Unless you have a turbo charged airplane, as your altitude increases your
engine power decreases thus your MP will drop.
in a turbo charged airplane you can just increase MP untill you reach the
critical altitude for the turbo charger (12000 ft for the turbo arrow)

when you have reached the critical altitude for your engine, you should be
at full throttle, then if you have not done it already, you can increase the
RPM which will give you another inch or so of MP, but after that, your MP
will just decrease as you go higher.

what kind of plane did you get ?


Journeyman wrote:

So, I'm going through the performance charts for my new ride (in
case anyone missed my long postings), and there's a graph that
lists fuel flow for a given power setting (eg. 9.16 GPH @ 65%).
Another charts lists MP at altitude for each power setting.

The weird thing is the MP drops with altitude. ISTM, at constant
power, MP should increase to compensate for reduced air density.
I.e. at a given fuel flow, which translate to a given power, you
need a bigger volume of air to maintain the proper mixture.

We're talking small changes in MP, few 1/10th of inches per 1000',
but they're definitely decreasing with altitude.

Am I wrong or are the tables bogus?

Morris (so why didn't Jim Fisher comment on my transition to low wings?)