What's your M20J RPM on Take off Roll?

[N231BN]

Well folks, now we have the rest of the story. The IO-360-A1A has a governor drive speed of 0.866:1 while the IO-360-A3B6D has a drive speed of 0.850:1. Your governor has run out of adjustment because it is turning the wrong speed.

 

Simply overhauling your governor will not correct the issue you are having. You will need to acquire the correct governor or see if the prop shop can modify yours to work on your engine.

 

Check page 10 of the attached file.https://cloud.tapatalk.com/s/5ece5a9376c22/1E10_Rev29%20%281%29.pdf

[N231BN]

What was the approval for installing that engine in an E model? If it was a STC the installation drawings should list what governor to use.

[David Lloyd]

The difference in drive pad ratio would account for an RPM difference of 2650 versus 2700 (.850/.866*2700=2650)  I had a similar problem when I bought a gov for my RV that had a narrow deck engine versus a wide deck engine.  In that case there was enough adjustment to bring the revs up to 2700.  I thought it was a matter of setup at the certified repair station.

[N231BN]

1 hour ago, David Lloyd said:

The difference in drive pad ratio would account for an RPM difference of 2650 versus 2700 (.850/.866*2700=2650)  I had a similar problem when I bought a gov for my RV that had a narrow deck engine versus a wide deck engine.  In that case there was enough adjustment to bring the revs up to 2700.  I thought it was a matter of setup at the certified repair station.

That is correct, there is obviously a bigger issue with his particular governor. Either way he has the wrong part unless they can be configured for the different drive speeds.

[corn_flake]

Things we find in a 50 years airplane.....  When my AP trys to remove the governor, the bracket promptly snapped off the governor.  A quick examination of the bracket shows the bracket was modified.  Dare I say by someone with access only to stone tools.  Showing in the picture, the part circled in red is only part where the inner strip of aluminum connect with the actual bracket.  This thing could have broke off in-flight!!  In any case, a freshly overhauled Mccalley governor with Mccalley bracket are now install on the airplane.  My static run RPM has now reach 2574, still short of the 2600 by 25 rpm.   We didn't have time to mess with the stop screw since it was getting dark.  I will be back at the field in the morning to back the adjustment screw on the governor out by one turn, which should increase the rpm by 25.  Let's hope this will get me the 2600 rpm I was shooting for.  During take off row, I should be able to get 2700.  

 

[David Lloyd]

Is that even a real prop gov bracket?  Looks more like an aileron rib.  I would have expected the bracket to be steel, not aluminum.

Looked in the parts manual, the part is similar but not the same.  No matter, you need a new one.

[N231BN]

Corn flake, that is not exactly how it works. The governor stop will not change your static RPM unless it is being limited by the governor. If adjusting the screw gets you up to 2600, then that will be your max RPM in flight also.

Another item to check is the rigging of the rod end on the prop control. You need to make sure the governor arm is contacting the stop before the blue knob hits the stop in the cockpit.

[corn_flake]

@David Lloyd  It is a real governor bracket.  The guy at the governor repair station confirmed the old bracket was made by Woodward.   I have no doubt the aluminum bracket would have work just fine if no one has "improved" its design.  Nevertheless, I now have a new Mccalley bracket.  

@N231BN The governor arm is contacting the stop before the blue knob reaching the end of the travel in the cockpit.  We made sure of that.   I will review the Mccalley governor adjustment procedures.  

[N231BN]

[mention=17095]David Lloyd[/mention]  It is a real governor bracket.  The guy at the governor repair station confirmed the old bracket was made by Woodward.   I have no doubt the aluminum bracket would have work just fine if no one has "improved" its design.  Nevertheless, I now have a new Mccalley bracket.  
[mention=12631]N231BN[/mention] The governor arm is contacting the stop before the blue knob reaching the end of the travel in the cockpit.  We made sure of that.   I will review the Mccalley governor adjustment procedures.  

That sounds good, you will probably just have to fly it to get the governor set right.

[Guest]

Its hard to imagine that that cable support bracket has been passing Annual Inspections and that no one has spotted.  Time to seek out a new maintainer.

Clarence

[corn_flake]

Acquired the airplane last year.  So, it now has a new owner and A&P to make sure things are done right.  Log shows this governor was installed in 2011.  Shockingly, a Mooney Service Center did an annual in 2012 and didn't find the issue. 

I begin to believe the collective knowledge on MS is probably far greater than most shop - except Don Maxwell....    

[corn_flake]

Guys, I just want to close the loop and provide some updates after the governor replacement.  

After the governor was replaced with a unit using the correct gear ratio, I was able to get 2674 RPM on a take-off roll.  This is almost 70 rpm improvement comparing to the before number - 2607 RPM.  I'm still not getting 2700 RPM, but I also didn't lean the engine for best power.  The OAT was 90 plus.   Therefore, I suspect I could probably easily get another 25 rpm if I lean the engine before take off.  

For reference below are the numbers

Before full rich Static Run: ~2450RPM

Before take off RPM: ~2607 RPM

After full rich static run: ~2510RPM

After best power static run: ~2576RPM

After take off RPM: ~2674RPM

While I was sorting out the governor issue, we also found the fuel hose that feeds the fuel to the fuel servo was lose.  I doubt it contributed to the problem since the fuel drip was slow.  In any case, I think I can mark this as solved.  

Now on to the next problem - Hot running #2 cylinder. Isn't fun to own an airplane!!