"xerj" wrote in message
...
To fly the same IAS requires the same power.

You mean the same *thrust*. The same IAS at a higher altiitude will be a
higher velocity, but the same thrust. The same thrust will give the same
dynamic pressure, which is basically what the ASI shows calibrated in
speed. However, thrust does not equal power. Power = thrust x velocity.

Power is net force time velocity. Thrust equals drag, net force is zero.
The energy change of the airframe overtime is zero. All energy from the
engine is going into the air. The power to move air to make the same thrust
is the same regardless of velocity. Same IAS, same engine power
requirement. Look at some aircraft performance charts.

Danny Deger


The drag curve (which is the same as the thrust curve in straight and
level flight) shifts to the right. The power curve shifts to the right AND
up.

To fly the same TAS, requires less power. Because the air is thinner,
you need a higher throttle setting to get the same power out of the
engine. Maybe you are getting throttle setting confused with power.

No, I'm not talking about how open the throttle is. I'm talking about the
effect above. I was trying to think of a way to explain it without
neeeding to refer to IAS and TAS and power curves. Still not sure how to
do that.