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  #1  
Old 12-02-2020, 03:42 PM
The Wizzard's Avatar
The Wizzard The Wizzard is offline
 
Join Date: Nov 2009
Location: Cincinnati, Ohio
Posts: 154
Default Mt Prop Governor question

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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Last edited by The Wizzard : 12-02-2020 at 04:24 PM. Reason: added 7 and 8
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  #2  
Old 12-02-2020, 04:17 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 646
Default 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.
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2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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  #3  
Old 12-02-2020, 04:22 PM
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The Wizzard The Wizzard is offline
 
Join Date: Nov 2009
Location: Cincinnati, Ohio
Posts: 154
Default

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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Last edited by The Wizzard : 12-02-2020 at 04:26 PM. Reason: re worded
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  #4  
Old 12-02-2020, 04:30 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 646
Default

Pull unit, check/clean the screen, then send it off for O/H...
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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  #5  
Old 12-02-2020, 04:33 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,361
Default

Two things:
1. If you are aggressive enough with either the throttle or the prop control this overspeed can happen. The governor canít 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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  #6  
Old 12-02-2020, 04:45 PM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,020
Default

Adjust the prop low pitch stop.
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #7  
Old 12-02-2020, 04:58 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,540
Default

Quote:
Originally Posted by Walt View Post
Adjust the prop low pitch stop.
Plus 1 for this suggestion
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