Question for the Veterans M20F

[ilikethewoods]

This my first aircraft purchase and it's a complex aircraft, so if the question seem a bit elementary I apologize. Just purchased my M20F. IO-360 A1A. Before take off checks: 1900-2000 RPM, I pull the propeller control full aft (decrease RPM) <<<My Mooney doesn't do anything, zero drop. Even the flight instructor was like: Usually we see a drop...?

Radial Red line (rated) 2700RPM

Green Arc 2500-2700 (operating range) 

ect. 

On take off/climb, my RPM needle swings past the Radial Red line 2700 RPM. Two flight instructors have flown with me and said the needles are supposed to go past that mark 2700RPM on take off. Now in flight,  we bring the propeller back, into the green arc. I know my propeller governor is working or I wouldn't be able to change the pitch which wouldn't allow me to bring the RPM's into the green. My concern is we're going past the red arc on the RPM's 2700on take off, I couldn't give you precise numbers yet as I'm staring down the runway. Any help would be awesome. 

[Bob_Belville]

The governor is adjustable and should be set so as to not exceed 2700, even on take off.

You might need to exercise the prop at a little higher RPM, you should see a drop. Try 2100. Do you have an EDM? Oil pressure okay? 

[carusoam]

Say again?

Something has gotten lost between you and two CFIs...

According to the two CFIs the engine is supposed to exceed redline?  (Maybe briefly, part of a second or so... but not steady...)

While doing the run-up...

• prop full in...
• MP in until rpm hits 1700 (follow what your procedure says, until you have better guidance)
• higher rpms will deliver more oil to the prop... and will work better... and you still have it not working....
• you pull the prop back and nothing happens?
• you should see an oil pressure change and an rpm change like you have been trained...

If nothing happens... oil isn’t being sent to the prop, oil pressure isn’t building in the prop...

A prop that fails this pre-flight test is talking to you...

Expect that oil is leaking out of the system (internally) and the prop is staying on its high pitch stops... if the stops have been set properly and didn’t change over time, this may protect you...

If the seal at the front of the crank shaft is leaking internally... you have a high chance of the prop over speeding... adjusting the MP to control prop rpm may leave you with not enough power to fly...

It doesn’t make sense to fly in this condition because the penalty for over speeding the prop can result in a tear down requirement... See the engine manufacturer’s details... they are well documented...

See if you can add more details... start talking with your mechanic...

PP thoughts only... My O360 lost the shaft seal, no pressure builds in the prop... taking it into the air wasn’t a good idea... testing the seal is pretty easy on some engines... Expect if the seal is leaking a little... it will probably leak more in a short period of time...

Good catch!

Best regards,

-a-

[ilikethewoods]

31 minutes ago, carusoam said:

Say again?

Something has gotten lost between you and two CFIs...

According to the two CFIs the engine is supposed to exceed redline?  (Maybe briefly, part of a second or so... but not steady...)

While doing the run-up...

• prop full in...
• MP in until rpm hits 1700 (follow what your procedure says, until you have better guidance)
• higher rpms will deliver more oil to the prop... and will work better... and you still have it not working....
• you pull the prop back and nothing happens?
• you should see an oil pressure change and an rpm change like you have been trained...

If nothing happens... oil isn’t being sent to the prop, oil pressure isn’t building in the prop...

A prop that fails this pre-flight test is talking to you...

Expect that oil is leaking out of the system (internally) and the prop is staying on its high pitch stops... if the stops have been set properly and didn’t change over time, this may protect you...

If the seal at the front of the crank shaft is leaking internally... you have a high chance of the prop over speeding... adjusting the MP to control prop rpm may leave you with not enough power to fly...

It doesn’t make sense to fly in this condition because the penalty for over speeding the prop can result in a tear down requirement... See the engine manufacturer’s details... they are well documented...

See if you can add more details... start talking with your mechanic...

PP thoughts only... My O360 lost the shaft seal, no pressure builds in the prop... taking it into the air wasn’t a good idea... testing the seal is pretty easy on some engines... Expect if the seal is leaking a little... it will probably leak more in a short period of time...

Good catch!

Best regards,

-a-

Per the POH, you test the propeller governor at 1900-2000. I’m going to double check this again today for sure. Now the Mag check is at 1700RPM. Like I said I’m going to double check, but I do know that on take off we do go past the redline. Thanks.

[Yetti]

I think you will find the Run up RPM to be 1700rpm in the manual

Sounds like the prop Governor needs a looking at.  Probably the Governor prop cable is slipping.

At higher altitudes it is easier for a prop to go over 2700rpm

[ilikethewoods]

41 minutes ago, Bob_Belville said:

The governor is adjustable and should be set so as to not exceed 2700, even on take off.

You might need to exercise the prop at a little higher RPM, you should see a drop. Try 2100. Do you have an EDM? Oil pressure okay? 

Oil pressure is great, I’m going to do a ton of run ups on the ground. It just came out of pre-buy. 

[Yetti]

You should see the oil pressure take a dip when you pull the prop control back.

[jaylw314]

My IO-360 is able to run the prop off the fine pitch stops easily at 1700 RPM.  Not being able to reduce RPM at runup speeds sounds problematic and I would not fly again until the problem was identified...

[carusoam]

Woodsy,

Got a JPI ? Or other engine monitor?

It may be possible for you to share what you are seeing... download data, post in Savvy.com copy link here...

Often some people will grab some video... upload to YouTube and copy link here...

Grab a video carefully... to share with your mechanic...

The prop isn’t doing what you are asking it to do... is reason enough to start the conversation...

As far as the choice of rpms go... 1700 to 2000... the prop will activate slower at the lower rpms... but it still changes pitch.

The Governor has its own oil pump to supply pressure to the prop... it has an oil control valve connected to some fly weights...

governors are known to wear out as well... choosing the shaft seal was the last thing on my list... I got a nicely OH’d gov in the meantime...

Best regards,

-a-

[steingar]

That tachometer might be the original one put in decades ago.  How accurate is it?  Are you certain you're not getting normal propellor speeds that are being reported inaccurately by an old instrument.

[drapo]

If my Mooney was to fail that prop check at run-up, I would taxi back and talk to my Mx.

Questions to ask  yourself so you can steer the converstion:

- Did you hear a change in Prop noise  (may need to take those Zulu or Bose off) that would  indicate the tachometer is not working properly?

- How long ago (flight time and date) were the prop and governor overhauled or replaced?

It could be a minor problem or something a little more serious you don’t want to experience at 500’ just off the runway!

 

[Shadrach]

I have a 67 F and my prop will go course pitch at 1000rpm. If you’re unable to get a drop at 1700, something is wrong. If it came out of pre buy that way, I would be call the shop ASAP.

Edited September 17, 2019 by Shadrach

[gsxrpilot]

I do my run up between 1500 and 1600 RPM. Sometimes on the first flight, cold morning, or right after an oil change, it takes a few seconds for the prop to cycle the first time. But after cycling the oil, it works instantly every time in that RPM range.

And ditto what everyone is saying about the red line. You shouldn't see the prop go over that redline.

Get your governor checked.

[Browncbr1]

Ditto gsxr and above.  

 

[ilikethewoods]

Thanks for all the replies, I'm heading out the plane tonight to get an better idea of whats going on. I've seen like 6 Youtube vids (M20J's) everyone of them, the prop drops off at 1700RPM. 

[Bob_Belville]

The original Owners Manual for my '66E (IO360A1A) calls for doing MAG check at 1700 RPM and to exercise prop at 1800-2000 RPM. While much of the wisdom from so long ago has been superseded I would not find fault with those RPM recommendations. You report that once airborne at higher power the prop control does reduce the RPM which is why I suggest you try using more power for your prop exercise for trouble shooting at least.

[Oldguy]

From an overspeed perspective, Lycoming Mandatory Service Bulletin 369R is specific and unforgiving. Getting that problem resolved should jump to #1 on your priority list. The requirements given in the SB are extensive and expensive. While there may be some who say no harm no foul on an overspeed, if you hit the threshold shown in the SB, I would say ignoring it would be the same risk as ignoring a “mild” prop strike. Don’t. 

[Guest]

4 hours ago, ilikethewoods said:

This my first aircraft purchase and it's a complex aircraft, so if the question seem a bit elementary I apologize. Just purchased my M20F. IO-360 A1A. Before take off checks: 1900-2000 RPM, I pull the propeller control full aft (decrease RPM) <<<My Mooney doesn't do anything, zero drop. Even the flight instructor was like: Usually we see a drop...?

Radial Red line (rated) 2700RPM

Green Arc 2500-2700 (operating range) 

ect. 

On take off/climb, my RPM needle swings past the Radial Red line 2700 RPM. Two flight instructors have flown with me and said the needles are supposed to go past that mark 2700RPM on take off. Now in flight,  we bring the propeller back, into the green arc. I know my propeller governor is working or I wouldn't be able to change the pitch which wouldn't allow me to bring the RPM's into the green. My concern is we're going past the red arc on the RPM's 2700on take off, I couldn't give you precise numbers yet as I'm staring down the runway. Any help would be awesome. 

Accuracy of old mechanical tachometers is questionable. See if you can borrow a portable optical tachometer to check the ships gauge.

When you cycle the propeller control the rpm should fall, manifold pressure should rise and oil pressure should drop momentarily, all should return to normal when you push the prop control full forward.

Clarence

[bgpilot1]

I had Don Maxwell in Longview, TX replace the prop governor on my 1967 M20F a few years back.  I didn't have the same symptoms.  Once the prop wouldn't decrease when at altitude for a few minutes, then it got better and operated normally for a short time before it went to Maxwell.  Give him a call.  

From my invoice: Removed prop governor for overhaul. Governor not serviceable. Replaced governor with new ATH-1
governor, Sn. 15205147. Installed using new provided stud kit and MS9144B gasket.  Parts and labor came to $2400.  

[Immelman]

Something is likely wrong, time to stay on the ground and address it.

On exceeding 2700rpm:

You absolutely should not exceed 2700rpm, but old (mechanical) tachs can be quite off, so as part of this troubleshooting procedure, while you're at it see if your mechanic has an optical tach or something similar to see how accurate the tach in the airplane is. This information could be useful after this problem is solved, as you fine tune how you operate your airplane, and avoid any placarded limitations which your plane/prop may or may not have (my E has a red band where you are not to run continuously).

Now with that said, if there were no problem with your airplane there could be a very small and momentary overspeed as the prop governor delivers oil to adjust prop pitch once you reach 2700rpm, but it should not be much. And if you bring your power in slowly, and smoothly (think a good 5-mississippi count to apply takeoff power) any momentary overspeed should be barely perceptible.

Edited September 18, 2019 by Immelman

[N201MKTurbo]

You can find the minimum speed of the prop by pulling the prop control all the way back at idle, then advancing the throttle until the RPM stops increasing.

[Ragsf15e]

While I agree with generally doing what the manual says, mine also exercises the prop easily at 1700 rpm.

Importantly, I don’t think you should just pull the prop control full aft at 1700 (or 2000) rpm just to get a 100 drop.  Pull it halfway at most.  Slowly.  I usually see plenty of drop without ripping it all the way back at 1700 rpm.

[Hank]

I check mags and prop at 1700 per the Manual for my C. The posted photo above for the F says to test both at 1900.

On the other hand, as instructed I pull the prop lever all the way back, and am usually pushing it forward about the time it gets all the way back; if I haven't flown in a while, it may sit all the way back for a couple of seconds (especially in cold weather) before anything happens, but the second pull is pretty quick. It never goes more than a couple hundred RPM, with a sound that can't be missed even with a headset--like a loud, low-pitched Bronx cheer.

If it's not doing anything, wait a few seconds and see if it moves. If it still does nothing, taxi to your mechanic.

[M00N37]

I pull the blue lever all the way back and quickly all the way forward. I tried to time it so I get exactly 100RPM.

When the engine is started up from cold, first prop cycle barely does anything. 

For take off, pushing the throttle slow enough would prevents it from going over 2700. I do this when doing static take off or the runway is way too long. 

[carusoam]

 

22 minutes ago, M00N37 said:

 

When the engine is started up from cold, first prop cycle barely does anything. 

 

While the engine sits for days... the prop’s oil system basically drains a pint of oil or so (estimate) back to the oil sump...

To pressurize the system requires pulling the blue knob... (unless you fly a Missile or Rocket)

The first time after start-up has a few things going on...

• The system is empty, and starts to fill when the knob is pulled...
• No pressure is generated until after the volume is filled...
• Once the pressure rises, the blades start to move...
• Pushing the blue knob back in, dumps the excess oil pressure, and the blades spring back to their flat pitch...
• If the oil is cold... things work slower... probably an OWT.  Our oil pumps are gear type pumps... gear pumps deliver fluids from very thick to kind of thin... without any noticeable change in efficiency...  so the same volume is being delivered hot or cold...

Another thing to keep in mind... the oilP in the engine doesn’t really effect the oil pressure occurring in the prop... there are two gear pumps one for the engine, one for the prop...  of course, if the engine isn’t supplying oilP, the prop, won’t have any to work with...

when oil flows to the prop... the OilP for the engine does sense the pressure drop caused by the extra flow... that’s why we are looking for the oilP wiggle on the gauge...

We have a gear pump in the accessory case, and one in the govenor...

 

So the first pull of the blue knob does the same thing as the following ones each time... it just takes longer for the results to show... 

PP thoughts only, not a mechanic...

Big question... the first pull of the blue knob is slow because the oil is cold...? Is this not an OWT for our engines?

if it is an OWT... call it the Carusoam OWT... i’ll Clean up the explanation to help... 

Best regards,

-a-