January 2009 Issue
LOP Lab Report : Lean Run is a Home Run
Critics of lean-of-peak engine operation claimed it would ruin engines. Two years and 600 turbo’d Cirri later, they’ve been proven utterly wrong.
Start with a heaped serving of ignorance, add equal measures of industrial inertia and mediocre engineering, add a dash of petulant, not-invented-here intransigence and you’ll have a lucid understanding of how the airplane industry looked at the mundane world of engine management 10 years ago. Or, more accurately, how it looked at engine leaning. Five years before that, General Aviation Modifications, Inc. had begun marketing its calibrated fuel injectors to wide market acceptance. Along with that, came the old-new idea of running engines lean of peak EGTs to save fuel and tame high CHTs. Reaction from the entrenched interests was harsh. You’ll fry the cylinders, said Lycoming. You’ll fry the valves, said mechanics. You’ll fry everything, said some engine shops. What was needed was a controlled experiment whereby a fleet of airplanes running lean of peak could be carefully monitored. Yes, we know the orginal Piper Malibu specified lean of peak, too. But its engine service history was spotty, probably for reasons not related to leaning. When it introduced the SR22 TN in late 2006, Cirrus provided a better lab rat because every SR22 has sophisticated engine data monitoring. Here was an airplane whose POH required lean-of-peak operation. It was nothing if not a bold stroke.
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