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

I'd suggest a REALLY GOOD flight review next time you need one with a REALLY
GOOD instructor who knows the relationship between power, altitude, and true
airspeed.

Or did ..maniac assume a pseudonym?

Jim



"xerj" wrote in message
...
I was trying to explain to a non-pilot why increased power is required with
altitude. She said "isn't the air thinner up there so there isn't as much
resistance?" I said "yes, but the plane needs to fly fast enough for the
air over the wings to feel like it does down low. So the speed required
goes up you get higher. More speed need more power."

"RST Engineering" wrote in message
...
I'd suggest a REALLY GOOD flight review next time you need one with a
REALLY GOOD instructor who knows the relationship between power, altitude,
and true airspeed.

Or did ..maniac assume a pseudonym?

As you can probably see by the length of the thread, this one has gone on
for a while. I was talking about trying to explain the phenomenon of how to
keep the same IAS you need higher power as you increase altitude, but
without actually referring to concepts like IAS and TAS. I wasn't talking
about TAS increasing with altitude. I should have made that clearer in the
initial post. The whole thing started when a non-pilot friend of mine asked
how high planes could fly. I said that it depended on a few things, one of
them being the fact that engine power decreases with altitude because of air
density. At some point you'll hit an altitude where it can no longer
generate the power required for level flight. HOWEVER, even if you have an
engine that was turbocharged so well that it didn't lose power with altitude
all the way up to space, you'll still probably hit a limit (unless the
engine was extremely powerful) because the actual power required goes up
with altitude as well. Is there anything unreasonable in what I have just
said there? I don't think so. Where I went wrong is in not explaining my
question well enough, and people very reasonably thinking that I either
meant TAS or how open the throttle has to be.

As has been established, I am now certain that my understanding of power,
altitude and TAS was and remains correct. I was merely seeking a good layman
non-mathematical explanation of it. Hardly a major sin, I think.

"xerj" wrote in message
...

"RST Engineering" wrote in message
...
I'd suggest a REALLY GOOD flight review next time you need one with a
REALLY GOOD instructor who knows the relationship between power,
altitude, and true airspeed.

Or did ..maniac assume a pseudonym?

As you can probably see by the length of the thread, this one has gone on
for a while. I was talking about trying to explain the phenomenon of how
to keep the same IAS you need higher power as you increase altitude, but
without actually referring to concepts like IAS and TAS. I wasn't talking
about TAS increasing with altitude. I should have made that clearer in the
initial post. The whole thing started when a non-pilot friend of mine
asked how high planes could fly. I said that it depended on a few things,
one of them being the fact that engine power decreases with altitude
because of air density. At some point you'll hit an altitude where it can
no longer generate the power required for level flight. HOWEVER, even if
you have an engine that was turbocharged so well that it didn't lose power
with altitude all the way up to space, you'll still probably hit a limit
(unless the engine was extremely powerful) because the actual power
required goes up with altitude as well. Is there anything unreasonable in
what I have just said there? I don't think so. Where I went wrong is in
not explaining my question well enough, and people very reasonably
thinking that I either meant TAS or how open the throttle has to be.

As has been established, I am now certain that my understanding of power,
altitude and TAS was and remains correct. I was merely seeking a good
layman non-mathematical explanation of it. Hardly a major sin, I think.


I would just leave it that the engine looses power with altitude and not
mention the fact that for a propeller aircraft the power required also goes
up. Keep in mind for a jet the thrust required does not go up with
altitude. More output being required is strictly for props.

Danny Deger