CHECK SIX: Chikuhei Nakajima and his Aircraft Company

So here's something from the "Persons in Aviation History that Don't Get Enough Attention" Department- this is Chikuhei Nakajima, the founder of the Nakajima Aeroplane Company in Japan. Prior to World War II, there were three dominant aircraft manufacturers in Japan- Mitsubishi, Kawasaki, and Nakajima. Both Mitsubishi and Kawasaki were capitalized from their founding by government contracts for military aircraft. Nakajima, on the other hand, was the only major Japanese aircraft company of the time that not only was independent of any other industry (both Mitsubishi and Kawasaki were divisions of per-exisiting industrial corporations), it also was privately capitalized on account of its success with flying its aircraft on air mail routes within Japan. 

Nakajima was a former naval officer with a background in engineering. While he was still in the Navy, in 1912 he spent time in the United States as a student and observer of naval aviation. He spent time studying aircraft manufacturing with Curtiss Aircraft and even learned to fly during his time with the company. When he returned to Japan, he left the Imperial Japanese Navy and started Nakajima Aircraft in December 1917. His business connections helped him raise capital- while Mitsubishi and Kawasaki's aircraft manufacturing was funded by military orders, Nakajima focused on civilian designs that could fly air mail routes in Japan. By 1924, Nakajima was also designing and building his own aircraft engines. In 1931 he retired with his younger brother taking over the company. 

By the end of the war, only Mitsubishi had built more aircraft for the Japanese war effort than Nakajima. By the terms of the surrender agreement and subsequent military occupation of Japan postwar, aircraft companies were forbidden from aircraft development and production. This wasn't so bad for companies like Mitsubishi and Kawasaki which were diversified. Nakajima had to be dissolved, but many of its managers and engineers stayed together in smaller ventures until 1950 when they formed Fuji Heavy Industries. 

The Fuji T-1 jet trainer was Japan's first indigenous jet aircraft following World War 2 when aircraft production was allowed to resume. Fuji builds trainer aircraft for the JASDF and is a subcontractor for several US aerospace companies, but you all might know Fuji more from their automobile division, Subaru. Many of the Nakajima engineers who couldn't work in aviation after the war turned their attention to Japan's then-fledgling automobile industry. Subaru has been such an important part of Fuji Heavy Industries that the Subaru logo in 2003 became the official logo for Fuji itself.

Further reading: 

Nakajima's Demon: The Ki-44 Shoki

The 1937 Kamikaze Flight That Didn't End in a Fiery Crash

The Japanese Spruce Goose: The Kawanishi H11K Soku

The Japanese Balloon Offensive of 1944-1945

(Photo: Wikipedia)

The End of the Line for Curtiss Aircraft

XP-87 Blackhawk prototype
(USAF Museum)

In the summer of 1945 the US Army Air Force was in the process of outlining its combat aircraft needs in the post-war world. For fighter aircraft, there were three classes of aircraft that the USAAF wanted- an all-weather offensive fighter, a point-defense interceptor, and a long-range penetration fighter. It was expected that because of the state of the technology of the day that the all-weather offensive fighter would be the biggest of the three. On 28 August 1945 the USAAF issued its RfP (Request for Proposals) for the all-weather offensive fighter- a speed of 525 mph at 35,000 feet, 12 minutes to reach 35,000 feet and a 600-mile combat radius. It was thought at the time that piston engines would be necessary, but a refinement of the USAAF requirements a few months later laid out the service's desire for an aircraft that could seek out and destroy both enemy aircraft and ground targets in all weather conditions, day or night. Bell, Consolidated (Convair), Curtiss, Douglas, Goodyear, and Northrop submitted entries; Bell, Convair, and Goodyear were eliminated quickly due to performance deficiencies. Curtiss submitted a large four jet design based on the XA-43 attack jet design they had been working on for a different ground attack specification. Douglas submitted a land-based version of their F3D Skyknight, and Northrop submitted three designs- a refined version of the P-61 Black Widow, one based on the XP-79 flying wing fighter, and an all-new twinjet design. 

The political winds of change meant that the USAAF favored Curtiss heavily for the reasons that the previously dominant aircraft manufacturer had no contracts to sustain it in the postwar period and no civilian designs readily available for the growing passenger market. What was left of the funding for the XA-43 project was used to contract with Curtiss for prototypes of their design to be designated the XP-87. But the USAAF was sufficiently interested in Northrop's all-new twinjet design to contract for prototypes of that design as well to be designated XP-89. The USAAF also contracted with Martin Aircraft for a nose mounted turret that would allow the cannons to be swiveled to off-center targets that was to be fitted to both the XP-87 and XP-89. 

The XA-43. Note the differences from the XP-87 design.
(The Unwanted Blog at up-ship.com)

The designation XA-43 is often and mistakenly used interchangeably with the XP-87 designation- they were in fact two different aircraft that only resembled each other in basic layout. The XA-43 had a tandem cockpit, oval cross-section nacelles that were mounted inline with the wing, and was 65% larger than the XP-87 which had a side-by-side cockpit, rectangular nacelles under the wing. The XA-43's horizontal tail was low set and the design also featured a tail gun. The fact that the first XP-87 prototype was contracted with XA-43 funding led to the confusion that still is seen to this day. The XA-43 was ordered in November 1944 for a jet-powered ground attack bomber but it soon outgrew its proposed powerplants. By the time of the all-weather fighter RfP, the USAAF had lost interest in the XA-43 and allowed Curtiss to redirect its XA-43 efforts to the XP-87. But since policy of the time dictated two prototype aircraft in case of the loss of one, the original XA-43 contract was amended to allow for the construction of a second XP-87 prototype. In August 1946 Curtiss requested to name the XP-87 the Bat, but as there was already a US Navy glide bomb called the Bat, the request was turned down and a month later the XP-87 was given the name Blackhawk. 

By 1947 a review was underway to determine which of the fighters under development at the time might be suitable as a tactical reconnaissance aircraft- due to the size and carrying capacity of the XP-87, it was decided that it would also be developed into a reconnaissance version designated the RP-87. In order to not slow down the development, Curtiss was to complete both prototypes as all-weather fighters and then convert the second aircraft into the reconnaissance configuration at the completion of the prototype flight tests. In June 1947 Curtiss raised concerns with the USAAF on the power output of using four Westinghouse J34 engines in the paired nacelles and suggested changing to the Allison J33 as a single J33 engine had the power of two J34s not to mention the simplification of maintenance having only two engines instead of four. The change was approved for the production model but the prototypes would be completed with the four J34 engines. 

Only the XP-87 prototypes were to have four paired engines
(USAF Museum)

The first prototype was built at Curtiss' production facility in Columbus, Ohio, that once housed wartime production of the SB2C Helldiver. Taxi testing and ground tests took place at Columbus, but the USAAF wanted all flight testing to occur at Muroc AAF (later renamed Edwards AFB) in California. The first XP-87 was partially disassembled and loaded onto a trailer for transport to California- on going under the first highway overpass near the Columbus plant, the height was misjudged and the vertical fin hit the overpass, resulting in significant damage. With the damaged fin removed, he convoy headed out again and outside of Tulsa, Oklahoma got into an accident that damaged the nacelle for the left two engines. It was felt repairs could be made at Muroc and after month, the convoy reached the base where a new vertical fin and a team of  engineers were waiting to repair the prototype. The first flight was finally made on 1 March 1948 on a reasonably uneventful 58-minute maiden flight. The next several flights discovered buffeting in the tail due to it having a lower critical Mach number than the rest of the aircraft. Curtiss proposed a redesigned swept empennage for the production aircraft that was also duly approved by the USAAF. A total of 55 contractor test flights were made with the Blackhawk prototype and the flights confirmed the need to change to the Allison J33 on the production fighter- the Westinghouse J34s were unreliable and needed constant repair and replacement. By the time of the next series of flights with service test pilots, the USAAF was now the US Air Force and the first USAF flights were made on 3 June 1948. A week later the USAF placed a preliminary order for 57 P-87B Blackhawks (J33 engines and swept empennage were features of the production "B" version) and 30 RP-87B photo-recon aircraft. The following day the USAF switched from P-for-pursuit to F-for-fighter, the Blackhawk becoming the XF-87.

The now-designated XF-87 from the rear
(USAF Museum)

After 19 USAF test flights, a recommendation was made to Curtiss for a slightly larger wing to help reduce the stall speed and it was agreed that the second prototype XF-87 under construction would have the larger wing, the J33 engines, the swept empennage and reconnaissance modifications and would be designated XF-87C. In October 1948 the USAF held a fly-off evaluation with the XF-87 Blackhawk prototype, the Northrop XF-89 which got the name Scorpion, and a borrowed Navy F3D Skyknight to represent the Douglas submission as it was felt the Douglas design was close enough to the production Skyknight that it could act as a stand-in. With pilots of the Air Defense Command participating, while the XF-87 Blackhawk and F3D Skyknight had their strong points (side-by-side seating being one of the strongest suits of both designs in the opinion of the ADC pilots), the Northrop XF-89 Scorpion came out overall ahead in the evaluation and it was selected for production as having the best development potential. 

It was a crushing blow for Curtiss-Wright as the XF-87 was its only postwar jet design to take to the air. The Navy had canceled the XF15C mixed-propulsion fighter a few years earlier after only three examples were built. The company, in effect, was betting its future as an aircraft manufacturer on the XF-87 Blackhawk. The first prototype was  ferried to Wright-Patterson AFB in Ohio in December 1948 and was eventually scrapped by 1950. The second unfinished prototype was never completed and what was done got parted out for other projects that the company was attempting. With no other designs in advanced development, Curtiss-Wright was forced to shut down its Airplane Division and its assets were sold to North American Aircraft and the Columbus plant would be used for the manufacture of the F-86 Sabre. Curtiss-Wright's propeller division remained active into the 1960s and was responsible for the X-19 radial lift test aircraft. Some feel the X-19 was Curtiss' last aircraft design, but in reality it was the XF-87 Blackhawk that represented the end of the line for Curtiss-Wright Aircraft, a company that just ten years earlier was one of the dominant aircraft manufacturers of the United States. 

Related Reading:

The Massive Curtiss XP-71 Fighter
The Barrier Patrols: Extending the US Radar Net Out to Sea

Source: Experimental & Prototype U.S.Air Force Jet Fightersby Dennis R. Jenkins and Tony R. Landis. Specialty Press, 2008, p95-101. 

The Humble Birth of Grumman Aircraft

Leroy Grumman (Time Magazine)

In October 1920, the head of the Loening Company, Grover Loening, had been supervising the construction of a two-seat naval floatplane at two locations- at Loening's own plant at 31st Street on the East River in mid-town Manhattan and at the Naval Aircraft Factory in Philadelphia. It was in Philadelphia that Loening convinced one of the Navy's test pilots to resign his commission and join his company. That young 25-year old naval lieutenant was Leroy Grumman. The young Grumman rose quickly to the top ranks of Loening's company and by 1924 Loening had hired two other talented individuals to support Grumman- Jake Swirbul and Bill Schwendler. Loening's company prospered right until the 1927 when Lindbergh's solo flight across the Atlantic sparked the imagination of American business which was already riding a bull market in Wall Street. Though well-run, Loening began to falter and in 1928 Grover Loening sold his company which was to be absorbed by the Keystone Aircraft Company which at the time was building a twin-engine bomber for the US Army Air Corps. In less than a year, Keystone itself was purchased by Curtiss Wright. Under the terms of the sale, Loening's Manhattan factory would be shut down and all the employees were assured employment if they moved to Keystone's main facility in Bristol, Pennsylvania.

Leroy Grumman and his two closest friends, Jake Swirbul and Bill Schwendler, weren't happy about having to move to Pennsylvania as they had settled in the New York City area and had families that would have to be moved. So in 1929 the trio decided they'd form their own aircraft company and stay in the New York City area. Since Grover Loening and his brother were barred from forming another aircraft company as part of the terms of the sale, they decided that investing in Grumman's fledgling enterprise would be the next best thing. Their first act was to hire Loening's treasurer who also happened to be from a prosperous New York family that offered to invest with Grumman as well. In contrast to the businesses of the day, however, Grumman decided that control of the company would rest only with a few individuals and to not canvas Wall Street for further investors. It proved to be a wise move with the Wall Street crash just over a month away. 

Grumman then set about to recruit the thirty most skilled employees at the Loening plant. His years of service under Loening endeared him to many of the Loening workers and all asked, with the exception of one or two, threw their fate into Grumman's hands. In addition, Grumman, being a financially cautious individual, decided that his new company would only seek the business of the US military, preferably the US Navy given Grumman's background as a naval aviator and their long history of doing business with the sea service during their employment with Loening. In order to fund their day-to-day operations, they would repair existing Loening amphibians at a rented facility in Long Island. 

On 5 December 1929, Leroy Grumman and his five founding associates met for the first time and the following day the Grumman Aircraft Engineering Company was born. Much of the company's initial capital came from Grumman's severance pay from Loening. Jake Swirbul's widowed mother worked for a wealthy Long Island family that so much of her that they lent Swirbul enough money to become the first vice-president of Grumman. A few months later in March 1930, the rest of the tiny company's employees were allowed to purchase stock (On the eve of the maiden flight of the Grumman F-14 Tomcat, those employees' initial investment over 40 years had multiplied by a factor of 7,700!). 

Their first design proposal was for the US Navy, which at the time had a two-seat scout biplane, the Vought O2U Corsair. The Corsair could be fitted with floats for operation from cruisers and battleships or it could be fitted with landing gear for operation from aircraft carriers. Grumman's proposal was for a new float that was not only lighter and stronger than the existing main float used on the Corsair, but it would also incorporate a fully-retractable landing gear to allow true amphibious capability. In 1930, fully-retractable landing gear were a novelty- on the Loening amphibians, the landing gear simply swung upward out of the way but what Grumman and his team proposed was a streamlined arrangement in which the gear would be fully retracted into the sides of the central float. 

Vought O2U with the Grumman-design center float (Wikipedia)

The Navy was intrigued by this modification of its O2U scoutplanes, and asked Grumman for a demonstration. Many in the Navy were skeptical that a float lighter than the existing float could be stronger, let alone be strong enough to accommodate a full-retractable landing gear. But Grumman's design was an early pioneer in monocoque construction in which the skin of the float carried a good portion of the stress loads and as such, didn't need a heavy internal framework that was the standard in aircraft construction of the day. The Navy paid Grumman $33,700 for two such prototype floats for testing at the naval yards in Anacostia in Washington, DC. The floats would be attached to Vought O2Us that would be launched from test catapults as that was the most stress anticipated on such a float arrangement. The landing gear was manually operated, but was designed so that either mechanical or hydraulic power could be added.

On the day of the flight tests, the Navy couldn't find an observer willing to sit in the second seat of the modified scoutplane. Many thought Grumman's float would either crumple up on launch or collapse on landing either on land or on water. Not wanting to delay the flight tests, both Leroy Grumman and Jake Swirbul both volunteered to sit in the observer's seat on different flights to prove their faith in the monocoque design. The day's test flights were of course successful and Grumman walked away with his first Navy contract for what was called the Grumman Model A float. In addition, the Navy had asked Grumman the possibility of using the retractable landing gear on its single seat carrier fighters. Grumman offered to go one better and on February 1930 began work on what would be come the first Grumman fighter, the FF-1. Grumman's landing gear design would go on to be used on not just the FF-1, but also the F2F and F3F biplane carrier fighters and on the F4F Wildcat used in the Second World War. 

Source: The Grumman Story by Richard Thruelsen. Praeger Publishers, 1976, p17-41.

The USAAF Looks for Something Better than a C-47

Loading a Jeep into this RAAF C-47 shows it wasn't ideal for large or bulky loads.

During the interwar period of the 1920s, US military air transport was modest at best and consisted primarily of "off the shelf" civilian designs that were modestly modified with things like reinforced cabin floors and wider doors but were essentially airliners without seats. Until 1934, for example, the US Navy and Marine Corps relied on Ford Trimotors for transport! The arrival of the Douglas DC-2 offered a big improvement in capability for the US military. With war clouds looming in Europe and Asia in the 1930s, the US Army Air Corps went about looking for something better than adapted DC-2s. Bids were requested and Douglas offered an attractive proposal for upgraded DC-2 aircraft better tailored to military transport operations. Not long after, General Henry "Hap" Arnold became head of the USAAC (which later became the USAAF) and being a personal friend of Donald Douglas, was well aware of a DC-2 upgrade in the works that was the result of a marathon telephone conversation between Donald Douglas and the head of American Airlines, C.R. Smith. That aircraft was a leap in performance and capability over the DC-2 and at the time was called the Douglas Sleeper Transport (DST). In due time, of course, the DST became the DC-3 but General Arnold saw the DST's design and performance as an ideal basis for a transport. Army officials met with the designer of the DST, Arthur Raymond, and the C-47 was born. When the war finally broke out with the German invasion of Poland in September 1939, the C-47 wasn't yet in production and suddenly the branches of the US military needed air transport aircraft. The C-47 Skytrain (Dakota in RAF service) made its first flight on 23 December 1941 as Douglas embarked on a major facility expansion to meet the demand for the C-47. At production peak in May 1944, the company was building just under 19 C-47 aircraft each day! Despite the massive expansion and number of C-47s needed, the Army did have several issues with the C-47 but it was the best aircraft available at the time. There were three main issues the Army had- the first was that the tailwheel configuration and side cargo door made it difficult to load large items. Secondly, the maximum payload was too light as it was based on the maximum civilian load for the DC-3, and thirdly, the Army felt that as it was a DC-1/DC-2 derivative, it was old technology. With the United States now in the war, the Army thought that aluminum production was best used for armed combat aircraft and that cargo aircraft which operated in support roles ought to use non-strategic materials. While there was never a formal competition for a C-47 replacement but rather a series of issued requirements, quite a bit of money was spent over the course of the war to develop a transport that was better than the C-47. 

Budd C-93/RB-1 Conestoga

At the outbreak of war, several aircraft made out of the non-strategic materials made the first attempt at replacing the C-47. The first came from the E.G. Budd Company of Philadelphia- they had developed the shotweld technique for joining two pieces of metal- it used a short burst of electrical current to bond two pieces of metal. Invented in 1932 by a Budd engineer, shotwelding was used on the products Budd was known for- railroad cars and road vehicle bodies made of stainless steel. In discussions with the US Navy, Budd hired an aeronautical engineering staff to design a shotwelded (therefore no rivets) transport that would be made of readily available stainless steel. The Navy ordered 300 to be designated the RB-1 and the Army ordered 600 to be designated the C-93. Though made primarily of thin-gauge stainless steel, the wing aft of the spar and the moving surfaces of the tail were fabric covered to offset the weight of the steel. 

The design of the Conestoga was radical for the day and set the pattern for an efficient military transport even to this day. A high mounted wing allowed for an unobstructed main deck with a tricycle landing gear to keep the main deck level and low to the ground to ease loading. An aft loading ramp/door allowed rolling stock to be driven on/off of the aircraft. The flight deck sat up above the main cargo deck to maximize the cargo volume of the fuselage. In addition, there was an integrated hoist in the cargo deck to ease loading an locations that lacked ground equipment. The first flight was on 31 October 1943 and three prototypes conducted the flight test program. Using the same engines as the C-47, the Conestoga was underpowered and possessed sluggish handling- pilots joked that for a plane made by a railroad car company, it sure handled like one! By time time cost overruns and construction delays were resolved at the Budd factory, aluminum production had vastly increased in the United States and the need for an aircraft made of non-strategic materials diminished. The Army canceled its order for the C-93 and the Navy reduced its order from 300 to just 25. Just 17 RB-1s were delivered to the Navy by March 1944 and that small number served primarily as hacks for naval air stations. With such a small number in the fleet, the Navy found the RB-1s uneconomical and sold them off as surplus in early 1945 before the war even ended. Twelve Conestogas were purchased by a new cargo operation, National Skyways, that was founded by a group of pilots that had once served with the American Volunteer Group in China. National Skyways would later change their name to Flying Tigers- but that's a story for future blog article!

Curtiss C-76 Caravan

Another aircraft from the Army's concerns in 1941 that was a contemporary of the Budd C-93/RB-1 Conestoga was the Curtiss C-76 Caravan. The company was engaged by the Army that year to build a transport aircraft that like the Conestoga, would not only be made out of non-strategic materials but also exceed the performance and utility of the C-47. The Caravan was designed by the chief designer at Curtiss, George Page, who was also responsible for the C-46 Commando. While the Conestoga would be made of stainless steel, Page elected to use wood for the Caravan but interestingly, the only high performance aircraft at the time in production made from wood, the De Havilland Mosquito, wasn't used as a source of expertise. De Havilland used a layered plywood construction using a lightweight balsa wood core that made the Mosquito strong but light. Curtiss engineers instead favored mahogany in layers- being a much denser wood than what was used on the Mosquito, the Caravan soared in weight. Despite this, the Army helped Curtiss secure large stocks of mahogany and a number of furniture manufacturers were set up as component subcontractors with final assembly at Curtiss's new plant in Louisville, Kentucky. 

Much like the layout of the Conestoga, the C-76 Caravan featured a retractable tricycle landing gear to keep the main deck level. It also had a high wing layout for an unobstructed main deck hold and also put the flight deck above the main deck. Instead of an aft loading door and ramp, the Caravan had a swing nose that opened to the side ahead of the flight deck. The prototypes were built at existing Curtiss facilities in St. Louis as well as the new Louisville plant with the first flight on 3 May 1943. The flight test program was a disaster. The aircraft, using the same engines as the C-47 but made of dense mahogany, was woefully underpowered with a cargo payload not much more than the C-47. On the first flight, the aircraft vibrated so badly the flight test crew made a hasty return to the St. Louis Lambert Field. On the second test flight, the prototype literally shook itself apart with the loss of the pilots. In addition, when empty, the Caravan had to be ballasted to maintain its center of gravity- amusingly, the ballast needed to maintain an empty load CoG was more than the maximum payload! The control surfaces suffered from buffet and even shook while the plane was on the ground if it was windy. The wing spar failed load testing eight times, only holding up to 40% of the predicted maximum load. The Army wasn't pleased and was more than happy to cancel their order for 175 C-76s, particularly as aluminum production had vastly increased as the war progressed. Only 14 aircraft were built and most spent their days as ground instructional airframes. 

Wind tunnel model of the Waco C-62

There was a third aircraft that stemmed from the Army's 1941 call for something better than the C-47, but it never flew. Waco Aircraft had been building both training and assault gliders for the military and they tendered a design that received the designation C-62. Like the Curtiss C-76 Caravan, the Waco design was made out of wood and featured a high wing and rear loading door/ramp. The tadpole-shaped aircraft had the empennage cantilevered over the aft ramp on a boom. The undercarriage was fixed as well. Using the same engines as the C-47, the Army placed orders for 13 pre-production examples and 240 production aircraft. However, again, like the Conestoga and Caravan, the anticipated shortage of aluminum never occurred and the C-62 was canceled. Allegedly the first aircraft was nearing completion at the time of the cancellation, but this hasn't been confirmed. 

Fairchild C-82 Packet at the National Museum of the USAF

The last aircraft that sprang from the 1941 call was the Fairchild C-82 Packet. Designed by Fairchild's chief designer, Armand J. Thieboldt, the original plans were for the C-82 to be made of wood. Like the other three aircraft, the Packet had a high wing and tricycle landing gear to allow for a level main cargo deck that was unobstructed. The flight deck was raised above the cargo deck and a twin boom layout was chosen to leave the tail area completely clear for straight though loading and unloading. With the fortunes of war shifting in favor of the Allies in the summer of 1942 after the Battle of Midway and an expansion of domestic aluminum production eased shortage concerns, the USAAF requested that Fairchild abandon wood for the C-82 and go with aluminum. Of four aircraft designs for a C-47 replacement, the decision to switch to aluminum more than likely contributed to the reasons why the Packet did get to production and service. Being the last submission probably saved the design as it was also redesigned to take a more powerful engine, the Pratt & Whitney R-2800 Double Wasp instead of using the same engines as the C-47. As a result, the C-82 had the highest cargo payload of the four designs. 

First flight took place on 10 September 1944 at Fairchild's plant in Hagerstown, Maryland. The first series of flights were so encouraging that the USAAF ordered 100 C-82s just 18 days after the first flight. With an eye towards the coming invasion of Japan, North American's Dallas plant was planned for an additional 1000 C-82s on top of an additional 100 from Fairchild for a total of 200 from the Hagerstown plant. The first C-82s were delivered to the USAAF in June 1945 but the sudden end of the war with the Japanese surrender in September 1945 resulted in the cancelation of the North American production run at Dallas with only just three Dallas-built C-82s being built. Despite the drawdown in US military forces, the C-82 Packet was the C-47 replacement the USAAF wanted and the 200-aircraft order from the Fairchild plant in Maryland stood to fulfill postwar airlift requirements. Five C-82s participated in the Berlin Airlift, bringing in heavy equipment and vehicles that couldn't be accommodated onto the Douglas C-54 Skymasters. Operational use of the C-82 revealed several shortcomings, the most concerning of which was that with a full load, a C-82 with one engine out couldn't maintain level flight. Thieboldt and his team at Fairchild went about improving the C-82 design first by incorporating more powerful engines in the form of the Pratt & Whitney R-4360 Wasp Major as well as a host of other improvements to satisfy the newly-independent US Air Force's concerns. Originally designated XC-82B, the changes were so significant that a new designation was assigned to the upgrade which became the C-119 Flying Boxcar. The first flight was made on 17 December 1947. As C-119s were delivered to USAF units, the C-82s were retired. A total of 220 Packets were built. Quite a few Packets had long civilian careers, but that's a story for future blog article! 

Source: The Legacy of the DC-3 by Henry M. Holden. Wind Canyon Publishing, 1996, pp 141-148. Information also from National Museum of the USAF, Wikipedia and www.c82packet.com. Photos: Wikipedia, Australian War Memorial, National Museum of the USAF. C-62 wind tunnel model from R/C Groups forum.

The Development of the Boeing Flying Boom

World War II USAAF tests with B-24 tankers and B-17 receivers

Though the United States had explored using air refueling to extend the reach of strategic bombing missions during the Second World War, nothing operational had come of the work by the time the war ended in 1945. In the immediate post war years, the newly independent United States Air Force and its nuclear deterrent arm, the Strategic Air Command, had both the weapons and the aircraft to carry out nuclear strikes, but what was lacking given the technology and geopolitical climate of the day was overseas bases that would allow SAC's bombers to reach the Soviet Union. As it was, the Boeing B-29 Superfortresses that were the main strike force of SAC lacked the range to hit Soviet targets nonstop from bases in the United States. While the US government placed priority on securing overseas bases for SAC, the USAF made inquiries to the leading experts of air refueling of the day, Flight Refueling Limited in Great Britain. It was Flight Refueling that consulted with the US Army Air Forces during the Second World War and assisted with several trials using B-24 Liberators as tankers and B-17 Flying Fortresses as receivers. Several sets of air refueling equipment were procured from Flight Limited and installed on a very limited basis on several B-29 Superfortresses to get crews trained on the procedure. However, the USAF was dissatisfied with the system as it took time to rendezvous and get into the proper position, change positions, and then transfer fuel. Using Flight Refueling's method, the receiver trailed a hauling line with a weight and hook at the end. The tanker approached from the side and below and deployed a contact line that crossed over the hauling line of the receiver and engaged the hook. The tanker then moved above the receiver, pulling in the hauling line with the contact line. The refueling hose was then attached to the hauling line and it was then pulled down to the receiver which had a refueling receptacle in the tail gunner's position and refueling commenced. The lines and refueling hoses used created tremendous drag that imposed air speed restrictions that may have been acceptable for a piston-engined bomber but wholly impractical for a future jet-powered bomber. 

The USAF contacted Boeing in November 1947 if they would be willing to look at the air-refueling problem within the purview of the company's ongoing research programs. In the following month, the Preliminary Design Group and the Experimental Manufacturing Division at Boeing formally signed a contract with the Air Force to work on improving air refueling. Boeing's first step was to determine what formation can two Superfortresses operate most closely for an extended period of time safely to conduct air refueling. Boeing's engineers figured the refueling solution would be easier the closer the aircraft could fly to each other and not have to do the position changes that the Flight Refueling method entailed. To this end, in May 1948, the USAF ran a series of tests out of Wright-Patterson AFB in Dayton, Ohio, using B-29s flown in every possible formation and relationship to each other. Escorting aircraft photographed the formations from every angle and Boeing's team would then analyze the photographs to determine their three-dimensional relationship to each other. For every possible formation, the flight crews involved were also queried on things like workload and visibility in maintaining the formation. As a result of these test flights, it was determined the optimum position that provided a relatively low workload with good visibility was to put the aircraft in trail formation with the trailing aircraft vertically displaced 25 feet and longitudinally displaced 10 feet. This gave the flight crew in the trailing aircraft the best view of the lead aircraft with the closest possible distance. Pilots in the trailing aircraft found that if they flew less than 25 feet vertically displaced below the lead aircraft, they got buffeting from the wake of the lead aircraft which gave the formation an inherent safety feature. 

After determining the most optimal close formation, the next step for the Boeing team was to figure out the best fuel transfer method. Five different refueling systems were explored. The first three systems were probe-and-drogue applications with the tanker trailing a hose with a drogue at the end with the receiver flying a probe into the drogue to make the connection. Though this method is used today by the US Navy and US Marine Corps as well as a large number of air arms like the RAF, the Boeing team felt that the hose movement could be unpredictable in rough air and required too much maneuvering by the trailing aircraft to make hose contact. Such maneuvering might be fine for a smaller tactical aircraft, but Boeing was less than thrilled about the prospect of a large receiver aircraft having to maneuver frequently before contact so close to the tanker. 

The imaginative fourth proposed system involved a gun-turret like assembly on the tanker's forward dorsal fuselage. The tanker would take the trailing position and the turret would deploy a rigid boom up and forward to engage a receptacle on the underside of the tail of the receiver. The boom would be maneuvered like a gun turret by an operator aboard the tanker and when not in use, the boom would slew 180 degrees and stow atop the dorsal fuselage of the tanker. While imaginative, it was soon realized the aerodynamic loads on the boom would be significant. But what if their positions were reversed? What if the tanker lowered the boom aft and down to the receiver who had a receptacle on the top of the fuselage? This way the operator did all the work from the tanker and the receiver flight crew could focus on holding the prescribed position in trail behind the tanker. Flight test personnel with experience with the flight refueling systems of the day were consulted and all agreed that a boom lowered from the lower aft fuselage of the tanker to the top of the fuselage of the receiver would be the most ideal. A rigid boom would allow fuel transfer rates much higher than a hose system and small aerodynamic surfaces would be used on the end of the boom to maneuver it to the receptacle of the receiver- which is how Boeing came to call it the "flying boom". 

B-50 "Lucky Lady II" taking on fuel from a KB-29 hose tanker

While Boeing's engineers in Seattle worked on the flying boom concept, the Air Force's first secretary after its creation, Stuart Symington, had testified before the Senate Armed Services Committee in March 1948 that the latest air refueling systems would allow the new Boeing B-50 Superfortress to reach any part of the Soviet Union, but the reality of it was that all the USAF had were the first Flight Refueling hose units on a handful of B-29s and that the flying boom was still a paper project. Quite literally on the following day, the USAF instructed Boeing's Wichita division to get as many hose units onto KB-29 tankers as possible and get the new B-50s up to speed as receivers with an interim system until the flying boom was operational. The first operational installation was ready in less than 30 days and by the end of 1948. On 26 February 1949, the B-50 Superfortress "Lucky Lady II" took off from Carswell AFB in Fort Worth, Texas, and flew around the world nonstop in 94 hours, taking fuel from hose-equipped KB-29s four times during the record-breaking flight. 

The flying boom equipped KB-29P Superfortress tanker

Despite this very public success, Boeing continued to develop the flying boom and interestingly, had funded the development internally without outside USAF funds. Two dry booms were built for KB-29s as proof of concept. Though not able to transfer fuel (hence the term "dry booms"), the dry booms were actually installed on KB-29s in June 1948, a full seven months before the circumnavigation flight of "Lucky Lady II". Dry receptacles for the purposes of flight test were installed on a B-47 Stratojet and an F-86 Sabre. Flight tests using the dry boom were conducted through the summer of 1948 out of Seattle, Wichita, and Wright-Patterson AFB in Ohio. The tests were successful and the USAF requested Boeing transfer the flying boom work to Curtiss Aircraft. As the company had an absence of work postwar, the USAF wanted to keep Curtiss in business, but quite obviously, Boeing wasn't happy with that request, particularly since development had so far involved company funds without any USAF funding. By April 1949, Boeing was already constructing wet booms (flying booms able to transfer fuel) and was resisting USAF pressure to transfer the program to Curtiss Aircraft. Boeing won the dispute with the USAF by insisting its flying boom work was proprietary and would have commercial applications in refueling jet airliners. Since no USAF funds had been used in development so far, the USAF found it didn't exactly have financial clout to compel Boeing to transfer the program to Curtiss. Up to this point, the flying boom program was classified and the USAF had insinuated that the program's classified status meant that it couldn't be used for commercial applications. But the flight test program had already been publicly revealed by the USAF itself in an October 1949 press release! Boeing did finally get its contract for the flying boom. From 1950 to 1951, the Boeing Renton plant converted over 100 B-29 Superfortresses into KB-29P flying boom tankers with the first tanker delivered to SAC in March 1950. A fixed cradle structure supported the flying boom when it was raised. A hemispheric plexiglass dome replaced the tail turret and laying in a prone position, the boom operated "flew" the boom to the receiver. Boeing had always considered the KB-29P an interim tanker and soon enough was working on a tanker version of the C-97 Stratofreighter- not only did a tanker version of the C-97 offer more fuel carrying capability, it could also carry cargo when not being used for air refueling, offering mission flexibility for the USAF. The first flying boom-equipped C-97 was flight tested by Boeing in September 1950 and so impressed the USAF that all remaining orders for the C-97 were to be completed as KC-97s. In fact, the first KC-97 was delivered to the USAF only eight months after the KC-97 contract was signed with the first units operational in July 1951. Boeing then suggested a turboprop-powered KC-97 to the USAF, but the military was ambivalent to the idea, but by that point, Boeing was already working on a new breed of transport that would eclipse even the turboprop powered KC-97. But I'm pretty sure you know how that story ends! 

Source: Passing Gas: The History of Inflight Refueling by Vernon B. Byrd. Byrd Publishing, 1994, pp 123-136. Photos: National Museum of the United States Air Force.

The Complexities of Aiding the Free French Air Force in World War II

Free French Air Force pilot wings with the Cross of Lorraine

With war clouds in Europe looming on the horizon, the British were first to send a mission to the United States in 1938 to determine if their aircraft needs could be met by the Americans since British industry was still barely getting spooled up on a war footing. Encouraged by the British, the French also sent a mission in the same year that resulted in the order of 100 Curtiss Hawk 75 fighters (P-36 being the US Army Air Corps equivalent). In the following year further contracts were finalized for more aircraft which also included the first orders by any nation, including the United States, for the Douglas DB-7 light bomber which would later enter US service as the A-20 Havoc. With the outbreak of war on 1 September 1939, deliveries temporarily ceased according to the terms of the US Neutrality Acts, but an amendment was quickly put in place that allowed British as well as the French to "carry" their own war materiel on their own ships. Following the fall of France and the signing of the French-German armistice in June 1940, the outstanding contracts with the United States were transferred to the British. The unoccupied portion of France became Vichy France with Marshall Petain as its leader. As part of the armistice agreement with the Axis, a German-Italian commission was put in charge of the activities of the Vichy Air Force that were full of restrictions and disbandment of French units as the Axis powers feared continued defections of French pilots to the Allies. French units in North Africa, however, were not under the jurisdiction of the German-Italian commission and continued to operate their US-built aircraft and it was these forces loyal to the Vichy regime that briefly resisted the Allied landings during Operation Torch. 

British Blenheims were some of the first aircraft given to the Free French.

A nucleus of French forces under General Charles De Gaulle (made up mostly of those evacuated from Dunkirk and other defections from the Vichy regime) tried to get Allied support as the "Free French", but this proved to be complex given that the legal French government at the time was Marshall Petain's Vichy regime which signed the armistice following the fall of France. And if that wasn't hard enough determining how to support a group fighting what was recognized as the legal government of France, the Roosevelt Administration even had recognized the Vichy regime as the legitimate French government! De Gaulle's efforts weren't helped any when despite a promise to Roosevelt to not seize the Vichy-controlled islands of St-Pierre and Miquelon off the Canadian coast, he did anyway. But on a perhaps moral level, aid would have to be provided to the Free French forces. Initially aircraft for the new Free French Air Force were diverted from British deliveries with the approval of the Roosevelt administration. In 1941 the Free French formed the French National Committee with General De Gaulle as its head to represent French interests independent of the Vichy regime. 

The Cross of Lorraine was used in addition to the French roundel.

With the coming of the landings in North Africa during Operation Torch, the Roosevelt Administration tried to develop an alternative to De Gaulle as he was seen as too difficult to work with for the war in Europe. Secret contacts had been made with dissidents within the Vichy government and General Henri Giraud was seen as an altnerative to De Gaulle- General Giraud had been captured by the Germans during the fall of France and sent to a prison camp, from which he had escaped back to Vichy France. This dissident element in the Vichy regime were promised large infusions of American aid if they could get the Vichy forces in North Africa to not contest the Torch landings, the idea that this group would then be put under Giraud's command as an alternative to De Gaulle. It would have worked as there were many French personnel who were loyal to Giraud and considered De Gaulle a traitor for having escaped to Britain before the fall of France. On the day of the landings on 7/8 November 1942 the Allies found themselves juggling three French factions- De Gaulle's Free French forces, Giraud and the dissidents in Vichy France, and Marshall Petain's defense minister, Admiral Francois Darlan, who was in North Africa at the time of the invasion and lobbied to halt Vichy resistance to the Allied landings. In exchange, Darlan would be made head of the new French government. This ended up enraging De Gaulle. Vichy resistance did end and Darlan ordered the French fleet at Toulon scuttled to prevent their takeover by the Germans. Darlan would later by assassinated in December 1942 and replaced by General Giraud, but by this point De Gaulle managed to emerge as the uncontested leader of the Free French following a 1943 agreement between Giraud and De Gaulle to unify their forces with Giraud as commander in chief and De Gaulle as the political head of the Free French. 

French B-26 units had their Cross of Lorraine on the nose in blue.

On 3 July 1943 De Gaulle's Free French Air Force was formally merged with Giraud's forces in North Africa with the set up of a joint commission with both US and British representatives in addition to the Free French to determine the aircraft needs of the Free French Air Force. By this point most aircraft used by the Free French could be identified with the use of the Cross of Lorraine in addition to the French roundels. Perhaps symbolically, the Escadrille Lafayette would be the first Free French unit to be re-equipped with American aircraft, Curtiss P-40 Warhawks diverted from USAAF stocks that were North Africa already. Over the next several months more aircraft arrived direct from US factories, from Bell P-39 Airacobras, Lockheed F-4/F-5 Lightnings for reconnaissance duties, to Douglas A-24 Dauntless dive bombers and C-47 transports. French trainees were sent to to the United States for flight training and completed their operational training with French units in North Africa prior to the liberation of France. The French Navy also received American aircraft to include Consolidated PBY Catalinas, Lockheed PV-1 Venturas and Douglas SBD Dauntless dive bombers, but rather than operated under De Gaulle's command like the Free French Air Force, the French naval air arm units were placed under US Navy command. 

French Lend-Lease deliveries would continue for most of the war but were cut off prematurely in April 1945 by order of President Harry Truman before war's end due to a diplomatic dispute started when French units chose to obey orders from General De Gaulle instead of the Supreme Allied Commander, General Dwight Eisenhower. De Gaulle had agreed earlier to Eisenhower's overall command and those deliveries outstanding were never released due to the German surrender on 7 May 1945. These issues would continue to simmer between De Gaulle and the United States in the post-war period that would complicate matters in French Indochina and ultimately result in France's withdrawal from NATO in 1967. 

Source: Air Arsenal North America- Aircraft for the Allies 1938-1945 Purchases and Lend-Lease by Phil Butler and Dan Hagedorn. Midland Publishing, 2004, p17, 105-114.

The Massive Curtiss XP-71 Fighter

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.

The First Steps to a Turboprop Transport, Part Two

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.

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.

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.

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.

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.