Allison V-1710

The Allison V-1710 aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 engine was the only indigenous US
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

-developed V-12 liquid-cooled engine to see service during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Versions with a turbosupercharger gave excellent performance at high altitude in the twin-engined Lockheed
Lockheed Corporation
The Lockheed Corporation was an American aerospace company. Lockheed was founded in 1912 and later merged with Martin Marietta to form Lockheed Martin in 1995.-Origins:...

 P-38 Lightning
P-38 Lightning
The Lockheed P-38 Lightning was a World War II American fighter aircraft built by Lockheed. Developed to a United States Army Air Corps requirement, the P-38 had distinctive twin booms and a single, central nacelle containing the cockpit and armament...

, and turbosuperchargers were fitted to experimental single-engined fighters with similar results. The US Army preference for turbosuperchargers early in the program meant that less effort was spent on developing suitable superchargers, and when smaller or lower-cost versions of the engine were desired, they generally had poor performance at higher altitudes. The V-1710 nevertheless gave excellent service when turbosupercharged, notably in the P-38 Lightning, which accounted for much of the extensive production run.

Design and development

The Allison
Allison Engine Company
The Allison Engine Company was a U.S. aircraft engine manufacturer. In 1929, shortly after the death of James Allison, the company was purchased by the Fisher brothers. Fisher sold the company to General Motors, who owned it for most of its history...

 Division of General Motors began developing the ethylene glycol
Ethylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...

-cooled engine in 1929 to meet a US Army Air Corps
United States Army Air Corps
The United States Army Air Corps was a forerunner of the United States Air Force. Renamed from the Air Service on 2 July 1926, it was part of the United States Army and the predecessor of the United States Army Air Forces , established in 1941...

 need for a modern, 1000 hp, 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 everything from fighters
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...

 to bomber
A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...


The U.S. Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 purchased the first V-1710s, the B model (the only V-1710 that did not have a gear-driven supercharger) in 1931 and installed them on the airships Akron
USS Akron (ZRS-4)
USS Akron was a helium-filled rigid airship of the United States Navy that was lost in a weather-related accident off the New Jersey coast early on April 4, 1933, killing 73 of the 76 crew and passengers on board...

 and Macon
USS Macon (ZRS-5)
USS Macon was a rigid airship built and operated by the United States Navy for scouting. She served as a "flying aircraft carrier", launching Curtiss F9C Sparrowhawk biplane fighters. In service for less than two years, in 1935 Macon was damaged in a storm and lost off California's Big Sur coast,...

. The U.S. Army Air Corps purchased its first V-1710 in December 1932. The Great Depression
Great Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...

 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 Army 150 hour Type Test on April 23, 1937 at 1000 hp, the first engine of any type to do so. The engine was then offered to aircraft manufacturers where it powered the Curtiss X/YP-37. All entrants in the new pursuit competition were designed around it, powering the Lockheed P-38, Bell P-39 and Curtiss P-40
Curtiss P-40
The Curtiss P-40 Warhawk was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational...

. When war materiel procurement agents from England asked North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...

 to build the P-40 under license, NAA instead proposed their own improved aircraft design, using the V-1710 in their P-51A.

Technical description

The V-1710 has 12 cylinders with a bore and stroke of 5.5 by in 60° V-format, aggregating to 1710.6 cu in (28.1 l) total displacement, with a compression ratio of 6.65:1.

The engine design benefited from the General Motors philosophy to build-in production and installation versatility. 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 a tailored reduction gear for power output at the front. This approach allowed easy changes of the supercharger(s) and supercharger drive-gear ratio. That gave different critical altitude ratings ranging from 8000 to 26000 ft (2,438.4 to 7,924.8 m). It allowed a variety of propeller drives and also remote placement of the reduction gear.

The P-39, P-63, and XB-42 installations used V-1710-E series engines that exchanged the integral reduction gear for an extension shaft that drove a remotely located reduction gear and propeller. Aircraft such as the P-38, P-40, P-51A, and P-82 used close-coupled propeller reduction gears, a feature of the V-1710-F series.

Another feature of the V-1710 design was its ability to turn the output shaft either 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 and accessories and by installing a starter turning the proper direction. There was no need to re-arrange the ignition wiring, firing order, or the oil and Glycol circuits to accommodate the direction of rotation.

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
Rolls-Royce Merlin
The Rolls-Royce Merlin is a British liquid-cooled, V-12, piston aero engine, of 27-litre capacity. Rolls-Royce Limited designed and built the engine which was initially known as the PV-12: the PV-12 became known as the Merlin following the company convention of naming its piston aero engines after...

 built by Packard as the V-1650
Packard V-1650
The Packard V-1650 was a liquid cooled 27 litre 60° V12 piston aircraft engine variant of the Rolls-Royce Merlin produced under licence by the Packard Motor Car Company...

 and used in the P-51B Mustang and subsequent variants. The US Army 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 turbosupercharger as was featured in the P-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 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 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 one hour of flight.

Although the early V-1710 powered P-39, P-40 and P-51A airplanes were limited to combat operations at a maximum of about 15000 feet (4,572 m) they were available in comparatively large numbers and were the mainstay of some Allied Air Forces in all but the European theater
European Theatre of World War II
The European Theatre of World War II was a huge area of heavy fighting across Europe from Germany's invasion of Poland on September 1, 1939 until the end of the war with the German unconditional surrender on May 8, 1945...

 of war. The engines proved to be robust and little affected by machine-gun fire. In total, over 60 percent of the US Army Pursuit aircraft operated during WWII were powered by the V-1710.

Allison continuously improved the engine during the war. The initial rating of 1000 hp was incrementally increased; the final V-1710-143/145(G6R/L) was rated for 2300 hp. By 1944, the War Emergency Power
War emergency power
War Emergency Power is an American term for the throttle setting on some World War II military aircraft engines. For use in emergency situations, it produced more than 100% of the engine's normal rated power for a limited amount of time, often about five minutes...

 rating on the P-38L was 1600 hp.

The most powerful factory variant was the V-1710-127, designed to produce 2900 hp at low altitude and 1550 hp at 29000 feet (8,839.2 m). This engine was static tested at 2800 hp 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 turbosupercharger, but to return that energy to turning the crankshaft. This was called a "turbo-compound
Turbo-compound engine
A turbo-compound engine is a reciprocating engine that employs a blowdown turbine to recover energy from the exhaust gases. The turbine is usually mechanically connected to the crankshaft but electric and hydraulic systems have been investigated as well. The turbine increases the output of the...

" arrangement.

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 powerplants. 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 Allison engine and the Rolls-Royce Merlin engine 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 the part count was nearly half that of the Merlin engine which facilitated mass production greatly. The British-made Merlin engines were still reliant upon hand-crafted and fitted parts from skilled craftsmen, something which was corrected by the redesign and success of the Packard V-1650
Packard V-1650
The Packard V-1650 was a liquid cooled 27 litre 60° V12 piston aircraft engine variant of the Rolls-Royce Merlin produced under licence by the Packard Motor Car Company...

 license-produced version of it in the United States, built with American production-line techniques. There also was 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! Allison employed a modular design, 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 standardized, 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 Army had earlier decided to concentrate on turbosuperchargers for high altitude boost, believing that further development of turbochargers would allow their engines to outperform European rivals using superchargers. Turbosuperchargers are powered by the engine exhaust and so do not draw power from the engine crankshaft, whereas superchargers are connected directly by gears to the engine crankshaft. Turbosuperchargers 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 make up for that decrease. Crankshaft-driven superchargers require an increasing percentage of engine power as altitude increases (the two-stage supercharger of the Merlin 60 series engines consumed some 230-280 horsepower at 30,000 ft). General Electric was the sole source for research and production of American turbosuperchargers during this period.

Turbosuperchargers 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 turbosupercharger and was also successful, apart from its large bulk, which was caused by the need for the ductwork for the aft-mounted turbosupercharger.

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 turbosupercharger. 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 Type B-5 turbosupercharger as specified by Fighter Projects Officer Lieutenant Benjamin S. Kelsey
Benjamin S. Kelsey
Benjamin Scovill "Ben" Kelsey was an American aeronautical engineer and test pilot who brought 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...

 and his colleague Gordon P. Saville
Gordon P. Saville
Gordon Philip Saville was a United States Air Force major general who was an outspoken proponent of tactical aviation amidst a brotherhood of airmen who promoted strategic bombing. With Benjamin S. Kelsey, Saville co-wrote the technical specifications which led to the P-38 Lightning and the P-39...

. Numerous changes were made to the design during a period of time when Kelsey's attention was focused elsewhere, and Bell engineers, NACA
National Advisory Committee for Aeronautics
The National Advisory Committee for Aeronautics was a U.S. federal agency founded on March 3, 1915 to undertake, promote, and institutionalize aeronautical research. On October 1, 1958 the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and...

 aerodynamicists 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
Lend-Lease was the program under which the United States of America supplied the United Kingdom, the Soviet Union, China, Free France, and other Allied nations with materiel between 1941 and 1945. It was signed into law on March 11, 1941, a year and a half after the outbreak of war in Europe in...

. The Soviets were able to make good use of P-39s because of its excellent maneuverability 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 turbosupercharged V-1710s. The operating conditions of the Western European air war – flying for long hours in intensely cold weather at 30000 feet (9,144 m) – revealed several problems with the turbosupercharged V-1710. These had a poor manifold fuel-air distribution and poor temperature regulation of the turbosupercharger air, which resulted in frequent engine failures (detonation occurred in certain cylinders as the result of persistent uneven fuel-air mixture across the cylinders caused by the poor manifold design). The turbosupercharger 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 suboptimal engine management techniques taught to many pilots during the first part of WWII, including a cruise setting that involves running the engine at a high RPM and low manifold pressure with a rich mixture. These settings can contribute to overcooling 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-38H pilots of 55FG, 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 so the P-38s were steadily withdrawn from Europe until they were no longer used for bomber escort duty with the Eighth Air Force by October 1944. 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
Charles Lindbergh
Charles Augustus Lindbergh was an American aviator, author, inventor, explorer, and social activist.Lindbergh, a 25-year-old U.S...

 during his P-38 flight testing in the PTO,) the fuel quality was consistently superior 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 that was carrying Admiral Isoroku Yamamoto
Isoroku Yamamoto
was a Japanese Naval Marshal General and the commander-in-chief of the Combined Fleet during World War II, a graduate of the Imperial Japanese Naval Academy and a student of Harvard University ....

. 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, 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 with a slightly improved single-stage, two-speed supercharger, yielding only modest gains in performance.

The first production P-51A had the Allison V-1710 without turbosupercharger and thus, poor high altitude performance. At low altitudes, the P-51A was substantially faster than the Spitfire, which very much impressed the British when they first received the plane; they quickly realized the P-51 had an outstanding low-drag airframe and the airplane could become one of the best of the war if the Allison V-1710 engine were replaced by the two-stage-supercharged Merlin. Conversion proceeded on both sides of the Atlantic, with North American Aviation engineers making the definitive changes to the airframe to fully integrate the Packard-Merlin V-1650-3 into the P-51B. Ironically, because the P-51 was not originally developed for the USAAF, this was allowed to proceed rapidly with no Army input (or interference). A similar attempt to cure the problems of the P-38 by replacing its Allisons with Merlins was quashed by the USAAF, after protests from Allison.

Starting with the V-1710-45 around 1943, Allison attached an auxiliary supercharger to some of its engines in an effort to improve high-altitude performance, with limited success. Although described as a two-stage supercharger, it was essentially an afterthought and did not have the full refinements of the two-stage Merlin, such as the pressure-altitude governed two-speed gearbox and the intercooling system. 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 variants of the Boeing XB-38
XB-38 Flying Fortress
|-See also:-References:NotesBibliography* Francillon, René J. Lockheed Aircraft since 1913. London:Putnam, 1982. ISBN 0-370-30329-6.* Hess, William N. and Jim Winchester. ""Boeing B-17 Flying Fortress:Queen of the Skies". Wings Of Fame. Volume 6. London:Aerospace Publishing, 1997. ISBN...

, Republic XP-47A, both with turbo-superchargers (AP-10), Curtiss XP-55 Ascender
XP-55 Ascender
|-See also:-References:NotesBibliography* Balzer, Gerald H. American Secret Pusher Fighters of World War II: XP-54, XP-55, and XP-56. North Branch, Minnesota: Specialty Press, 2008. ISBN 1-58007-125-2....

, and Douglas XB-42 Mixmaster
XB-42 Mixmaster
|-See also:-References:NotesBibliography* Francillon, René J. McDonnell Douglas Aircraft since 1920. London: Putnam, 1979. ISBN 0-370-00050-1.* O'Leary, Michael, ed. "Elegant Failure." America's Forgotten Wings, Volume 1, 1994, pp. 4–11....


F-82 use

The F-82 did see brief action in the Korean War, but 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.

In total, over 70,000 V-1710s were built by Allison during the war, all in Indianapolis, Indiana
Indianapolis, Indiana
Indianapolis is the capital of the U.S. state of Indiana, and the county seat of Marion County, Indiana. As of the 2010 United States Census, the city's population is 839,489. It is by far Indiana's largest city and, as of the 2010 U.S...


Other uses

The V-1710's useful life continued, as thousands were available on the surplus market. In the 1950s, many drag racers
Drag racing
Drag racing is a competition in which specially prepared automobiles or motorcycles compete two at a time to be the first to cross a set finish line, from a standing start, in a straight line, over a measured distance, most commonly a ¼-mile straight track....

 and land speed racers
Land speed record
The land speed record is the highest speed achieved by a wheeled vehicle on land. There is no single body for validation and regulation; in practice the Category C flying start regulations are used, officiated by regional or national organizations under the auspices of the Fédération...

, attracted by its reliability and good power output, adopted the V-1710; Art Arfons
Art Arfons
Arthur Eugene "Art" Arfons was the world land speed record holder three times in 1964 – 1965 with his Green Monster series of jet-powered cars, after a series of Green Monster piston-engine and jet-engined dragsters...

 and brother Walt
Walt Arfons
Walt Arfons is 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's mother, Bessie, was half Cherokee, and died in...

 in particular used one, in Green Monster
Green Monster (car)
The Green Monster was the name of several vehicles built by Art Arfons and his half brother Walt Arfons. These ranged from dragsters to a turbojet-powered car which briefly held the land speed record three times during 1964 and 1965....

. It proved unsuccessful as a drag racing engine, being unable to accelerate rapidly, but "could taxi all day at 150". Unlimited hydroplane racing
Hydroplane racing
Hydroplane racing is a sport involving racing hydroplanes on lakes and rivers. It is a popular spectator sport in several countries.-International Professional Outboard 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 4000 hp—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
A turboshaft engine is a form of gas turbine which is optimized to produce free turbine shaft power, rather than jet thrust...

 power, tractor pullers began using the Allison engine, again developing unimagined power. Finally, the warbird
Warbird is a term used, predominantly in North America, to describe vintage military aircraft.- Naming :Although the term originally implied piston-driven aircraft from the World War II era, it is now often extended to include all military aircraft, including jet-powered aircraft, that are no...

 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 Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n Yak-3 and Yak-9 airplanes, originally powered by Klimov
Klimov M-105
-See also:-External links:*...

 V-12s in World War II, as well as ambitious projects such as a replica Douglas World Cruiser and Focke-Wulf Fw 190
Focke-Wulf Fw 190
The Focke-Wulf Fw 190 Würger was a German Second World War single-seat, single-engine fighter aircraft designed by Kurt Tank in the late 1930s. Powered by a radial engine, the 190 had ample power and was able to lift larger loads than its well-known counterpart, the Messerschmitt Bf 109...

D by Flug Werk of Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...


Specifications (V-1710-F30R)

See also

External links

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