A proper burn out procedure


I would like to comment on the spark plug “burn out” procedure discussed in Paul McBride’s Sept. 4 column, “Tips to reduce spark plug fouling.”

Operating lean really troubles me. My mechanic son observed a Mooney do several aggressive burn outs and taxi back a couple of times. The last time they commented they had REALLY done a burn out. Shortly after departure they lost the engine and barely made it straight into an adjacent airport.

I once chartered a Piper for a 30-minute photo flight. A plug was fouled and the pilot did several burn outs. The last was full throttle while leaning the mixture until it smoothed out. Had it not been over Iowa corn fields, I would have refused the ride.

As a young DC-3 copilot I was taught the Pratt & Whitney burn out procedure: In full rich and both mags, from idle, start a one minute, slow steady power increase, so as to reach takeoff power at the end of the minute. (The rate can be adjusted at the 30-second point.)

I once was scheduled to test hop a DC-3 with a new engine. The engine would barely run on one mag and after several tries, I was ready to take it back to maintenance. Knowing I would be asked if I had done a Pratt & Whitney burn out, I did one for the record. At the end of one minute the engine was running like a well-oiled clock and no stress had been placed on any of the parts, such as valves.

DOUG MILLARD, Wasilla, Alaska


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