Plane & Pilot
Tuesday, January 28, 2014

Some Thoughts On Engine Reliability


Heed the advice of a master mechanic


"A CHT of 340 to 380 degrees is fairly optimum for most aircraft engines," Sloan continues. "Shock cooling is also tough on an engine, again because of the rate of contraction of different metals. If you can maintain the CHT at 350 degrees or more throughout every flight, you'll have a better chance of making your engine last well past TBO."

Sloan feels a proper warmup and cool­down are extremely important, too, especially in the big-bore Lycomings and Continentals. "An oil temperature of at least 100 degrees is essential before you apply run-up power if you hope to make it to TBO," says Sloan. "It's also a good idea to allow even a normally aspirated engine to cool down before you pull the mixture to idle/cutoff. There's no specific interval to worry about as there is with a turbo, usually three to five minutes, but any engine benefits from a minute or two to let things cool and settle down after delivering power.

"Similarly, shock cooling or shock heating can induce stress on engine components and cause premature fatigue," Sloan explains. "A number of advanced heat dissipation processes are available, such as high-emissivity electrostatic black powder coating, high-temperature ceramics and isotropic internal parts finishing. Unfortunately, these processes are not yet available through the engine manufacturers.

"A high frequency of engine use and intelligent cycling of engine power can also enhance engine life," says the engine overhaul expert. "Air show legend Bob Hoover is living proof of the concept. His big Shrike Commander was truly a working airplane, often flying 1,000 miles or more every week between air show venues. Hoover flew his two turbocharged Lycoming engines to TBO three times, flying 380 air shows without any major problems." Hoover retired his Commander to the National Air & Space Museum, Udvar-Hazy Center in Chantilly, Va.

In other words, run your engine by the book, change the oil regularly, avoid conditions that might overheat it and fly as frequently as possible, and you, too, may someday have your airplane enshrined at the Smithsonian.



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