Prop not going to full rpm on takeoff

[mgan]

I have an E model with the hartzell H1 gov.

Sometime (especially when it's cold out) when I go to takeoff, the prop will only go to like 2500-2540 rpm and the plane will obviously be very lethargic on acceleration.  If it happens, I'll abort takeoff and taxi back and go again and it goes to 2630-2670 and takes off and flies with no issues after that.

The first time it happened, I didn't notice till after takeoff... it was lethargic on climb out till about 30-60 seconds after takeoff then the rpm all the sudden went up to rev-d up to mid 2600s and you could feel the extra power kick in.... it flew just fine with no issues after that.

I'm assuming this has to either be a propeller or gov issue?  my first thought was that maybe it was cold oil in the hub? but on a 60f day I waited till the oil was 140f to cycle prop and cycled several times only to have it not reach full rpm on takeoff roll.

anyone have any thoughts? could it be the gov even though it works just fine during flight and doesn't have any issues holding an rpm? could there have been an issue with the last propeller reinstall after AD check?

Any thoughts are appreciated.  Can't just fly it without predicable takeoff performance.

[Mooney Dog]

My E at sea level has been showing somewhere between 2500-2560 for full power takeoffs. It never given me an actual issue and get very close to the book numbers for takeoff distances. 

When i recently went up to reno in the higher elevations, the rpm easily goes to 2600 to 2680 for full powered takeoffs.

[Guest]

2 hours ago, mgan said:

I have an E model with the hartzell H1 gov.

Sometime (especially when it's cold out) when I go to takeoff, the prop will only go to like 2500-2540 rpm and the plane will obviously be very lethargic on acceleration.  If it happens, I'll abort takeoff and taxi back and go again and it goes to 2630-2670 and takes off and flies with no issues after that.

The first time it happened, I didn't notice till after takeoff... it was lethargic on climb out till about 30-60 seconds after takeoff then the rpm all the sudden went up to rev-d up to mid 2600s and you could feel the extra power kick in.... it flew just fine with no issues after that.

I'm assuming this has to either be a propeller or gov issue?  my first thought was that maybe it was cold oil in the hub? but on a 60f day I waited till the oil was 140f to cycle prop and cycled several times only to have it not reach full rpm on takeoff roll.

anyone have any thoughts? could it be the gov even though it works just fine during flight and doesn't have any issues holding an rpm? could there have been an issue with the last propeller reinstall after AD check?

Any thoughts are appreciated.  Can't just fly it without predicable takeoff performance.

First start with a check of the tachometer for accuracy.  Then check for a loose, failing or a slipping cable at the governor, last check the governor and propeller.

Clarence

[Jim Peace]

5 hours ago, M20Doc said:

First start with a check of the tachometer for accuracy.  

Stupid question.....if you have a JPI 900 or any other late model engine analyzer can you assume the tach is fine?  can these electronic ones be off at all?

[AerostarDriver]

It sounds like you tach is correct based on the performance you described. Are you doing a prop cycle and a governor check as part of your runup?

[EricJ]

If the prop cycled on runup it isn't an issue of cold oil in the hub.   Cycling the prop cycles fresh oil into the hub.

 

[mgan]

1 hour ago, AerostarDriver said:

It sounds like you tach is correct based on the performance you described. Are you doing a prop cycle and a governor check as part of your runup?

yes it is definitely not a tachometer problem because I can feel the lack of acceleration and I could hear/feel the difference that one time I took off like that when it went from partial to full rpm.

yeah I cycle the prop several times to try to make sure it gets fresh oil.

[Guest]

3 hours ago, Jim Peace said:

Stupid question.....if you have a JPI 900 or any other late model engine analyzer can you assume the tach is fine?  can these electronic ones be off at all?

Most electric or electronic tachometers are very accurate.  In Canada they are exempt from annual accuracy check requirements.

Clarence

[PT20J]

If the tach is correct and the engine isn't turning nearly rated rpm at the beginning of the takeoff roll, there are two possibilities: The engine isn't putting out full power, or the prop blade pitch is too high. 

During normal operation, the blades would be sitting on the low pitch stops and the governor would not be controlling the rpm at the very beginning of the takeoff roll. As airspeed increases, the increased airflow will tend to speed up the prop and the governor will hold the rpm to 2700 (assuming it is set correctly). The governor does this by sending high pressure oil to the prop hub to move the piston to increase the blade pitch which increases blade drag and slows the prop rotation. So, it takes oil pressure from the governor to decrease rpm. 

The governor is pretty simple: it is basically a oil pump and a pilot valve to control oil pressure to the prop hub. The position of the pilot valve is controlled by the counteracting forces of centrifugal fly weights and a speeder spring. The tension of the spring is controlled by the cockpit prop control. 

So, I would first check all the control components and make sure that the governor control arm is fully moving all the way to the stop screw. If that's not the case, it might be a governor problem. Dan Long at West Coast Governor Service is my "go to" guy for governor issues. He's very knowledgeable and helpful. I'd discuss it with him after eliminating prop control and engine power issues. https://westcoastgovernorservice.com/

Skip

[AerostarDriver]

2 hours ago, mgan said:

yes it is definitely not a tachometer problem because I can feel the lack of acceleration and I could hear/feel the difference that one time I took off like that when it went from partial to full rpm.

yeah I cycle the prop several times to try to make sure it gets fresh oil.

Do you also do a governor check? Throttle up to 2100 RPM, bring the RPM back to 2000 then add an inch of MP then reduce 2 inches of MP and verify the RPM stays at 2000 (with a slight rise and fall with power changes). Then return prop to full fine.

If your governor check passes but at takeoff power is still restricted to 2500 RPM then I would make the argument, your hub might be the problem. If your governor check fails I would start with the governor. That being said, the governor is the cheaper item to start with. Some googling shows me your airplane had a gear up in 2016 with what looks like a new prop installed; Hartzell has a 2000 hour TBO or 5 years on most of their 6 bolt props, might be time for an overhaul if you have not already done one.

[Yourpilotincommand]

I carry a Hangar 9 Micro Digital tachometer in my flight bag. I found my E reads 100rpm lower than it actually is. It works nicely though the windscreen and is inexpensive. I also fly several Cessnas and Pipers and most of the time the dash tach is dead on.

[mgan]

It is definitely not a tachometer problem as there is a vast difference in acceleration and sound when it is at proper rpm vs when it is stuck at a lower rpm.

[takair]

It would be good to know if the governor was trying to govern to the lower RPM….but takeoff roll is not a good time to check….perhaps early in the roll or with two people….but it still may not be the best idea….   When operations are normal, what kind of static RPM do you get?  

Do you have an engine analyzer?  Is it possible you have a leaky/stuck valve?  You would usually get a rough idle..how is the idle?

[mgan]

On 11/16/2021 at 9:23 PM, takair said:

It would be good to know if the governor was trying to govern to the lower RPM….but takeoff roll is not a good time to check….perhaps early in the roll or with two people….but it still may not be the best idea….   When operations are normal, what kind of static RPM do you get?  

Do you have an engine analyzer?  Is it possible you have a leaky/stuck valve?  You would usually get a rough idle..how is the idle?

Idle is fine. The everything runs just fine in every other phase of flight.

I have a cgr30p engine monitor.

This weekend I'll try to see what the static rpm is... I'm assuming you are thinking of adjusting the prop control while it's at full throttle and when it is not going to full RPM to see if it changes?

[takair]

Just now, mgan said:

Idle is fine. The everything runs just fine in every other phase of flight.

I have a cgr30p engine monitor.

This weekend I'll try to see what the static rpm is... I'm assuming you are thinking of adjusting the prop control while it's at full throttle and when it is not going to full RPM to see if it changes?

Yes.  If the governor is active, it may be more sensitive to adjustment…

Also, check EGTs at time of the problem to see if there is any indication of a cylinder or valve or fuel injector issue…….cheap troubleshooting.

[mgan]

13 minutes ago, takair said:

Yes.  If the governor is active, it may be more sensitive to adjustment…

Also, check EGTs at time of the problem to see if there is any indication of a cylinder or valve or fuel injector issue…….cheap troubleshooting.

Thanks for the suggestions.  I will attempt this weekend.

Of course now that I'm wanting it to act up, it will probably be a month before it acts up again...

[A64Pilot]

On 11/15/2021 at 7:40 PM, EricJ said:

If the prop cycled on runup it isn't an issue of cold oil in the hub.   Cycling the prop cycles fresh oil into the hub.

 

Sort of, the prop is a dead end, there is no actual flow, it’s like taking a syringe and pulling liquid into and out of the syringe, a lot of the fresh fluid is the fluid you expelled, your not fully emptying the the prop

When you remove a prop it’s not uncommon to find a lot of sludge there, because you can’t really flush all of the oil out.

That is why I cycle a prop three times even though it’s not really needed, I’m trying to flush out as much old oil as I can.

If he can’t find anything loose or otherwise wrong, I wonder if it could be sludge?

Edited November 19, 2021 by A64Pilot

[Jim Peace]

My 1964C with O-360 in the last month or two has not been giving me the 2650 RPM I have been set up for the last several years.  I have also been seeing a high EGT on #3 with my JPI and all the downloaded data confirmed #3 may be going south.  I had it borescope at my airport and compression checked.  It did not look good inside.  The rest of engine checked out fine.  

I just brought my plane to JB engines in Sebring and they confirmed that #3 is bad. I will enclose pictures.  The cam shaft looked great and the rest of the cylinder compressions checked out fine.

I wonder if this could be the reason I could not get my desired 2650 RPM for takeoff.  I pick up my plane next week. Someone remind me to check in here with an update.

Enclosed is a picture of my JPI during climb and pictures of what they found.

The cylinder had 1000 hours on it as do the rest. 16 years old.

 

[mgan]

11 minutes ago, Jim Peace said:

My 1964C with O-360 in the last month or two has not been giving me the 2650 RPM I have been set up for the last several years.  I have also been seeing a high EGT on #3 with my JPI and all the downloaded data confirmed #3 may be going south.  I had it borescope at my airport and compression checked.  It did not look good inside.  The rest of engine checked out fine.

That was a good find.  Do check back with your results.  I'm really interested in the fact that both your CHT and EGT was high.  it's almost like that cylinder was getting a really lean mixture.  Seems like most valve issues would cause either EGT or CHT to be high and the other to be low.... so yours must have been a friction issue?

I am going to be digging into my engine monitor data.  The interesting thing to me is that it only happens very occasionally and only on takeoff roll.  I've never had an issue going full rpm and climbing full power at any other phase of flight.  Engine pulls strong and climbs/cruises well.

[mgan]

On 11/19/2021 at 7:35 AM, Jim Peace said:

My 1964C with O-360 in the last month or two has not been giving me the 2650 RPM I have been set up for the last several years.  I have also been seeing a high EGT on #3 with my JPI and all the downloaded data confirmed #3 may be going south.  I had it borescope at my airport and compression checked.  It did not look good inside.  The rest of engine checked out fine.  

Hey you might be on to something.

After digging through engine monitor data, I see a drop in egt#2 when going full throttle on those occasions where the rpm does not come up all the way.... then when the RPM goes back up to 2650, that egt comes back up

right now I'm thinking maybe a little morning sickness valve stick? gonna go discuss with IA to see his thoughts and talk options.

[AerostarDriver]

Do you have MP at the time of the EGT drop off?

[mgan]

On 11/22/2021 at 7:37 PM, AerostarDriver said:

Do you have MP at the time of the EGT drop off?

29"

We pulled the cylinder and it is being overhauled by a local engine shop as we speak.