Prop governor won’t cycle on the ground but works fine in the air

[tigers2007]

I’ve spent about an hour perusing the historic threads here regarding the governor. If it won’t cycle at 1800 RPM’s but works fine when I’m in the air, do I have a critical issue here?

I’ve put about four hours on the engine since it sat for a few months in a very dry and freezing hangar. When I pull back all the way I’m the prop control when on the ground nothing happens (at 1800RPM’s). After reading the threads it seems I need to try higher RPM’s to see if it budges. When I’m climbing at full throttle and full prop after takeoff I see 2600RPM on the tach. Pulling back on the prop control it let’s me set 2550 and later 2500 for cruise just like normal. 

Do I need to send this to a prop shop (Cody?) to have it IRAN’d or can any A&P take a simple look at it and replace the notorious leaking seal? 

I have a Hartzell HC-C3YR-1RF three blade

[Cody Stallings]

What is your oil pressure at 1800 rpms?

[tigers2007]

“Green” pressure? Good question I’ll head to the hangar on Wednesday and take some specific measurements. Before I push the motor up on RPM’s I make sure everything is in the green. I just have the ancient Garwin six-pack gauges.


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[Jim Peace]

I have seen the same issue with mine and I am based in a warm climate and fly a lot.  20 hours in the last 4 weeks.

I have found that when I check the prop on the ground  it works 100% of the time but when I fly with a friend who slowly pulls the prop lever back nothing will happen.  I then instruct him to pull it aft at a quicker speed, which is what I would call normal in the business, and then it works.

1964 M20c

 

 

[Bob_Belville]

Per my checklist, I use 1800 RPM for MAG check but bump throttle up to 2000 for prop cycling. I'm sure Cody is right that the real factor is oil pressure though I haven't carefully noted how much 1800 RPM to 2000 RPM raises OP. IO360 not your O360.  

[tigers2007]

I've never had this problem in the past. It even cycled fine at 1500RPM (as written on the checklist sheets provided by the previous owner). The MSC CFII that originally gave me 10 hours of dual instruction insisted that I cycle the prop at 1800RPM just after doing the mag and carb heat checks. The aircraft sat idle from Oct. 2018 to Feb. 2019 (when it had its annual). It then sat until the end of this April when I picked it up. A&P didn't note any issues with the prop governor from the Feb. annual. 

[Guitarmaster]

I've never had this problem in the past. It even cycled fine at 1500RPM (as written on the checklist sheets provided by the previous owner). The MSC CFII that originally gave me 10 hours of dual instruction insisted that I cycle the prop at 1800RPM just after doing the mag and carb heat checks. The aircraft sat idle from Oct. 2018 to Feb. 2019 (when it had its annual). It then sat until the end of this April when I picked it up. A&P didn't note any issues with the prop governor from the Feb. annual. 

If this is a change from normal operation, something definitely is amiss.
As previously stated, check your oil pressure. I would put a manual gauge on it. That's the easiest and cheapest thing to check.


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[steingar]

Sounds hinky to me.

[Shadrach]

I can only speak to the PCU5000 in my F but mine will go full course pitch at almost any RPM. I cycle it at 900-1000 during taxi and get a discernible drop just like when it’s cycled at any other RPM, it just takes a split second longer to respond at low rpm. If you have good oil pressure to the governor, it seems like perhaps the governor is not stepping up the pressure as it should.

Edited May 6, 2019 by Shadrach

[orionflt]

Be careful flying it like that, It may seem to be controlling the prop in "normal situations" but it may not be able to handle emergency situations.

I had a Lancair that someone left a shipping gasket in place on the prop gov when it was installed, everything worked fine for a couple hundred hours until the new owner was doing training and the instructor had him do an emergency decent. the sudden load change was more then the gov could handle with the partial restriction from the shipping gasket. the prop overspeed to a max of 3510 RPM. the whole incident from initial overspeed until RPM recovery was just under 10 sec, in that 10 sec 2 prop bolts were sheared and the rest stretched. thankfully the instructor didn't let the owner reapply any power or adjust the prop except to pull back what little power they had set when the landed. on the ground you could rock the prop on the hub, the prop was toast and the engine required a complete overhaul with a crank and cam replacement. thankfully everyone walked away unhurt. 

Brian  

[Hank]

When my C sits for a while, prop response at runup is slow. It may take 3-5 seconds for anything to happen the first time I pull the lever back, but once it moves all subsequent responses are immediate. 

It may be worthwhile having it checked. 

[jaylw314]

3 hours ago, tigers2007 said:

I've never had this problem in the past. It even cycled fine at 1500RPM (as written on the checklist sheets provided by the previous owner). The MSC CFII that originally gave me 10 hours of dual instruction insisted that I cycle the prop at 1800RPM just after doing the mag and carb heat checks. The aircraft sat idle from Oct. 2018 to Feb. 2019 (when it had its annual). It then sat until the end of this April when I picked it up. A&P didn't note any issues with the prop governor from the Feb. annual. 

Just out of curiousity, does it fail to cycle when you're on the ground AFTER a flight? Or have you only tested this on the runup BEFORE a flight?

[tigers2007]

I didn't think about that. I'll try this out on Wednesday when I'll go for a loop around the pattern.

[skydvrboy]

Like Shadrach, I've cycled my prop sub 1000 RPM's and it cycled just fine.  I have noticed first flight of the day when it's cold it takes a few seconds from when I pull the lever to when the prop actually moves.  I thought this was normal and perhaps it is (if not, someone let me know).

I know I'm a low time pilot, but I always thought the prop check was a go, no-go test.  If it didn't cycle for me on the ground, I'd have no way of knowing whether or not it would cycle in the air... 'cause I ain't goin' there.  I'm not saying that's the right decision for anyone else and maybe as I gain more experience, knowledge, and familiarity with the plane that might change, but that is what my instructors have all taught.  Of course they also taught that the flap check was a go, no-go test and now I fly formation without using (or even checking) the flaps. 

 

[tigers2007]

I wonder if flying out of 7,000+ foot runways interferes with my decision making sometimes. I've survived one wreck and what saved my bacon is that it was 5,200 foot long and not the regular 3,500 foot or less runways we normally see. In fact the runway where I'm at now and where I used to be based out of still have 12,000+ feet of hard surface available due to the Cold War days. They downsized them to reduce maintenance costs (and an epic snow removal burden).  

[Guitarmaster]

A great way to force your brain into the proper decision making mode:

Think of every decision as a bet. In other words, 'would I bet $10,000 the decision I'm about to make is the correct one?'
If the answer is no, the problem is one of two things... 1.) You don't have enough information to make a proper judgment and decision. The solution is to get more information.
2.) It's the wrong decision.

it's interesting what happens to your brain when you start thinking like this. Seriously changes your perspective on the decision making process.


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[Bolter]

Did you review the work done on the plane during the annual?  Was the prop removed or other opportunity to block an oil passage?  Anything else that could have interfered with rigging the governor control cable?  

Real-Life Mooney Example (not my story, so no names will be given): Prop removed and a rag stuffed in the crankshaft to stop the oil from weeping out.  Prop reinstalled.  Rag still there.  Failed the run-up and rag was found inside.  

-dan

[larrynimmo]

please keep in mind that the prop governor limits the RPM of the engine.   if it fails to limit at 2,700 you may overspeed your engine...keep watch over.

When I replaced my engine, I sent mine out to get it rebuilt and the company said they can't get parts for it, so they charged me $1,750 for a new one...I think they send me a McCauley brand...worked perfectly

[Shadrach]

7 hours ago, orionflt said:

Be careful flying it like that, It may seem to be controlling the prop in "normal situations" but it may not be able to handle emergency situations.

I had a Lancair that someone left a shipping gasket in place on the prop gov when it was installed, everything worked fine for a couple hundred hours until the new owner was doing training and the instructor had him do an emergency decent. the sudden load change was more then the gov could handle with the partial restriction from the shipping gasket. the prop overspeed to a max of 3510 RPM. the whole incident from initial overspeed until RPM recovery was just under 10 sec, in that 10 sec 2 prop bolts were sheared and the rest stretched. thankfully the instructor didn't let the owner reapply any power or adjust the prop except to pull back what little power they had set when the landed. on the ground you could rock the prop on the hub, the prop was toast and the engine required a complete overhaul with a crank and cam replacement. thankfully everyone walked away unhurt. 

Brian  

This reads like there were other issues as well. Doesn’t the prop have a course and a fine pitch stop. I understand that a prop will fail to fine pitch if the governor fails which can result in an overspeed. However, 30% past redline is a huge overspeed. I don’t think that is a common failure scenario.

[gsxrpilot]

4 hours ago, Guitarmaster said:

Think of every decision as a bet. In other words, 'would I bet $10,000 the decision I'm about to make is the correct one?'

This is aviation... you need to raise the bet. $10,000 is the kiddie table at this casino 

[Bob_Belville]

2 hours ago, gsxrpilot said:

This is aviation... you need to raise the bet. $10,000 is the kiddie table at this casino 

I was thinking the same thing. 

[Cody Stallings]

Your Governor may not be online at 1800 rpm.

if it has been in the past I would be getting thing checked out till you found it.

 

You can find what RPM you Gov checks in my pulling you Propeller knob all the way out, then pushed in 1/4 inch at idle.

Then from idle raise RPM till it dumps an reduced RPM for you. 

 

Missile an Rocket drivers, don’t try this at home!!! 

[81X]

3 hours ago, gsxrpilot said:

This is aviation... you need to raise the bet. $10,000 is the kiddie table at this casino 

The “Wednesday at 2PM table”?  So true. I wonder when the “AMU” becomes representative of a different dollar amount. 

[tigers2007]

Your Governor may not be online at 1800 rpm.
if it has been in the past I would be getting thing checked out till you found it.
 
You can find what RPM you Gov checks in my pulling you Propeller knob all the way out, then pushed in 1/4 inch at idle.
Then from idle raise RPM till it dumps an reduced RPM for you. 
 
Missile an Rocket drivers, don’t try this at home!!! 

I’ll give it a try as soon as I can get out to the airport. I’ll take a video.


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[carusoam]

A post I never sent...

 

1) Are you familiar with the fly-weights in the gov?

2) They should be operational as they have a range they can attain while on the ground...

3) If it requires a higher MP than normal, Something is no longer working as expected....

4) How old is the gov? Age and hours...  log book check...

5) Sounds like the valve that is operated by the fly weights may need some cleaning...

6) our engines have two oil pressures... one is measured and indicated on the instrument panel... the other is down stream of the gov’s gear pump... not measured at all.... this is the oil pressure that operates the blades.  

7) the first gear pump delivers oil to the gov... the second one delivers oil to the prop.   Both gear pumps  deliver oil volumetrically, based on engine rpm...

8) If you have 5khrs on the gov and no history of OH... it may be time for a replacement... OH cost about as much as a new PCU5000...

Thanks to Cody for sharing great prop insight! 

Best regards,

-a-