Hartzell C/S - Slight Variation in RPM at Cruise

[Mountain Time]

I have a carbed O-360-A1A with the Hartzell BA prop and McCauley governor, about 450 hrs since new on all of these components.

The last few months, I've noticed a slight hunting or variation in RPM at cruise - say, if set at 2400 RPM with constant throttle position I will see it vary up and down perhaps 10-30 RPM or so. It is just enough to notice it from the sound and feel of the plane, and its visible on the RMI Micromonitor RPM readout. So I don't think it is just an instrumentation issue.

It doesn't happen all the time; sometimes RPM is rock steady, as it has been historically in years past. But then it will go into this slight variation/hunting mode, which may last just a couple minutes, or sometimes longer.

Engine, prop, governor, etc. all seem to work normally in all other respects. Given the symptoms it seems like it must be a governor issue of some kind.

Any suggestions on what this might be, and/or best way to troubleshoot further? Thanks in advance your your suggestions.

 

[Flying again!]

When I sent my governor to be resealed they told me I had to replace the flyweight assembly because of wear where it touches the speeder spring assembly which will cause hunting during cruise. Most noticeable at the RPM you usually fly.

More great info here:

http://www.avweb.com/news/maint/propeller_governor_diagnostics_195565-1.html

TJ

 

[cajunwings]

Rpm hunting

First place to start is the rod end and attach bolt at the governor. Make sure there is no slack. Then make sure the cable is securely attached to the governor bracket and the bracket has no cracks or any other issues that would allow it to be more flexible than in the past. Governor should not have much internal wear at 450 hrs but that is where I would go next.

Don B. A&P, IA and some other letters

RV 9 Rebuild in Progress

 

[Mountain Time]

Good information in that Avweb article - thanks for the tips, guys. I'll do a little more sleuthing this weekend......