912 over reving

[rhtrudder]

Got a mate towing gliders and noticed first tow the engine revs to high then settles down, could the clutch be slipping in the box , engine is low hours any ideas ?

 

 

[planesmaker]

What prop is on it? A fixed pitch, in flight adjustable/constant speed?

 

 

[rhtrudder]

What prop is on it? A fixed pitch, in flight adjustable/constant speed?

Inflight adjustable , Kašpar

 

 

[planesmaker]

Could be clutch or possibly the adjusting mechanism at fault. Have someone check the clutch IAW rotax manual.

 

 

[facthunter]

The clutch is only a damper for a cam as far as I know. I don't think it can actually slip. The mechanical linkage ones (Pitch control) are sensitive. Might be a temperature related thing. Nev

 

 

[Downunder]

Sounds a bit like there is some lag between the c/s prop sensing the rpm then coarsening up to compensate?

 

Not sure about the clutch.

 

 

[frank marriott]

Sounds a bit like there is some lag between the c/s prop sensing the rpm then coarsening up to compensate?Not sure about the clutch.

Unless it is a more advanced system then I have come across, an inflight adjustable does just that i.e adjusts the pitch as commanded as opposed to a CSU. There may be more advanced systems that I have not seen to which you may be referring?

 

 

[rhtrudder]

The clutch is only a damper for a cam as far as I know. I don't think it can actually slip. The mechanical linkage ones (Pitch control) are sensitive. Might be a temperature related thing. Nev

I thought the clutch was designed to slip in case of prop strike which I turn saves the pressed crank from twisting. It's not a csu you manually set the pitch using a crank handle in the cab

 

 

[Camel]

I had a Kaspar in flight adjustable on my Sportstar and if the prop is left fine after take off it will definitely over rev.

 

Great propellor when operated correctly.

 

 

[rhtrudder]

I had a Kaspar in flight adjustable on my Sportstar and if the prop is left fine after take off it will definitely over rev. Great propellor when operated correctly.

It over revs on the fine set for glider tow on the first flight after that on the same setting it performs ok,

 

 

[facthunter]

The mechanical ones are very sensitive. If there's play or any springing/binding in the control linkage it could settle down in a slightly different position after a while. We are not talking of a constant speed here. It's just in flight controllable pitch. Nev

 

 

[rhtrudder]

The mechanical ones are very sensitive. If there's play or any springing/binding in the control linkage it could settle down in a slightly different position after a while. We are not talking of a constant speed here. It's just in flight controllable pitch. Nev

Thanks nev, you might be on the right track

 

 

[facthunter]

There's a big centrifugal load on the blades and the bearings. The shape of the blades drives them toward fine when at high(er) RPM's. Nev

 

 

[rhtrudder]

Plane is set up for glider towing, so as it starts its run the at full fine it can't over rev because of the glider hanging off the back but with no glider it will , the owner is worried that the clutch maybe letting go as it over revs on the first tow also makes a different noise , we think the easiest way to test is to send the box back to floods, reading the Rotax manuals I think there is a way to check the torque but looks hard enough to figure out