Constant Speed Propeller

Those are high oil temps with a relatively low OAT, particularly when you have a large oil cooler. Are you sure that you have an unrestricted flow around the oil circuit? Are there any sharp radii in any of the oil hoses, particularly the one that connects to the oil pump inlet?

Do you have the correct crankcase pressure to force the oil back to the tank?

I know someone who operates with a similar prop on a tightly cowled Europa with only a small oil cooler on a 912UL. He doesn't have any oil temperature problems.

If a prop is over pitched regardless of the type it will cause higher oil temps and more stress on the engine. Even if you use a reduced rpm the prop can still be over pitched. If you give it WOT in level flight and the rpm is below 5500 rpm then it's over pitched.

Roger Lee wrote:

If a prop is over pitched regardless of the type it will cause higher oil temps and more stress on the engine. Even if you use a reduced rpm the prop can still be over pitched. If you give it WOT in level flight and the rpm is below 5500 rpm then it's over pitched.

Hi Roger,

The prop manufacturer claims to set the WOT to 50 RPM below Rotax specifications, so MAX Continuous - 5450 rpm  & MAX TO - 5750 rpm.

I can adjust this in flight by switching to manual and for a more permanent fix also change the manufacturers settings.

I don't usually fly at WOT in cruise, so usually see 5350 rpm in cruise - I will try WOT in cruise, next flight & report back.

Kevin Stewart wrote:

Those are high oil temps with a relatively low OAT, particularly when you have a large oil cooler. Are you sure that you have an unrestricted flow around the oil circuit? Are there any sharp radii in any of the oil hoses, particularly the one that connects to the oil pump inlet?

Do you have the correct crankcase pressure to force the oil back to the tank?

I know someone who operates with a similar prop on a tightly cowled Europa with only a small oil cooler on a 912UL. He doesn't have any oil temperature problems.

Hi Kevin,

To ensure that the return oil lines/pipes do not collapse, I have added an internal spring to the oil line tank/oil cooler pipe and an external spring to the short oil cooler/pump pipe, so there should be no chance of a collapsing oil line.

The long line from tank has no sharp bends, however the short line from cooler to pump is a 90 degree.

The oil cooler is new (as is the rest of the engine), however this is no guarantee that its not partially blocked. I have taken steps to ensure that there is no air trapped in it. Not sure that I know how to assess a partial blockage. I guess a back flush, with petrol, may dislodge any loose stuff but if its a fixed obstruction, how would I know?

Crank case pressure? I get the "Burp" within one slow turn of the prop, so I assume all good.

I have the same engine/propeller on my Europa. It will constantly run at 5750 inTO, 5450 in climb and 5050 in cruise. I’m in the California desert and the airflow (single opening) to the oil cooler is almost closed off and directed to the radiator and it works best with about a 90kts or more of airflow. Think you might be over pitch with the low rpm and low airspeed and probably improve the airflow through your cooling system. It was a bit of experimenting to get it sorted out, but worth it.