The Allison V-1710 aircraft engine designed and produced by the Allison Engine Company was the only US-developed V-12 liquid-cooled engine to see service during World War II. Versions with a turbocharger gave excellent performance at high altitude in the twin-engined Lockheed P-38 Lightning, and turbo-superchargers were fitted to experimental single-engined fighters with similar results.
The United States Army Air Corps (USAAC) preference for turbochargers early in the V-1710's development program meant that less effort was spent on developing suitable mechanically-driven centrifugal superchargers for the Allison V-12 design, as other V-12 designs from friendly nations like the British Rolls-Royce Merlin were already using.
When smaller-dimensioned or lower-cost versions of the V-1710 were desired, they generally had poor performance at higher altitudes. The V-1710 nevertheless gave excellent service when turbocharged, notably in the P-38 Lightning, which accounted for much of the extensive production run.
|Allison V-1710 C-series engine|
|Type||Liquid-cooled V-12 piston engine|
|Manufacturer||Allison Engine Company|
|Major applications||Bell P-39 Airacobra |
Curtiss P-40 Warhawk
Lockheed P‑38 Lightning
North American P-51 Mustang
North American F‑82 Twin Mustang
|Developed into||Allison V-3420|
The Allison Division of General Motors began developing an ethylene glycol-cooled engine in 1929 to meet a USAAC need for a modern, 1,000 hp (750 kW), engine to fit into a new generation of streamlined bombers and fighters. To ease production the new design could be equipped with different propeller gearing systems and superchargers, allowing a single production line to build engines for various fighters and bombers.
The United States Navy (USN) hoped to use the V-1710 in its rigid airships Akron and Macon, but both were equipped with German-built Maybach VL-2 engines as the V-1710 was still in testing when the Macon was lost in February 1935 (the Akron having been lost in April 1933). The USAAC purchased its first V-1710 in December 1932. The Great Depression slowed development, and it was not until December 14, 1936, that the engine next flew in the Consolidated XA-11A testbed. The V-1710-C6 successfully completed the USAAC 150 hour Type Test on April 23, 1937, at 1,000 hp (750 kW), the first engine of any type to do so. The engine was then offered to aircraft manufacturers where it powered the prototype Curtiss XP-37s. All entrants in the new pursuit competition were designed around it, powering the Lockheed P-38, Bell P-39 and Curtiss P-40. When war material procurement agents from the United Kingdom asked North American Aviation to build the P-40 under license, NAA instead proposed their own improved aircraft design, using the V-1710 in their NA-73.
The V-1710 has 12 cylinders with a bore and stroke of 5.5 by 6 in (139.7 by 152.4 mm) in 60° V format, for a displacement of 1,710.6 cu in (28.032 L), with a compression ratio of 6.65:1. The valvetrain has a single overhead camshafts per bank of cylinders and four valves per cylinder.
The engine design benefited from the General Motors philosophy to build-in production and installation versatility, embracing a philosophy of modular design for aviation powerplants. The engine was constructed around a basic power section, from which different installation requirements could be met by fitting the appropriate accessories section at the rear, and an appropriate power output drive at the front. A turbo-supercharger could be used, if desired.
The P-39, P-63, and Douglas XB-42 Mixmaster used V-1710-Es, exchanging the integral reduction gear for an extension shaft driving a remotely located reduction gear and propeller. Aircraft such as the P-38, P-40, P-51A, and North American P-82E used close-coupled propeller reduction gears, a feature of the V-1710-F series.
The accessory end had a one- or two-speed engine-driven supercharger that might have a second stage with or without an intercooler, the ignition magnetos and the customary assortment of oil and fuel pumps, all dictated by the application requirements. The front of the engine could have one of a number of different output drives. The drive might be a "long-nose" or close coupled propeller reduction gear, an extension drive to a remote gearbox, or a gearbox that could drive two wing-mounted propellers from a fuselage-mounted engine. Another key feature of the V-1710 design was its ability to turn the output shaft clockwise or counter-clockwise by assembling the engine with the crankshaft turned end-for-end, by installing an idler gear in the drive train to the supercharger, camshafts, and accessories, installing a starter turning the proper direction, and re-arranging the ignition wiring on the right side to accommodate a changed firing order. No change to the oil pump nor coolant pump circuits was needed. The ability to reverse the direction of rotation with a minimum of extra parts to achieve the task allowed the use of either a "tractor" or "pusher" propeller. This approach allowed easy changes of the supercharger(s) and supercharger drive-gear ratio. That gave different critical altitude (the maximum altitude at which the engine could produce full power) ratings ranging from 8,000 to 26,000 feet (2,400 to 7,900 m).
The V-1710 has often been criticized for not having a "high-altitude" supercharger. The comparison is usually to the later, two-stage, versions of the Rolls-Royce Merlin 60-series engines also built by Packard as the V-1650 and used in the P-51B Mustang and subsequent variants. The USAAC had specified that the V-1710 was to be a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use their newly developed turbo-supercharger as was featured in the XP-37(YP-37), P-38, and XP-39.
The benefits of a two-stage supercharger eventually became so clear that Allison did make some efforts in this direction. Allison attached an auxiliary supercharger in various configurations to the existing engine-mounted supercharger and carburetor. Early versions of these two-stage supercharger engines were used on the P-63. No intercooler, aftercooler, or backfire screen (flame trap) were incorporated into these two-stage V-1710 engines (except for the V-1710-119 used on the experimental P-51J, which had an aftercooler). The two-stage Merlin engines had all of these features, which were designed to prevent detonation from charge heating and backfire into the supercharger. The G-series V-1710s installed on the F-82 E/F/G models had only anti-detonation injection (ADI) to deal with these problems, and not surprisingly had severe reliability and maintenance problems. In one record, it was stated that the F-82 required 33 hours of maintenance for each hour of flight.
Although the early V-1710 powered P-39, P-40 and P-51A were limited to combat operations at a maximum of about 15,000 feet (4,600 m) they were available in comparatively large numbers and were the mainstay of some Allied Air Forces in all but the European theater of war. The engines proved to be robust and little affected by machine-gun fire. In total, over 60 percent of the post-June 1941 USAAF's pursuit aircraft operated during WWII were powered by the V-1710.
Allison slowly but continuously improved the engine during the war. The initial rating of 1,000 hp (750 kW) was incrementally increased; the final V-1710-143/145(G6R/L) was rated for 2,300 hp (1,700 kW). By 1944, the War Emergency Power rating on the P-38L was 1,600 hp (1,200 kW).
The most powerful factory variant was the V-1710-127, designed to produce 2,900 hp (2,200 kW) at low altitude and 1,550 hp (1,160 kW) at 29,000 feet (8,800 m). This engine was static tested at 2,800 hp (2,100 kW) and was planned for installation in an XP-63H aircraft. The end of the war ended this development, so this promising experiment never flew. The extra power of this version was derived from using exhaust turbines, not to drive a turbo-supercharger, but to return that energy to turning the crankshaft, called a turbo-compound engine.
Improvements in manufacturing brought the cost to produce each engine from $25,000 down to $8,500 and allowed the installed lifetime of the engine to be increased from 300 hours to as much as 1,000 hours for the less-stressed power-plants. Weight increases needed to accomplish this were minimal, with the result that all models were able to produce more than 1 hp/lb (1.6 kW/kg) at their takeoff rating.
Comparisons between the Allison V-1710 and the Rolls-Royce Merlin engine "families" are inevitable. What can be said for the Allison; is that it made more power at less boost, with a longer time between overhauls, and with a parts-count that was nearly half that of the Merlin engine; which greatly facilitated mass production. There was also a high degree of commonality of parts throughout the series. The individual parts of the Allison series were produced to a high degree of standardization and reliability, using the best technology available at the time. Even after the war, racing Merlins used Allison connecting rods. As stated previously, General Motors' policies regarding versatility meant that their Allison division would also employ modular design features on the V-1710 from its "long block" core V-12 unit outwards, so that it was capable of being mated to many different styles of turbo-superchargers and various other accessories, although the variety of turbo-superchargers available for installation was limited due to the constraints of single-engine fighter design. Since it was produced in large numbers and was highly standardised, the engine has been used in many postwar racing designs. Its reliability and well-mannered operation allowed it to operate at high rpm for extended periods.
Following the war, North American built 250 P-82E/F for air defense roles into the early 1950s. This was the final military role for the V-1710.
The USAAC had earlier decided to concentrate on turbo-superchargers for high altitude boost, believing that further development of turbo-superchargers would allow their engines to outperform European rivals using displacement superchargers. Turbo-superchargers are powered by the engine exhaust and so do not draw power from the engine crankshaft, whereas displacement superchargers are coupled directly by shafts and gears to the engine crankshaft. Turbo-superchargers do increase the exhaust back-pressure and thus do cause a decrease in engine power, but the power increase due to increased induction pressures more than makes up for that decrease. Crankshaft-driven superchargers require an increase in directly driven percentage of engine power as altitude increases (the two-stage supercharger of the Merlin 60 series engines consumed some 230–280 hp (170–210 kW) at 30,000 ft (9,100 m). General Electric was the sole source for research and production of American turbo-superchargers during this period, from its four decades worth of steam turbine engineering experience.
Turbo-superchargers were indeed highly successful in U.S. bombers, which were exclusively powered by radial engines. The P-47 fighter had the same combination of radial engine (R-2800) and turbo-supercharger and was also successful, apart from its large bulk, which was caused by the need for the ductwork for the aft-mounted turbo-supercharger.
However, mating the turbocharger with the Allison V-1710 proved to be problematic. As a result, designers of the fighter planes that utilized the V-1710 were invariably forced to choose between the poor high-altitude performance of the V-1710 versus the increased problems brought on by addition of the turbo-supercharger. The fates of all of the V-1710 powered fighters of World War II would thus hinge on that choice.
The original XP-39 was built with a V-1710 augmented by a General Electric Type B-5 turbo-supercharger as specified by Fighter Projects Officer Lieutenant Benjamin S. Kelsey and his colleague Gordon P. Saville. Numerous changes were made to the design during a period of time when Kelsey's attention was focused elsewhere, and Bell engineers, NACA aero-dynamic specialists and the substitute fighter project officer determined that dropping the turbocharger would be among the drag reduction measures indicated by borderline wind tunnel test results; an unnecessary step, according to aviation engineer and historian Warren M. Bodie. The production P-39 was thus stuck with poor high-altitude performance and proved unsuitable for the air war in Western Europe which was largely conducted at high altitudes. The P-39 was rejected by the British, but used by the U.S. in the Mediterranean and the early Pacific air war, as well as shipped to the Soviet Union in large numbers under the Lend Lease program. The Soviets were able to make good use of P-39s because of its excellent manoeuvrability and because the air war on the Eastern Front in Europe was primarily short ranged, tactical, and conducted at lower altitudes. In the P-39, Soviet pilots scored the highest number of individual kills made on any American, or British fighter type.
The P-40, which also had only the single-stage, single-speed-supercharged V-1710, had similar problems with high-altitude performance.
The P-38 was the only fighter to make it into combat during World War II with turbo-supercharged V-1710s. Political questions arise from the exclusivity of use of TWO GE turbo-superchargers per aircraft. The operating conditions of the Western European air war – flying for long hours in intensely cold weather at 30,000 feet (9,100 m) – revealed several problems with these engines. These had a poor manifold fuel-air distribution and poor temperature regulation of the turbo-supercharger air, which resulted in frequent engine failures (detonation occurred as the result of persistent uneven fuel-air mixture across the cylinders caused by the poor manifold design). Specially formulated fuels were a necessity for the P-38 as were specific spark plugs needed for specific cylinders. The turbo-supercharger had additional problems with getting stuck in the freezing air in either high or low boost mode; the high boost mode could cause detonation in the engine, while the low boost mode would be manifested as power loss in one engine, resulting in sudden fishtailing in flight. These problems were aggravated by sub-optimal engine management techniques taught to many pilots during the first part of WWII, including a cruise setting that ran the engine at high RPM and low manifold pressure with a rich mixture. These settings can contribute to over-cooling of the engine, fuel condensation problems, accelerated mechanical wear, and the likelihood of components binding or "freezing up." Details of the failure patterns were described in a report by General Doolittle to General Spatz in January 1944. In March 1944, the first Allison engines appearing over Berlin belonged to a group of P-38Hs of 55th Fighter Group, engine troubles contributing to a reduction of the force to half strength over the target. It was too late to correct these problems in the production lines of Allison or GE, and as the numbers of Merlin-engined P-51 Mustangs based in England mounted up through the end of 1943 and into 1944, the P-38s were steadily withdrawn from Europe until October 1944 when they were no longer used for bomber escort duty with the Eighth Air Force. A few P-38s would remain in the European theater as the F-5 for photo reconnaissance.
The P-38 had fewer engine failures in the Pacific Theater, where operating techniques were better developed (such as those recommended by Charles Lindbergh during his development work in the theater),) and the Japanese did not operate at such high altitudes. Using the same P-38Gs which were proving difficult to maintain in England, Pacific-based pilots were able to use the aircraft to good advantage including, in April 1943, Operation Vengeance, the interception and downing of the Japanese bomber carrying Admiral Isoroku Yamamoto. New P-38 models with ever-increasing power from more advanced Allisons were eagerly accepted by Pacific air groups.
When Packard started building Merlin V-1650 engines in America in 1942, certain American fighter designs using the Allison V-1710 were changed to use the Merlin. The P-40F, a Lend Lease export to Britain, was one of the first American fighters to be converted to a Packard-Merlin engine. However, the installed engine was the V-1650-1 (a Packard-produced Merlin XX) with a slightly improved single-stage, two-speed supercharger, yielding only modest gains in performance due to the airframe's own limitations.
The last Allison powered P-51, the Mustang I(II)/P-51A, used the single-stage, single-speed Allison V-1710-81, with a 9.6:1 blower ratio. This allowed the P-51A to reach a maximum speed of 415 mph (668 km/h; 361 kn) at 10,400 ft (3,200 m) and maintain 400 mph (640 km/h; 350 kn) at 23,000 ft (7,000 m). This was more than 70 mph (110 km/h; 61 kn) faster than the Merlin 45-powered Spitfire V at 10,000 ft (3,000 m), and more than 30 mph (48 km/h; 26 kn) faster at 25,000 ft (7,600 m). Its speed impressed the British, and the RAF quickly realized the airplane would possess excellent high altitude performance if the Allison V-1710 engine were replaced by the 60-Series Merlin. A similar proposal to cure the P-38's problems by replacing its Allisons with Merlins was quashed by the USAAF, after protests from Allison.
Starting with the V-1710-45 around 1943 (after the P-51 had been fitted with a Merlin 61 by Rolls Royce), Allison attached an auxiliary supercharger to some of its engines in an effort to improve high-altitude performance. The two-stage supercharged Allison was essentially developed as an "add on" to the single-stage engine, and required minimal changes to the base engine. While it lacked the refinement, compactness and after-cooler of the two-stage Merlin, the Allison used a pressure-altitude governed variable-speed first stage. Various configurations of this auxiliary supercharger were used in production versions of the V-1710 that powered aircraft such as the Bell P-63 and North American P-82E/F/G series. In addition, it was tried or studied as the powerplant for many experimental and test aircraft such as the Curtiss XP-55 Ascender, North American XP-51J "lightweight Mustang", Boeing XB-38 Flying Fortress, and Republic XP-47A (AP-10), both of the latter with turbo-superchargers.
The V-1710-powered F-82 did not arrive in time for World War II, but did see brief action in the Korean War, although the type was completely withdrawn from Korea by the end of 1950. It had a short service life that was probably due to a combination of factors: poor reliability from the G-series V-1710 engines, low numbers of F-82s produced, and the arrival of jet fighters. The initial production P-82B had Merlin engines, but North American was forced to use the Allison V-1710 for the E/F/G models when Packard stopped production of the Merlin engine.
The V-1710's useful life continued, as thousands were available on the surplus market. In the 1950s, many drag racers and land speed racers, attracted by its reliability and good power output, adopted the V-1710; Art Arfons and brother Walt in particular used one, in Green Monster. It proved unsuccessful as a drag racing engine, being unable to accelerate rapidly, but "could taxi all day at 150". Unlimited hydroplane racing also became a big sport across the U.S. at this time and V-1710s were often tuned for racing at up to 3,200 hp (2,400 kW)—power levels that were beyond design criteria and significantly reduced durability.
Later, as purpose-built V8 engines became available for drag racing and unlimited boats shifted to turboshaft power, tractor pullers began using the Allison engine, again developing unimagined power. Finally, the warbird movement began to restore and return to the air examples of the classic fighters of the war and many V-1710-powered pursuit airplanes began to fly again, with freshly overhauled engines. The reliability, maintainability, and availability of the engine has led others to use it to power flying examples of aircraft whose original engines are unobtainable. This includes newly manufactured Russian Yak-3 and Yak-9 airplanes, originally powered by Klimov V-12s in World War II and the two (so far) airworthy examples of the Ilyushin Il-2, taking the place of the Mikulin V-12 it originally used, as well as ambitious projects such as a replica Douglas World Cruiser and Focke-Wulf Fw 190D by Flug Werk of Germany.
Allison's internal model designation for the V-1710 started with the letter A and proceeded to the letter H. Each letter designated a family of engines that shared major components, but differed in specific design details. Each of these designs were identified by a number, starting with number 1. The last letter, which was introduced when both right hand turning and left hand turning engines were built, identified by the letter R or L respectively.
The military model numbers were identified by a "dash number" following the engine description "V-1710". The USAAC/USAAF models were the odd numbers, starting with "-1" and the USN models were the even numbers, starting with "-2".
"A" series engines were early development engines for the USN and USAAC. The first military model was a single V-1710-2, which was first sold to the USN on June 26, 1930. The "A" engines had no counterweights on the crankshaft, 5.75:1 compression ratio, 2:1 internal spur gear-type reduction gear boxes, 8.77:1 supercharger ratio, 9.5 in (240 mm) impeller, SAE #50 propeller shaft, a float-type carburetor, and produced 1,070 hp (800 kW) at 2800 rpm on 92 octane gasoline.
"B" series engines were designed for USN airships. The military model was V-1710-4. They differed from the "A" series engines in that they did not have a supercharger, had two float-type down-draft carburetors were mounted directly to the intake manifold, an SAE #40 propeller shaft, and could be brought from full power to stop and back to full power in the opposite rotation in less than 8 seconds. They produced 600–690 hp (450–510 kW) at 2400 rpm.
"C" series engines were developed for highly streamlined pursuit aircraft for the USAAC, and are easily identified by the long reduction gear case. The military models were V-1710-3, -5, -7, -11. -13, -15, -19, -21, -23, -33, producing between 750–1,050 hp (560–780 kW) at 2600 rpm. These engines came in two groups, one group rated at full power at sea level, the other rated at full power at high altitude. The altitude rating difference was in the supercharger gear ratio, four of which were used: 6.23:1, 6.75:1, 8.0:1 and 8.77:1. These engines received heavier crankcases, a stronger crankshaft, SAE #50 propeller shaft, and Bendix pressure carburetors.
"D" series engines were designed for pusher applications using propeller-speed extension shafts and remote thrust bearings mounted to the airframe. The military models were V-1710-9, -13, -23, and -41, producing 1,000–1,250 hp (750–930 kW) at 2600 rpm. Supercharger ratios were 6.23:1, 8.0:1 or 8.77:1, depending on altitude rating. These engines had the compression ratio increased to 6.65:1. Marvel MC-12 fuel injection, which was unsatisfactory and quickly replaced by a float-type carburetor on -9 and -13 models. Later dash number engines used Bendix pressure carburetors. These engines were being designed at the same time as the V-3420 engine, and shared many assemblies as they were developed. The "D" series engines were the last of the "early" V-1710 engines.
"E" series engines were designed for remote gearbox applications using crankshaft-speed extension shafts and remote 1.8:1 gearboxes with SAE #60 hollow propeller shafts. The military models were V-1710-6, -17, -31, 35, -37, -47, -59, -63, -83, -85, -93, -103, -109, -117, -125, -127, -129, -133,-135 and -137, producing 1,100–2,830 hp (820–2,110 kW) at 3000 rpm. Supercharger gear ratios were: 6.44:1, 7.48:1, 8.10:1, 8.80:1 and 9.6:1 depending on altitude rating. These engines were a complete redesign, and did not share many components with the earlier engine series. Almost all components were interchangeable with later series engines and the V-3420, and could be assembled as right hand or left hand turning engines in either pusher or tractor applications.
"F" series engines were designed for late model pursuit aircraft, and are identified by the compact external spur gear-type reduction gear box. Military models were V-1710-27, -29, -39, -45, -49, -51, -53, -55, -57, -61, -75, -77, -81, -87, -89, -91, -95, -99, -101, -105, -107, -111, -113, -115, -119, producing 1,150–1,425 hp (858–1,063 kW) at 3000 rpm. The V-1710-101, -119 and -121 models has an auxiliary supercharger, some with a liquid-cooled aftercooler. Supercharger gear ratios were: 6.44:1, 7.48:1, 8.10:1, 8.80:1 and 9.60:1 depending on altitude rating. These engines had either a six or twelve weight crankshaft, revised vibration dampeners that combined to allow higher engine speeds, SAE #50 propeller shaft, and higher horsepower ratings. The "E" series and "F" series engines were very similar, the primary difference being the front crankcase cover, which was interchangeable between the two series engines.
"G" series engines were designed for high-altitude pursuit aircraft, and are identified by the auxiliary supercharger with a Bendix "Speed-Density" fuel control. Military models were V-1710-97, -131, -143, -145, and -147, producing 1,425–2,000 hp (1,063–1,491 kW) at 3000 rpm. Supercharger gear ratios were: 7.48:1, 7.76:1, 8.10:1, 8.80:1 and 9.60:1 depending on altitude rating. These engines were equipped with an SAE #50 propeller shaft and a single power lever to regulate engine performance, reducing the pilot's workload when managing this very complex engine.
"H" series engines were to use a two-stage supercharger driven by a two-stage air-cooled power recovery turbine. The engine was to have an aftercooler and port-type fuel injection. This variant, however, was never built.
|AEC Model||Military Model||Arrangement||Notes|
|A1||GV-1710-A||1 built. Rebuilt 2 times as XV-1710-2.|
|A2||XV-1710-1||Long reduction gear housing||Testing. 1 built.|
|B1R, B2R||XV-1710-4||Quick reversing, remote 90 degree gearbox||3 built for airships|
|C1, C2, C3, C4, C7, C10, C15||XV-1710-3, -5, -7, -9, -21, -33||Type test engines||16 built. C2 rebuilt from -5 to -7. C4 first flight engine in A-11A and later in XP-37|
|C8, C9||V-1710-11, -15||Long nose||3 built. C8 RH turn for XP-37, XP-38, C9 LH turn for XP-38|
|C13||V-1710-19||Long nose||Early production P-40 engine|
|D1, D2||YV-1710-7, -9, XV-1710-13||Pusher with extension shaft||6 built for XFM-1|
|E1, E2, E5||V-1710-6, -17, -37||Remote gearbox||5 built for XFL and XP-39|
|E4, E6||V-1710-35, -63||Remote gearbox||P-39C engine|
|E11, E21, E22, E27, E30, E31||V-1710-47, -93, -109, -117, -133, -135||Remote gearbox||P-63/A/C/D/E/F/G/H engine|
|E23RB, E23LRB||V-1710-129||Remote gearbox||Douglas XB-42 dual installation with combining gearbox and extension shafts|
|F1||V-1710-25||Short nose||1 built Development engine for XP-38|
|F2R, F2L||V-1710-27, -29||Short nose||P-38D/E engines|
|F3R||V-1710-37||Short nose||2 built for NA-73X Mustang prototype|
|F3R||V-1710-39||Short nose||P-40D/E and P-51A Production engine|
|F4R||V-1710-73||Short nose||P-40K engine|
|F5R, F5L||V-1710-49, -53||Short nose||P-38F engine|
|F10R, F10L||V-1710-51, -55||Short nose||P-38G engine|
|F15R, F15L||V-1710-75, -77||Short nose||XP-38K engine, 1,875 hp (WEP), geared 2.36 to 1 for use with Hamilton Standard Hydromatic "high activity" propellers|
|F30R, F30L||V-1710-111, -113||Short nose||P-38L engine|
|F32R||V-1710-119||Short nose and two-stage supercharger||XP-51J|
|G1R||V-1710-97||WER test engine|
|G4R||remote extension shaft drive version of G3R|
|G6R, G6L||V-1710-145 -147||P-82E/F engine|
The Allison V-3420 was an American large experimental W-configuration American piston aircraft engine, designed in 1937.Bell P-39 Airacobra
The Bell P-39 Airacobra was one of the principal American fighter aircraft in service when the United States entered World War II. The P-39 was used by the Soviet Air Force, and enabled individual Soviet pilots to collect the highest number of kills attributed to any U.S. fighter type flown by any air force in any conflict. Other major users of the type included the Free French, the Royal Air Force, the United States Army Air Forces, and the Italian Co-Belligerent Air Force.Designed by Bell Aircraft, it had an innovative layout, with the engine installed in the center fuselage, behind the pilot, and driving a tractor propeller with a long shaft. It was also the first fighter fitted with a tricycle undercarriage. Although its mid-engine placement was innovative, the P-39 design was handicapped by the absence of an efficient turbo-supercharger, preventing it from performing high-altitude work. For this reason it was rejected by the RAF for use over western Europe but adopted by the USSR where most air combat took place at medium and lower altitudes.
Together with the derivative P-63 Kingcobra, the P-39 was one of the most successful fixed-wing aircraft manufactured by Bell.Bell P-63 Kingcobra
The Bell P-63 Kingcobra is an American fighter aircraft developed by Bell Aircraft in World War II from the Bell P-39 Airacobra in an attempt to correct that aircraft's deficiencies. Although the P-63 was not accepted for combat use by the United States Army Air Forces, it was adopted by the Soviet Air Force.Bell P-76
The Bell P-76 was the proposed designation for a production model derivative of the XP-39E, a single-engine American fighter aircraft prototype of World War II.Bell YFM-1 Airacuda
The Bell YFM-1 Airacuda was an American heavy fighter aircraft, developed by the Bell Aircraft Corporation during the mid-1930s. It was the first military aircraft produced by Bell. Originally designated the Bell Model 1, the Airacuda first flew on 1 September 1937. The Airacuda was marked by bold design advances and considerable flaws that eventually grounded the aircraft.
The Airacuda was Bell Aircraft's answer for a "bomber destroyer" aircraft. Although it did see limited production, and one fully operational squadron was eventually formed, only one prototype and 12 production models were ultimately built, in three slightly different versions.Benjamin S. Kelsey
Benjamin Scovill Kelsey (March 9, 1906 – March 3, 1981) was an American aeronautical engineer and test pilot. Serving as America's chief fighter projects officer, he helped bring success in World War II to the United States Army Air Forces by initiating the manufacture of innovative fighter aircraft designs, and by working to quickly increase American fighter production to meet the needs of the coming war.
Kelsey co-authored the technical specifications which led to the development of the P-39 Airacobra and the P-38 Lightning. He worked around Air Corps strictures to initiate the development of drop tanks for American fighters. Kelsey was the driving force behind a program of advanced airfoil research which eventually resulted in the P-51 Mustang.
After the war, Kelsey served in various staff assignments supervising weather operations, personnel and materiel. He was an important committee member of the group that approved and funded the rocket-powered North American X-15.Big Al II (Funny Car)
Big Al II is a pioneering funny car built in 1963 by Jim Lytle. It started the trend to flip-top fiberglass 'flopper' bodies.Lytle's chopped '34 Tudor project cost just US$2000, and was powered by an Allison V-1710. The body was hand made.Big Al II ran just three times, all in 1964 at Lion's Dragway, setting a record for full-bodied drag racers, before being retired.The idea was copied by Ford and Mercury for their Mercury Comet Cyclones. It would inspire “every flopper body ever formed”.Boeing Model 306
The Boeing Model 306 was the designation for a series of aircraft drafted in 1935 that achieved neither design nor production status. They included the Model 306 bomber, Model 306 flying boat, and Model 306A airliner.Boeing XB-38 Flying Fortress
The XB-38 Flying Fortress was a single example conversion of a production B-17E Flying Fortress, testing whether the Allison V-1710 V type engine could be substituted for the standard Wright R-1820 radial engine during early World War II.Curtiss P-37
The Curtiss P-37 was a fighter aircraft made by Curtiss-Wright in 1937. A development of the Curtiss P-36 Hawk, the P-37 never entered production.Curtiss P-60
The Curtiss P-60 was a 1940s United States single-engine single-seat, low-wing monoplane fighter aircraft developed by the Curtiss-Wright company as a successor to their P-40. It went through a lengthy series of prototype versions, eventually evolving into a design that bore little resemblance to the P-40. None of these versions reached production.Curtiss XP-46
The Curtiss XP-46 was a 1940s United States prototype fighter aircraft. It was a development of the Curtiss-Wright Corporation in an effort to introduce the best features found in European fighter aircraft in 1939 into a fighter aircraft which could succeed the Curtiss P-40, then in production.Hyper engine
The hyper engine was a 1930s study project by the United States Army Air Corps (USAAC) to develop a high-performance aircraft engine that would be equal to or better than the aircraft and engines then under development in Europe. The project goal was to produce an engine that was capable of delivering 1 hp/in3 (46 kW/L) of engine displacement for a weight of less than 1 lb/hp delivered. The ultimate design goal was an increased power-to-weight ratio suitable for long-range airliners and bombers.
At the time, no production engine could come close to the requirements, although this milestone had been met by special modified or purpose-built racing engines such as the Napier Lion and Rolls-Royce R. A typical large engine of the era, the Pratt & Whitney R-1830 Twin Wasp radial, developed about 1,200 hp (895 kW) from 1,830 in3 (30 L) so an advance of at least 50% would be needed. Simply scaling up an existing design would not solve the problem. While it would have increased the total available power, it would not have any significant effect on the power-to-weight ratio; for that, more radical changes were needed.Several engines were built as part of the hyper program, but for a variety of reasons none of these saw production use. Air-cooled engines from a variety of US companies were delivering similar power ratings by the early 1940s, and the licensed production of the Rolls-Royce Merlin as the Packard V-1650 provided hyper-like performance from an inline while the Allison V-1710 did the same from a US design, one produced as a private effort outside the hyper program.Jurca Spit
The Jurca MJ-10 Spitfire is a sport aircraft designed by Marcel Jurca in France as a replica of the Supermarine Spitfire and marketed for homebuilding. Plans for two versions were produced, the MJ-10, at 3/4 scale, and the MJ-100, at full-scale. Construction throughout is of wood, and the builder may choose to complete the aircraft with either a single seat or two seats in tandem. The version represented is the Mk.IX Spitfire, but allowances are made to allow the builder to portray other versions, in particular the Mk.Vc and the Mk.XIV. Additionally, the MJ-100 version may be built with a fuselage structure of welded steel tube if desired. Plans for both versions were marketed by Falconar and later Jurca Plans West.As of July 2017 two MJ-100s are known to have flown, one each in France (originally with a Hispano-Suiza but later refitted with an Allison V-1710) and the USA (with a V-1710), with several others under construction around the world.Lockheed XFM-2
The Lockheed XPB-3, later designated XFM-2, (PB - Pursuit, Biplace / FM - Fighter, Multi-seat), was a proposed American heavy fighter aircraft, developed by the Lockheed Corporation during the mid-1930s. Intended as a heavy fighter and bomber destroyer for operation by the United States Army Air Corps, it failed to win a contract for construction of a prototype, the Bell YFM-1 Airacuda being preferred.Lycoming O-1230
The Lycoming O-1230 was a flat-twelve engine for aircraft designed and developed by Lycoming Engines in the 1930s. Although the engine was flown in an aircraft, it was not fitted to any aircraft selected for production. It later served as the basis for the Lycoming H-2470 engine.Martin XB-16
The Martin XB-16, company designation Model 145, was a projected heavy bomber designed in the United States during the 1930s.North American A-36 Apache
The North American A-36 Apache (listed in some sources as "Invader", but also called Mustang) was the ground-attack/dive bomber version of the North American P-51 Mustang, from which it could be distinguished by the presence of rectangular, slatted dive brakes above and below the wings. A total of 500 A-36 dive bombers served in the Mediterranean and Southeast Asia theaters during World War II before being withdrawn from operational use in 1944.Walt Arfons
Walter Charles "Walt" (Poppy) Arfons (December 10, 1916 – June 4, 2013) was the half brother of Art Arfons, his former partner in drag racing, and his competitor in jet-powered land speed record racing. Along with Art, he was a pioneer in the use of aircraft jet engines for these types of competition.Walt was born Walter Stroud. His mother, Bessie, was half Cherokee, and died in 1983 at age 84. Walt had one brother, Dale, two years younger, as well as his ten years younger half-brother Art and an eight and a half years younger half-sister "Lou", both from his mother's marriage to Tom Arfons. Arfons' family operated a feed mill in rural Springfield Township, Ohio, where the Arfons brothers exercised their mechanical skills and ingenuity.Walt began building dragsters with Art in 1952; their first car was a three-wheeler with an Oldsmobile six-cylinder engine, and a particularly ugly Oliver farm tractor green paint finish. The announcer at the drag strip laughingly announced the car as the Green Monster, and the name was to stick to his joint projects with Art. Along with many other racers, the duo switched to using surplus aircraft piston engines, particularly the Allison V-1710 engines, due to their abundance, cheapness, and great reliability. They were the first drag racers to reach 150 miles per hour in the quarter mile. In the late 1950s, however, the brothers amicably split up.
On August 6, 1960, Walt introduced the first jet-engine dragster. He used a parachute to stop the car since, unlike the piston engines, the jet engine did not provide braking when shut off. Arfons is also credited with being the first to incinerate a junked car with the exhaust from his jet dragster, in order to provide entertainment for the crowd at Indianapolis Raceway Park one year when the race had been rained out.
In the midst of the Detroit automakers' performance competition in 1967, Chrysler Corporation gave Arfons a Dodge Dart, Plymouth Barracuda and Dodge Charger to convert into dragsters. He simply fastened jet engines into the stock cars, with most of the accessories still installed and working. These were such crowd pleasers that he later built fiberglass-bodied jet funny cars, a Chevrolet Camaro, a Mercury Comet, and Ford Mustangs.
Arfons also commissioned Tom Green to drive the jet-powered Wingfoot Express, as a result of a severe hand injury sustained when unloading the Wingfoot upon arrival at the Bonneville Salt Flats in Utah. The car held the World Land Speed Record for three days during the battle between Art Arfons and Craig Breedlove.
In 1965, Walt Arfons built Wingfoot Express 2, which reached 605 miles per hour (974 km/h), but it did not qualify for an official record. It was powered by JATO rocket bottles.
† Joint development aeroengines
|H (four-bank |
|I (inverted-V inline)|
|L (single-bank inline)|
|V (upright-V inline)|
|W (three-bank |