Teach Me About Prop Governors

Mine was slinging grease last year with 200-250hrs on it. The seal between the crank and hub was the wrong one so the hub was getting flooded with engine oil and it was mixing with the prop grease. $1150 fix
 
Followup to this thread. Prop is coming off the plane this week and being sent out for a reseal. To recap, the issue had nothing to do with the governor as the thread title says. I was just ignorant. It was leaking grease, not oil.

Question: is there anything I could be doing with the prop that would have caused this? I am new to constant speed flying so am I using the blue knob wrong? I am hoping not and this just happened as a non pilot induced failure.
 
NealRomeoGolf said:
Followup to this thread. Prop is coming off the plane this week and being sent out for a reseal. To recap, the issue had nothing to do with the governor as the thread title says. I was just ignorant. It was leaking grease, not oil.

Question: is there anything I could be doing with the prop that would have caused this? I am new to constant speed flying so am I using the blue knob wrong? I am hoping not and this just happened as a non pilot induced failure.
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They just wear out. Like Subaru head gaskets. LOL
 
Briar Rabbit said:
450 hours is not a lot of time on a prop governor but if the governor goes bad in flight it likely will take the prop to low pitch and typically an engine does not generate enough power to maintain level flight, i.e. you are going to land even if you don't have an airport near your position. It is usually recommended the prop governor gets overhauled when the prop does.
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Would you mind elaborating a bit more on this?

My understanding is that if the prop governor goes bad in flight and there are no other issues (eg. oil leaks, engine oil pump) then the springs in the prop will force the blades back to their flattest pitch. That pitch is like a climb prop. But a plane can both climb ad cruise just fine with the prop full forward (lowest pitch). Why would the engine not have enough power to maintain level flight. Wouldn't it cruise just the same as if the prop knob is full forward?
 
Some mixing up of the governor and the stuff in the prop hub going on here.

Governor is the oil pressure controlling needle valve and the spinning weights that also is where the physical linkage from the cockpit control ends up at — to adjust the resting position of the needle valve.

The springs (or in some designs on twins, the nitrogen pressure charge, or both...) are in the prop hub...

(And twins push the blades to feathered usually in a loss of oil pressure, vs going flat in singles.)

Failure modes for the governor itself would be stuck needle valve (prop no longer holds a particular RPM and acts like a regular prop / can’t be changed / overspeeds / underspeeds ), mechanical / metallurgical failure like flinging a weight off, linkage from the cockpit to the governor falls off / gets stuck, something big/gooey/metal shavings clogged in the thing (probably something not good that shouldn’t be in the engine oil), stuff like that.

Not listed in any particular order of how common any of those are. Most of those above are rare, other than the stupid control linkage having problems. That is probably the most common and isn’t truly a governor failure unless the little lever snapped off. Ha.

But you can’t always tell which of any it is from the cockpit. The blue thingy just won’t work anymore. :)

Most true governor failures, you’d still have engine oil pressure, but you may need to throttle back, for various reasons. But usually the engine is still producing power.

Oil pressure losses from “whatever” are waaaaaaay more common.

Those do tend to lead to the engine needing an abrupt power loss, as in shut it down, before it seizes up and lowers its power for you. Ha.

Quite a few folks have noted engines that have kept happily idling or windmilling without oil pressure over the years, though.

Not too many have reported them able to maintain any serious power without oil pressure. :)

Of course a governor itself could spring a leak too... resulting in a pressure loss... but again, pretty rare.

If you did have an over speed in a single from a failed or stuck governor... do you REALLY trust that oil pressure gauge in the cockpit or do you wonder if it’s lying and all the oil just exited on the belly? Ha.

The gauge says you’re good, but are you leaving the throttle wide open above redline? Maybe not such a good idea...? :)

Sooo... there’s a certain practical side to this that says you’d better put the thing on the ground or be ready to very soon, with an extremely skeptical eyeball on the pressure gauge, temperatures, and MP/RPM... when props start behaving badly... in singles. And probably a forced / chosen power reduction.

In twins, precautionary shutdown, get it feathered, and get thy self to an appropriate airport... same deal, but less likely to be off airport.

You’re right though. A true governor failure rarely directly relates to any engine power loss.

It may mandate an engine power change quickly, though. :)

The really “fun” failures are when the whole system starts surging. Also rare, but you read about a few from time to time... ;-) Doesn’t sound particularly fun.
 
Sinistar said:
Would you mind elaborating a bit more on this?

My understanding is that if the prop governor goes bad in flight and there are no other issues (eg. oil leaks, engine oil pump) then the springs in the prop will force the blades back to their flattest pitch. That pitch is like a climb prop. But a plane can both climb ad cruise just fine with the prop full forward (lowest pitch). Why would the engine not have enough power to maintain level flight. Wouldn't it cruise just the same as if the prop knob is full forward?
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For single engine airplanes essentially that is correct (I had a brain cramp when I replied earlier), and for twins may lead to feathering the prop as Nate pointed out. Also depends on what fails inside the governor and if it starts generating metal in the engine. However it is likely in a single to go to flat pitch but not 100% that it will, this was the wording in the recent McCauley AD for their prop governors:

"The non-conformity of the bearing may cause premature failure of the idler gear bearing. Early symptoms that the idler gear bearing may fail include inability of the governor to hold the selected RPM, hunting, surging, etc. An investigation identified 23 occurrences of airplane operation problems related to erratic governor behavior that may have resulted from the unapproved idler gear bearing. The NPRM proposed to require replacing an affected governor with a governor eligible for installation. The FAA is issuing this AD to prevent failure of the idler gear bearing, which could result in failure of the governor, loss of propeller pitch control, engine and propeller over speed, engine oil contamination, and loss of airplane control."
 
I should also include that they found that whomever lubed it last (which would be prior owner's A&P) used the wrong grease.

facepalm2.gif
 
Radar Contact said:
Wow! I thought new governors were around 2K.
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All I know is the fork was out of tolerance, the hub needed work and there is something at the base of the blades that needs to be addressed. And I got the dreaded "well, I've never seen this before." Maybe I should post the pics and some A&Ps can tell me I'm being fleeced.
 
NealRomeoGolf said:
All I know is the fork was out of tolerance, the hub needed work and there is something at the base of the blades that needs to be addressed. And I got the dreaded "well, I've never seen this before." Maybe I should post the pics and some A&Ps can tell me I'm being fleeced.
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My mistake. I was thinking you were just talking about the governor. Around 4K for a prop makes sense. I think mine were about 4400 each when I did them.
 
Radar Contact said:
My mistake. I was thinking you were just talking about the governor. Around 4K for a prop makes sense. I think mine were about 4400 each when I did them.
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Yeah, sorry, the thread title was wrong from the start because I'm an ignoramous. Governor is fine. We are in hub land.
 
NealRomeoGolf said:
$4k....ish.
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Sounds similar to numbers we heard and know you’re already into it with that shop... might have been a tad lower but all said “depends on what we find when we open it”.

So ... (shrug).

Sucks that they mislubed and probably caused more damage.

Awfully glad that thing didn’t give up on you on your trip.

Now go look at your logbook and see how many night flights you did with it slowly eating itself. Ha. That’ll give you the willies.
 
denverpilot said:
Sounds similar to numbers we heard and know you’re already into it with that shop... might have been a tad lower but all said “depends on what we find when we open it”.

So ... (shrug).

Sucks that they mislubed and probably caused more damage.

Awfully glad that thing didn’t give up on you on your trip.

Now go look at your logbook and see how many night flights you did with it slowly eating itself. Ha. That’ll give you the willies.
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Yes, the big silver lining in all this is it started talking to me at home. Would not be fun to be doing this from afar.

I've only had the plane 3 months. Still haven't done a night flight with it. But I do have 70 hours day VFR in it. :)
 
We had to rebuild the prop hub on the second year we had the plane. So it goes...
 
Sorry, this is what I feared when you started the thread. Hey, look on the bright side. At least your hub doesn’t have a 100 hour inspection ad on it like mine did. I had to chose between continued inspections every 100 hours or buy a new hub. It probably would have been cheaper to just do the inspections, but if they found something I’m buying a new hub anyway, and it’s a hassle to do the inspections so often. So, when I overhauled my prop I just bought the new hub.
 
Salty said:
Sorry, this is what I feared when you started the thread. Hey, look on the bright side. At least your hub doesn’t have a 100 hour inspection ad on it like mine did. I had to chose between continued inspections every 100 hours or buy a new hub. It probably would have been cheaper to just do the inspections, but if they found something I’m buying a new hub anyway, and it’s a hassle to do the inspections so often. So, when I overhauled my prop I just bought the new hub.
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This hub is just 7 years old. They changed hubs in 2013 and got out of the AD for it.

One thing I'm learning is that the serial number for the prop is actually the hub and not the blades. Learn something every day.
 
NealRomeoGolf said:
This hub is just 7 years old. They changed hubs in 2013 and got out of the AD for it.

One thing I'm learning is that the serial number for the prop is actually the hub and not the blades. Learn something every day.
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The blades have serial numbers too, and will probably be listed on the 8130 when you get the prop back.
 
Prop is supposed to be back from overhaul on Monday. Fuel tank (being resealed at the same time) beat it by a few days. If luck is on my side, could get her back next Friday.

20201113_160130.jpg
 
NealRomeoGolf said:
Prop is supposed to be back from overhaul on Monday. Fuel tank (being resealed at the same time) beat it by a few days. If luck is on my side, could get her back next Friday.

View attachment 91783
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If it goes well you’re having a better Fri 13th than I did!

(Nothing horrible. Just continued critical system outages for two days straight when nothing has been down for months. LOL. I swear someone is going to call in a minute and say Godzilla himself is rampaging through our server room. )
 
Unrelated to my prop, can someone confirm this is my oil quick drain valve? Looks to be coming off the sump. Not sure what else it would be. First time I've seen the whole front with no cowlings on since I bought him so making sure I know where everything is.

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NealRomeoGolf said:
since I bought him
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Wait, your Lance is a boy? Maybe I can bring over and they can make Cubs. Of course the risk is they both have the recessive t-tail gene and we end up with Tomahawks.
 
At least all this time has made it so the avionics weren't holding up anything. New toys:

PSE 8000G replaced and old KMA20 and PSE 3000.
GNC255 replaced an ancient King KX170B
Garmin 345 transponder replaced a Garmin 330ES.

Now have dual nav inputs to my G5 HSI. Sweet.

20201114_063204.jpg
 
I spy a fresh gas tank too...

Wait...they forgot a blade! :eek:
 
Jim K said:
I spy a fresh gas tank too...

Wait...they forgot a blade! :eek:
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Hahahaha.

And yes, the painted gas tank is back too. Install tomorrow, gas it up and let it sit over the weekend for leak check. Hopefully prop balance on Monday.
 
NealRomeoGolf said:
Hahahaha.

And yes, the painted gas tank is back too. Install tomorrow, gas it up and let it sit over the weekend for leak check. Hopefully prop balance on Monday.
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Byerly?
(I'm assuming that's a turbo commander)
 
Jim K said:
Byerly?
(I'm assuming that's a turbo commander)
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Yep. Been trying to keep it local. Not the cheapest but not the worst. And I can drive over whenever I want. They did my GNC355 in my Archer. Their old avionics manager would never return my emails. New guy does great for the most part.
 
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