War emergency power
Encyclopedia
War Emergency Power is an American term for the throttle
setting on some World War II
military aircraft engine
s. 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. Similar systems used by non-US forces are now often referred to as WEP as well, although they may not have been at the time.
was rated at 1,380 hp, but WEP would deliver up to 2,218 hp.
, the model most produced and used during WWII, the WEP increased the HP from 1490 to 1720. The Vought F4U Corsair, not originally equipped for WEP, later boasted a power increase of up to 410 hp (17%) when WEP was engaged. Several methods were used to boost engine power by manufacturers, including water injection
and methanol-water injection. Some earlier engines simply allowed the throttle to open wider than normal, allowing more air to flow through the intake
. All WEP methods result in greater-than-usual stresses on the engine, and correspond to a reduced engine lifetime. For some airplanes, such as the P-51D, use of WEP required that the engine be inspected for damage before returning to the air. 5 hours use of WEP on the P51D required a complete tear down inspection.
British and Commonwealth aircraft could increase power by increasing the supercharger boost pressure.. This modification was common by the Summer of 1940, with the widespread availability of 100 octane fuel. Raising supercharger boost pressure from 6lb to 12lb increased the Merlin III engine rating to 1310hp, an increase of over 250hp. Pilots had to log the use of emergency boost and were advised not to use it for more than 5 minutes continuously.
The German MW50 system methanol-water injection system required additional piping, as well as a storage tank, increasing the aircraft's overall weight. Like other boost techniques, MW50 was restricted by capacity and engine temperatures and could only be used for a limited time. The GM 1 nitrous oxide injection system, also used by the Luftwaffe
, provided extreme power benefits of 25 to 30 percent but required cooling on the ground and added significant weight. One of the few German aircraft that could be equipped with both systems, the late war Focke-Wulf Ta 152
H high-altitude fighter, could attain a velocity of some 756 km/h (470 mph) with both systems used together, reportedly as Kurt Tank
once did in using both boost systems simultaneously when he was flying a Junkers Jumo 213
E-powered Ta 152H prototype fitted with both MW 50 and GM-1, to escape a flight of P-51D Mustangs in April 1945.
The MiG-21bis received the upgraded Tumanski R-25 engine, which retained the standard 42 / 65 kN normal and forsazh
power settings of earlier R-13 powerplants, but added a new super-afterburning system. Use of this "diamond regime" provided a massive 97.4 kN of thrust for no more than 3 minutes in actual wartime use. Use of this temporary power gave the MiG-21bis slightly better than 1:1 thrust-to-weight ratio
and a climbing rate of 254 meters/second, equalling the F-16's nominal capabilities in close-quarters dogfight.
In air combat practice with the MiG-21bis, use of WEP thrust was limited to 1 minute, to spare on the engines' 800 flight hours lifetime, since every second of super-afterburner use counted as several minutes of regular power run due to extreme thermal stress. When WEP was on, the MiG-21bis's R-25 engine produced a huge 5 meter long blowtorch exhaust - there were six or seven brightly glowing rhomboid "shock diamond
s" visible inside the flames, caused by shock wave interference patterns, thus giving the emergency-power setting its "diamond regime" name.
) sports a 12-cylinder 1200 bhp diesel engine developed by the German MTU company. When the EFV is swimming the powerplant can be boosted to 2700 hp via the use of open circuit seawater-cooling. Such extreme war power setting allows the MTU engine to drive four massive water-jet exhausts which propel the surface-effect riding EFV vehicle at sea speeds reaching 35 knots.
Although the EFV prototypes have demonstrated revolutionary performance on water and land, the reliability of their extremely boosted powerplants
has yet to meet stringent military standards and the vehicle failed to enter Marine Corps service as of autumn 2007.
Throttle
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...
setting on some 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...
military aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
s. 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. Similar systems used by non-US forces are now often referred to as WEP as well, although they may not have been at the time.
WEP in WWII aircraft
Maximum normal power would be limited by a mechanical stop, for instance a wire across the throttle lever slot, but a more forceful push would break the wire allowing extra power. In normal service, the P-51H MustangP-51 Mustang
The North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and in several other conflicts...
was rated at 1,380 hp, but WEP would deliver up to 2,218 hp.
P-51 Mustang
The North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and in several other conflicts...
, the model most produced and used during WWII, the WEP increased the HP from 1490 to 1720. The Vought F4U Corsair, not originally equipped for WEP, later boasted a power increase of up to 410 hp (17%) when WEP was engaged. Several methods were used to boost engine power by manufacturers, including water injection
Water injection (engines)
In internal combustion engines, water injection, also known as anti-detonant injection, is spraying water into the cylinder or incoming fuel-air mixture to cool the combustion chambers of the engine, allowing for greater compression ratios and largely eliminating the problem of engine knocking...
and methanol-water injection. Some earlier engines simply allowed the throttle to open wider than normal, allowing more air to flow through the intake
Intake
An intake , or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power...
. All WEP methods result in greater-than-usual stresses on the engine, and correspond to a reduced engine lifetime. For some airplanes, such as the P-51D, use of WEP required that the engine be inspected for damage before returning to the air. 5 hours use of WEP on the P51D required a complete tear down inspection.
British and Commonwealth aircraft could increase power by increasing the supercharger boost pressure.. This modification was common by the Summer of 1940, with the widespread availability of 100 octane fuel. Raising supercharger boost pressure from 6lb to 12lb increased the Merlin III engine rating to 1310hp, an increase of over 250hp. Pilots had to log the use of emergency boost and were advised not to use it for more than 5 minutes continuously.
The German MW50 system methanol-water injection system required additional piping, as well as a storage tank, increasing the aircraft's overall weight. Like other boost techniques, MW50 was restricted by capacity and engine temperatures and could only be used for a limited time. The GM 1 nitrous oxide injection system, also used by the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
, provided extreme power benefits of 25 to 30 percent but required cooling on the ground and added significant weight. One of the few German aircraft that could be equipped with both systems, the late war Focke-Wulf Ta 152
Focke-Wulf Ta 152
The Focke-Wulf Ta 152 was a World War II German high-altitude fighter-interceptor designed by Kurt Tank and produced by Focke-Wulf. The Ta 152 was a development of the Focke-Wulf Fw 190 aircraft...
H high-altitude fighter, could attain a velocity of some 756 km/h (470 mph) with both systems used together, reportedly as Kurt Tank
Kurt Tank
Kurt Waldemar Tank was a German aeronautical engineer and test pilot, heading the design department at Focke-Wulf from 1931-45. He designed several important aircraft of World War II, including the Focke-Wulf Fw 190 fighter aircraft.-Early life:Tank was born in Bromberg , Province of Posen...
once did in using both boost systems simultaneously when he was flying a Junkers Jumo 213
Junkers Jumo 213
|-See also:-Bibliography:* Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989. ISBN 0-517-67964-7-External links:*...
E-powered Ta 152H prototype fitted with both MW 50 and GM-1, to escape a flight of P-51D Mustangs in April 1945.
Modern times
Perhaps the most dramatic WEP feature was found in the MiG-21bis fighter jet. This late variant of the standard Soviet light fighter plane was built as a stopgap measure to counter the newer and more powerful American F-16 and F/A-18 fighters until the next-generation MiG-29 could be introduced to service.The MiG-21bis received the upgraded Tumanski R-25 engine, which retained the standard 42 / 65 kN normal and forsazh
AfterBurner
The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...
power settings of earlier R-13 powerplants, but added a new super-afterburning system. Use of this "diamond regime" provided a massive 97.4 kN of thrust for no more than 3 minutes in actual wartime use. Use of this temporary power gave the MiG-21bis slightly better than 1:1 thrust-to-weight ratio
Thrust-to-weight ratio
Thrust-to-weight ratio is a ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine. It is a dimensionless quantity and is an indicator of the performance of the engine or vehicle....
and a climbing rate of 254 meters/second, equalling the F-16's nominal capabilities in close-quarters dogfight.
In air combat practice with the MiG-21bis, use of WEP thrust was limited to 1 minute, to spare on the engines' 800 flight hours lifetime, since every second of super-afterburner use counted as several minutes of regular power run due to extreme thermal stress. When WEP was on, the MiG-21bis's R-25 engine produced a huge 5 meter long blowtorch exhaust - there were six or seven brightly glowing rhomboid "shock diamond
Shock diamond
Shock diamonds are a formation of stationary wave patterns that appears in the supersonic exhaust plume of an aerospace propulsion system, such as a supersonic jet engine, rocket, ramjet, or scramjet, when it is operated in an atmosphere...
s" visible inside the flames, caused by shock wave interference patterns, thus giving the emergency-power setting its "diamond regime" name.
WEP in surface vehicles
Some modern military surface vehicles also employ WEP features. The EFV (next generation US Marine Corps Expeditionary Fighting VehicleExpeditionary Fighting Vehicle
The Expeditionary Fighting Vehicle is an amphibious assault vehicle that was being developed for the U.S. Marine Corps. It is launched at sea, from an amphibious assault ship beyond the horizon, able to transport a full Marine rifle squad to shore...
) sports a 12-cylinder 1200 bhp diesel engine developed by the German MTU company. When the EFV is swimming the powerplant can be boosted to 2700 hp via the use of open circuit seawater-cooling. Such extreme war power setting allows the MTU engine to drive four massive water-jet exhausts which propel the surface-effect riding EFV vehicle at sea speeds reaching 35 knots.
Although the EFV prototypes have demonstrated revolutionary performance on water and land, the reliability of their extremely boosted powerplants
has yet to meet stringent military standards and the vehicle failed to enter Marine Corps service as of autumn 2007.
Boost systems
- Water injectionWater injection (engines)In internal combustion engines, water injection, also known as anti-detonant injection, is spraying water into the cylinder or incoming fuel-air mixture to cool the combustion chambers of the engine, allowing for greater compression ratios and largely eliminating the problem of engine knocking...
- MW50 (German, methanol/water mixture)
- GM 1 (German, nitrous oxideNitrous oxideNitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
injection) - Forsazh (Russian)