Question about being unpressurized at higher (Class A) altitudes

"es330td" wrote

To all: This discussion has been very educational. I haven't learned
yet at what altitude a plane gives maximum performance at cruise power
though from these responses it appears that under FL100 is expected
and preferred. I guess I'll leave Class A to the turbine powered
airplanes.

At low altitudes, you can get the engine to produce a lot of power, and go
pretty fast. Unfortunately, you burn a LOT of fuel.

You go up to 7 or 8 thousand feet, and the engine does not produce much
power; perhaps 60 percent, with the throttle wide open. But, since there is
a LOT less drag, (as compared to low altitudes) you can go a lot faster than
60 percent at the lower altitudes.

So, you climb up to 8 thousand feet, and go as fast or faster than you were
going at sea level burning almost twice as much fuel.

There is a trade off between altitude and speed, and each design airplane is
going to have its ideal altitude, to go the fastest, with the least fuel
burn. It all depends on the different types of drag, and how much that
design's drag is reduced, and the power output of the engine.

This is a general overview of the concept that you are trying to grasp, I
hope. Apologies if it is stuff you know already.
--
Jim in NC