governor response

[jimgreen]

I have a WW200RV prop and a PCU5000X governor. I have to be pretty smooth with throttle application not to overshoot max rpm on t/o. I don't hear other aircraft getting that kind of overshoot. I'm wondering if my governor is overly sluggish. Comments?

[Steve Barnes]

I am sure you are not doing this, but just in case. On the first take off of the day you need to cycle the prop to get warm oil in it or you will get an over speed. Don't ask me how I know.

Steve The Builders Coach

[BobTurner]

"pretty smooth" is subjective. "pretty rough" and any governor will overshoot, at least some.
Might not be the governor, either. The transfer collar could be excessively leaking.

[hydroguy2]

Me,too. Same set up

[Captain_John]

Might not be the governor. Might be the prop hub.

I have the same setup but am not flying yet.

A wise man once told me that if what you are describing happens, it could be a prop hub adjustment.

If someone here knows more and could lead the discussion in that direction, it could solve your problem. If not, i could talk to the guy who told me about it.

CJ

[jimgreen]

Just to define smooth, I am sometimes airborne before I get all the power in.
Got to love these machines.

[hydroguy2]

Originally Posted by Captain_John

Might not be the governor. Might be the prop hub.

I have the same setup but am not flying yet.

A wise man once told me that if what you are describing happens, it could be a prop hub adjustment.

If someone here knows more and could lead the discussion in that direction, it could solve your problem. If not, i could talk to the guy who told me about it.

CJ

I'm interested in your wise man. I've asked several folks and the consensus around here is "normal". But I can overspeed my prop if I jam the throttle forward on any start.

[Captain_John]

DOH!!! The wise man was certainly not me!!!

I seemingly cannot read. I saw WW but thought Hartzell.

Anyways... I called Mitch and he says that on a HARTZELL the Minimum Pitch Blade Angle is adjusted by the allen screw in the center of the hum. a half turn in usually prevents this overspeed from occurring.

Now, I am not sure about the WW but there must be a similar setting for min pitch, no???

He also went on to say that the prop guv cannot keep up with the instant surge that you see on takeoff and that is why Hartzell has this adjustment.

Les, am I right? You know this stuff. Can you confirm or deny it for us Hartzell guys?

WW guys, let us know if yours is similar.

CJ

[lesdoud]

Yes, setting the low pitch stop properly is the best way to prevent or minimize RPM overshoots during max power static/takeoff conditions. I normally set the low pitch stop for 25-50 RPM below rated RPM during a max power static run-up. I do this by starting at a high angle and running a series of decreasing blade angles to develop a relationship between blade angle and RPM. This allows me to pick an angle that includes the factory assembly tolerance on the low side. This should minimize or prevent any RPM overshoots during static/initial takeoff throttle slams. It will do nothing for you in flight since the prop is off the low pitch stop at ~40 kts.

I realize this would be difficult for someone that doesn't have the tools to measure blade angle, so I would recommend you first confirm the governor high RPM stop is set properly in flight, say 2700. Then I would start increasing the low pitch stop setting during a series of max power run-ups until you see it drop just below the max rating. I understand max power run-ups on lightweight RVs carries some risk so you might want to do this iterative process by noting RPM overshoots during normal takeoffs. You can increase the low pitch setting a little each time until the overshoots diminish or go away entirely.

Yes, ambient conditions will affect your results. Do this on a low/cold day and you are likely to set the angle a little high; on a high/hot day you will probably be a little low. If you are turbocharged it gets more complicated...

The low pitch stop adjustment on Hartzell props is very easy. The procedure is in the Owner's Manual 115N. I'm not familiar with how the WW low pitch is set or even if it can be adjusted on-wing?

The low inertia of composite props increases the likelihood of overshoots; they spin-up faster making it harder for the governor to catch it before exceeding the high RPM setting.

I have an example chart I can share once I figure out how to post/attach it to a message.

Les Doud
Hartzell Propeller

[Captain_John]

Thanks Les!

Guys, sorry about the confusion about the brands.

Does your hub have the same thing?

CJ