No change in RPM or OilP when cycling prop

[JamesMooney]

My M20F just came back from having the prop governor o/h'd, the prop IRAN'd, and the engine case, cam & lifters were replaced (i.e. the engine was IRAN'd and reinstalled). It had a test flight and no issues were reported by the A&P that flew it.

On my first flight with it, when I did the prop check during run-up (2000 RPM, outside temps were warm, oil pressure & oil temps both green), there was almost no (or none at all) change in RPM or oil pressure. Any ideas?

Also... maybe this is related, maybe not... when applying take-off power, the RPMs surge from 2600 RPM to 2800 RPM - back and forth - until airspeed picks up to around 60 knots, then RPM stabilizes and behaves completely normal. (FYI, my tach is off - previously it was diagnosed as over-reporting by ~75 RPM... so.... 2800 RPM is actually more like 2725 RPM.)

Finally, after one flight, I noticed that the freshly painted prop already showed a fair amount of wear at the tips - no nicks or damage to the blades, but the paint was already appreciably peeling off.

Currently using mineral oil and have a SureFly mag also newly installed. Not sure if either of these variables make a difference here.

Thoughts? Am I just being overly nervous about post-major-work behavior, or is there something here for concern?

[Hank]

@Cody Stallings is our prop guy. Maybe he has ideas?

[Yetti]

First maybe check that your Tach is accurate...   It is possible to get the tips to supersonic.  Which is bad.  

[JamesMooney]

Just now, Yetti said:

First maybe check that your Tach is accurate...   It is possible to get the tips to supersonic.  Which is bad.  

Think that explains the unusual wear on the paint right away?

[EricJ]

Did it govern in flight at all?

For me if it didn't respond during run-up I wouldn't have flown it.   If it doesn't cycle something has failed.    A possible failure is the hard line carrying oil pressure from the governor to the prop may have broken or become disconnected and might be pumping your oil overboard, so a non-cycling prop is good reason to abort the flight.

 

[JamesMooney]

Just now, EricJ said:

Did it govern in flight at all?

For me if it didn't respond during run-up I wouldn't have flown it.   If it doesn't cycle something has failed.    A possible failure is the hard line carrying oil pressure from the governor to the prop may have broken or become disconnected and might be pumping your oil overboard, so a non-cycling prop is good reason to abort the flight.

 

Ya... Lesson learned, big time. I mistakenly attributed the lack of significant change during run-up to being a 'normal' condition of a nicely o/h'd governor. Anyway, that's in the past. Now to diagnose what 'it' is...

It governed fine in flight - no concerns that I could identify. Oil pressure was fine. No oil leaks anywhere when inspecting after landing.

[Yetti]

It won't govern well when the oil is cold.  Your warm is still Texas cold. That does not look like standard color paint.   It looks like you were hitting bugs with it.   Not sure color the primer is supposed to be.   chat with whoever painted it.

[JamesMooney]

Just now, Yetti said:

It won't govern well when the oil is cold.  Your warm is still Texas cold. That does not look like standard color paint.   It looks like you were hitting bugs with it.   Not sure color the primer is supposed to be.   chat with whoever painted it.

Funny enough, I was in Texas It was about 70 degrees F outside.

Yes, LOTS of bugs. After that flight, the plane looked like I flew through a million cicadas (maybe I did this time of the year!). Didn't realize that could strip paint off the prop....

[1964-M20E]

What type of governor?

Double check everything on the outside.

1. Prop cable
2. linkage
3. travel of governor linkage 
4. Maybe a bad OH on the governor?  I have had issues on OH governors before.

 

Next the scarier options i.e. something inside the engine.  

1. Was the governor gasket installed incorrectly?  hard to do but....
2. You reused the main bearings?
3. Did the front main bearing spin during installation?  This can happen and can partially block the oil passage from the governor.
4. However, the engine would probably not spin over easily in this condition.
5. Did someone leave a rag or paper towel in the engine somewhere and it is blocking the oil ports?
6. Did you change the oil an check the finger screen and filter?
7.  

[markgrue]

This sounds a lot like air in the prop governor and prop.  Did you try another run-up after flying?   Did you allow time for the prop to react when doing the run-up?   Just a  quick guess. 

 

Mark 

[AerostarDriver]

My governor typically requires about 2 cycles before it will start to govern on the first flight of the day. My first runup of the day takes 2 cycles at 2100 RPM before I start to see the effects of governor, then I cycle 3 times checking the oil pressure, MP and RPM. The rest of the flights for the day require just the 3 cycles to do the check. Then I go right in to governor function testing, I bring the prop lever back to 2000 rpm and then increase/decrease the MP by an inch to verify governor function. If at any point I don't get this normal behavior, I scrub the flight.

[Guest]

Just a crazy thought, what about a rag or shipping plug left in the crankshaft bore?

Clarence

[JamesMooney]

14 minutes ago, M20Doc said:

Just a crazy thought, what about a rag or shipping plug left in the crankshaft bore?

Clarence

Would that have an effect on the ground but otherwise operate ok in flight?

[Guest]

Just now, FlyingCanuck said:

Would that have an effect on the ground but otherwise operate ok in flight?

Possibly, combined with cold thick oil initially until it warms.

Clarence

[Marauder]

I’m hoping they used a crappy paint on the prop. I have never seen a prop do that after any of my overhauls. The only time I have seen that is when I have been flying in rain a lot.

As for cycling, I flew out of Buffalo for a number of years and even on the coldest days, the prop will always cycle. It may be a sluggish cycle but it will cycle. Something is not right. Hope it isn’t too serious.


Sent from my iPad using Tapatalk Pro

[EricJ]

5 minutes ago, FlyingCanuck said:

Would that have an effect on the ground but otherwise operate ok in flight?

Something to try on the ground is cycling it at higher rpm.   When my governor was failing it was very lazy at 2000 rpm where I normally check it, but would work much better at 2500-2600.    It was working fine in flight when it started failing runup checks at 2000 rpm.    So if it cycles at high rpm but not at normal check rpms, the prop just isn't getting enough oil pressure at low rpms for whatever reason, which might be the governor, but might be something else.

 

Edited June 8, 2021 by EricJ
Added reason for editing.

[hammdo]

I had a inner crank plug loose causing my no cycle issue...

Gov IRAN (overhaul was 580 hrs ago), PROP inspected (new 580 hrs ago), engine IRAN 580 hrs ago...

plug was not replaced during IRAN...

We replaced the plug - bingo - cycles...

AP and I devised a simple ck - with the prop off...

-Don

[A64Pilot]

I believe to get the tip of a 74” diameter prop to mach, you have to turn it at 3500 RPM on a standard day.

‘I believe this calculator is correct

https://warpdriveprops.com/propspd2.html

[Cody Stallings]

That’s a strange one, prop works properly in flight, but nothing on the grd.

I have always been told when replacing a component(prop or gov) the first start up afterwards to pull the propeller knob out about 1/4 travel an let the engine warm up normally.

That will allow the Governor time to slowly push all of the air from the system as you wait on oil temp an CHT to come up.

Then taxi to the run up area leaving propeller control in the same spot, if everything is working correctly the Governor should stop you from making 1900-2000 RPMs.

[PT20J]

The paint is not just abraded at the tips; it is peeling and flaking along all of the visible leading edge. I can't tell from the lighting: Is the color coat peeling from the primer or is bare metal showing? Propeller paint is two part polyurethane and properly cured, it is pretty tough. This looks like it flew through rain (you mentioned cicadas) before the paint was fully cured. Or, maybe there is a problem with paint adhesion due to application or mixing. I'd talk to the prop shop about it.

My M20J with a McCauley prop and governor will cycle the first time at temps down to freezing using Philips 20W50. Even when I ran Aeroshell W100 it always cycled well on the first pull. In fact, I only cycle once during run up as I don't see any advantage to the wear and tear from multiple cycles on these little props. I think the cycle three times thing probably comes from the old radial engine airplanes. On the museum DC-3 we sometimes have to cycle the prop a few times, but those Hamilton-Standard hydromatic prop hubs must hold a couple of quarts of thick W120 oil and the oil circulates differently in that design.

Skip

[carusoam]

Just some homework...

1) That paint looks like it didn’t adhere properly...  discussion for the person who painted it...

2) The oilP referenced in this discussion is good for keeping the engine running... but is not very helpful regarding the gov...

3) Prop gov has its own gear pump that provides OilP (unmeasured, no gauge)...

 

4) Have a good look at Don’s thread above...  it is a very recent... similar experience, followed by all the steps taken to find out what isn’t working right...

5) +1 Do not fly when the gov indicates it’s not working on the ground... it will not get any better in the air...

6) If it doesn’t get better in the air... you may find out how well your prop stops have been set...

7) If your prop’s stops haven’t been perfectly set... you may see incredibly high rpm to provide enough power to maintain flight...

8) I got the experience, but was able to have enough power, and control rpm, to go around the traffic pattern once...

+1 departing after a failed run-up... crummy idea... 

Best regards,

-a-

[EricJ]

34 minutes ago, PT20J said:

I think the cycle three times thing probably comes from the old radial engine airplanes. On the museum DC-3 we sometimes have to cycle the prop a few times, but those Hamilton-Standard hydromatic prop hubs must hold a couple of quarts of thick W120 oil and the oil circulates differently in that design.

Skip

That's my understanding as well, that the "three pulls" thing was to get air out of the hub on some Hamilton Standard props.

[PT20J]

Here's some troubleshooting info from the McCauley Operators Manual. 

McCauley_20210608_0001.pdf

[Hair_Helmet]

Probably not helpful, but I found it interesting.  I just put the MT on my 62 in place of the Hartzell 3 blade.  The Hartzell (100 hours on prop/gov overhaul) responded appropriately to rpm drop and was slow but steady returning to runup rpm since day 1.  The MT is instantaneous in drop and back to runup rpm.

[JamesMooney]

49 minutes ago, Hair_Helmet said:

Probably not helpful, but I found it interesting.  I just put the MT on my 62 in place of the Hartzell 3 blade.  The Hartzell (100 hours on prop/gov overhaul) responded appropriately to rpm drop and was slow but steady returning to runup rpm since day 1.  The MT is instantaneous in drop and back to runup rpm.

Interesting. I have the Hartzell 3 blade Top Prop conversion on mine