Blueskies wrote:

I've always assumed (dangerous I know) that 100% rpm = 1 hour on the tach meter. As prop speed went down so does the
tach hour. So if 2700 is redline = 1 hour, then 2500 rpm = .92 per hour, 2200 = .81, etc...

That would not be a good assumption. Tachs are calibrated to record 1 hr.
at various rpms, depending on the installation. Check the Mitchell tachs
on the link below. They'll record an hour anywhere from 1800 rpm to 2566 rpm.


http://www.aircraftspruce.com/catalo...mech_tachs.php

John Galban=====N4BQ (PA28-180)

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