Rotax 915iS Fixed Pitch Prop Pitch Adjustment

by Tom Delaney in 915iS Technical Questions 6 years ago

My Magni M24 915iS Gyroplane also has a fixed pitch.prop. It is a DUC 5-blade prop. It was developed for Magni and is advertised as having a “constant speed effect”
I would appreciate some guidance in setting the pitch.

The static WOT is 5300 rpm.
The best angle T/O (65 mph) is ~ 5460 rpm

That is all the info I have at this point but would like to get some pointers on the next adjustment. Previously I owned an RV12 and remember that a static WOT in the range of 4950 was a good starting point. I am wondering if the rpm suggestions are the same from one Rotax engine to another?

Thanks,

Tom

E931E122-1F9D-4E8B-A082-5A0573E1165E.jpeg (You do not have access to download this file.)

Re: Rotax 915iS Fixed Pitch Prop Pitch Adjustment

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.98k

Static RPM is only a rough starting point for the maiden flight.
It means very little in the air once the prop unloads with increased airspeed.

You need to decide what is most important to you.
Do you want to go UP fast or do you want to go Somewhere Fast? Climb or Cruise?
You are probably about right as it is if you cruise at WOT.and 5500rpm.

If you flatten the prop slightly to get above 5700rpm in a 65mph climb, you will have better performance for clearing trees and mountain tops and will have a higher service ceiling.

If you normally back off the throttle once you reach cruising altitude, you really are not trying to maximize cruise.
If you set the prop for maximum climb performance, you will need to be diligent at reducing the throttle when accelerating to cruise speed or you will risk over-revving. You already need to reduce throttle during descents so this should not be anything new. It is just something to keep higher on your watch list.

You spent the extra money on a 115hp turbo engine.
It only makes 115hp at 5800rpm at WOT.
If you are going to limit it to 5400rpm you might as well have installed a 912 100hp version.
You need to be able to get to 5800rpm at some point in the flight envelope or you are not making use of the Power available to you.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

Thank you said by: Tom Delaney

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Rotax 915iS Fixed Pitch Prop Pitch Adjustment

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