. It was determined that 20 to 30 megawatts were needed which was within the capacity of a large commercial power station. Design work began on the needed equipment, but the "Mightiest Magnet" program ended when the launch sites in Pas de Calais were overrun by Allied forces.

Source: International Air Power Review, Volume 27, Winter 2010/11. "Pioneers & Prototypes- Vergeltungswaffe 1- Adolf Hitler's revenge weapon" by Dr. Alfred Price and P.G. Cooksley, p150-159.