Unwanted prop feather on PA-30 Twin Comanche

[Thomas R.]

Yesterday after 5 hours of total flying and 2:20mins straight as I pulled off the runway my right prop randomly feathered. Oil temps were a little high on both engines today but not at or near redline.

Im trying to figure out if the service bulletin's have been done on the props that add the springs and lower the dome pressure from 70 to 40psi. That being said I'm curious if there is anything else I should be looking out for. Fingers crossed I'm not buying a new governor. I am a new A&P by the way but have never seen/dealt with this before so I'm looking for a little help.

Thanks in advance.

Thomas

***********************AVWEB ARTICLE**************************
A few factors to also consider are the peculiarities of some models of props. The Hartzell used on the Aztec and some twin Comanches relies on just the air-charge in the prop, the ATM (aerodynamic twisting moment) and the internal spring to counteract or balance the governor pressure. There are no counterweights. If the dome air charge is low, the RPM will be airspeed sensitive; that is, the RPM will increase with airspeed and decrease with airspeed. This is true of most Hartzells but especially of this particular model because of the lack of counterweights.

Hartzell also changed the air pressure in the domes of most of their other piston propellers (see Hartzell Service Bulletins 111D, 112, 114D, and 115D). These Service Bulletins add a feather-assist spring in the air-charge side of the dome and lower the air-charge pressure accordingly. In these props the dome pressure is now down around 40 psi, whereas before it was around 70. If you put 70 psi in a prop that has had this Service Bulletin accomplished, you may have trouble with props going into feather at low idle-speed and hot oil. Like a leaky transfer system, this will generally show up on landing rollout.
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[Ted]

If you start it up again and it works, I wouldn't worry about it. I've had that happen a few times on Hartzell props on twins after a long flight with warm oil. It was never repeatable.

What do you have for oil instrumentation? You oil may be hotter than you think.

 

[Thomas R.]

I've got the standard oil temp gauges that came in the plane in there.
I'm going to fly her again today and see what happens.

Maybe ill switch from phillips 20-50 to 100W i guess its possible that could contribute to the warmer oil temps too.

Thanks for the input.

 

[mondtster]

If you start it up again and it works, I wouldn't worry about it. I've had that happen a few times on Hartzell props on twins after a long flight with warm oil. It was never repeatable.

I agree with Ted. I wouldn't make a big deal out of it happening once. If it becomes a regular occurrence then you might start looking deeper.

I personally have not had this happen to me, but an acquaintance had an occasionally feathering prop on a Baron. He complained about it a lot until he called a prop shop about it and found out that it would most likely require the prop going to the shop to be fixed. After that he magically quit complaining...

I've also heard of excessive clearance on the long crankshaft nose bearing causing trouble with this.

 

[Ted]

The stock oil temp gauge isn't great. That said, it's also what I used on the Aztec and now 310.

Your oil temp may be relatively hot. If you operate in a hot environment, going to 100W may not be a bad idea.

Just keep an eye on things and see if it happens again.