REFLECTOR: Static RPM Question

[nmflyer1 at aol.com]

John,?? 



Yes, it will change if you are not turbocharged. The amount will depend on if you have a constant speed prop or not. 

My experience is that higher density altitude will cause more of a RPM drop on a fixed pitch prop. 



For normally aspirated engines, a rough calculation of effect on engine HP is 3% loss of horsepower for every 1000' of density altitude. So, by the book, a 10,000' density altitude takeoff would be operating on about 70% of the horsepower you would have at sea level. Humidity makes a difference as well, but I use the 3%/1000' rule of thumb.



One of the best consistent tables that I have used for density altitude effects on takeoff/climb is a Koch Chart. 

Take your normal takeoff/climb numbers & adjust acording to the chart. I have found it to be very accurate. 



Kurt Winker


-----Original Message-----
From: aminetech at bluefrog.com
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Tue, Aug 18, 2009 10:39 am
Subject: REFLECTOR: Static RPM Question




I'm planning a trip to WY next month and was wondering if the static rpm changes 
at higher altitudes.

John
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