Charging for tach time in a fixed pitch airplane

In a previous article, Charlie Axilbund said:
So recently, a friend and I took a 172 to do some pattern work. We were
out a little over an hour according to the Hobbes meter and our
wris****ches, but the tach registered about half that. Now I've flown a

That seems like an excessive difference. Our club charges by tach time,
and the tach is calibrated for 2400 rpm. With an Archer in the pattern,
I'm usually 2450 on climb out, 2000 on downwind, and 1600 on base and
final. When I was training, I got about a 15-25% premium on days when all
I did was pattern work.

Now I fly mostly a Dakota and a Lance, and the rpm/mp chart on the back of
the sun visor shows valid 65% power setting at 2200 or 2300 rpm for the
altitudes I normally fly. That gives a tiny premium, but nowhere near
what I got doing pattern work.

--
Paul Tomblin http://blog.xcski.com/
My group's mission statement - 'You want *what* ? By *WHEN* ?'
-- Simon Burr