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RPM revisited

by jan kerstens in 912 / 914 Technical Questions 12 years ago

Hello,

RPM with the brakes on: 5100 RPM
RPM during climb: 4700 RPM

Cruise OK.

Is this normal?

BR Jan

Re: RPM revisited

by Roger Lee » 12 years ago

Roger Lee

125 5.11k 4.52k

Hi Jan,

Static rpm only gets you in the ballpark when you are putting on a prop and have some unknowns, but the fine tuning comes when you can get in the air. Go up to your average altitude. Go full throttle for about 1 minute. You should be somewhere between 5550-5650 rpm WOT. I would not go lower. If you have special circumstances like floats or some times high density altitude take offs then you may want a little higher WOT rpm in straight and level flight, but shoot for around the the 5600 mark and I think you'll be happy with the balanced all around performance characteristics of the plane.
A little while back I did a test for Sensenich props and they sent me 5 props, plus I had for other types here. The static varied between 2-3 blades quite a bit, but once in the air they were set to 5600 rpm WOT. The performance on these different length props and prop Mfg's were almost the same if they were all set to 5600 rpm WOT. They were all flown side by side against 3-4 different props in the same model and year aircraft at the same time, so comparison was really good.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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