Not by the book

I just read your article on low cruise speed on an O-320 powered 172 (What causes engines to develop less-than-rated power? June 17 issue). I’ve been flying over 30 years (5,000-plus hours) and have rarely found a plane that does book numbers. They will, however, do closer to the book if the power is set according to the power charts in the owner’s manual with a bit of attention to altitude and temperature.

I can’t say how many times I’ve flown with a pilot who thinks 2,400 rpm is 75% power. It may be, but it’s likely not 75% for the temperature and altitude being flown. There is a reason the manufacturer makes the manual’s power charts and better performance is to be had by looking there.

Boyd Birchler
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