First Church of Combustion

Never operate your airplane engine lean of peak exhaust gas temperature. These guys aren’t buyin’ it

Air & Space Magazine | Subscribe

(Continued from page 3)

In June 2002 about 35 pilots from the Dallas chapter of the Experimental Aircraft Association flew to Ada to hear about the new way to operate their engines. They departed converted, and that visit led to the first formal seminar in Ada in September 2002 for paying customers.

It's hard to overcome the orthodoxy of the operating manuals and the notion that if engines were meant to be run this way, the aircraft and engine manufacturers would revise the manual. Four years ago, Textron Lycoming issued an advisory to its customers explaining the company's operating recommendations. "Operating an engine 'on the edge' is possible," the advisory states, "provided the pilot is extremely precise, has good instrumentation, and monitors the engine condition full time. For 98% of the pilots, it is an invitation to potential trouble."

Some people depart the weekend in Ada unmoved and cling to the old ways. But to date, Braly and his disciples have converted several hundred pilots, who return to their homes merrily pulling the mixture controls on their engines with abandon. Pull the mixture, all ye souls! Fly lean of peak and be free! Until you have done it yourself, some of them say, you have not tasted of the fruit.

Fred Scott, a farmer and Beech Baron owner from southern Virginia, recalls his first experience: "A friend and I had climbed to 11,000 feet on the way back home from the school. And we pulled it back through the peak [EGT]. 'Engine's gonna melt,' they used to tell us. We're thinking, Well, we gotta believe. And sure enough, the head temperatures went down and it was like a book opening, a complete revelation to see the science you learned in the school made sense. All of a sudden it was all true. We were like two little kids."

Students at the seminar are surprised when they don't hear the bad-mouthing of Continental or Lycoming engines that's common among pilots-"Lyconentals," they call them, a derisive term that encapsulates the notion that both engines are old technology and essentially interchangeable. All three teachers certainly have the chops to criticize, but they're very complimentary of the durability and efficiency of both manufacturers' engines.

As for Braly, he and the GAMI crew are now working on an electronic spark ignition system that monitors intra-cylinder pressure and adjusts the spark timing automatically to manage the pressure generated by combustion and eliminate detonation ("engine knock," in car talk), a condition in which combustion occurs too early, raising intra-cylinder pressure and ultimately destroying the engine. Each seminar class watches as the big TIO-540, running on 100-octane low-lead aviation gasoline, is switched to rotgut unleaded auto gas without missing a beat. Braly can't give a firm date by which FAA certification will be complete. Pray it's soon.

About George C. Larson

George C. Larson served as editor of Air & Space from 1985 to 2005. He is currently an inactive pilot, but holds a commercial pilot's license, with instrument and multi-engine ratings. He is between airplanes at this time, but has owned or operated a Grumman American AA-5B Tiger and a Mooney 201. He has been writing about aviation since 1972, when he joined the staff of Flying Magazine.

Read more from this author

Comment on this Story

comments powered by Disqus