None of the aircraft that were designed in response to the R-40C proposal ever entered full production. Most of the 50+ entrants didn't even make it past the design and concept stage, without even an order for a prototype aircraft.
Of the ones that did make it, where prototypes were ordered, none of them made the final leap to full production. So far, three of these aircraft have been covered on this blog, the Vultee XP-54, the Curtiss XP-55, and the Northrop XP-56. But there was another aircraft that had prototypes ordered, yet never made it past the mockup stage. The story of the Bell Model 16 fighter leads into the story of the cutting edge of American fighter and engine design, one of the first-ever true 'Black' projects, and the first operational American jet fighter.
R-40C was posted by the US Army Air Corps in the winter of 1939, looking for a new fighter that would be better than existing types, while being cheaper, and easy to maintain. Specifically noted was the willingness to consider unusual designs.
Bell submitted their Model 16, which they'd worked up a few months before. Like many Bell designs, the Model 16 was unorthodox, though comparable to the other designs that were selected from the proposals.
The Model 16 had a fuselage shaped like a barrel, with the large Continental IV-1430 engine located in the rear driving a set of counter-rotating propellers. The pilot sat close to the nose, and in an unusual feature, the air intake for the radiators was a large hole in the middle of the nose, not unlike many jet aircraft. A pair of 20mm cannons were to be mounted in the nose, towards the bottom of the fuselage.
The wings were located centrally on the fuselage and had a slight 20-degree sweep towards the tail. Two tail booms extended back from the wings about a third of the way from the fuselage to the wingtips. These booms contained the planned armament of six .50 Browning machine guns that were to be mounted vertically, and they were connected at the back by the horizontal tailplane.
Continental's engine is of note, as it was one of the results of the 1930s 'Hyper Engine' program, with the audacious requirements of 1hp per 1 in^3 of displacement, and a power to weight ratio of 1:1 or better. Over the years of development, engine technology caught up with the Hyper Engines and left them to obscurity.
The XI-1430/IV-1430 was a 12-cylinder, inverted Vee, liquid-cooled engine that displaced 1,425 cubic inches and generated 1,600 horsepower at takeoff, and could reach 2,100 at full emergency power. In comparison, the later models of the venerable Allison V-1710 turned out 1,500 horsepower and the V-1650-7 Merlin managed about 1,580 at the most.
But for aircraft, there are more things to consider than just power. The IV-1430 weighed 1,615 pounds dry, the V-1650 was 1,645 pounds, and the V-1710 was a mere 1,395 pounds. More significantly, the Allison and the Merlin had already been in production and testing when the IV-1430 was first started, with their first run tests in 1930 and 1933 respectively. This was the reason that only 23 IV-1430 engines, redesignated to IX-1430, were ever constructed.
Despite this, the engine was tested in the XP-49 'Chain Lightning', the XP-67 'Moonbat', and was planned to be the engine for the production version of the Bell P-76/XP-39E. But even these tests weren't enough to bring the interest to tool up factories to make the XI-1430.
Specifications: XP-52 (Estimated)
Continental IV-1430-5
1,250 horsepower
Dimensions:
Wingspan: 35 feet
Length: 34 feet
Height: 9 feet, 3 inches
Wing Area: 233 feet^2
Weight:
Empty: 6,840 lbs
Gross: 8,750 lbs
Performance:
Top Speed: 425 @ 19,500 feet
Rate of Climb: 20,000 feet in 6.3 minutes
Service Ceiling: 40,000 Feet
Maximum Range: 960 Miles
But with the war in Europe taking a decidedly grim turn in 1939-1941 and the rising threat of Japan in the Far East, speed of development suddenly became more important. The experimental XI-1430 was canned, and replaced with the venerable Pratt & Whitney R-2800 Double Wasp. The engine that powered the likes of the F6F Hellcat, P-47 Thunderbolt, the B-26 Marauder, and another product of R-40C, the XP-56.
The change in engine brought with it a change in designation to XP-59, but at the same time, things were taking another turn. This time, for the highly secretive.
Specifications: XP-59 (Estimated, mostly taken from XP-52, differences denoted by '*')
Pratt & Whitney R-2800-52*
Dimensions:
Wingspan: 35 feet
Length: 34 feet
Height: 9 feet, 3 inches
Wing Area: 233 feet^2
Weight:
Empty: 6,840 lbs
Gross: 8,750 lbs
Performance:
Top Speed: 450 @ 22,000 feet*
Rate of Climb: 20,000 feet in 6.3 minutes
Service Ceiling: 38,000 Feet*
Maximum Range: 960 Miles
United States Army Air Force Major General Henry Harley 'Hap' Arnold visited England in April 1941, and while there he was shown the most secret developments in aircraft powerplants they had to offer. In particular, Frank Whittle's W2B turbojet engine and the Gloster E.28/39 aircraft that it powered. The United States had nothing close to being as far along in development, and a German jet (the Heinkel He 178) had flown as early as August 27th, 1939. so he asked for plans for the engine for licensed manufacture in the US. The British obliged.
Later that year, on September 4th, General Arnold worked out a deal with General Electric at Wright Field for a production run of 15 engines. GE's long experience with turbines made them the obvious choice for this project, which was to be carried out in total secrecy.
On the 5th, Bell was asked if they would build a fighter aircraft with the new GE turbojet as the powerplant. There are a few theories as to why Bell was selected, such as them having a penchant for bold and unconventional designs, or that they had the least production work to do for the war effort, or that they were located very close to the GE plant in Schenectady, New York. Bell was based in Buffalo, New York.
But regardless of the reasons, Bell accepted the contract to build three prototype aircraft. The deadline was for the first prototype to be ready eight months after the signing of the contract on September 30th, 1941.
Both the airframe and the engine were highly secret projects, which resulted in several measures to conceal their true intent. GE called the engine the I-A in an effort to make it appear like a new turbosupercharger. The development of Bell's XP-59 was wound down over the next few months, with work being directed towards the deceptively designated XP-59A, which had no relation to the piston-engined fighter.
By December 1st, 1941 the XP-52 and XP-59 were canceled without ever reaching the prototype stage. But the work on the XP-59A and the I-A engine accelerated ahead.
Since no one knew how much power the I-A would generate, Bell's engineers made a very conservative airframe. The XP-59A had a mid-mounted, cantilever, laminar flow wing, tricycle landing gear, and two I-A engines located on the bottom of the wing roots. The fabric-covered tail control surfaces were located high and away from the jet exhaust, and the cockpit was pressurized, still a somewhat new feature for fighter aircraft at the time. Access to the cockpit was via the side-hinged canopy.
Even though the XP-59A was intended as a test aircraft, there were provisions for a pair of nose-mounted 37mm cannons, with 44 rounds per gun.
The design was approved by the USAAF, and construction started on January 9th, 1942. In March, 13 YP-59A aircraft were ordered as service test aircraft. These aircraft were to be constructed with rear-sliding canopies and use improved versions of the GE turbojet known as the I-16, which would later be known as the J-31.
The I-A and I-16 were both single-stage, centrifugal compressor turbojets, which were simpler and shorter than axial engines at the expense of being much greater in diameter. The I-A produced a maximum thrust of 1250 pound-feet or 5.56 kilonewtons, weighed 780 pounds dry, was 70.5 inches long, and was 44 inches in diameter.
The I-16 produced 1,650 foot-pounds of thrust (7.33 KN), weighed 850 pounds dry, was 72 inches long, and was 41.5 inches in diameter. A total of 241 of these engines had been built, and was used on the P-59A, the first Navy fighter with a jet engine, the Ryan FR Fireball, and the experimental Ryan XF2R Dark Shark. Both of those aircraft are very interesting with their hybrid propulsion systems, but they are outside the scope of this post.
Centrifugal compressor turbojets are relatively simple. In the photo above air enters through openings on the right side of the engine, located forward and aft of the impellor blade. Air is then forced out from the center of the compressor into the diffuser, which is a series of stationary ducts that turn the velocity of the air coming from the impeller into pressure. Roughly 50% of the compression achieved is in the impeller and the other 50% in the diffuser.
From there the compressed air moved towards the cannular combustion chambers, of which there are ten. These chambers were used because the material science of the 1940s meant that industrial-scale production of modern annular chambers was not feasible. Here, fuel was sprayed into the compressed air and ignited.
Last of all, the combusting air-fuel mixture passed through a single turbine, which turned a shaft, which was what drove the compressor at the front of the engine.
This type of engine is simple, and robust in operation. However, they are limited in how much they can compress air since the way to do that is to make the diameter greater, as only two stages of compressor have been feasible due to excessive speeds of the impeller in the third stage. Because of the increasing diameter, there is a need for a larger and larger airframe to contain the engine, which results in increased drag and weight.
In a very good single-stage centrifugal engine, a compression ratio of 4:1 is possible. So the air going into the combustion chamber is at four times the pressure of the ambient air. In a two-stage engine, a ratio of 12:1 is roughly the limit.
Specifications I-16/J31
Type: Turbojet
Length: 72 inches, 183 cm
Diameter: 41.5 inches, 105 cm
Dry weight: 850 lbs, 386 Kg
Fuel type: AN-F32 Kerosene or 100/130 octane gasoline
Components
Compressor: Single-stage double-sided centrifugal
Combustors: Ten cannular
Turbine: Single-stage
Performance
Maximum thrust: 7,161 N (1,610 lb) at 16,500 rpm
Overall pressure ratio: 3.8:1
Turbine inlet temperature: 1,220 °F (660 °C)
Specific fuel consumption: 1.2 lb/lbf/hr, 0.1223 kg/kN/hr
Thrust-to-weight ratio: 1.94:1
In late summer 1942 the first prototype XP-59A, SN 42-108784, was sent across the country from New York to Muroc Dy Lake in California, later known as Edwards Air Force Base. It arrived on September 12th and was quickly fitted with a mock wooden propellor in an effort to keep the project secret for a bit longer.
Bell's test pilot, Robert Stanley, 'inadvertently' made the first flight with the XP-59A during a high-speed taxi trial on October 1st. The official first flight was the next day with a USAAF pilot in the cockpit. It had only taken 13 months for Bell to make a flying prototype from when the contract was signed.
Video of some of the test flights of the XP-59A.
Specifications: XP-59A
General Electric I-A
Dimensions:
Wingspan: 45 feet, 6 inches
Length: 38 feet, 2 inches
Height: 12 feet, 4 inches
Wing Area: 385 feet^2
Weight:
Empty: 7,320 lbs
Maximum: 12,562 lbs
570-850 gallons of fuel
Performance:
Top Speed: 404 mph @ 25,000 feet
Service Ceiling: 45,756 Feet
The XP-59A had several issues, it's top speed of 404 miles per hour was below expectations, the engines were heavy and produced relatively little power, and there were issues with turbine blades overheating. Bell's positioning of the engines was also poor, causing interference and 'snaking', which made the XP-59A a poor platform for guns. Prototype two flew on February 15th, 1943 and the third flew in late April of that same year.
Work had continued on the improved I-16 engine and the improved YP-59A, and the YP-59A arrived in Muroc in June, 1943. At this time, the name 'Airacomet' was given to the plane. The YP-59A flew in August 1943, but despite the more powerful engine, there was little improvement in performance.
Specifications: YP-59A
General Electric I-16/J-31
Dimensions:
Wingspan: 45 feet, 6 inches
Length: 38 feet, 2 inches
Height: 12 feet
Wing Area: 385 feet^2
Weight:
Empty: 7,626 lbs
Gross: 10,532 lbs
Maximum: 12,562 lbs
290-590 gallons of fuel
Performance:
Top Speed: 409 mph @ 35,000 feet
At Sea Level: 350 mph
Cruising Speed: 314 mph
Landing Speed: 80 mph
Service Ceiling: 43,200 Feet
Normal Range: 640 Miles
Rate of Climb: 2970 feet / 1 minute, 36,000 feet / 20.4 minutes
The last four YP-59As were fitted with the armament for the production model, three AN/M2 .50 Browning machine guns with a total of 600 rounds and a single Browning M4 37mm cannon with 44 shells.
A deal was made with the RAF, and the third YP-59A (Serial Number 42-22611) was sent to England in exchange for the first Gloster Meteor. The Meteor was the first British jet fighter and was the only Allied jet aircraft to see combat in WWII. The Airacomet (RAF number JRJ326/G) was flown only 20 times between December 20th, 1943 and April 26th, 1944 due to lack of spare parts, and the disappointing performance of the fighter. It was found to be badly underpowered, and had an excessive takeoff run, along with poor acceleration.
The US Navy received the eighth and ninth YP-59s (Serial numbers 42-108779 and 42-100779) in December 1943. Testing proved that the Airacomet was totally unsuited to operations from aircraft carriers due to its poor acceleration, bad view from the cockpit, and lack of drag when coming to land. The last issue was because Bell didn't add any sort of dive breaks to the aircraft due to it's anticipated lackluster performance. Bell delivered the last YP-59A in June 1944.
The USAAF had ordered a production run of 100 P-59As before the prototype had even flown. However, the shortcomings of the prototype and the YP-59A showed that the Airacomet would not be an acceptable fighter and that further improvements wouldn't be quick in coming. So on October 30th, 1943 the order was halved, and then only 20 were finished as P-59As. Most of them were fitted with J31-GE-3 engines with 1650 pounds of thrust, but a few at the end of the run were fitted with the J31-GE-5 turbojet which generated 2,000 pounds of thrust.
Specifications: P-59A
General Electric I-16/J-31
Dimensions:
Wingspan: 45 feet, 6 inches
Length: 38 feet, 10 inches
Height: 12 feet, 4 inches
Wing Area: 385 feet^2
Weight:
Empty: 7,950 lbs
Gross: 10,822 lbs
Maximum: 13,000 lbs
290-590 gallons of fuel
Performance:
Top Speed: 413 @ 30,000, 380 @ 5,000
Cruising Speed: 375 mph
Service Ceiling: 46,200 Feet
Range: 375 Miles @ 400 MPH, 550 miles @ 308 mph
Rate of Climb: 10,000 feet / 3.2 minutes, 30,000 feet / 15.5 minutes
The twenty-first through to the last Airocoments were built as P-59Bs, with 55 more gallons of fuel, and all fitted with the J31-GE-5 turbojets. Airacomets never saw combat, and most of them were sent to the 412th Fighter Group at Muroc as training aircraft. A handful were modified later to control drones or as manned target aircraft with another cockpit in the nose in place of the guns.
Specifications: P-59B
General Electric I-16/J-31
Dimensions:
Same as P-59A
Weight:
Empty: 8,165 lbs
Gross: 11,040 lbs
Maximum: 13,700 lbs
356-656 gallons of fuel
Performance:
Same as P-59A Except
Normal Range: 375 Miles @ 400 mph, 525 @ 371 mph, 950 @ 304 mph
Total Production for the P-59 in all forms:
Three XP-59A, Serial numbers 42-108784/108786
Thirteen YP-59A, Serial numbers 42-108771/108783
Twenty P-59A, Serial numbers 44-22609/22628
Thirty P-59B, Serial numbers 44-22629/22658. Fifty more (S/N 44-22659-22708) canceled.
In total sixty-six aircraft were built.
Six survive as outlined below, seven P-59Bs crashed and four YP-59As crashed. Two P-59As collided in midair on March 1st, 1945 near Gray Butte AAF, resulting in the deaths of both pilots. But these are the only fatalities from the P-59 that the author was able to find, an impressive result considering the revolutionary nature of the aircraft.
There is another semi-derivative of the P-59 though. Bell was working on the XP-59B, a low-winged monoplane with a single I-16 turbojet in the rear of the fuselage and air intakes in the wing roots. The Bell plant in Buffalo, New York was so occupied with other projects that the drawings were transferred to Lockheed by the USAAF.
Lockheed took these drawings, and they were influential in their development of the P-80 Shooting Star, which was the first successful American jet-powered fighter, which was mere hours away from going on combat missions over Italy when the war in Europe ended.
What Is Left?
There are six known P-59s left.
One XP-59A (42-108784) is on display at the National Air and Space Museum in Washington, D.C.
One P-59A (44-22614) is on display at the March Field Air Museum in Riverside, California
Three P-59Bs remain. One at the USAF Flight Test Center Museum at Edwards AFB (44-22633), one at Pioneer Village in Minden, Nebraska (44-22656), and one at the National Museum of the United States Air Force in Dayton, Ohio (44-22650).
The Planes of Fame Museum in Chino, California is restoring a YP-59A (42-108777) to flight status with an anticipated completion date in 2021.
Three IV-1430 engines are known to exist, one of which has been restored to running condition.
Sources:
Airframes
http://www.joebaugher.com/usaf_fighters/p52.html - History and stats of the XP-52.
http://www.joebaugher.com/usaf_fighters/p59.html - History and stats of the XP-59, XP-59A, and onward.
American Combat - Ray Wagner - Development history and specifications.
http://www.joebaugher.com/usaf_serials/1942_5.html - Serial numbers of XP-59A and YP-59A.
http://www.joebaugher.com/usaf_serials/1944_1.html - Serial numbers of P-59A and P-59B.
https://airandspace.si.edu/collection-objects/bell-xp-59a-airacomet - Smithsonian article about the XP-59A.
https://crgis.ndc.nasa.gov/historic/Additional_Photos_for_12-Foot_Low_Speed_Tunnel_3#Model_.2354A - Windtunnel test photos of the XP-52/59 design.
Engines
https://www.youtube.com/watch?v=wLbAuoZmw_M - Explanation of the operation of centrifugal and axial turbojets.
IV-1430
https://web.archive.org/web/20071212200459/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=818
http://www.enginehistory.org/Collections/IV-1430/iv-1430.shtml - Information on the restoration of an IV-1430 to running condition.
I-A, J31
http://www.enginehistory.org/GasTurbines/EarlyGT/W2B/W2B.shtml - Development of British and American turbojet engines.
https://www.neam.org/engine-collection-detail.php?name=gej31 - Photographs of a J31 engine.
https://airandspace.si.edu/collection-objects/ge-j31-turbojet-engine-cutaway-motorized?object=nasm_A19520085000 - Cutaway of a J31, showing how the engine worked.
Surviving P-59s
https://www.marchfield.org/aircraft/fighter/p-59a-airacomet-bell/ - March Field's P-59A.
http://www.johnweeks.com/p59/index.html - List of known surviving airframes.
https://planesoffame.org/index.php?page=restoration-projects - Planes of Fame restoration project.
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