WEP: The NOS of Aviation!

F4U Super Corsair (Photo: www.warbirdimages.com).

          For fans of the Fast and the Furious saga, many have seen in the middle of the race Vin Diesel or Paul Walker push that little button written NOS (Nitro Oxide System) and "kapow" the car flies leaving dust to the opponent. Well, I can not say that this NOS technology used in racing cars may have some relation to the War Emergency Power (WEP) used by fighters in the IIWW, but the system is similar.

          War Emergency Power (WEP) is an term for an acceleration adjustment on some WWII military aircraft engines. For use in emergency situations, it produces more than 100% of rated motor power for a limited period of time, often about five minutes. Similar systems used by non-US forces are now often referred to as WEP, as well as, although they may not have been at the time, such as the German Luftwaffe Notleistung (WEP) systems.

WEP in World War II Aircraft

          The maximum normal power may be limited by a mechanical stop, for example a wire through the throttle lever groove, but a stronger pressure would break the wire, allowing the use of the additional power. In normal service, the Mustang P-51H was rated at 1,380 hp, but with WEP driven the engine generated up to 2,218 hp. In the P-51D Mustang, the most produced and used model during World War II, WEP increased HP from 1490hp to 1720hp. The Vought F4U Corsair originally was not equipped with the WEP system, later it was verified a power increase of up to 410 hp (17%) when WEP was installed. Several methods have been used to increase engine power from manufacturers, including water injection and methanol-water injection. Some earlier mechanisms simply opened the throttle with a longer stroke than normal, allowing the intake of more air. All WEP methods have resulted in higher than normal voltages in the motor, resulting in reduced motor life. For some aircraft, such as the P-51D, the use of WEP resulted in an inspection of the engine before returning to the air.

Engine Rolls Royce Merlin P-51 (Photo: www.canonrumors.com).

          British and Commonwealth aircraft could increase power by the pressure of the supercharger turbo. This change was common in the summer of 1940, with the wide availability of AvGas 100LL. Triggering the 6 lb to 12 lb pressure boost supercharger increased the Merlin III engine rating to 1310 hp, an increase of more than 250 hp. Pilots had to record the use of emergency boost and were advised not to use it for more than 5 minutes continuously.

          In the MW50, German methanol-water injection system, additional piping was needed, as was a storage tank, increasing the total weight of the airplane. Like other pulse techniques, MW50 has been restricted by temperature and engine capacity, and can only be used for a limited period of time. The GM 1, nitrous oxide injection system, also used by the Luftwaffe, allowed extreme power of 25% to 30% at high altitude by adding oxidizing gases, but required cooling on the ground and added significant weight. One of the few German aircraft that was equipped with both Notleistung systems was the high-altitude fighter Focke-Wulf Ta 152H, which could reach a speed of about 756 km / h (470 mph) with both systems used together. To escape an American P-51D's attack, pilot Kurt Tank has already made use of both Notleistung systems when he was flying a Ta 152H prototype, powered by Junkers Jumo 213E and equipped with MW 50 and GM-1.

The Modern Times

          Perhaps the most striking feature of WEP was found on the MiG-21bis fighter plane. This variant of the standard Soviet light fighter aircraft was built as a palliative measure to contain the newer and more powerful American F-16 and F / A-18 fighters until the next generation of the MiG-29 could be brought into service.

Engine MIG-21 (Photo: The Aviation Forum).

          The MiG-21bis received the upgraded Tumanski R-25 engine, which retained the standard 42/65 kN normal power settings and standard "Forsazh" (WEP Russian) of the previous R-13 powerplants, but added a new super- combustion. The use of this "diamond regime" provided a huge thrust of 97.4 kN for no more than 3 minutes, with effective use of wartime. The use of this temporary power gave the MiG-21bis slight equality of nominal capabilities of the F-16 in close-quarters duel.

          In practical aerial combat with the MiG-21bis, the use of the WEP was limited to 1 minute to save the 800 hours of life of the engines. When the WEP was on, the engine of the MiG-21bis R-25 produced a huge five-meter long torch in the exhaust - the six or seven "shock diamonds" visible inside the flames gave this configuration the Diamond".

WEP in surface vehicles

          Some modern surface military vehicles also employ WEP capabilities. The EFV (next generation US Marine Corps expeditionary combat vehicle) boasts a 12-cylinder diesel-powered engine delivering 1200 bhp. When the EFV is running the power of the motor can be increased to 2,700 hp, through the use of seawater open circuit and cooling (WEP). This warp power setting allows the MTU engine to drive four huge water jet exhausts that propel the EFV vehicle at speeds at sea that reach 35 knots.

This content has been modified from the wikipedia.org site.

Rene Maciel / Rock Aircraft.

Editor and Private Pilot.