29 December 2009

By 1958 the Soviet air defense network had improved considerably and unlike the CIA and their U-2 operations, the Strategic Air Command lacked any illusions of the survivability of their jet bombers at high altitude through those air defenses. As a result, SAC began developing plans for the strike missions to be carried out a low-levels in an effort to fly under the radars along the perimeter of the Soviet Union. In 1959, SAC in cooperation with the FAA announced the creation of seven low-level training routes that were dedicated to SAC bomber training- given the code name "Oil Burner", these routes were located in thinly populated areas of the United States and were 20 miles wide, up to 500 miles long and restricted to altitudes no higher than 1,000 AGL.

General LeMay, the chief of staff of SAC, had already had established 13 radar bomb scoring (RBS) sites at fixed locations across the United States that were used in the training and assessment of the perfomance of SAC bomber crews. The problem arose that these 13 sites became very well-known to SAC crews and became less-challenging within a relatively short period of time given SAC's intensive training regimens.

The solution was to create a series of mobile RBS units that traveled the country in specially-modified trains called the RBS Express. These mobile RBS units could set up on any railroad siding and in effect, set up a totally new training target for SAC crews.

SAC's 1st Combat Evaluation Group (1CEVG) had three squadrons assigned to it that were charge of the fixed RBS sites- the 10th, 11th, and 12th RBS Squadrons were each assigned a particular geographic area of the United States. Each RBS Squadron had about 7 to 8 detachments and when the RBS Express was created, each squadron got a train.

These trains were pulled by commercial locomotives contracted by the Strategic Air Command. Outside of the commercial locomotive used, there were 21 cars in each RBS train. Four cars were flatbed cars with radar tracking vans and equipment attached and the other 17 cars were support cars for the RBS detachment- one car was a generator car to provide power to the RBS equipment, two boxcars for radar equipment support and maintenance, a dining car, two day room cars (acting as office and personnel transport), several supply cars, four Pullman sleeper cars that acted as dormitories for the RBS personnel, and an administrative car for the detachment commander which was usually the last car in the train. A B-25 Mitchell also accompanied each RBS train to act as a radar calibration target once the unit was set up at a given location.

The trains were immaculately maintained, with the radar units painted white and the other cars painted gloss blue, each with the SAC shield on it. The undercarriages were painted black. Approximately 30 or so personnel went with each RBS Express deployment which could last anywhere from several weeks to as long as six months.

The first two RBS Express trains deployed in August 1961 and were pulled by Union Pacific locomotives. Until the miniaturization the radar equipment made them road-portable, the RBS Express covered the country along the Oil Burner training routes well in the early 1970s.

Source: Boeing's B-47 Stratojet by Alwyn T. Lloyd. Speciality Press, 2005, p154-156.

28 December 2009

Although the Bristol Type 167 Brabazon is often labeled as a "white elephant", the aircraft had many milestones for commercial aviation and set the foundation for bigger successes by the British aviation industry than is widely known. The Brabazon design first originated as a bomber design to meet the Air Staff specification B.8/41 which laid down the features and performance of a very large bomber similar in class to the Convair B-36 Peacemaker. B.8/41 asked for a range of 5,000 miles with a speed of 300mph capable of reaching Russia or Japan. Bristol's design had an all-up weight of 225,000 lbs and a 225-foot wingspan. The project never got pursued, though, as the RAF preferred increased production of the Avro Lancaster.

When Lord Brabazon convened his famous committee to determine the course of British commercial aviation post-war to compete with the Americans, the Bristol bomber design was adopted for the Type I role, that of a large trans-Atlantic airliner with an anticipated service date of 1948. It was christened Brabazon in honor of the committee chairman himself.

When work began at Bristol's Filton works, the runway was 2,000 feet too short and had to be extended for the anticipated flight test program of the Brabazon. Despite local protests and the need for Cabinet approval to start work on the runway, when completed along with a massive assembly hall, it became the longest runway in Europe.

There were four features in particular that were commercial aviation milestones in the design of the Brabazon. It was the first aircraft to be designed from the outset to have 100% fully-powered flying controls, the first commercial aircraft designed to have a high pressure hydraulic system (the higher the pressure, the lighter the hydraulic system), and the first aircraft to have electric engine controls (electric control of engine power and mixture would lay down the foundation for modern FADEC systems). But most significantly yet little known, the Brabazon was the first airliner to be designed with cabin pressurization and air conditioning, and that pressurization was set at 8'000 above sea level, the current standard for modern airliners.

By 1949 the Brabazon was still in flight test and the De Havilland Comet prototype had just flown and BOAC was already using the Boeing 377 Stratocruiser on the trans-Atlantic routes intended for the Brabazon. In 1953 the project was canceled (despite the design of the Brabazon Mk.2 which used Proteus turboprops instead of the Centaurus radials of the prototype), but the expertise gained by Bristol formed the foundation for the more successful Bristol Britannia and when Bristol became part of the British Aircraft Corporation in 1960, the Filton works and its long runway and large assembly hall would be used for the Concorde program.

Source: Airliner Classics, November 2009. "The Bristol Brabazon: White Elephant or Technological Marvel?" by Gerry Sweet, p53-58

27 December 2009

While the long rivalry between British Airways and British Caledonian Airways is well-known, from 1978 to 1986 the two bitter rivals actually partnered together with the British Airports Authority to operate a helicopter shuttle service to connect interline passengers between London Heathrow and London Gatwick. Initially utilizing a Sikorsky S-61N registered as G-LINK and "Gatwick Heathrow Airlink" titles, later on both British Airways Helicopters and BCal Helicopters provided back up helicopters.

At the time of the service launch on 9 June 1978, the helicopter flight took 25 minutes to connect the two airports with 28 passengers on each run. The first flight left Gatwick at 0710 and the last flight returned at 2010 hours- uniquely, G-LINK was owned by the British Airports Authority, based at Gatwick with British Caledonian flight and cabin crews, administration and ticketing but the helicopter was maintained at British Airways Helicopters' base at Gatwick.

By the time of the route's last flight on 6 February 1986, flight times were only 12 minutes and 24 passengers were taken on each flight, a reduction of four seats due to the need for baggage space. A one way flight cost £21. The flights would be boarded with the rotors already turning and as such, the "Caledonian Girls" that were part of the cabin crew had lead weights sewn into the hemlines of their skirts to keep them from flying up in the rotor downwash.

The end of the unique service came at the instruction of the British government once the M25 freeway was completed.

Source: Aircraft, December 2009. "Gone But Not Forgotten...British Caledonian" by Bruce Hales-Dutton. Box feature "The Airlink Service", p41.

26 December 2009

The Saab 210 Lilldraken

It was in 1949 that a memo from the Swedish KFF (Royal Swedish Aircraft Board) that the specifications that resulted in the Saab J35 Draken began to take shape. Considering that the J29 Tunnan had made its maiden flight just a year earlier, the KFF asked for a supersonic interceptor. As supersonic flight was still a relative unknown in those days, in January 1950 several Saab engineers proposed a flying test aircraft christened Sound Barrier. As there was still unease about reliance on wind tunnel testing, it was hoped that the Sound Barrier test aircraft would go supersonic by 1952 and assist the aerodynamics layout work on the proposed J35.

Erik Bratt, the head of the J35 program, proposed use of a tailless delta as meeting the KFF's specifications and he assigned nine Saab engineers the task of building a subscale flying test bed to prove the planned double delta layout of the J35 Draken. Though less ambitious than the planned Sound Barrier aircraft, the small group of Saab engineers produced the Saab Model 210 "Lilldraken" in just nine months. Cost considerations meant that supersonic testing would have to be done on the full-scale Draken prototypes. Powered by a small 881-lb thrust Armstrong Siddeley Adder jet engine that was used on the Jindvik target drone as a pure jet derivative of the Mamba turboprop, it was barely enough to get the Lilldraken airborne and the Saab 210 would be limited to low-speed testing.

The layout of the Saab 210 alarmed the general staff of the KFF. One influential member, General Jacobsson, is said to have remarked "What the hell is this, an aircraft must have a damned tail, for heaven's sake!" To satisfy the KFF, Saab's drawings of the J35 included a small tail but there was never an intent to fit such a tail on the J35.

To assist Saab before the Model 210's first flight, a swing-line Draken powered by pulse jet engine was tested and the 1/7 scale models showed that of all the layouts being considered, General Jacobsson's tailed delta was the most unstable!

The Model 210 Lilldraken made its first flight on 20 December 1951. Despite the anemic performance of the test aircraft, Ollie Krinker, one of Saab's test pilots, gave a sparkling flight demo over Stockholm in July 1956 to mark the city's 700th anniversary. Modifications to the nose and intakes were made to be more representative of the J35 Draken's layout and after over 1,000 flights it was retired to the Flygvapen Museum at Linkoping.

Source: International Air Power Review, Volume Five (Summer 2002). AIRtime Publishing, 2002. "Warplane Classic: Saab 35 Draken, Sweden's double-delta dragon" by Bo Widfeldt and Stefan Wembrand, p126-131.

25 December 2009

The first pilots of the American Volunteer Group (AVG) arrived in the China-Burma-India combat theater in September of 1941, disembarking ships in Rangoon, Burma. Getting up to speed with General Claire Chennault's rigorous training program while battling supply problems sapped morale of the first Flying Tigers. While the main force of the AVG was based in Kumming, China, the Japanese occupation of French Indochina and subsequent arrival of Japanese forces in Thailand meant that the 750-mile Burma Road from Rangoon's port to Kumming was China's only real supply line to the outside world in their fight against the Japanese.

As a result, Chennault dispatched his 3rd Pursuit Squadron of the AVG back to Rangoon to support the small RAF Brewster Buffalo force of No. 67 Squadron already stationed there to defend the port city. On 23 December 1941 the Flying Tigers of the 3rd Pursuit Squadron went into action repelling a Japanese bombing raid on Rangoon- the AVG shot down 10 bombers and one fighter with a loss of four planes and two pilots. The Royal Air Force shot down three fighters but lost five Buffalos and their pilots.

Angered by their losses at what they thought were amateurs on the 23rd, a larger Japanese force of 60 bombers and 20 escorting fighters attacked on Christmas Day. The 3rd Pursuit Squadron mustered 13 Tomahawks (the most any AVG squadron had managed to do at once) and along with the RAF Buffalo fighters, their charged head-first into the large formation as it approached Rangoon.

The RAF shot down eight bombers but lost another five fighters and the rest of their Buffalo force was destroyed on the ground. The Flying Tigers, though, claimed 24 to 28 bombers (postwar research indicates that 10 were shot down, and another eight ditched in the sea off the coast of the city) with no losses to their own pilots. The 1941 Christmas Day air battle over Rangoon was the first time the Japanese faced serious aerial opposition and in post war interviews, the Japanese pilots reported being impressed with the aggressiveness and persistence of the Flying Tigers.

It marked a turn-around for the AVG and morale soared. Western newspapers reported on the success of the Flying Tigers at a time when the Allies were facing defeats on multiple fronts in Europe, the Mediterranean, and the Pacific. The Japanese Army Air Force had to adopt diversionary strikes which diluted the effectiveness of the main striking body. By the end of the month, the 3rd Pursuit Squadron was relieved by the AVG's 2nd Pursuit Squadron and they took an even more aggressive approach, raiding Japanese airfields in Thailand.

Source: Wings of Fame, Volume 9. Aerospace Publishing/AIRtime Publishing, 1997. "American Volunteer Group- The 'Flying Tigers'" by Robert F. Dorr, p6-13.

24 December 2009

On this Christmas Eve, I tried to go through my books to figure out what would be an appropriate bit of aviation trivia for a night like tonight. As we approach the end of the first decade of the 21st Century, we as a nation, as a society, have seen tremendous and often chaotic changes in the past decade. From a financial crisis, wars abroad, and, from the perspective an someone who has long found enjoyment and fascination in aviation, to have seen what I have long loved used as weapon of terror in 2001, it reminded me in some ways of a similar chaotic period in our history- the late 1960s.

The Christmas Eve broadcast of Apollo 8 from lunar orbit is still the most-watched television broadcast in history and though I have seen it many times, it still gives me goosebumps as I listen to the voices of Frank Borman, Jim Lovell, and William Anders read from the Book of Genesis as the first human beings to travel beyond Earth orbit.

It was a fitting way to end what was one of the most traumatic years in our nation's history- the Tet Offensive in Vietnam, the assassinations of Martin Luther King, Jr, and Bobby Kennedy, and the riots at the DNC Convention in Chicago. To think that at that singular moment, a short set of ancient biblical verses read by three intrepid explorers viewing our blue planet against the harsh backdrop of deep space, would, even for just a moment, give every person who heard it pause to think of themselves not in terms of race, nationality, political affiliation or religion, but as citizens of all of humanity.

I didn't realize that there was an Emmy Award for that broadcast. For me, though, that is only the least of honors that could ever be bestowed on a moment that always ties together my love of aviation with all that is greater than any one of us can ever be.

A very Merry Christmas and a Happy Prosperous New Year to all my readers, my fans, and the collectors of my artwork!

23 December 2009

Although the USAAF used the De Havilland Mosquito PR.Mk XVI primarily in the photo-reconnaissance role in Europe, there were two lesser-known types of missions flown by the two squadrons of the 25th Bomb Group at were equipped with the Mosquito.

"Mickey ships" were specially-modified Mosquitos that were equipped with the H2X radar set used on the B-17 Flying Fortress. A bulged nose housing held the H2X scanner with the amplifier and electronics crammed in the nose and bomb bay. The radar scope itself, though, was in the rear fuselage. Before the approach to the target, the observer had to climb over the equipment in the bomb bay and into the rear fuselage where he either photographed the radar display or filmed it with a movie camera. The purpose of the "Mickey ships" was to get radar navigation images of the approaches to German targets. These images would be then correlated with maps to provide the B-17 navigators with poor-weather approaches to high-priority targets in Germany.

The H2X drew a current that often was more than the electrical system of the Mosquito and the equipment often arced, aborting the mission. If bailout was necessary, the observer had to climb over the equipment and jump out the bomb bay- assuming of course, the crew remembered to open the bay doors.

The other lesser-known USAAF Mosquito mission was code-named "Red Stocking" and were done in conjunction with the OSS, the CIA's predecessor. Equipped the special equipment, the Red Stocking Mosquito flights flew deep into Germany to detect and record UHF transmissions from OSS agents in the field. The bomb bay was modified to take the receiving equipment, an oxygen system, and accommodations for the observer who operated the receiving set.

The OSS agent carried what was called the "Joan-Eleanor" device, which was a four-pound radio set that beamed the agent's reports on a very narrow beam that was nearly impossible for German counterintelligence to detect via triangulation. A Red Stocking Mosquito would fly overhead a predetermined point at a particular time so the OSS agent could point the Joan-Eleanor antenna in the right direction. The missions were flown singly and at high altitude, often at night. In one mission, a Red Stocking flight circled over Berlin at over 30,000 feet to communicate with several OSS agents in the city.

Source: Wings of Fame, Volume 18. AIRtime Publishing, 2000, "de Havilland DH.98 Mosquito (Bomber and PR Variants" by Martin Bowman, p84-87.

21 December 2009

Similar to the trends in the 1950s in the United States, when the first Russian air-to-air missiles were deployed, the Soviet defense industry shifted towards the development of weapons systems that comprised of not just the interceptor aircraft but also beam-riding radar-guided missiles and the fire control radar. While several design bureaus (OKBs) in the 1950s were working on weapon systems, it was OKB Lavochkin that was the first to propose the weapons system concept with what became the La-250 "Anaconda" in 1953.

The idea behind a weapons system was the each component would be optimized for each other, resulting in a more effective supersonic interceptor. Lavochkin proposed what would be designated the K-15 system which comprised of the La-250 aircraft, the K-15U radar system, the izdeliye ("article") 275 semi-active radar homing air-to-air missile as well as associated GCI equipment. The K-15 weapons system involved 11 manufacturing divisions of the Soviet aerospace industry, six other OKBs, and the Central Aerodynamics and Hydrodynamics Institute (TsAGI), all supervised and integrated by OKB Lavochkin.

Another of the Lavochkin La-250's firsts was the use of an analogue "iron bird" simulator to test the flight control system on the ground before the first flights of the aircraft. The simulator would prove to be instrumental in determining that the loss of the prototype aircraft could have been prevented with a better flight control system. Ultimately, the loss of the first La-250 prototype was only the beginning of problems with the K-15 weapons system that ultimately led to the cancellation of the entire program in July 1959 as the requirements proved to not match the technology of the day.

The La-250 was the last aircraft to be produced by OKB Lavochkin but the effort wasn't in vain- it was the first time in the Soviet Union that research institutes like the legendary TsAGI worked in close cooperation with the design bureaus and manufacturing complexes and it proved the feasibility of such a comprehensive approach. Lavochkin's expertise benefitted OKB Tupolev which introduced the large Tu-128 "Fiddler" interceptor in 1961 which remained in operational service for many years.

Source: Wings of Fame, Volume 19. AIRtime Publishing, 2000, "Beyond the Frontiers: The Lavochkin La-250 Anaconda" by Yefim Gordon, p150-157.

20 December 2009

The last Avro Canada CF-100 Canuck flight took place on 28 June 1982, but it wasn't with an operational role. Since 1967, Pratt & Whitney Canada had operated a CF-100 on loan from the Canadian Armed Forces to serve as an engine testbed for the JT15D small turbofan. PWC needed a two seat aircraft (the rear seat of the CF-100 being occupied by a flight test engineer) and one with sufficient ground clearance for an underslung nacelle for the JT15D engine.

The CF-100's ability to cruise up to Mach 0.8 as high as 48,000 feet made it ideal for testing an engine destined for business jets. The aircraft arrived at PWC's St-Hubert test center in November 1967 for conversion. The first flight took place on 22 July 1968 with the first flight with a JT15D engine on 14 August 1968. The first air start of the JT15D took place less than two weeks later on 22 August 1968.

The loan of the CF-100 got extended several times as PWC tested different versions of the JT15D engine, ultimately making over 400 flights totalling 1,017.6 flying hours with the test engines.

The JT15D engine is unique in that it has a centrifugal high pressure compressor which was common on early generation jet engines. However, in the JT15D it made the engine more compact and simpler in terms of complexity and parts as opposed to what it would have been had it used a traditional axial-flow compressor. The JT15D first went into use on the Cessna Citation 500 (later rebranded Citation I) and has been used on the Hawker Beechjet/T-1A Jayhawk, Aerospatiale Corvette, and the Citation II, Ultra, and Citation V as well as the military T-47 and UC-35 versions of the Citation.

Source: Wings of Fame, Volume 18. AIRtime Publishing, 2000, "Avro Canada CF-100 Variant and Operator Briefing" by Jeff Rankin-Lowe, p114, 133.

19 December 2009

While BAe Nimrod maritime patrol aircraft were deployed to the South Atlantic in 1982 Falklands War to protect the British naval task force from Argentine surface vessels and submarines, the Nimrod also had two little-known roles during that conflict. The first role was that of "the largest fighter aircraft" when AIM-9 Sidewinder missiles were cleared for firing from underwing hardpoints with the intent of targeting the Argentinian's Boeing 707s that were being used to shadow the British naval task force. In addition, the AGM-84 Harpoon missile was cleared for use on the Nimrod in the anti-shipping role, though neither the Sidewinder or the Harpoon were fired in anger during the conflict.

The more obscure role of the Nimrod during the Falklands was that as a back up for the Avro Vulcan "Black Buck" bombing missions. The long range of the Nimrod made it a natural for the overland bombing role and a rudimentary bombsight was configured for use by the co-pilot to drop either 1000 lb air-retarded bombs or BL755 cluster bombs. A trial drop was even conducted at the Garvie Island range in Scotland.

Source: Air Forces Monthly, December 2009. "More Than A Sub-Hunter!" by Jon Lake, 32-35.

18 December 2009

With the expansion in the numbers of jet-powered military aircraft in the USAF as well as the other branches of the military in the 1950s, concerns were raised about the flow control of high-performance jet aircraft with slower civilian piston traffic in the airways system. The Strategic Air Command alone in 1955 operated over a thousand jet aircraft. The USAF's Airways & Air Communications Service, in charge of all Air Force navigation and communications facilities, expressed concern that without the development of new control procedures, airways and navaids, it would be like inadequate highways being paired with modern automobiles.

As the Civil Aeronautics Administration (the FAA's predecessor) had no jet aircraft capable of performing the flight check role, the task was assigned the USAF AACS. In what became known as the High Altitude Project, both CAA and USAF navaids and procedures were to be evaluated using Boeing B-47 Stratojets. The objectives of the project were to evaluate ATC procedures, determine the capabilities of navaids at high speeds between 20,000 to 40,000 feet and develop new high altitude control procedures. The Douglas C-47s and C-54s then operated by the CAA would conduct the low altitude flight checks as they had been doing since the Second World War.

Between 1955 and 1962 B-47s based at Tinker AFB, Oklahoma, were fitted out with the necessary flight check equipment for the High Altitude Project. In 1963, Lockheed C-140 Jetstars would replace the Stratojets in the flight check role.

Two sets of navigational charts resulted from the High Altitude Project, an updated set of low-altitude charts and procedures for altitudes up to 18,000 feet and a jet navigation set of charts and procedures for altitudes from 18,000 feet to 40,000 feet. In addition, a new set of airfield approach plates suitable for jet aircraft were developed.

Source: Boeing's B-47 Stratojet by Alwyn T. Lloyd. Speciality Press, 2005, p182-183

16 December 2009

It wasn't until summer of 1965 that the USAF's Air Rescue Service finally had a helicopter capable of sustained combat search and rescue operations in the expanding war in Vietnam. Previous helicopter rescue efforts relied on either the short-ranged Kaman HH-43 Husky or Air America's Sikorsky UH-34s, both of which weren't well-suited to the role demanded by the ARS. The transport version of the Sikorsky SH-3 Sea King, the CH-3C, had an aft loading ramp and boasted significantly better performance and load-carrying capability than anything else in-theater for CSAR. Due to their green and tan camouflage, the CH-3Cs got the nickname "Jolly Green Giant" which became their radio callsign, JOLLY GREEN.

But the Air Rescue Service wanted more out of the CH-3C despite the leap it presented. The USAF and Sikorsky developed a modified CH-3C version custom-tailored to combat search and rescue designated the HH-3E that had more powerful engines, titanium armor plating, gun mounts for M60s or GAU-2B Miniguns, and most importantly, more fuel. Not only did the HH-3E carry 200 more gallons of fuel over the CH-3C, but the landing gear sponsons were also plumbed to carry 200-gallon drop tanks. But the great technological and operational leap would be the ARS's desire to be able to refuel the HH-3E in midair.

No helicopter had been refueled in midair- the USAF had standardized on the Boeing flying boom which would have been impossible to use on a helicopter in addition to the speed mismatch between the KC-135 Stratotanker and the HH-3E. It was decided to use the Navy's probe and drogue method, but the slipstream of the tanker and rotor downwash made airborne refueling still tricky.

Sikorsky's engineers developed a telescoping refueling probe that when fully extended, put the tip of the probe just outside the rotor downwash. The USAF borrowed a US Marine Corps KC-130 Hercules for flight trials at Wright-Patterson AFB in Ohio. Pilots found that the boat-like hull of the HH-3E could in effect "float" on the Hercules' slipstream. Tests were completed in 1966 and Lockheed was contracted to convert 11 C-13oHs into HC-130 aerial tankers that also functioned as airborne controllers for any rescue operation. The first HC-130Ps arrived in SE Asia in November 1966 to join up with the HH-3Es already in theater since late 1965 (with the CH-3Cs being phased out by January 1966).

The Sikorsky HH-3E "Jolly Green Giant" would be the world's first helicopter equipped for aerial refueling, giving USAF combat search and rescue a quantum leap in capability at a time when the war effort in Vietnam was expanding daily.

Source: Wings of Fame, Volume 14. AIRtime Publishing, 1999, "'That others may live': USAF Search and Rescue, Part Two, 1958-1975 - The war in Southeast Asia" by Larry Davis, p22-25.

13 December 2009

Despite both the Northrop YB-49 and the B-2 Spirit stealth bomber being of flying wing configuration and even sharing the same wingspan, the YB-49 was never a starting point in the B-2 design process. Early B-2 studies did feature a flying wing as from the beginning Northrop's engineers goal was a configuration with a very low radar cross section and from that basis, that made a flying wing configuration favorable. The engineers had determined that a flying wing was the optimum configuration for getting low radar cross section characteristics in a large aircraft.

According to Irv Waaland, one of the founding engineers who formed the initial design team for the B-2 Spirit in the late 1970s, what the YB-49 provided the B-2 design team was a "feasibility establishment"- the first B-2 configuration studies had vertical tails as part of the flying wing design. But in an era of powered controls and digital flight computers, the B-2 team realized that they could get rid of the vertical tails (which dramatically reduced the RCS of the B-2) as their study of the YB-49 program showed that it had small vestigial vertical fins (smaller than what the initial B-2 configuration studies had, actually) and that was in a day before digital flight control technology.

Because of the unique flying characteristics of the flying wing configuration, Irv Waaland and his team of engineers extensively interviewed the engineers from the YB-49 like William Sears and Irv Ashkenas as well as the chief test pilot in those days, Max Stanley (he had flown the XB-35, the prop-driven antecedent of the YB-49, on its maiden flight).

In fact, Max Stanley was cleared for the B-2 program which was one of the most classified programs at the time. He often flew the flight control simulator and provided input to the design team which saved them extensive time and effort. In one area in particular, the wind tunnel studies of the B-2 suggested that the ground effect would make it difficult to land the B-2 and the engineers were preparing to create a second flight control configuration for the B-2's flight computers that would kick in on landing to overcome this perceived issue.

When this issue was brought to Max Stanley's attention, he had indicated that there were similar fears about the XB-35/YB-49 and that as his impressions in the B-2 sim were that it flew very similarly to the YB-49, he assured the engineers that the B-2 would land just fine. He had convinced the design team to leave out the alternate flight control configuration and sure enough, when the B-2 made its maiden flight in July of 1989, the stealth bomber landed just as Max Stanley had predicted.

Source: Northrop Flying Wings: A History of Jack Northrop's Visionary Aircraft by Garry R. Pape with John M. Campbell. Schiffer Publishing, 1995, p201-204.

10 December 2009

One of the more unusual but little known Supermarine Spitfire variants was the Mk.IIC (later redesignated ASR.II) of which there were fifty used in the Second World War. The ASR.II were specialist air-sea rescue Spitfires converted from retired Spitfire Mk.IIs when production switched over the more powerful and capable Mk.V. The conversions took place from 1942 to 1943 and involved removal of the armament and chutes were added in the lower fuselage aft of the cockpit that could drop rescue packs that consisted of a dinghy and rations, smoke bombs to mark the location of downed pilots and flares. Additional packs could be carried on underwing racks as well.

In addition to these provisions, the Rolls-Royce Merlin XII that was standard for the Mk.II variant was swapped out with a more powerful 1,460-horsepower Merlin XX that had a 2-speed/1-stage supercharger (the Merlin XII developed 1,175-horsepower and had a 1-speed/1-stage supercharger).

The Spitfire ASR.II served with five search and rescue squadrons that operated over the Thames Estuary and the English Channel during the war.

Source: Spitfire by Stewart Wilson, Sovereign Series #1. Aerospace Publications, 1999, p28.

09 December 2009

Following the Second World War, engine maker Pratt and Whitney found itself lagging behind in jet engine development as the wartime and immediate postwar demand for its piston engines was an all-time high. Nearly 50% of all engines built for US aircraft during World War II were Pratt and Whitney engines. The company's head, the legendary Frederick Rentschler (who quite literally built Pratt and Whitney into the dominant engine company it had become during World War II after leaving Wright Aeronautical in 1924), directed his head of engineering, Leonard Hobbs, to begin efforts to catch up in jet engine development.

Rentschler's goal was to catch up with the competition like General Electric, Westinghouse, and Allision by 1950 and become the dominant jet engine maker. Hobbs and his boss, however, had trouble finding an aircraft design tailored to their proposed engine designs. Gaining valuable experience by license-building the Rolls-Royce Nene turbojet for the Grumman F9F Panther as the J42, they found the USAF was in the midst of deciding between a turboprop and a turbojet for its new long range bomber that would become the Boeing B-52 Stratofortress.

Hobbs' initial design was for a larger turboprop than the Wright T35 being considered. Designated the T45, it combined the gearbox of a turboprop with the compressor/turbine core of one of their own jet engine designs. To achieve the necessary specific fuel consumption, Hobbs increased the pressure ratio to an unheard of 8:1. However, this would make the engine difficult to start and sluggish in acceleration. Hobbs' technological leap was to make the engine dual-spooled, with the front of the engine running at a slower speed than the back of the engine which ran at a faster speed. By optimizing the speeds of the different sections of the engine core, the engine would run not only more efficiently, but could generate more thrust than single spool engines of the day could ever create.

When Boeing's bomber design grew in size, the USAF decided only a turbojet could meet the needs of the design and Pratt and Whitney abandoned the T45 and the jet engine core of the turboprop became the J57 engine. With its compressor ratio increased to 12:1 (which was over double the industry standard of the day), the engine ran for the first time in January 1950 and would become the first jet engine to produce more the 10,000 lbs of thrust.

The J57 would be used in many fighter aircraft including the North American F-100 Super Sabre, Vought F8U Crusader, Douglas F4D Skyray, Convair F-102 Delta Dagger and McDonnell F-101 Voodoo. It also powered the Boeing B-52 Stratofortress and the KC-135 Stratotanker. The civilian JT3 version would be used on the Boeing 707 and Douglas DC-8 jetliners. The J57 and the JT3, would become the dominant large aircraft engine as well as fighter engine for a good part of the 1950s and 1960s, realizing Frederick Rentschler's goal set in 1945.

Source: US Naval Air Superiority: Development of Shipborne Jet Fighters 1943-1962 by Tommy H. Thomason. Specialty Press, 2007, 151-152.

08 December 2009

The Complicated Path to Nighttime Interdiction in Vietnam

Project Black Spot NC-123K

When it was realized that interdiction of the nighttime movement of supplies along the Ho Chi Minh Trail was the best way to stop the flow of materiel to the Vietcong in the South, the USAF in February 1966 established Operation Shed Light to pool together research efforts and various subprojects into improving the night fighting capabilities of the USAF in Vietnam. Projects Red Sea and Lonesome Tiger belonged to a series of experiments using Douglas AC-47s and Douglas B-26K Invaders equipped with FLIR. Tropic Moon I concerned the use of a low-light television camera (LLTV) to seek out targets at night. A Douglas A-1E Skyraider flew with the Tropic Moon I package, becoming the first aircraft to use a self-contained night attack system in combat.

Tropic Moon II was the modification of three Martin B-57 Canberras into night attack configuration and Tropic Moon III was a further development that involved the modification of 16 Martin B-57Gs with more sophisticated attack avionics.

Briteye was a new battlefield flare that could be used to illuminate the target area and that led to the BIAS (Battlefield Illumination Airborne System) that used 28 xenon arc lamps in a Fairchild C-123K's cargo compartment to produce daylight conditions in an area 2 miles wide from 12,000 feet. Also used on the Lockheed C-130 Hercules, unfortunately BIAS gave enemy anti-aircraft gunners a nice bright target at night.

Operation Shed Light identified the need that a night attack aircraft be completely self-contained and autonomous but had to be large enough to carry the heavy electronics of the day. Initial aircraft candidates were the McDonnell F-4 Phantom, Martin B-57 and Grumman OV-1 Mohawk. There were too few B-57s to spare, the F-4s were already heavily committed and the Air Force didn't want to stoke interservice rivalries by selecting the Army's OV-1 Mohawk. The General Dynamic F-111 was considered the most ideal, but at the time the aircraft wasn't yet operational so the study group next looked at the North American OV-10 Bronco, but it didn't have the load carrying capability.

The most ideal aircraft at the time was considered to the be the Navy's Grumman S-2 Tracker ASW aircraft- it already had a large weapons bay, it was twin-engined, could operate at low level as that was its natural regime when hunting submarines, and it also had good endurance and had a built-in search light. The aircraft was to have been designated the AS-2D and eventually the AS-2D had to be cancelled in 1968 due to difficulties with funding the modifications and problems in getting S-2 Trackers from the US Navy.

Desperate for a platform the Shed Light group turned to a low-level project initiated in 1965 called Project Black Spot which was to use a modified Fairchild C-123K as a self-contained night attack aircraft that instead of bombs or guns, dropped cluster submunitions from chutes in the fuselage. The first Black Spot aircraft, designated NC-123K, began evaluations at Eglin AFB in Florida in 1968 and after some initial trials in Korea to see if its night vision equipment could spot North Korean infiltration teams using boats, debuted in Vietnam operationally in November 1968.

Source: Gunships: The Story of Spooky, Shadow, Stinger and Spectre by Wayne Mutza. Specialty Press, 2009, p161-165.

07 December 2009

In the late 1940s the Navy's BuAer was responsible for the development of airborne countermeasures systems and the idea of spraying chemicals into the air to produce large radar echoes as a "liquid chaff" attracted significant effort. Iron pentacarbonyl, a straw-colored liquid used in the cores of electrical transformers and in the magnetic coils of certain radio and TV coils, was the subject to much experimentation in 1948. Upon contact with the air, iron pentacarbonyl undergoes a chemical reaction which results in a cloud of iron oxide particles which the Navy surmised might block radar beams. Initial experiments involved spraying the chemical from a boat, but results were inconclusive.

On 10 November 1948 a Curtiss SB2C Helldiver was used to spray 60 gallons of iron pentacarbonyl over Chesapeake Bay while flying at 130 knots and 500 feet altitude. Along the shoreline, the Navy set up various radar systems at six different locations operating at different wavelengths from 200 to 9100 MHz to track the Helldiver as it sprayed the chemical.

There was a brief signal at 700 MHz, but for the most part the radars saw nothing. Visually, however, it was spectacular according to eyewitnesses to the tests. As the clear chemical came in contact with the air, it turned into a black vapor which several feet behind the aircraft then burst into a brilliant flame that varied between dark red and light orange that extended past the Helldiver for approximately 10 plane lengths and persisted for several seconds. As the flame darkened to a red color, the cloud turned black again and then a rust color before dispersing.

The pilot during the tests refused to fly further missions to test the iron pentacarbonyl and the Navy ended its tests with no indication that it blocked radar beams. However, for days after that November tests, reports came from different communities along Chesapeake Bay of some sort of "burning rain" that damaged paint on cars, discolored houses, and allegedly damaged clothing on clotheslines. With the Pentagon and the Navy quiet, the state of Maryland conducted an investigation and concluded that the culprit were rotting skunk cabbages on the bay shore that exuded sulphur dioxide that reacted with water vapor to produce sulphuric acid vapor (acid rain).

Naturally, the Navy didn't feel the need to correct the conclusions of the state investigation and no further tests of liquid radar countermeasures were attempted again.

Source: The History of U.S. Electronic Warfare, Volume II- The Renaissance Years, 1946-1964 by Alfred Price. The Association of Old Crows/Port City Press, 1989, p24-25.

06 December 2009

Although the Martin Model 162 is better known as the PBM Mariner flying boat, its experimental antecedent was the Model 162A which was a three-eighths scale flying testbed of the PBM Mariner's hull and aerodynamic layout. Built from wood framing with aluminum skin, the Model 162A is believed to be the first subscale flying model built of a production aircraft in the United States. Due to its size and single pilot, it was nicknamed the "Tadpole Clipper" and began its flight tests in support of the PBM Mariner program in December 1937.

As there were no radial engines in existence that could fit the small scaled cowlings of the Tadpole Clipper, a single 120-horsepower four-cylinder inverted-vee piston engine inside the fuselage drove the twin props in the nacelles via drive belts. The Tadpole Clipper survived its flight test program and was restored by the Smithsonian Air & Space Museum and is on permanent loan and display in the Decker Gallery of the Baltimore Museum of Industry.

Source: Wings of Fame, Volume 7, Aerospace Publishing 1997. "Variant Briefing: Martin Flying Boats- Mariner, Mars, and Marlin Variants" by Robert F. Dorr, p122.

04 December 2009

Prior to the arrival of the Lockheed U-2 in Europe in 1956, reconnaissance overflights were entrusted to a small unit of specially-modified North American F-100 Super Sabres codenamed "Slick Chick" but designated RF-100As. The Slick Chick birds were modified to carry five cameras in an enlarged underfuselage where the F-100s gun bay was located. The large central air intake duct of the F-100 made installing a viewfinder for the pilot a challenge- the solution ended up being mirror at the bottom of the air duct that picked up the ground image and reflected it to a glass window at the top of the air duct that in turn led to the pilot's camera viewfinder.

The RF-100A could carry up to four external fuel tanks as some of the photo runs were made on afterburner at altitudes of approximately 50,000 feet. With four fuel tanks, however, the RF-100A had marginal stability with a yawing motion and increased elevator sensitivity due to the significant shift in the center of gravity. On takeoff, the four-tank configuration was very sensitive in pitch and takeoffs were prone to what we now know today as pilot-induced oscillation. Amongst the Slick Chick pilots, PIO was called the "JC maneuver" as all a pilot could say after getting out of that state was "Jesus Christ!"

Between 1955 and 1956 it is believed that six Slick Chick missions were flown over targets in Hungary, Czechoslovakia, and East Germany.

Source: FlyPast, December 2009, No. 341. "Through the Curtain" by Doug Gordon, p24-27.

03 December 2009

From 1943 to 1947 the Swedish airline Svensk Intercontinental Lufttrafik AB (SILA- Swedish Intercontinental Air Traffic Ltd.) had the unique distinction of operating the only Boeing B-17 Flying Fortresses to be used as airliners. When SILA was established in 1943 for the purpose of developing international air routes, negotiations had been dragging along for airliners from either Great Britain or the United States. On 24 July 1943 the first of an eventual 69 USAAF B-17 bombers landed in Sweden, usually due to battle damage on missions over occupied Europe.

As the numbers of bombers increased, negotiations began with the United States to legally transfer some of these aircraft for use as airliners. With the assistance of the American air attache in Stockholm, Felix Hardison, ten B-17s with spares were transferred to the Swedish government and Saab began a conversion program to transform the B-17 into an airliner.

All military equipment was removed from the aircraft with the nose section lengthened to be used as a cargo compartment. The bomb bay was also converted into a cargo bay and in the aft fuselage two passenger cabins were installed with sound proofing and amenities suitable for long distance passenger transport. Six seats were in the first cabin and eight seats were in the rearmost cabin with the lavatory sharing space with the retraction gear of the tailwheel. The conversion took five months and in Swedish service the converted bombers were designated F17 in honor of the US air attache, Felix Hardison.

No SILA F17s were lost during the Second World War, though one did crash after the war in December 1945. Two of the seven aircraft converted were transferred to Danish Airlines, and one of those aircraft operated with the Danish Air Force as a survey aircraft over Greenland. That particular F17 was restored back to its original configuration as the B-17G "Shoo Shoo Baby" and is on display at the National Museum of the USAF in Dayton, Ohio.

Source: Aeroplane Monthly, November 2009. "From Bombs to Ball-Bearings" by Jan Forsgren, p14-17.

02 December 2009

In 1944 the USAAF launched the MX-472 project to examine possible solutions to giving long range intercontinental bombers like the Convair B-36 the necessary fighter escort. As air-to-air refueling wasn't in common use and there were concerns about pilot fatigue on a mission that might last up to 30 hours, the USAAF decided in 1944 that the bomber itself would have to carry its own "parasite" fighter. However, the Army Air Forces found that none of the established manufacturers of the day were interested in the project.

In St. Louis, the USAAF approached Curtiss-Wright but found them less than receptive, in the words of one engineer at Curtiss "they didn't need the aggravation". However, across town, a more obscure company led by James S. McDonnell was willing to take a risk. Having only built Fairchild AT-21 Gunner trainers under license and the failed XP-67 Moonbat fighter, McDonnell had little to lose. However, in negotiating with the Army, James McDonnell would only proceed with the parasite fighter project only if the Army would give him a contract for a conventional jet fighter in exchange. After much discussion, the Army relented and McDonnell began work on the McDonnell Model 27 which would become the XF-85 Goblin in the postwar period.

McDonnell hired away one of Curtiss-Wright's most promising designers, Herman Barkey to work on the Model 27. Having had key roles in the Curtiss Helldiver and C-46 Commando aircraft, Barkey would go on to lead roles in not only the XF-85 but also on the F2H Banshee, F3H Demon, F-4 Phantom II and the aircraft that was given to McDonnell as a quid pro quo for the Goblin project- the XF-88.

While it performed well in testing and evaluation, the nascent US Air Force changed to specifications that led to the XF-88 leading to it not being adopted by the service as previously agreed with James McDonnell. However, Barkey would further develop the XF-88 design to a larger and more capable aircraft as the F-101 Voodoo.

Source: Wings of Fame, Volume 7, Aerospace Publishing 1997. "Beyond the Frontiers: McDonnell XF-85, The Built-In Fighter" by Robert F. Dorr, p26-27.

01 December 2009

The first laser designation system used on a fighter aircraft probably goes to the AVQ-9 Pave Light system that was first fielded by the USAF on the McDonnell Douglas F-4D Phantom in the late 1960s. First tested at Eglin AFB on an F-4C, the "Zot Box" was mounted on the left canopy frame of the WSO's cockpit and the aircraft had to be flown in a left pylon turn (similar to that used on the big gunships in Vietnam) so the WSO could keep the laser manually pointed at the target while other aircraft dropped the laser-guided bombs.

In case of ejection, the WSO would have to demount the "Zot Box" before ejecting, an obvious limitation that eventually led to pod mounted systems, the first of which was the AVQ-10 Pave Knife. The nickname "Zot Box" came about from the anteater character in Johnny Hart's "BC" cartoon strip.

Source: McDonnel F-4 Phantom- Spirit in the Skies, by Jon Lake and David Donald, eds. AIRtime Publishing, 2002, p136.