Saturday, May 1, 2004
An Advanced Course In Engine Management
When you have to pay for fuel, repairs and overhauls, you’ll want to treat your powerplant to the values of science, not hearsay
|Today, bookstores have shelves of self-help and how-to books targeted at people just like me. You know, books like Brain Surgery For Dummies, Taxes For Dummies or The Idiot’s Guide To Juggling. There is one guide, however, that you won’t find in your local bookstore or, unfortunately, at your local airport. The Advanced Pilot Seminar (APS), better than books like Engine Management For Dummies, can only be found in Ada, Okla. |
Lean of peak is not new and it hasn’t been good advertising. When the marketing department is trying to make the latest Bonanza, Piper or Cessna look faster than its competition, they only want to know one thing. Where is the best power? The power charts very clearly show the best power.
Highest horsepower is achieved rich of peak EGT. A review of all Pilot Operating Handbooks
from the 1950s to the 1980s shows a narrowing of engine management recommendations and displayed power charts. Speed was the important thing; maintenance and fuel consumption were not considered, easy assumptions to make when the cost of fuel was less than 30 cents a gallon and engine overhauls didn’t represent 30% or more of the value of an aircraft.
There is a better way, and it has been used successfully for decades. The Wright 3350 radial occupied the pinnacle of piston-engine development and flew hundreds of thousands of hours on military airplanes and airline DC-7s. As a standard procedure, the engine was leaned to a 10% effective drop in the best power and lean of peak EGT. R-3350 operators were looking for lower cylinder head and exhaust gas temperatures, greater detonation margin and, coincidentally, lower fuel consumption.
Lean of peak may give greater range, but it meant flying slower and that was not a desirable option. Fast is what we wanted and fast was easy to find. Just lean to roughness and richen the mixture a bit. Voilá, 50 degrees rich of peak and very near the best power. Rough running was explained away in dozens of different ways.
When it’s someone else’s engine, advice like that is easy to follow. When you have to pay for the fuel, the repairs and the overhauls, it’s a different story entirely. The trouble is how do we know what is right? How do we know the best way to operate our engines under any situation?
Advanced Pilot Seminar attempts to answer exactly these questions. You may be surprised, but the answers are not simple. Sometimes, you want to fly fast, sometimes you want to fly cheap. You can’t do both. George Braly and Tim Roehl at General Aviation Modifications, Inc. (GAMI) were determined to find out why.
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