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assuming that you tune the prop for the desired altitude and the rpms stay
up at the rated level:
you loose roughly 1/30 of the maximum power per 1000 feet of altitude.
or more precisely at 10,000' there is a pressure of about
0.7 atmospheres (0.696 bar) -> so you can achieve roundabout 0.7 times your
max sea level hp.
Pull out any old airplane handbook and check the power chart, some charts
allow rated power of 75% up to e.g. 5000 feet, because the old Lycomings and
Continentals are not designed to withstand 100% power for more than a few
minutes. So if you want to limit maximum manifold pressure (as to not
overload your con-rods ;-)) to lets say 27" then you can go to about 4000 to
5000 feet before you run fully open on the throttle and only when you're
going higher than that will you see a power reduction of 1/30 max hp per
1000'
If you listen to the old Rutan reasoning you can keep 75% power to even
higher levels by simply revving the engine higher. With a rotary there is a
lot of leeway.
Marko
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of Chad Robinson
Sent: Wednesday, April 07, 2004 4:38 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] HP and turbos / altitude
What kind of losses can I expect in horsepower based on altitude?
I'd be doing
most of my flying around airports that are between 100-1000 MSL
so I don't
exactly need a turbo to help get off the ground. However, since
this is a Cozy
and it climbs quickly, it wouldn't be unusual to cruise between
8000-10000'.
I'm debating whether a turbo would be beneficial, and if so how much.
Regards,
Chad
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