Hartzell Governor and MT Prop interface:

[garymail]

I have an MT prop, began to surge with the MT (AVian) governor, not worth the price of an overhaul.

I installed a new Hartzell governor, now the prop will not reduce rpm unless I really pull the throttle back, then reduce rpm, and then increase throttle. I sent a message to Hartzell, but in the meantime, anyone had similar issues?

Gary gdbrown@minetfiber.com

[WAM120RV]

I do not understand the problem you are trying to describe.

The prop will only reduce Rpm if you coarsen it, unless it is in fully fine pitch and you are just operating it like a FP.

We had a lot of surge problems with MT's on WAMS.... it turns out MT put a a dampening piston in some and not in others. Some worked fine without for a while and then developed the fault.

So, can you give a better explanation of your current problem please?

[Russ McCutcheon]

I think what Gary is saying is that during flight when he pulls the prop lever back the RPM does not reduce but if he retards the throttle lo a very low setting then advances it the prop will then go courser as if at the higher throttle setting the governor does not have the power to increase prop pitch.

If you had not been changing governors and possible having governor problems I would say it sounds like your prop is having what MT would describe as sluggish pitch changes which could indicate problems with the prop itself, however with a new GV maybe it?s not making the pressure needed to increase pitch.

I?m running an MTV-15B-183-33 with a Woodward GV.

[RVjim]

Have you been getting the 450 RPM drop when you cycle the propeller during the mag check?

One common problem is not having full travel of the governor arm.

For the symptoms you describe, another more likely problem is a flow restriction between the governor and the piston in the propeller hub.
The most common restriction is caused by leaving the plastic plug in the hub when the propeller is installed. (ask me how I know. :-) )

The governor is the highest pressure oil pump in the engine. It flows 8 quarts per minute at 375 PSI. I was told the propeller hub needs about 150 PSI to hold the propeller in position for cruise.

Jim Ayers
MT Propeller distributor

[garymail]

After some exhausting research, I found that the new "S" series Hartzell governors will not produce enough presssure to operate the MTV-15 (MT) props. Also, there is a known defect in the MT Governor, which requires an upgrade to fix to keep the prop from "hunting" called the "F" mod (now the "G" mod, about $800.00 from MT USA. The newer style Hartzell governor will work, but requires placing an .032 washer on top of the relief valve spring to up the pressure output about 50 psi. The MT propellers require about 320-240 psi, and the hartzell propellers require only about 260-280 psi. I received the data from hartzell, Wings West governor shop, and MT. Hopefully, this will keep others from having to endure the research project I just concluded on my governor problems.

Regards,

Gary