Duane Dieterich wrote:

Paul,

   I am confused about the statement "Aircraft engines run closer to
100% (rated HP)."  I own a Cessna 175 (with the GO-300 geared
Continental engine) and have flown many other types of NA single engine
aircraft.  Almost every one of them uses a cruise (or cruise climb)
configuration of 65% to 75%.  Rarely do you see cruise recommended at
85%.  Most aircraft performance charts won't show high HP output
numbers, especially at higher altitudes, because a NA engine can't/won't
do it.  Additionally, my GO-300 has operating limitations at lower
altitudes that preclude high HP output.

The only time I have seen 100%HP from a NA "aircraft engine" is with a
constant speed prop at take-off.  Again, operating limitations require a
power reduction just after take-off (300ft. AGL).  These aircraft
engines are not (normally) run as hard as one might think.

Duane
http://dmdiet.com/Cessna175

P.S. I have been watching this E-mail traffic for less than 1 month, so
I hope I am not speaking out of turn.  Thanks for hosting this e-mail
distribution!

You are absolutely right. I think that was in reference to an automotive
engine the higher power version of which cruise at only 20%.

Only during takeoff from sea level and initial
climb does the aircraft engine see 100% rated HP. What they see however is wide
open throttle. My old 182 engine was rated full power for as long
as you wanted it. As I recall there was no required time limit.
At least I never observed one :) I used to run it flat out all the time 
climbing out of Calexico over the 10K mountains to Torrance.

My new 182 engine does have a full power limit however but the TBO is
now 2000 hours instead of only 1500 :) I think it is five minutes.


Paul Lamar
 
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