Help with CS Prop Adjustment

I have a Hartzell HC-M2YR-1BFPX prop on my Rocket, controlled by a Jihostroj governor (marketed as a PCU5000). I am unable to get the engine to turn up to the max 2700 rpm, I can only get 2680. I would really like to get the additional 20 rpm if I can.

What have I done so far?

• Confirmed the rpm with an optical tachometer
• Adjusted the governor in half turn increments (started out getting only 2650) till the screw is all the way out.
• Adjusted the screw on the front of the hub by an eighth of a turn, then another eighth for a total of a quarter turn. The manual says this will increase rpm by ~200 rpm per full turn out. This adjustment made no difference.

Are there any prop gurus out there that can tell me what I have done wrong, and what I should do next?

I suspect the governor is limiting the rpm, but don't want to do anything else without some qualified guidance.

EDIT: A little more research indicates I need to adjust the lever on the governor - move it by a spline or two to get a little more travel in the "fine" direction. I will return the prop stop back to its original location.

The static RPM should be in the order of 2600. This is controlled by the fine pitch stop. As the aircraft accelerates, the RPM will increase until the governor kicks in and starts increasing the pitch. As I understand it, this is normally set to 2675 to allow for some over-swing.

I don't see the advantage in trying to get the extra few RPM......

paul330 said:

The static RPM should be in the order of 2600. This is controlled by the fine pitch stop.

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My Hartzell manual says the fine pitch stop is set at 2700.

I don't see the advantage in trying to get the extra few RPM......

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1. I don't like it when adjustments are at the end of their travel.
2. Who knows when max power at 2700 gets me out of a jam where 2680 won't quite do it? Probably never, but I like all the controllable odds in my favour.
3. Obsessive/Compulsive personality.

I'm not a "guru" but I have done a lot of research and reading......

As I understand it, the first step is to set the max RPM with full static power to around 2550-2600. This is achieved by adjusting the fine pitch stop - finer = more RPM. Doing this assures that as you put power on at the start of the TO run, you don't over-speed the prop as the governor tries to catch up. Apparently, the factory setting should normally be right.

As the aircraft accelerates, the RPM will increase. At this stage the governor picks up control of the RPM. So this adjustment can only be done in flight. My MT manual says to put the aircraft in a slight dive at full power and watch the RPM. If it wants to go past 2700, then reduce using the prop control and leave it there for the rest of the flight. After landing, adjust the governor screw to the stop plate.

If you can't get more than 2680 no matter what you do with the governor, then perhaps your fine pitch stop is set too coarse so the RPM never gets high enough to wake up the governor. This would be indicated by a lower static RPM and you are effectively operating a fixed pitch prop.

I think all props/governors basically use these principles but I'm sure any genuine expert out there can put me right.

The 250hp versions of the 540 produce that at 2500rpm. So the extra 20rpm is worth about 1hp. I would suggest that in terms of risk assessment, it would be better to set the max at 2675 so as to avoid potential overspeeds/distractions at a critical stage of flight - but that's just me...........

Adjust static stop on prop dome for desired max (ground) rpm. Adjust governor high rpm stop (set screw stop at control arm) for desired max rpm in flight.