Need advice - in flight adjustable prop

by John Fleming in 912 / 914 Technical Questions 6 years ago

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Re: Need advice - in flight adjustable prop

by Rodrigo Echenique » 6 years ago

Rodrigo Echenique

5 19 0

Hi John,
Your question was how much is too much MP with an inflight adjustable prop, right?
Well MP that is manifold pressure indicate how open is your carburator and with an inflight adjustable prop you can have your throtle wide open and you can lower the RPM of the engine and you can go with full throtle and low RPM but you will burn a lot of fuel.

Do this is when you need top speed, you have your throtle wide open and increase the pitch of your prop and it is ok as long you don´t use more tan 5800 for one or two minutes but for take off is best to set your propeller for 5700 for takeoff and as son your takeoff adjust the pitch to 5000 rpm and you can play with MP and pitch and depending on your plane you can set the RPM at 5000 for cruise or even 4800 closing a little bit the throtle.

Regards

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Re: Need advice - in flight adjustable prop

by Ken Coles » 6 years ago

Ken Coles

0 2 0

I have similar question. I have in flight adjustable prop and on take off if I go WOT it will exceed the 5800 so I pull back on the throttle. Would it be better to adjust prob on take off to max out at 5800 WOT on take off and then adjust once you get to cruise altitude
Thanks in advance
This is 912 uls 860 hours Titan tornado ss

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Re: Need advice - in flight adjustable prop

by John Fleming » 6 years ago

John Fleming

15 92 111

Hi Ken,

I have had time to play around with my prop now, and had a really good chat to my engineer. He has my plane setup to max out at 5800RPM on WOT on take off.

I have checked and it does not get above 5800. By the time I get down the runway and nose up to climb, it will be a little less than that. Once I am about 500 to 800ft, I wind the throttle back a few turns to ease off on the motor, and bring her back to about 5500. Still climbing all good. Once up high enough, and I want to cruise, level out and pull throttle back to get her settled in a cruise at around 5200. Then, when my nose is pointed toward my destination, I start winding the throttle back in and upping the pitch of the prop to keep the RPM around the 5200-5300 mark. So.... Bit more throttle, bit more pitch, bit more throttle, bit more pitch etc etc, until I am happily cruising along.

On my last flight I hit 120 very easily but had to back off as it was a little too lumpy to be going that hard.

I wind the throttle on first, then adjust pitch. That way I reduce the chances of over pitching and lugging the motor.

Anyways... that's where I am at the minute. :) Hope it was helpful to you.

Cheers
John

Thank you said by: Ken Coles

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Re: Need advice - in flight adjustable prop

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.96k

... I have an in-flight adjustable prop and on take off if I go WOT it will exceed the 5800 so I pull back on the throttle. Would it be better to adjust prob on take off to max out at 5800 WOT on take off and then adjust once you get to cruise altitude ...

Maximum power occurs at 5800 RPM and WOT.
This is OK for up to 5 minutes.
If you are reducing throttle, you are not producing Max power and reducing your climb performance.
Increase the prop pitch until the RPMs are just under 5800.
Once you reach a safe altitude, set 5500 rpm for the remainder of the climb.

When you reach cruise altitude reduce the throttle or add in some more pitch to hold the RPMs under 5500.
An In-Flight Adjustable prop will be adjusted more than once In-Flight.
It is Not a Set it and Forget it item.

To simplify your climb outs;
On the next flight, adjust the prop to produce just under 5800 rpm in the initial climb.
Then, without changing the prop pitch, land the plane.
Taxi back to the run-up pad and apply full throttle.
You may see something like 5300-5400 rpm.
Take note of this number and set the prop before each departure to produce this rpm at full throttle.
This should produce your 5800 RPM on the initial climb without any further adjustments.

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

Thank you said by: Ken Coles

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Re: Need advice - in flight adjustable prop

by John Fleming » 6 years ago

John Fleming

15 92 111

Not a bad idea Bill.

Wouldn't it be a good idea though for him to get the prop ground adjusted and set up properly though? Then he should be able to set full fine and blast away! :)

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Need advice - in flight adjustable prop

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