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RPM creeps up well over 2700 during climb


Peter T

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Aircraft is a 1993 M20J with the original McCauley prop. During a static run up I can get the RPM up to about 2600. During the take off roll and early in the climb, I will see 2700 RPM. Then  a very short time later, if I let it, the RPM will move all the way to almost 3000. So right after take off I have to start rolling the prop control back to prevent that. I have had the tach checked and it is accurate. Prop has about 2800 hrs ttsn and 120 ttsoh in 2013. Any thoughts?

 

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That sounds terrible - what kind of rpm gauge? Unless it’s reading inaccurately at the high rpm it may warrant a tear down.  But I’ve had my JPI EDM 900 do something very similar, causing my heart to stop. It turned out to be a lousy contact between the sensor and the harness to the monitor.  If it’s really surging to 3000rpm, you should hear it happening too- otherwise I bet it’s the gauge.

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Thoughts requested,  PP thoughts delivered...  :)

Thought one...  don’t let that happen...

There are limitations set by the engine manufacturer for how much the overspeed is, and how long it can happen...  so this issue can lead to an engine tear down in a very short period of time... for real reasons...

 

Thought two... it could be a prop governor... not generating the oil pressure it uses to adjust the prop angle... there is no oil pressure gauge after that oil gear pump, so it isn’t easy to see or tell.

 

Thought three...  not so common... everything is working correctly, but their is an internal oil seal at the end of the shaft.... that little 50 cent piece of aluminum at the end of the crank can fall away from its position, allowing the prop’s oil to leak into the sump... no pressure to adjust the prop angle...

 

Unfortunately, there isn’t a way to fly the plane in a fixed prop kind of way... the prop will fix itself too flat, leading to too high rpm... setting the MP lower to fly at 2700 doesn’t generate enough power to fly safely... the side tour lead to OHing things that didn’t quite need it yet... (sort of, the whole thing needed a giant OH in my case)

 

This is from my M20C experience... its O360 lost the internal seal... fixing it required pulling the prop and resetting the shaft seal... PP thoughts only, not a mechanic... might have only taken an hour or two by a guy who knows what he is doing... a lot of bolts, in a circular pattern, all being tightened at the same time.... torqued properly, and safety’d...

Best regards,

-a-

 

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My governor failed this year.   I agree with @N201MKTurbo you should take the governor to a prop shop and have it tested.   Overspeed is a bad thing.   Lycoming says overspeed for more than a certain number of RPMs for more than a certain number of seconds,  you should tear down the engine.  Don't remember the exact numbers, but they are very concerned about overspeed.

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It might be a problem as simple as your RPM Gauge. The wire on my RPM gauge cables touch the engine block and  would cause resistance on the cables causing the RPM to jump from 2400 RPM to like 26 or 2700RPM. I bought a Trutach 2 RPM gauge and found out it was the gauge and not the prop or the governor. I think its most likely this. And id recommend starting with this. doesnt hurt to start with the cheapest option.

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Couple questions.

When this thing spins up to 3000 Rpm, are you just seeing it? Can you feel extra Acceleration? An Hear it?

Or can you feel Decleration Like when downshifting a 5 speed. RPM comes up, speed goes down.

 

Also, Which Governor do you have?

PCU 5000

McCauley 290D

Hartzell H-1

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8 hours ago, Peter T said:

Aircraft is a 1993 M20J with the original McCauley prop. During a static run up I can get the RPM up to about 2600. During the take off roll and early in the climb, I will see 2700 RPM. Then  a very short time later, if I let it, the RPM will move all the way to almost 3000. So right after take off I have to start rolling the prop control back to prevent that. I have had the tach checked and it is accurate. Prop has about 2800 hrs ttsn and 120 ttsoh in 2013. Any thoughts?

 

Potentially bad news for you.  If the engine did indeed make 3000 RPM you’re looking at ena engine overhaul.  Lycoming has an SB which tells you the actions required at 5% and 10% overspeed.  At 10% or greater it’s an overhaul, unless they’ve changed it.

Do you have an engine monitor with speed recording, this would confirm the overspeed value.

As Cody points out, at 3000 you should notice a big increase in performance and noise level.

Clarence

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Potentially bad news for you.  If the engine did indeed make 3000 RPM you’re looking at ena engine overhaul.  Lycoming has an SB which tells you the actions required at 5% and 10% overspeed.  At 10% or greater it’s an overhaul, unless they’ve changed it.

IF it was for more than 3 seconds, here is SB I believe you’re referring to:
https://www.lycoming.com/sites/default/files/SB369Q%20Engine%20Inspection%20after%20Overspeed.pdf
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51 minutes ago, teejayevans said:


IF it was for more than 3 seconds, here is SB I believe you’re referring to:
https://www.lycoming.com/sites/default/files/SB369Q%20Engine%20Inspection%20after%20Overspeed.pdf

It appears that the definition of momentary only applies to a max of 10%.  If 3000 rpm was reached, then that would be greater than 10% and would require a teardown according to the SB. Sucks.:angry:

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13 hours ago, Cody Stallings said:

Couple questions.

When this thing spins up to 3000 Rpm, are you just seeing it? Can you feel extra Acceleration? An Hear it?

Or can you feel Decleration Like when downshifting a 5 speed. RPM comes up, speed goes down.

 

Also, Which Governor do you have?

PCU 5000

McCauley 290D

Hartzell H-1

I don’t hear or feel it increasing but I do notice when I bring it back down..

3A583510-D212-4BA2-9C86-85E167E8DF11.thumb.jpeg.e69b36e1f78a0ea0a919e027f7a2f37a.jpeg

This is the information on the prop. Is that what you were looking for?

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When Mandatory SBs come up there's usually a chorus of folks pointing out that SBs aren't mandatory for part 91.  I'm curious whether this SB is a CYA for Lycoming or if there is evidence that overspeed usually causes actual damage. Do any of the pros on MS have experience with overspeed teardowns?

This is a serious question with no intent to be argumentative. 

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These are the sort of issues that scare the dickens out of me when I consider buying a used aircraft.  There is absolutely no way of knowing if an engine has had an overspeed, or a prop strike unless the owner puts it in the logbook.  Every owner knows that putting such an event in the logbook (even with the appropriate remedial action) devalues the airplane and makes it hard to sell.

One of my neighbors engine failed, he made a somewhat successful off-field landing (he wasn't hurt, but the airplane was totaled).  Turns out, the prop strike AD was not done properly.

While I'm not pointing fingers, it would be reasonable to assume that "a few" owners might not 'fess up.

Jet engines with FADECs, etc. tell every detail of the engine's operation.  Jet's have very good reliability and a very low failure rate.  Don't you wish our engines had such a feature?

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1 hour ago, carusoam said:

What is the date for that data?  Recent?

 

Also...

The governor is a device mounted on the engine...

So it is probably in the engine log...

Look for the name Woodward...?

Best regards,

-a-

Data as of March 2018

governor is a MCCAULEY C290D5G/T17

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15 hours ago, Cody Stallings said:

Couple questions.

When this thing spins up to 3000 Rpm, are you just seeing it? Can you feel extra Acceleration? An Hear it?

Or can you feel Decleration Like when downshifting a 5 speed. RPM comes up, speed goes down.

 

Also, Which Governor do you have?

PCU 5000

McCauley 290D

Hartzell H-1

Governor is McCauley 290D

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The guidance on this is typically Engine specific for for various reasons... counter weights are probably one of those things at risk during an overspeed...

Some Mooney engines have them, some don’t...

 

Peter do you have an engine monitor that may have recorded the RPM and how long the unusual event lasted?

If the sensor has gone out of calibration for some reason, it can be tested quite easily using a phone tach app...

additional PP thoughts only, not a mechanic...

Best regards,

-a-

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Peter, If your tach indications are correct, your prop governor needs repair.  Do not fly your airplane to a repair facility.  Remove the pump, take it to the shop, tell them what it is doing, they will put the pump on a test stand and verify the problem.  They will want money to proceed from there.  McCauley governors can generally be repaired.  Addressing the prop overspeed service bulletin is a whole different thing. 

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I hear say that you can download an app for your phone that has a remarkably accurate tachometer based on noise.  That would allow you to do a run up to something reasonable and check to see if your tachometer is working correctly.

My prop governor was the original.  When I took it to the prop shop they said "That is an antique."   Followed  a few days later with "It has so many SB's that it would cost much more than the PCU 5000 to bring it up to snuff".   So, we installed a PCU 5000.

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1 hour ago, Peter T said:

Data as of March 2018

governor is a MCCAULEY C290D5G/T17

Okay.

If this is not an Indication(I hope it is).

The Gov is not able to Counter the Overspeed.

I would have the Governor pulled off an bench check to verify its operation.

The 290D is a very good Governor.

I had the same thing in my Former F Model  an it was great.

My personal opinion.

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