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View Full Version : Did Wright Aeronautical invent "war emergency power"?


stepwilk
8th May 2010, 18:23
Somewhere I recently read, in what seemed to be a relatively reliable source--a necessary proviso in this era of Internonsense--that Wright developed for the R-3350 the concept of "war emergency power"--limited overboosting in order to create the power necessary for hot-weather, overgross takeoffs.

Is this true? I always thought that "going through the gate" or otherwise creating a temporary more-than-100-percent power setting was a pretty general thing with World War II piston engines.

Load Toad
8th May 2010, 22:31
Well the 'going through the gate' expression I'm confident I've read about RAF pilots using in the early war years. It'd be interesting to know when engines were so designed to have such a throttle setting.

Wiki, but anyway...

War emergency power - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/War_emergency_power)

So given 'pushing it through the gate' was in common usage in the BoB and that I think the recent Spitfire book commented on pilots using WEP a little too often and wearing out engines faster than expected - it doesn't sound like it was specific to the development of a particular American engine. But maybe the term 'WEP' was to describe the effect?

Brian Abraham
9th May 2010, 06:24
Stephan, Wright certainly did not invent the "war emergency", was a feature on a lot of aircraft. The P-38 had a "war emergency" and the P-51 had a "emergency boost control" - a lever separate to the throttle which was safety wired. The 29 flight manual lists the war emergency rating of the 3350 as 2,800RPM, 50.5"Hg (49" for take off), 1,320GPH, 5 minute time limit. Does not give a horsepower rating, but read elsewhere of it being 2,500 vice the take off rating of 2,200.

onetrack
9th May 2010, 09:02
I believe that the statement that Wright originated the idea of emergency overboost is a fallacious statement. It was a procedure that was instituted by many military aero engine and aeroplane manufacturers, that were produced just before WW2.
Like a lot of ideas, once brought to light, it rapidly gains acceptance amongst other manufacturers. It would probably be impossible to define which manufacturer actually produced the idea first - but remember, that at all times in the 1920's and 1930's, increased power was always being sought, within reliability limits - and overboosting was just one more tool available.

The Spitfire is the most famous of all these, in the annals of overboost stories. The overboost cut-out control in the Spitfire is mounted on the lower left of the dash. Regular boost of the Merlin III was 6.25lbs - overboost was limited to 12lbs and a maximum of 5 minutes.
Use of overboost had to be recorded in the pilots log book to ensure that possible shortened engine life could be investigated by the maintenance engineers, and reduced TBO instructions initiated.

Spitfire Overboost instructions .. http://www.spitfireperformance.com/ap1590b.jpg

Spitfire overboost cut-out control location .. http://www.spitfireperformance.com/spit1pn-port.jpg

Without doubt, one of the most important factors that led to increased performance and gave a real leg-up to Allied pilots, was the supply of 100 octane fuel for Allied fighter aircraft, just weeks before the Battle of Britain.

Coupled with new constant-speed props, the overboost ability, plus the 100 octane fuel, the Spittys always showed a clean pair of heels to any Luftwaffe pilots. The Germans did not have the technology for 100 octane fuel and ran 87 octane all through the critical part of WW2. The story of the development of 100 octane fuel, and the secrecy surrounding it, is nearly a book in itself.

If you read this following main page, related to the above links, you will get extensive information and stories related to the use of overboost in the Spitfires .. Spitfire Mk I versus Me 109 E (http://www.spitfireperformance.com/spit1vrs109e.html)