High RPM (2,900-3,000) After Take Off

[Mooneymite]

Engine overspeeds, like "minor prop strikes" are something that require attention when they occur, but the damage may not make itself known until hundreds of hours later.  We count on owners to do the right thing as far as log entries, but everyone makes their own evaluation.  Was the overspeed 9%, or 11%?  Who knows?

This is another reason why buying a plane with a runout engine and starting out with a new, or factory reman makes sense.  One just doesn't know what the real history of any particular engine is unless he starts out with a blank new log book.

[canuckpilot]

I had a very similar incident.  Mine surged to 2800 moments after takeoff, I immediately pulled back prop, and it responded right away.  I had it checked it out after landing, they checked the governor/governor limit stops and the tach. Both checked out fine.  Just like you, this happened soon after an oil change...  my POH states: "If surging of the propeller occurs during takeoff or climb out, it may be caused by air in the system or foreign matter in the governor passages."  (1965 M20E POH, page 28)  The shop suggested I simply keep an eagle eye on it - that was many hours and 4 months ago, and no problems since.  I suspect it was just air in the system.

[Bob_Belville]

Hum, youse guys are exercising the prop pre take off, right?

[canuckpilot]

6 minutes ago, Bob_Belville said:

Hum, youse guys are exercising the prop pre take off, right?

Yes, without exception.

[carusoam]

Keep in mind... some additional detail...

The gov has its own oil gear pump.  It will be somewhat independent of the engine's oil pressure...

With the prop control pushed in, the control valve opens dumping the prop's oil pressure back to the sump...

With no oil pressure the prop blades flatten out, lightening the load on the prop, thus allowing the increase in rpm...

a gear pump is a great device to deliver oil even when it has air entrained in it. Gear pumps can wear or fail...

The valve that controls the oil pressure can create a similar problem if it gets stuck.  It is operated by a pair of fly-weights that are sensitive to engine rpm.  Flyweights wear and can get stuck...

There is a maintenance manual for the gov.  That is worth reading...

 

Sounds less likely to be...

• an internal or external oil leak.
• oil pressure generation issue.

Sounds more likely to be...

• Gov valve operation...

Invite our prop guy to the conversation to see if he has some prop related input.

@Cody Stallings

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Skates97]

21 minutes ago, Bob_Belville said:

Hum, youse guys are exercising the prop pre take off, right?

Yes, every run-up. I don't cycle it 3 times like some but will cycle once or twice.

RPM to 2,000, slowly pull prop control until oil pressure drops at which point the RPM's begin to drop. Immediately push the prop control back in which results in a drop of about 100-200 RPM before it comes back up to 2,000. POH says looking for a drop of 100.

46 minutes ago, canuckpilot said:

I had a very similar incident.  Mine surged to 2800 moments after takeoff, I immediately pulled back prop, and it responded right away.  I had it checked it out after landing, they checked the governor/governor limit stops and the tach. Both checked out fine.  Just like you, this happened soon after an oil change...  my POH states: "If surging of the propeller occurs during takeoff or climb out, it may be caused by air in the system or foreign matter in the governor passages."  (1965 M20E POH, page 28)  The shop suggested I simply keep an eagle eye on it - that was many hours and 4 months ago, and no problems since.  I suspect it was just air in the system.

Interesting, that it is also in the 1965 C POH but the most recent one for 1977 they don't have any mention of it. I am still going to have the shop check things out and I'm interested to know how accurate the tach really is when they check it with the strobe.

[N601RX]

6 hours ago, M20Doc said:

Tweaking the propeller fine pitch blade stop to get rated static RPM is allowed in the Hartzell manual and is not unusual.

Clarence

 

The hartzell manual also has this warning statements in the same section. In this case the type cert says +-0.

 

LOW PITCH BLADE ANGLE ADJUSTMENTS MUST BE MADE IN ACCORDANCE WITH THE APPLICABLE TYPE CERTIFICATE OR SUPPLEMENTAL TYPE CERTIFICATE HOLDER'S MAINTENANCE DATA. 

[Hank]

2 hours ago, Skates97 said:

Yes, every run-up. I don't cycle it 3 times like some but will cycle once or twice.

RPM to 2,000, slowly pull prop control until oil pressure drops at which point the RPM's begin to drop. Immediately push the prop control back in which results in a drop of about 100-200 RPM before it comes back up to 2,000. POH says looking for a drop of 100.

Huh . . . My 1970 Owners Manual says to do the runup at 1700. I pull the lever all the way to Low and wait for RPM to change, and push it back in. Typical change is ~200 RPM. In winter, after sitting for a few days, it can take a few seconds for RPM to move; in summer weather, or on hot starts, it's immediate.

[Yetti]

So if you look up the overspeed rpm for the Io-360 you will find that the max rpm speced by Lycoming is something over 2700  Also if you look up the the 72 inch prop tip speed for super sonic it is also over 2700.    I think that Mooney did not want to redo the Type Data sheet so they left the 2700 max RPM alone. 

[Skates97]

18 minutes ago, Hank said:

Huh . . . My 1970 Owners Manual says to do the runup at 1700. I pull the lever all the way to Low and wait for RPM to change, and push it back in. Typical change is ~200 RPM. In winter, after sitting for a few days, it can take a few seconds for RPM to move; in summer weather, or on hot starts, it's immediate.

Hmm... I apparently am doing it wrong, based off my transition training. I just re-read that section of the POH and it states "Exercise the propeller at 1800-2000 RPM by pulling the propeller control to the "full-out" position. After the tachometer has shown a drop-off of 100 RPM, push the propeller control to the "full-in" position."

Perhaps this is a contributing factor. Still going to see what the mechanic comes up with.

[Cody Stallings]

3000RPM in the climb! Not sure you have enough power to twist that Propeller that fast.

Which Propeller do you have?

If your tach cable isn’t trying to give you a stroke, might wanna think about an Overspeed inspection.

Check the cheaper stuff first though

[takair]

On 11/9/2017 at 9:30 PM, Skates97 said:

Hmm... I apparently am doing it wrong, based off my transition training. I just re-read that section of the POH and it states "Exercise the propeller at 1800-2000 RPM by pulling the propeller control to the "full-out" position. After the tachometer has shown a drop-off of 100 RPM, push the propeller control to the "full-in" position."

Perhaps this is a contributing factor. Still going to see what the mechanic comes up with.

I suspect your technique is not causing this.  You really just want to get warm oil in the prop and you are showing that the prop cycles.  Moving the prop to fast and two far seems a little abusive and I have heard it can damage the harmonic balancer on those engines that are equipped....who knows if it’s true....you hear people abusing the prop check all the time.

I had a less significant intermitttant over speed a few years ago.  The symptoms would change with temperature, engine temperature, and age of oil.  After chasing the governor, prop, and the engine I sent the governor to a second shop who found significant grooves in the pump vanes.  Never really found the cause, but it looked like safety wire had gone through the pump at some point.  The grooves would cause the pump to leak and lose pressure.  New governor solved the issue, in my case.  So, there may be some correlation to the oil change....but likely not the direct cause.

Edited November 11, 2017 by takair
Corrected “Garmin” to harmonic.

[Skates97]

I'm not sure the oil change had anything to do with it, just that was the only thing that had been done. The departure from Corona going to Phoenix was normal, it was the departure on return that wasn't. 

I have heard the guys that cycle the prop way down as well and was told that wasn't good. I have read that it's not really necessary on our planes as well. However I was taught that I'm looking for the drop in oil pressure along with the change in rpm to tell me that the governor is working properly. 

@Cody Stallings, I don't know if you read through the whole thread so I'll repeat a few things. (Apologies for the repetition if you read the rest of it) The prop is a Hartzell, Model #HC-C2YK-1BF/F7666A-2. I don't really know if it was 3,000, details are not crystal clear and no monitor to record the data. What I can say with certainty is that after taking off I heard the engine running faster than normal, looked over, saw it above redline and immediately adjusted the prop which responded right away. It was somewhere between 2,800-3,000 but I can't say exactly where. Previous checks months ago with a cheap hand held showed rpm at 2,640-2,650 when tach read 2,700, but that could just be the cheap monitor.

When the mechanic uses the strobe to see what it really is then I'll know. He'll start with the cheap and hopefully have the answers before it moves all the way to the expensive end of the spectrum. 

[M20C_AV8R]

Thanks for sharing, good read and learning for newbs like me to plane ownership. Have you ever considered recording your takeoffs/flights from the cockpit so you can go back and replay the event? The right placement of the camera can tell you quite a bit including what your tach, oil pressure and how long it was exactly before you counteracted this probable over speed. I record all of mine and it has made me a better pilot as well I could show the video to my mechanic etc if something goes whack. Plus it’s great to watch if you do the whole flight.

[Skates97]

I haven't thought much of recording inside the cabin. The next time I fly I'll have the EDM 830 though so I will be able to analyze what is going on should anything be amiss. However the next time I fly it will also be after my mechanic has looked at it so hopefully whatever it was will be resolved and not a further issue. 

[gsxrpilot]

8 hours ago, M20C_AV8R said:

Thanks for sharing, good read and learning for newbs like me to plane ownership. Have you ever considered recording your takeoffs/flights from the cockpit so you can go back and replay the event? The right placement of the camera can tell you quite a bit including what your tach, oil pressure and how long it was exactly before you counteracted this probable over speed. I record all of mine and it has made me a better pilot as well I could show the video to my mechanic etc if something goes whack. Plus it’s great to watch if you do the whole flight.

I believe a proper data logging engine monitor will do this as well. I know that by regularly uploading my EDM-900 data to Savvy, I have a beautifully complete log of all my flights.

[Skates97]

They put a strobe on it this morning and when the tach is showing 2,700 it is actually only turning at 2,610-2,615 so the tach reads almost 100 rpm high. They checked the governor and couldn't find anything that seemed wrong and will do some more checking and run-ups after they get the EDM830 in and they can get better data.

[The Other Red Baron]

@Skates97 Did you ever find the root cause of this?  We recently had our oil change and we're having the exact same issue.  I caught it hitting 2800rpm on climb out and had to pull everything back to get it under 2700.  Governor is 3 years old.  We had a couple flights since the oil change though and I didn't notice this issue it just kind of "appeared."

[Skates97]

20 minutes ago, The Other Red Baron said:

@Skates97 Did you ever find the root cause of this?  We recently had our oil change and we're having the exact same issue.  I caught it hitting 2800rpm on climb out and had to pull everything back to get it under 2700.  Governor is 3 years old.  We had a couple flights since the oil change though and I didn't notice this issue it just kind of "appeared."

We never did figure out the cause, and I didn't see it happen again. When the EDM 830 was installed it confirmed what I mentioned above, that the strobe showed that at higher RPM's the mechanical tach is not accurate. When the mechanical tach was reading 2,700 I was really only getting 2,610-2,615. I ended up replacing the governor about six months later with a PCU5000, not because of this issue but because the old one had developed an oil leak. With the new governor I see 2,700 just after rotation and the mechanical tach is showing somewhere right around 2,800, although reading the needle is more of an estimate than an exact number.

Sorry I can't provide any more info.

[Ibra]

Have you recycled cold oil completely between spinner-engine? Maybe it comes from two different oil viscosity in the mix? it seems you have a leak between the two? or a blocking piece?

If engine+CSU are running ok in cruise or climb rpm then it is surely an issue near the blades and the spinner return spring or oil rather than the governor...

Now 3000rpm is a lot and it is a big worry, AFAIK, 2900rpm for 5seconds is all you got to catch before sending to engine+prop shops

Edited July 20, 2020 by Ibra

[The Other Red Baron]

3 hours ago, Ibra said:

Have you recycled cold oil completely between spinner-engine? Maybe it comes from two different oil viscosity in the mix? it seems you have a leak between the two? or a blocking piece?

If engine+CSU are running ok in cruise or climb rpm then it is surely an issue near the blades and the spinner return spring or oil rather than the governor...

Now 3000rpm is a lot and it is a big worry, AFAIK, 2900rpm for 5seconds is all you got to catch before sending to engine+prop shops

 

I cycle it twice on runup like I do every runup.  It has been blazing hot here so I would think it would have been OK oil temp wise.  Leak is possible, they did have to remove the prop to put the alternator on but I haven't noticed any dripping anywhere.  Engine seemed to run ok, numbers on the EDM were in the green (aside from the initial rpm)

[carusoam]

There is a thread around here about chasing an internal leak and how to search for it...

With an IO360 or O360 there is a shaft seal that keeps the gov’s oil pressure going to the prop...
 

If this seal gets out of place... it is as if the The gov is calling for more rpm and the blades flatten out... until they hit the mechanical stops...

Putting the seal back in place requires prop removal...  odd that the prop just came off and this challenge just appeared...
 

PP thoughts only, not a mechanic...

Best regards,

-a-

[time_adc]

Reviving this topic. 

 

Several members have said that failure of a start seal can result in high uncommanded prop RPM. To clarify, this dating seal in the front seal for the crank shaft? Therefore, the oil would leak out the front seal resulting in reduced prop control pressure?

 

Thanks!