Hyper engine
Encyclopedia
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 purpose-built racing engines. 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.
s. Aluminum was being introduced in place of steel as the quality and strength of aluminum alloys improved during the 1930s; this lowered engine weight noticeably, but not enough to achieve a 50% overall improvement. To reach that goal, the power of the engine would also need to be increased. Power
is a combination of energy and the rate it is delivered, so to improve the power-to-weight ratio, one would need to increase the operating pressures of the engine, the operating speed, or a combination of both. Further gains could be made by eliminating losses like friction, combustion inefficiencies and scavenging losses, delivering more of the theoretical power to the propeller
.
The USAAC engineers determined that it would study all three improvements. Before long, they concluded that increasing the combustion temperature and scavenging efficiency promised the greatest increases of all of the possibilities. To meet that goal, increasing engine speed seemed to be the most attractive solution. However, there were a number of practical problems that were impeding progress in these areas.
Increasing the compression ratio
is an easy change that improves the mean effective pressure
(MEP), but leads to engine knocking
from inconsistent detonation. Uncontrolled, knock can damage the engine and was a major block on the way to improved power settings. This change would also increase the operating temperatures, which presented a problem with the valves. Valves were already reaching temperatures that would cause pre-ignition of the fuel as it flowed based them.
Increasing operational speed is also, theoretically, a simple change to the engine design. However, at high operating speeds the valves do not completely close before the cam opens them again, a problem called "valve float
". Valve float allows gases in the cylinder to escape through the partially open valve, reducing the engine efficiency. Increasing valve spring pressure to close the valves faster led to rapid cam wear and increased friction, reducing overall performance by more than any horsepower gained.
As valves were a key issue in both approaches to improved performance, they had been a major area of research in the 1920s and 30s. In the UK, Harry Ricardo
written a influential paper on the sleeve valve
system for exactly these reasons, claiming it was the only way forward. He had some success in selling this idea, most notably to Bristol Aeroplane Company
Engines, where Roy Fedden
became "a believer". Ricardo's friendly competitor, Frank Halford
, designed his own sleeve valve engine with Napier & Son
, another prominent British engine maker.
The USAAC was not so convinced that the sleeve valve was the only solution. Ironically it was one of Ricardo's papers on the sleeve valve design that led to the USAAC's hyper engine efforts. In one late 1920s paper he claimed that the 1 hp/in³ goal was impossible to achieve with poppet valve type engines. The USAAC engineering team at Wright Field decided to test this claim by beating it. They proposed an engine of about 1200 cubic inches (20 L), hoping the engine's smaller size would lead to reduced drag and hence improved range
.
and a former colleague of Ricardo while Heron had been working at the Royal Aircraft Factory, Fanrborough, started working on the problem with a single-cylinder test engine that he converted to liquid cooling, using a Liberty L-12
engine cylinder. He pushed the power to 480 psi Brake Mean Effective Pressure
, and the coolant temperature to 300 °F (148.9 °C) before reaching the magic numbers. By 1932, the USAAC's encouraging efforts led the Army to sign a development contract with Continental Motors Company
for the continued development of the engine design. The contract limited Continental's role to construction and testing, leaving the actual engineering development to the Army.
Starting with the L-12-cylinder, they decreased the stroke from 7 in to 5 in in order to allow higher engine speeds, and then decreased the bore from 5 in to 4.62 in, creating the 84 in³ cylinder. This would be used in a V-12 engine of 1008 in³ displacement
. They used the L-12's overhead camshaft
to operate multiple valves of smaller size, which would improve charging and scavenging
efficiency. Continental's first test engine, the single-cylinder Hyper No.1, first ran in 1933.
They eventually determined that exhaust valves could run cooler when a hollow core filled with sodium is used - the sodium liquefies and considerably increases the heat transfer from the valve's head to its stem and then to the relatively cooler cylinder head where the liquid coolant picks it up.
Liquid cooling systems at that time used plain water, which limited operating temperatures to about 180 °F (82.2 °C). The engineers proposed using ethylene glycol
, which would allow temperatures up to 280 °F. At first they proposed using 100% glycol, but there was little improvement due to the lower specific heat
of the glycol (about 2/3 that of water). They eventually determined that a 50/50 mixture (by volume) of water and glycol provided optimal heat removal.
The Army apparently became concerned about the development of a suitable supercharger for high-altitude use, and for further development in 1934 they asked for a newer cylinder with slightly less performance and an increased volume of 118.8 in³ from its 5.5 in (139.7 mm) bore and 5 in (127 mm) stroke. This size cylinder would then be used in a 1,425 in³ 12-cylinder engine, delivering the same 1,000 hp, with a performance of 0.7 hp/in³. This placed its performance on a par with newer experimental engines from Europe like the Rolls-Royce PV-12
, at least when running on the higher-octane fuels the Army planned to use.
Another change was to the engine layout. The Army, convinced that future aircraft designs would use engines buried in the wings for additional streamlining, asked Continental to design a full-sized flat-opposed-piston engine for installation inside a wing. The resulting engine was the Continental O-1430, which would require a ten year development period which changed the layout to first an upright V-12 engine
and later, an inverted V-12 engine before becoming reliable enough to consider for full production as the Continental IV-1430 in 1943. By then other engines had already passed its 1,600 hp (1,200 kW) rating, and although the IV-1430 had a better power-to-weight ratio, there was little else to suggest setting up production in the middle of the war was worthwhile.
The project was eventually guided by the requirements in the "Request for data R40-C", which was included as a part of the Financial Year 1940 aircraft procurement program.
and the Curtiss P-36A, were just able to hit 300 mph (482.8 km/h). Against the 340+ mph Messerschmitt Bf-109 they would be completely outclassed. The twin-engined Lockheed XP-38 was entering an extended test program.
Although the XP-38 was able to fly at speeds in excess of 413 mph, it was big and heavy, and was therefore not as maneuverable as its stablemates. The XP-38 also had a newly introduced liquid-cooled engine, the Allison V-1710. The Allison's in-line vee cylinder arrangement allowed for a narrow aerodynamic shape that had much less drag than the air-cooled radial engine fighters that predominated America at the time.
The fighter aircraft procurement program for FY 1940 was contained in a document that was approved by Assistant Secretary of War Louis K. Johnson on 9 June 1939. That document was the "Request for Data R40-C", and unlike previous aircraft procurement requests, it was sent to only a limited number of aircraft manufacturers. The original document was to be sent to:
After final review and approval as Air Corps Type Specification XC-622, a further four manufacturers were added to the distribution:
These companies had only ten days to agree to the terms of the document, and only 30 days to submit their designs.
Only three of these ten designs were approved, and contracts were made for a limited prototype run of three aircraft for each.
The three aircraft/engine combinations that were selected:
Not to be left out, the US Navy selected the Lycoming XH-2470
for funding in FY 1942 as well.
Ironically, engines that were not considered under the program; the Allison V-1710, Pratt & Whitney R-2800 Double Wasp, Wright R-3350 Duplex-Cyclone and Pratt & Whitney R-4360 Wasp Major, all surpassed the USSAC requirements, and continue flying into the 21st century.
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...
(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
Power-to-weight ratio
Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources...
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 purpose-built racing engines. 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
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...
as 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...
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.
Design and development
Improvements in construction and lighter materials had already delivered some benefits on the way to higher power-to-weight ratioPower-to-weight ratio
Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources...
s. Aluminum was being introduced in place of steel as the quality and strength of aluminum alloys improved during the 1930s; this lowered engine weight noticeably, but not enough to achieve a 50% overall improvement. To reach that goal, the power of the engine would also need to be increased. Power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
is a combination of energy and the rate it is delivered, so to improve the power-to-weight ratio, one would need to increase the operating pressures of the engine, the operating speed, or a combination of both. Further gains could be made by eliminating losses like friction, combustion inefficiencies and scavenging losses, delivering more of the theoretical power to the propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
.
The USAAC engineers determined that it would study all three improvements. Before long, they concluded that increasing the combustion temperature and scavenging efficiency promised the greatest increases of all of the possibilities. To meet that goal, increasing engine speed seemed to be the most attractive solution. However, there were a number of practical problems that were impeding progress in these areas.
Increasing the compression ratio
Compression ratio
The 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...
is an easy change that improves the mean effective pressure
Mean effective pressure
The mean effective pressure is a quantity related to the operation of an reciprocating engine and is a valuable measure of an engine's capacity to do work that is independent of engine displacement. When quoted as an indicated mean effective pressure or imep , it may be thought of as the average...
(MEP), but leads to engine knocking
Engine knocking
Knocking in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.The...
from inconsistent detonation. Uncontrolled, knock can damage the engine and was a major block on the way to improved power settings. This change would also increase the operating temperatures, which presented a problem with the valves. Valves were already reaching temperatures that would cause pre-ignition of the fuel as it flowed based them.
Increasing operational speed is also, theoretically, a simple change to the engine design. However, at high operating speeds the valves do not completely close before the cam opens them again, a problem called "valve float
Valve float
Valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile...
". Valve float allows gases in the cylinder to escape through the partially open valve, reducing the engine efficiency. Increasing valve spring pressure to close the valves faster led to rapid cam wear and increased friction, reducing overall performance by more than any horsepower gained.
As valves were a key issue in both approaches to improved performance, they had been a major area of research in the 1920s and 30s. In the UK, Harry Ricardo
Harry Ricardo
Sir Harry Ricardo was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine....
written a influential paper on the sleeve valve
Sleeve valve
The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve-valve engines saw use in a number of pre-World War II luxury cars and in USA in the Willys-Knight car and light truck...
system for exactly these reasons, claiming it was the only way forward. He had some success in selling this idea, most notably to Bristol Aeroplane Company
Bristol Aeroplane Company
The Bristol Aeroplane Company, originally the British and Colonial Aeroplane Company, was both one of the first and one of the most important British aviation companies, designing and manufacturing both airframes and aero engines...
Engines, where Roy Fedden
Roy Fedden
Sir Alfred Hubert Roy Fedden MBE was an engineer who designed most of Bristol Engine Company's successful aircraft engine designs.-Early life:...
became "a believer". Ricardo's friendly competitor, Frank Halford
Frank Halford
Major Frank Bernard Halford CBE FRAeS was an English aircraft engine designer.-Career:Educated at Felsted, In 1913 he left the University of Nottingham before graduating to learn to fly at Brooklands and Bristol Flying School and became a flight instructor using Bristol Boxkites.He served in the...
, designed his own sleeve valve engine with Napier & Son
Napier & Son
D. Napier & Son Limited was a British engine and pre-Great War automobile manufacturer and one of the most important aircraft engine manufacturers in the early to mid-20th century...
, another prominent British engine maker.
The USAAC was not so convinced that the sleeve valve was the only solution. Ironically it was one of Ricardo's papers on the sleeve valve design that led to the USAAC's hyper engine efforts. In one late 1920s paper he claimed that the 1 hp/in³ goal was impossible to achieve with poppet valve type engines. The USAAC engineering team at Wright Field decided to test this claim by beating it. They proposed an engine of about 1200 cubic inches (20 L), hoping the engine's smaller size would lead to reduced drag and hence improved range
Range (aircraft)
The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....
.
Hyper No.1
Sam Heron, head of development at Wright FieldWright Field
Wright Field was an airfield of the United States Army Air Corps and Air Forces near Riverside, Ohio. From 1927 to 1947 it was the research and development center for the Air Corps, and during World War II a flight test center....
and a former colleague of Ricardo while Heron had been working at the Royal Aircraft Factory, Fanrborough, started working on the problem with a single-cylinder test engine that he converted to liquid cooling, using a Liberty L-12
Liberty L-12
The Liberty L-12 was a 27 litre water-cooled 45° V-12 aircraft engine of 400 horsepower designed both for a high power-to-weight ratio and for ease of mass production.-History:...
engine cylinder. He pushed the power to 480 psi Brake Mean Effective Pressure
Mean effective pressure
The mean effective pressure is a quantity related to the operation of an reciprocating engine and is a valuable measure of an engine's capacity to do work that is independent of engine displacement. When quoted as an indicated mean effective pressure or imep , it may be thought of as the average...
, and the coolant temperature to 300 °F (148.9 °C) before reaching the magic numbers. By 1932, the USAAC's encouraging efforts led the Army to sign a development contract with Continental Motors Company
Continental Motors Company
Continental Motors Company was an American engine and automobile manufacturer. The company produced engines for various independent manufacturers of automobiles, tractors, and stationary equipment from the 1900s through the 1960s. Continental Motors also produced Continental-branded automobiles in...
for the continued development of the engine design. The contract limited Continental's role to construction and testing, leaving the actual engineering development to the Army.
Starting with the L-12-cylinder, they decreased the stroke from 7 in to 5 in in order to allow higher engine speeds, and then decreased the bore from 5 in to 4.62 in, creating the 84 in³ cylinder. This would be used in a V-12 engine of 1008 in³ displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...
. They used the L-12's overhead camshaft
Overhead camshaft
Overhead cam valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods...
to operate multiple valves of smaller size, which would improve charging and scavenging
Scavenging (automotive)
In automotive usage, scavenging is the process of pushing exhausted gas-charge out of the cylinder and drawing in a fresh draught of air ready for the next cycle....
efficiency. Continental's first test engine, the single-cylinder Hyper No.1, first ran in 1933.
They eventually determined that exhaust valves could run cooler when a hollow core filled with sodium is used - the sodium liquefies and considerably increases the heat transfer from the valve's head to its stem and then to the relatively cooler cylinder head where the liquid coolant picks it up.
Liquid cooling systems at that time used plain water, which limited operating temperatures to about 180 °F (82.2 °C). The engineers proposed using 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...
, which would allow temperatures up to 280 °F. At first they proposed using 100% glycol, but there was little improvement due to the lower specific heat
Heat capacity
Heat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
of the glycol (about 2/3 that of water). They eventually determined that a 50/50 mixture (by volume) of water and glycol provided optimal heat removal.
Hyper No.2
A second cylinder was added to Hyper No. 1 to make a horizontal opposed engine for evaluation of an opposed-piston 12-cylinder engine. After running the modified engine with different combinations of cylinder bore and stroke, it was found that the high coolant temperatures required to maintain the required output was impractical. A third high-performance single-cylinder engine was then constructed with lower operating parameters. This engine was designated "Hyper No. 2", and became the test bed for developing the cylinders that would become the O-1430-1.Continental O/V/IV/XIV-1430
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...
, at least when running on the higher-octane fuels the Army planned to use.
Another change was to the engine layout. The Army, convinced that future aircraft designs would use engines buried in the wings for additional streamlining, asked Continental to design a full-sized flat-opposed-piston engine for installation inside a wing. The resulting engine was the Continental O-1430, which would require a ten year development period which changed the layout to first an upright V-12 engine
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
and later, an inverted V-12 engine before becoming reliable enough to consider for full production as the Continental IV-1430 in 1943. By then other engines had already passed its 1,600 hp (1,200 kW) rating, and although the IV-1430 had a better power-to-weight ratio, there was little else to suggest setting up production in the middle of the war was worthwhile.
The project was eventually guided by the requirements in the "Request for data R40-C", which was included as a part of the Financial Year 1940 aircraft procurement program.
Request for data R40-C
As 1938 came to an end, the war in Europe heated to its boiling point. At this point, European aircraft had greatly surpassed US designs. The two top USAAC fighters, the Seversky P-35Seversky P-35
The Seversky P-35 was a fighter aircraft built in the United States by the Seversky Aircraft Company in the late 1930s. A contemporary of the Hawker Hurricane and Messerschmitt Bf 109, the P-35 was the first single-seat fighter in U.S...
and the Curtiss P-36A, were just able to hit 300 mph (482.8 km/h). Against the 340+ mph Messerschmitt Bf-109 they would be completely outclassed. The twin-engined Lockheed XP-38 was entering an extended test program.
Although the XP-38 was able to fly at speeds in excess of 413 mph, it was big and heavy, and was therefore not as maneuverable as its stablemates. The XP-38 also had a newly introduced liquid-cooled engine, the Allison V-1710. The Allison's in-line vee cylinder arrangement allowed for a narrow aerodynamic shape that had much less drag than the air-cooled radial engine fighters that predominated America at the time.
The fighter aircraft procurement program for FY 1940 was contained in a document that was approved by Assistant Secretary of War Louis K. Johnson on 9 June 1939. That document was the "Request for Data R40-C", and unlike previous aircraft procurement requests, it was sent to only a limited number of aircraft manufacturers. The original document was to be sent to:
- Bell Aircraft CorporationBell AircraftThe Bell Aircraft Corporation was an aircraft manufacturer of the United States, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many important civilian and military helicopters...
- Consolidated Aircraft CorporationConsolidated AircraftThe Consolidated Aircraft Corporation was founded in 1923 by Reuben H. Fleet, the result of the Gallaudet Aircraft Company's liquidation and Fleet's purchase of designs from the Dayton-Wright Company as the subsidiary was being closed by its parent corporation, General Motors. Consolidated became...
- Curtiss-Wright CorporationCurtiss-WrightThe Curtiss-Wright Corporation was the largest aircraft manufacturer in the United States at the end of World War II, but has evolved to largely become a component manufacturer, specializing in actuators, aircraft controls, valves, and metalworking....
Curtiss Airplane Division - Curtiss-Wright Corporation, St. Louis Airplane Division
- Grumman Aircraft Engineering Corporation
- Lockheed Aircraft CorporationLockheed CorporationThe 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:...
- Republic Aviation Corporation
- Vought-Sikorsky Aircraft Division, United Aircraft CorporationVoughtVought is the name of several related aerospace firms. These have included, in the past, Lewis and Vought Corporation, Chance Vought, Vought Sikorsky, LTV Aerospace , Vought Aircraft Companies, and the current Vought Aircraft Industries. The first incarnation of Vought was established by Chance M...
- Vultee Aircraft Division, Aviation Manufacturing CorporationVultee AircraftThe Vultee Aircraft Corporation became an independent company in 1939 and had limited success before merging with the Consolidated Aircraft Corporation in 1943 to form the Consolidated Vultee Aircraft Corporation, or Convair.-History:...
After final review and approval as Air Corps Type Specification XC-622, a further four manufacturers were added to the distribution:
- Hughes Aircraft CorporationHughes AircraftHughes Aircraft Company was a major American aerospace and defense contractor founded in 1932 by Howard Hughes in Culver City, California as a division of Hughes Tool Company...
- McDonnell Aircraft CompanyMcDonnell AircraftThe McDonnell Aircraft Corporation was an American aerospace manufacturer based in St. Louis, Missouri. The company was founded on July 16, 1939 by James Smith McDonnell, and was best known for its military fighters, including the F-4 Phantom II, and manned spacecraft including the Mercury capsule...
- Boeing Aircraft CompanyBoeingThe Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
- Northrop Aircraft, IncorporatedNorthrop CorporationNorthrop Corporation was a leading United States aircraft manufacturer from its formation in 1939 until its merger with Grumman to form Northrop Grumman in 1994. The company is known for its development of the flying wing design, although only a few of these have entered service.-History:Jack...
These companies had only ten days to agree to the terms of the document, and only 30 days to submit their designs.
FY 1940
A total of 26 designs, with a mix of 16 engine models from six engine companies, were submitted by seven of the selected companies. These engines became known as the "Hyper Engines", a contraction of High-performance engines. The submitted designs were graded using a "Figure of merit" (FOM) rating system, and then, using the FOM results (which ranged from 444.12 for the Allison V-1710-E8 to 817.90 for the Pratt and Whitney X-1800-A4G), they were separated into one of three groups.- Those placed in the first group were little more than modifications to existing designs. They were not considered to be sufficiently advanced.
- Those placed in the third group proposed using am engine that was unlikely to be developed into flying condition by the time the airframe was ready to fly. They were not considered to be viable in the time frame allowed.
- The remaining ten designs were placed in the second group: those that were an advancement in aeronautical engineering, with an engine that would be ready to fly, when needed.
Only three of these ten designs were approved, and contracts were made for a limited prototype run of three aircraft for each.
The three aircraft/engine combinations that were selected:
- Vultee Aircraft's Model 70 Alternate 2, (FOM score: 817.9), which became the Vultee XP-54, powered by the Pratt & Whitney X-1800-A4GPratt & Whitney X-1800|-See also:-External links:*...
engine - Curtiss-Wright St Louis' Model P248C, (FOM score: 770.6), which became the Curtiss-Wright XP-55 Ascender, powered by the Continental IV-1430-3 engine
- Northrup's Model N2-B (FOM score: 725.8), which became the Northrop XP-56 Black Bullet, powered by the Pratt & Whitney X-1800-A3GPratt & Whitney X-1800|-See also:-External links:*...
engine
| Engine Model | Configuration | Displacement | Horsepower | Specific horsepower |
Weight | Power to weight ratio |
|---|---|---|---|---|---|---|
| Continental IV-1430-3 | inverted V-12 | 1,430 in³ | 1,600 hp at 3,200 rpm | 1.12 hp/in³ | 1,615 lb | .99 hp/lb |
| Pratt & Whitney X-1800-A3G Pratt & Whitney X-1800 |-See also:-External links:*... |
24 cylinder H-block | 2,600 in³ | 2,200 hp | .85 hp/in³ | 3,250 lb | .68 hp/lb |
| Pratt & Whitney X-1800-A4G Pratt & Whitney X-1800 |-See also:-External links:*... |
24-cylinder H-block | 2,600 in³ | 2,200 hp | .85 hp/in³ | 3,250 lb | .68 hp/lb |
FY 1941
Three additional high-performance engines were considered for the USAAC's FY 1942 "Hyper" engine procurement program. They were:- Wright R-2160 "Tornado"
- Pratt & Whitney H-3130Pratt & Whitney XH-3130|-See also:-External links:*...
- Allison V-3420Allison V-3420|-See also:-References:* Bridgman, L, Jane's fighting aircraft of World War II. Crescent. ISBN 978-0-517-67964-7-External links:...
Not to be left out, the US Navy selected the Lycoming XH-2470
Lycoming H-2470
|-See also:-References:* White, Graham, Allied Aircraft Piston Engines of World War II, SAE International, 1995* Balzer, Gerald C., American Secret Pusher Fighters of World War II, Specialty Press...
for funding in FY 1942 as well.
| Engine Model | Configuration | Displacement | Horsepower | Specific horsepower |
Weight | Power to weight ratio |
|---|---|---|---|---|---|---|
| Allison V-3420 Allison V-3420 |-See also:-References:* Bridgman, L, Jane's fighting aircraft of World War II. Crescent. ISBN 978-0-517-67964-7-External links:... |
24-cylinder W engine W engine A W engine is a type of reciprocating engine arranged with its cylinders in a configuration in which the cylinder banks resemble the letter W, in the same way those of a V engine resemble the letter V.... |
3,421.2 in³ | 2,100 hp | .61 hp/in³ | 2600 lb (1,179.3 kg) | .81 hp/lb |
| Lycoming XH-2470 Lycoming H-2470 |-See also:-References:* White, Graham, Allied Aircraft Piston Engines of World War II, SAE International, 1995* Balzer, Gerald C., American Secret Pusher Fighters of World War II, Specialty Press... |
12-cylinder horizontal opposed | 2,470 in³ | 2,300 hp | .93 hp/in³ | 2430 lb (1,102.2 kg) | .96 hp/lb |
| Pratt & Whitney XH-3130 Pratt & Whitney XH-3130 |-See also:-External links:*... |
24-cylinder H-block | 3,130 in³ | 2,650 hp | .84 hp/in³ | 3250 lb (1,474.2 kg) | .82 hp/lb |
| Wright R-2160 | 42-cylinder 6-row | 2,160 in³ | 2,350 hp | 1.09 hp/in³ | 2400 lb (1,088.6 kg) | .98 hp/lb |
Program end
In the end, all of these programs were canceled, and the surviving engines became museum pieces. One survivor, a Continental IV-1430, is privately owned, and is displayed publicly from time to time.Ironically, engines that were not considered under the program; the Allison V-1710, Pratt & Whitney R-2800 Double Wasp, Wright R-3350 Duplex-Cyclone and Pratt & Whitney R-4360 Wasp Major, all surpassed the USSAC requirements, and continue flying into the 21st century.