M20C seeing 2800 rpm on takeoff

[M20 Ogler]

Full power static rpm is 2700 but once I start building airspeed it increases. So I’ve been turning the prop control out a few turns before taking the runway. Does anyone else’s M20C do this?

* edit-redline is 2700

Edited June 3, 2022 by M20 Ogler

[ShuRugal]

how long was it at 2800?

https://www.lycoming.com/sites/default/files/SB369S Engine Inspection after Overspeed.pdf

In fixed wing aircraft, momentary overspeed is defined as an increase of no more than 10% of rated engine RPM for a period not exceeding 3 seconds. If the duration and amount of overspeed is calculated to fall within the limitations defined as momentary, no further maintenance actions are necessary

When the overspeed occurrence is less than 5% of the rated engine speed, the recommended corrective action for all engines is as follows: a. Identify and correct the cause of the overspeed. b. In the engine logbook, record the overspeed incident, any inspections, and corrective action

2800 is only a 4% overspeed, so if the duration was less than 3 seconds, it's acceptable.  If it was more than 3 seconds, it needs to go in your engine logbook and you need to have a mechanic investigate the cause.

Most likely the cause is that the high speed limit of your governor is incorrectly set.  this is simple to fix, the limit is just a stop screw on the travel arm of the governor.

Also, your tachometer may be reading high.  first step is have the plane checked against a calibrated tachometer.  if your tach is correct, proceed with having the governor set correctly.

[Utah20Gflyer]

My plane used to do this before I changed out the tachometer, ie it was an indication error.  I would try to verify the rpm before taking any other action.  

[carusoam]

First…. Determine if the tach is reading correctly…. There is an app for that…

Then have your mechanic check the blue knob to see if it is working correctly….

Chase everything from blue knob to prop govenor….

The engine rpm should sneak up to the red line as the plane accelerates…

Over speed for the engine is not normal….

There is a procedure for setting this value while on the ground…. Using static RPM…

PP thoughts only,

-a-

[Immelman]

+1 on the iphone app.

....agreed with my A&Ps optical tach...

...agreed with multiple (new) vehicle tachs....

 

[Guest]

On 6/3/2022 at 6:36 PM, M20 Ogler said:

Full power static rpm is 2700 but once I start building airspeed it increases. So I’ve been turning the prop control out a few turns before taking the runway. Does anyone else’s M20C do this?

* edit-redline is 2700

Verify the accuracy of the tachometer before making any adjustments.

Clarence

[AIREMATT]

22 hours ago, Immelman said:

+1 on the iphone app.

....agreed with my A&Ps optical tach...

...agreed with multiple (new) vehicle tachs....

 

Which app are you using? Thanks!

[Immelman]

On 6/7/2022 at 1:24 PM, AIREMATT said:

Which app are you using? Thanks!

"Engine RPM". Apple/ios.

[ArtVandelay]

"Engine RPM". Apple/ios.

But you have to you do the necessary calibration and setup, and make sure the RPMs match during idle and runup to get accurate results.

[MBDiagMan]

There is a way to manage this nail the Governor is sorted out.  

Start by ensuring that the Governor is governing.  Make sure it catches the over speed at some RPM and then slows it down.

Once you’re convinced that it’s governing and not freely overspending……If it’s rolling down the runway and climbing out at a high RPM, experiment and find how many turns from full in gives you 2700 on takeoff/ rollout.  Start with pushing the prop control full in, then turn it one full turn counterclockwise and see what that gives you.  Adjust from there.  If with one full turn it is 2750, then do two full turns and fine tune from there.  After that you will know how many turns behind full forward you need to set it too after run up and prop exercise.

I am not an A&P, but this has worked for me.  This should be a temporary workaround to be used until your mechanic gets the prop adjusted.  Also as others have said, check the tach.

Edited June 10, 2022 by MBDiagMan

[EricJ]

3 hours ago, MBDiagMan said:

There is a way to manage this nail the Governor is sorted out.  

Start by ensuring that the Governor is governing.  Make sure it catches the over speed at some RPM and then slows it down.

Once you’re convinced that it’s governing and not freely overspending……If it’s rolling down the runway and climbing out at a high RPM, experiment and find how many turns from full in gives you 2700 on takeoff/ rollout.  Start with pushing the prop control full in, then turn it one full turn counterclockwise and see what that gives you.  Adjust from there.  If with one full turn it is 2750, then do two full turns and fine tune from there.  After that you will know how many turns behind full forward you need to set it too after run up and prop exercise.

I am not an A&P, but this has worked for me.  This should be a temporary workaround to be used until your mechanic gets the prop adjusted.  Also as others have said, check the tach.

The manual for the governor should say how many rpms correspond to a turn of the high-speed rpm adjustment screw, but your method is a decent way to double check it during adjustment.