Journeyman wrote in message ...
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?

MP should drop about 1" per 1000 feet, given standard conditions. So,
to maintain a desired % power, you have to continually increase MP as
you climb. Of course, with a normally aspirated engine, there will
come a point that you can't achieve full MP. Here is where a turbo
charged engine comes in handy....