[Deans894]

Good evening,

I have just purchased an LSA aircraft with a ground adjustable Peszke propeller and i believe it is over pitched. My WOT throttle is 5200 RPM on a Rotax 912 ULS.

I'm hoping to find someone who is familiar with ground adjustable propellers who could help me adjust my propeller. I have the manual and the angle measuring tool and I'm based at Charlton Park (Near Kemble).

Thanks in advance

Dean

[carlmeek]

Dean,

When you say your WOT RPM is this on the ground while holding on the brakes, or during the takeoff roll, or in the cruise?

For a rotax, or any engine, they should be adjusted so that it never exceeds the stated redline RPM. In my experience this is usually highest a few seconds into the takeoff roll.

Once it's adjusted correctly to not exceed redline, the WOT whilst static or cruise is essentially irrelevant.

-C

[Flyin'Dutch']

In my experience this is usually highest a few seconds into the takeoff roll.

Once it's adjusted correctly to not exceed redline, the WOT whilst static or cruise is essentially irrelevant.

-C

Really?

I find it much easier to approach redline RPM in the cruise than during the take-off roll.

[carlmeek]

I didn't explain myself very well, sorry!

Indeed RPM will be highest during a WOT when unloaded, in cruise, and even higher when descending where you will need to reduce throttle to prevent exceeding redline.

I was trying to say that when adjusting you need to ensure that you can safely take off and climb without exceeding redline and the highest RPM is likely to be seen once the aircraft is rolling nicely during the takeoff roll.

[Paul_Sengupta]

Isn't it the case that in most fixed pitch aircraft you're not going to see anywhere near max RPM on the take off run unless you have a particularly fine pitched "climb" prop?

Unless of course you take off at close to cruise speed!

A fine pitched prop can be a pain at high density altitudes as you reach max RPM before max power/throttle, so you cruise slower and noisier.

[Deans894]

Hi, i get 5200 RPM in tbe cruise at WOT. Ive spoken with my engineers and they have said its overpitched. Ive done research and id like to pitch for 5600 RPM.

Thanks

[Shoestring Flyer]

What Carl is saying is correct. The prop will be at its highest rpm just after it has unloaded at rotation and the start of the climb assuming the throttle is wide open of course.
It varies depending on the make of prop prop but 5200 rpm WOT static is to low.
Usually you would expect on a fixed pitch prop to be getting 5400-5500 rpm WOT static so that just after the rotation prop unloading point you will have 5600-5700 which is just under the Rotax max rpm of 5800 rpm.
Without specific manufacturer advice you will need to experiment. Try reducing the pitch by 0.5 of a degree at a time until you get something of the order of 5400 rpm static and see what max just after the prop has unloaded that give you.
Also check WOT in the cruise in which you should be getting approx 5600 rpm.
Don't also forget that the max continuous rpm for a Rotax is 5500 for max 5minutes.

[Big Dex]

Don't also forget that the max continuous rpm for a Rotax is 5500 for max 5minutes.

Max continuous rpm is precisely that; 5500 for as long as you like. Max rpm is 5800 for a maximum of 5 minutes.

[Shoestring Flyer]

Ok..What I should have said was that maximum above 5500 and in the range 5500-5800 is limited to 5minutes!

[Flyin'Dutch']

What Carl is saying is correct. The prop will be at its highest rpm just after it has unloaded at rotation and the start of the climb assuming the throttle is wide open of course.
.

As I wrote in the second post - a prop will not be at its highest RPM during the take off roll or the initial climb....

[Rod1]

What is your max static rpm? This can be a limiting factor as if it is to low you will only be getting around 40-50hp at the start of your take off. I have experience setting up ground adjustable props but not the type you have and not recently. From memory you do not want to go below 4400 ish max static. Discuss this with your inspector, but provided you make small equal changes you can get to the right answer by trial and error without any issues. What type of aircraft have you got?

Rod1

[wjr2]

Hope you have better luck with your prop. My AS B-Line 1700/1950 on same Rotax 912 uls delaminated with less then 200 hrs. It is the second delaminated Peszke prop I heard delaminating in the last year.