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Mt Prop Governor question

The Wizzard

Well Known Member
I have had 3 small overspeeds in the last 10 hours of operation Two of them were on takeoff (with a very warmed up engine, not the first flight of the day)and one of them was bringing the prop from low rpm to high rpm. I believe the overspeed was about 100 RPM (2700-2800) with 2700 RPM being the limit. In all three cases the problem corrected itself before I could intervene. In other words the prop govenor caught it. The question is why did it go beyond the limit in the first place?

Facts.

!. MT Prog Gov with 675 hours since new
2. Oil Pressure 72 psi
3 Oil Temperature above 140 F
4. Everthing else appears normal
5.Whirliwind RV-200 Prop
6. Never happened since new
7. IO-375-M1B Engine
8. G3X with accessory case tach sensor

Im guessing the prop gov may need overhauling. If so can you recommend a overhaul facility. One onther thought, there is a screen on the gasket between the gov and accessory case. If I pull the gov off and find it obstructed might that be the problem? I can't imagine that being the issue since the oil has been changed every 30 hours on this engine nice new but I thought I would throw it out there.
 
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Similar...

I have an MT unit on my IO-360-A1B6, driving a Hartzell -7497-2 BA.

During the take off roll, if I "slam" the throttle to the stops, I will see a brief (~1 second) overspeed while the governor catches up -- this is in the <100 RPM range, so I never really worried about it.

The RPM is reported to and displayed on the G3X is from the Lightspeed Plasma III ignitions, so I am not 100% convinced the propeller/engine is actually making turns at 2760 or 2780; hand held "PropTach" doesn't show the O/S...

One thing I did find, is the arm that connects to the spline drive on the MT unit and the rod end on the cable, was loose and the arm was wiggling/fretting against the spline drive. This arm was installed at the factory and a bit of torque seal was applied, safety wired and never touched.

Tightening the clamp screw 3/4 of a turn resolved the issue.

MT service center is in Florida, if I recall.

Good luck.
 
Brian, I am very aggressive at applying throttle and this is definitely going over. I can hear it as well. It is not the normal less than one second overspeed that you get from slamming the throttle. I also have a G3X and it has been displaying properly. It gets it information from the sensor that Garmin supplied with the engine install kit.
 
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Two things:
1. If you are aggressive enough with either the throttle or the prop control this overspeed can happen. The governor can’t supply oil fast enough to coarsen the pitch quickly enough.
2. It should not happen at the start of your takeoff roll (unless you have a strong headwind). The static, mechanical fine pitch stop should be set to no more than 2700 rpm.
 
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