Increasing power required with altitude.. what's a good plain english explanation?

"xerj" wrote

I don't mean opening the throttle to make up for the engine power loss. I
mean the fact that to maintain the same IAS you need more power as you go
up.

Why the preoccupation with IAS?

At around 6,000 feet, the power of a non turbo piston engine is around 75%.
As you go higher, the power drops off, but the true air speed goes up.

Who cares about IAS? The question was does it take more power to go faster,
right? Any non pilot will think faster means true airspeed, not indicated.
--
Jim in NC

Who cares about IAS? The question was does it take more power to go
faster, right? Any non pilot will think faster means true airspeed, not
indicated.

True, but the conversation got to how high a plane can fly. I said that
going higher did two things: limited the amount of power that an engine can
put out because of density, and that even if you had an engine that didn't
lose power, the power required goes up regardless.

Also, not that it would matter to a non-pilot, but IAS obviously matters for
keeping best range speed for instance.

"xerj" wrote

Also, not that it would matter to a non-pilot, but IAS obviously matters
for keeping best range speed for instance.


How so?
--
Jim in NC

Also, not that it would matter to a non-pilot, but IAS obviously matters
for keeping best range speed for instance.


How so?

Best L/D occurs at a particular angle of attack. This corresponds fairly
well to indicated airspeed.

I don't mean opening the throttle to make up for the engine power loss.
I
mean the fact that to maintain the same IAS you need more power as you
go
up.

Why the preoccupation with IAS?

At around 6,000 feet, the power of a non turbo piston engine is around
75%.
As you go higher, the power drops off, but the true air speed goes up.

Who cares about IAS? The question was does it take more power to go
faster,
right? Any non pilot will think faster means true airspeed, not
indicated.
--
Ok, I confess, I'd rather have an angle of attack meter to correlate more
directly with the best coefficients of lift and drag independently of
current weight. But IAS and a little math based on initial weight and fuel
consumed should work well enough for us cheap-skates.

Even if you are operating at a speed other than best L/D, which seems mostly
reserved for Glider Pilots and Jet Jocks, reference to IAS is about the only
way (that I know of) to keep the theoretical discussion understandable

Peter
Cheapest of the cheap ;-))