Prop Governor Issue

[skydvrboy]

As part of my annual, my prop governor was leaking, but otherwise working fine.  So we sent it in to be resealed.  The prop governor shop got it and said there were other problems that had to be corrected in addition to the reseal, but I'm not sure what all they did to it.  

I picked the plane up today from annual and during my run up at 1800 RPM, the prop would not cycle.  I radioed back to the mechanic that I was returning and he suggested I try to cycle it at 2200 RPM.  At 2200 RPM it would cycle down to about 2000 RPM, but no lower.  He then suggested I try to cycle the prop at red line.  At red line, it would cycle down to about 2200 RPM.

We decided to do a test flight and the prop would adjust to my normal cruise settings, but in flight, I could not get the RPM's to drop below 2100.  On takeoff, RPM's were right at 2700 or just a bit higher at 2750.  Any ideas on what might be going on here?

Before the governor was sent off, I could cycle the prop at nearly any RPM.  Obviously, it's very frustrating to take off a functional, but leaking governor, pay to have it fixed, and end up with new problems.

[chriscalandro]

Just now, skydvrboy said:

As part of my annual, my prop governor was leaking, but otherwise working fine.  So we sent it in to be resealed.  The prop governor shop got it and said there were other problems that had to be corrected in addition to the reseal, but I'm not sure what all they did to it.  

I picked the plane up today from annual and during my run up at 1800 RPM, the prop would not cycle.  I radioed back to the mechanic that I was returning and he suggested I try to cycle it at 2200 RPM.  At 2200 RPM it would cycle down to about 2000 RPM, but no lower.  He then suggested I try to cycle the prop at red line.  At red line, it would cycle down to about 2200 RPM.

We decided to do a test flight and the prop would adjust to my normal cruise settings, but in flight, I could not get the RPM's to drop below 2100.  On takeoff, RPM's were right at 2700 or just a bit higher at 2750.  Any ideas on what might be going on here?

Before the governor was sent off, I could cycle the prop at nearly any RPM.  Obviously, it's very frustrating to take off a functional, but leaking governor, pay to have it fixed, and end up with new problems.

I’ll pm you

[MooneyMitch]

 Based on my experience, the governor shop has created some other negative issues for you.  The 2700 take off RPM is correct.  Return governor for correction, is my opinion. 

[carusoam]

Possibly something getting stuck...

1) The gov has a gear pump that generates oil pressure to operate the prop...

2) a set of fly weights senses the rpm...

3) the fly weights move with respect to rpm...

4) The moving fly weights operate a control valve...

5) the control valve sends oil pressure to the prop...

6) there is a return line for the oil flowing through the system...

7) the fly weight/valve system needs to operate smoothly to control rpm...

8) the gov’s gear pump needs to generate oil pressure to operate the prop...

9) Many MSers have opted for a new gov over OH‘ing the old gov...

10) Like all things mechanical... check the number of hours since the gov’s last OH...

11) Search PCU 5000 for the latest in governors...

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[N201MKTurbo]

This exact thing happened to me once. I assume you have a Hartzell H1.

Apparently,  there are two ways to set up the governor. They did it the other way. This happened to me back in 96.

The prop shop said they would fix it for nothing, but it takes about 4 hours to R&R the thing...

[carusoam]

@skydvrboy if you are checking messages... see Rich’s note above.... ^^^^

-a-

[skydvrboy]

9 hours ago, carusoam said:

@skydvrboy if you are checking messages... see Rich’s note above.... ^^^^

-a-

Yes, and all messages, posts, and other indications are giving me the news I didn't want to hear.  Take it off and send it back.  The plane has been down since January for the annual and it's been one problem after another.  I was hoping to finally get to use it again.  I'll call the mechanic and get this process started.  The sooner we start, the sooner it will be done. 

[HRM]

12 hours ago, skydvrboy said:

Yes, and all messages, posts, and other indications are giving me the news I didn't want to hear.  Take it off and send it back.  The plane has been down since January for the annual and it's been one problem after another.  I was hoping to finally get to use it again.  I'll call the mechanic and get this process started.  The sooner we start, the sooner it will be done. 

Your Mooney is 50+ years old. I feel your pain, mine is a year older.

[skydvrboy]

11 hours ago, HRM said:

Your Mooney is 50+ years old. I feel your pain, mine is a year older.

I can't complain too much as the cost of all these little repairs has been quite reasonable.  It's been the timeline, and subsequent loss of use of the plane that has been the most frustrating.  Well, that and the fact that the items causing the longest delay were all maintenance induced failures.

[AH-1 Cobra Pilot]

I had to have my governor rebuilt this last annual.  The overhaul shop said it would take a few days.  More like six weeks...

During the annual, the IA also noticed the prop was not on correctly, so they had to turn it 1/6 to get it on right.  Who makes that kind of installation error?  There are some real boobs out there.

[EricJ]

1 hour ago, Ah-1 Cobra Pilot said:

I had to have my governor rebuilt this last annual.  The overhaul shop said it would take a few days.  More like six weeks...

During the annual, the IA also noticed the prop was not on correctly, so they had to turn it 1/6 to get it on right.  Who makes that kind of installation error?  There are some real boobs out there.

What model year is your J model?    This happened during the dismal annual that just preceded my purchase of my 77 J model, and I've since sorted out that the distinction between an IO-360-A1B6D and an IO-360-A3B6D is how the prop is clocked on the crank flange.   I still haven't figured out whether it was in the A1B6D position and they moved it to the A3B6D position or vice-versa.    Either is legit and conforms to the Type Certificate, so from that perspective it isn't a big deal (for an engine with the dual mag).    There is a service bulletin (I think, or an SL) from Mooney that shows converting from an A1B6D to an A3B6D.

On IO-360-A3B6 engines (i.e., no dual mag), the prop has to be clocked consistent with the A3 position.

In my case the one guy that looked at the airplane prior to me brought a mechanic with him that told the IA doing the inspection that the prop was clocked wrong.   So the IA moved it.   I suspect it wasn't wrong at all.   The same mechanic told the prospective buyer to run away, apparently because there was so much wrong with the airplane.   I'm glad they did as I really like it. 

[Guest]

3 hours ago, EricJ said:

What model year is your J model?    This happened during the dismal annual that just preceded my purchase of my 77 J model, and I've since sorted out that the distinction between an IO-360-A1B6D and an IO-360-A3B6D is how the prop is clocked on the crank flange.   I still haven't figured out whether it was in the A1B6D position and they moved it to the A3B6D position or vice-versa.    Either is legit and conforms to the Type Certificate, so from that perspective it isn't a big deal (for an engine with the dual mag).    There is a service bulletin (I think, or an SL) from Mooney that shows converting from an A1B6D to an A3B6D.

On IO-360-A3B6 engines (i.e., no dual mag), the prop has to be clocked consistent with the A3 position.

In my case the one guy that looked at the airplane prior to me brought a mechanic with him that told the IA doing the inspection that the prop was clocked wrong.   So the IA moved it.   I suspect it wasn't wrong at all.   The same mechanic told the prospective buyer to run away, apparently because there was so much wrong with the airplane.   I'm glad they did as I really like it. 

You’re referring to M20-206.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-206-1.pdf
 

Clarence

[AH-1 Cobra Pilot]

On 3/26/2020 at 4:52 PM, EricJ said:

What model year is your J model?   

1978.  My mechanic said one of the keys was pushed off, since the keyways did not match.  Fortunately, one less still held the prop in place without damage.

[PT20J]

4 hours ago, Ah-1 Cobra Pilot said:

1978.  My mechanic said one of the keys was pushed off, since the keyways did not match.  Fortunately, one less still held the prop in place without damage.

Don't understand about keys.

The second number in the engine suffix 1 or 3 specifies the clocking. There is a bushing that sets it so you cannot put the prop on wrong. The engine part number on the data plate should match the flange bushing arrangement.

Skip

SI1098P Propeller Flange Bushing Location.pdf

[J0nathan225]

Any idea (I assume the F has the same engine space) if the engine needs to come off to R/R the prop governor?  

[1964-M20E]

28 minutes ago, J0nathan225 said:

Any idea (I assume the F has the same engine space) if the engine needs to come off to R/R the prop governor?  

The engine does not need to come off but it is a PIA to RR and is very tight.  If you replace it with the PCU governor the new one goes in much easier.

[orionflt]

3 hours ago, 1964-M20E said:

The engine does not need to come off but it is a PIA to RR and is very tight.  If you replace it with the PCU governor the new one goes in much easier.

Depending on your engine mount, you can hook a hoist to the engine, take off two mount bolts and tilt the engine forward to get more access to the back of the engine.  
 

brian

[N201MKTurbo]

4 hours ago, J0nathan225 said:

Any idea (I assume the F has the same engine space) if the engine needs to come off to R/R the prop governor?  

If you take off all the nuts on both the governor and the mounting adaptor, pull them both half way apart, you can swing the governor and the mount to the side and get them out without loosening the engine mount. the only down side is you have to buy a new gasket for the mount. $15 is a small price to pay.

[0TreeLemur]

4 hours ago, 1964-M20E said:

The engine does not need to come off but it is a PIA to RR and is very tight.  If you replace it with the PCU governor the new one goes in much easier.

In my experience, this isn't entirely correct.  Yes, the PCU is considerably smaller so after install it does open things up more near the firewall.   However, switching to a PCU governor requires changing to different interference studs, which can be an enormous PIA to replace.  Opposed to the originals which are asymmetrical, the studs for the PCU have the same length of thread on both ends.   Make sure you put them in correctly.   A nut will only go on one of the threads.