M20F 1967 trim problems

[Clipper]

Hi Guys

I’m  Having a problem in level flight where the plane keeps wanting to climb.

i notice in flight my trim tab doesn’t go all the way down to get the plane in level flight.

But when I’m taxiing the trim tab goes all the way down like it’s supposed to do.

I had an ÂME checked the tail setting and  it’s all good.

Has anyone ever I countered this problem?

if you did how did you fix it.

Cheers

Clipper

 

[Yetti]

might want to clean and lube the Trim drive line.   lots of u joints and chain.  Also the jack screw in the tail.   lots of threads on it.

[carusoam]

59 minutes ago, Clipper said:

Hi Guys

I’m  Having a problem in level flight where the plane keeps wanting to climb.

i notice in flight my trim tab doesn’t go all the way down to get the plane in level flight.

But when I’m taxiing the trim tab goes all the way down like it’s supposed to do.

I had an ÂME checked the tail setting and  it’s all good.

Has anyone ever I countered this problem?

if you did how did you fix it.

Cheers

Clipper

 

I don’t know what trim tab your Mooney has....

Most Mooneys have that whole hinged tail thing... 

 

Some Mooneys have added a trim tab, from the Mooney Miser... to automate the trim.... for altitude holding...

 

Either way... You seem to know what isn’t working....  time to clean and lubricate and check for things that aren’t working properly...

What trim tab do you have?

Best regards,

-a-

[Clipper]

I have a manual trim wheel between the seats.

thank you for the info I ll clean and lub all the joints

cheers

[Shiny moose]

Dont forget to clean and lube the chain behind the trim wheel, it can get very stiff 

[PT20J]

Lubricating is good - it’s part of the annual inspection checklist.

the trim wheel should rotate easily to both stops on the ground and in the air.

In flight, the horizontal stabilizer has maybe a couple of hundred pounds of down force. You might load the tail with shot bags and see if you can replicate the problem on the ground if simple lubrication doesn’t fix it.

Skip

[DCarlton]

I've had a 67 F for 15 years.  No trim issues although the plane does like to climb.  Next time I'm in a cruise, I'll look and see where it's trimmed.  Never ran out of trim margin.  I'm curious; if you lift up and down on your tail gently from the bottom below the rudder (under the tail cone), how much does it move?  There's a recommended limit on the amount of play.  

[tony]

I have never heard of a Mooney with a trim tab, the way you trim a money is the whole empennage moves.  Are you sure you have a trim tab?

[1964-M20E]

on the actuator that the chain drives from the trim wheel there is an adjustment stop item 15.  There is a set screw that keep this stop in place.  If the set screw loosens the stop can rotate on the threaded shaft and limit your trim travel.

 

 

 

 

[N201MKTurbo]

Just to get this straight. You can run the trim down until the trim indicator on the pedestal indicates full nose down, but in flight you cannot run it down that far? Is that the problem?

Or, is the problem that you can trim it for level flight and a few minutes later you have to retrim it for level flight because the trim wheel has rotated by itself?

[Guest]

On 5/18/2021 at 10:15 PM, Clipper said:

Hi Guys

I’m  Having a problem in level flight where the plane keeps wanting to climb.

i notice in flight my trim tab doesn’t go all the way down to get the plane in level flight.

But when I’m taxiing the trim tab goes all the way down like it’s supposed to do.

I had an ÂME checked the tail setting and  it’s all good.

Has anyone ever I countered this problem?

if you did how did you fix it.

Cheers

Clipper

 

Did your AME have the correct Mooney travel boards and tools?

Clarence

[Shadrach]

Something is not operating as it should. Trim travel should be the same on the ground as it is in the air. The yokes will move as you run the trim up and down. The yokes should be very close to the panel when trimmed for full nose down (handy when doing maintenance in the cockpit or under panel).  Long, mid and short bodies have different specs for the elevator rigging. Possible it could be rigged to the wrong spec, but that does not explain why it acts differently on the ground.  
 

My WAG is that the Jackscrew in the tail is dry and binding under air loads.  I have felt it in a number of Mooney’s and it would feel locked against the stop to someone who does not know better. Is the trim wheel stiff at cruise speed? 

[Flyman2456]

Could it be that it's just harder to turn the trim wheel in flight?

There is a service bulletin M20-154 that changes the gear ratios in the chain and sprockets to make it easier to turn at higher speeds. Applies to M20F serial numbers 660001-670362.

Would try lubricating first and if that doesnt get it as easy as you'd like, look into the SB

Edited July 12, 2021 by Flyman2456

[Clipper]

Hi guys

I took off all the panels and greased all the joints and warm screw also had the tail adjusted Now i m trimming alot better 

thank you for your input it was very helpful

[carusoam]

Great follow-up Clipper!

Thanks for sharing the results.

If further cleaning and lubing are required… be on the lookout for grease that has turned to stones…

Best regards,

-a-

[Clipper]

Thanks for the info i will keep an eye on the grease hardening