M20K left roll tendency

[carusoam]

Reports of funny things around here like bucking bars (tools) left from the days of manufacturing...

Animal homes...

Left over installed equipment that didn’t get uninstalled..

-a-

[bmcconnaha]

Did you ever get your roll figured out? I’m fighting a similar, but slightly different issue.  Mine flys straight but the ailerons are in different spots, and the yoke is turned to the right slightly.  

[Airways]

On 9/2/2021 at 3:07 AM, bmcconnaha said:

Did you ever get your roll figured out? I’m fighting a similar, but slightly different issue.  Mine flys straight but the ailerons are in different spots, and the yoke is turned to the right slightly.  

My annual is scheduled for next week. This is the time we’ll have a look at it.  I think we are onto something with the elevator. There is definitely some asymmetry. Not much, but it’s there. 
 

I can’t see anything unusual about the ailerons or how they interact.   I’ll keep you posted. 

[Airways]

Problem still there. A&P found the asymmetry too small to think much about it.  He made an adjustment to the left aileron. I took the Mooney up for a test and the left roll was still there. Nothing has changed.  I guess with the left weight protruding more than the right one you’d expect a right roll iso a left roll ?

The elevator being an inverted wing makes it complicated 

 

 

[Guest]

You need the travel boards a manual and a few basic tools to adjust the flight controls. Almost all Mooney’s work exactly the same.  Clamp the control wheels level across the tops or the bottoms, set the center bellcrank under the floor with the correct offset by measurement of by rig pin on newer models, set the left and right aileron bellcranks to the correct position as measured from the wing spar or by rig pins on newer models, adjust the length of the left and right aileron push rods to set the ailerons at zero degrees as measured with a travel board.  Adjust the left and right wing flap outer stop bolts to set the flaps at zero degrees as measured with the travel board.  
 

Test fly the plane, if it rolls the trailing edge of the aileron is gently bent down only to correct the roll.  I’d never use the 3” Visegrip as suggested in the manual, I use two lengths of pine board and a handful of C clamps to hold the boards on the aileron trailing edge, then the entire trailing edge is bent a very very small amount.

Clarence

 

[PT20J]

Shoptalk - rigging.pdf

[Airways]

@PT20J this document is very interesting and I'd like to use it in my communication with my maintenance shop.  But could you clarify the source of this document and maybe a reference to this "aeronautical engineering standard" and/or "structural standard that meets the FAA type certificate" ?  I'm not an engineer myself and I need to do a lot of reading on this subject before I can make a sensible argument.

[FlyingDude]

On 9/1/2021 at 9:07 PM, bmcconnaha said:

Did you ever get your roll figured out? I’m fighting a similar, but slightly different issue.  Mine flys straight but the ailerons are in different spots, and the yoke is turned to the right slightly.  

I fixed that exact same issue by fixing the flap rigging. Right flap was sliiiiightly lower than the left (2.5mm) which generated more lift on the right wing, thus needing to turn the yoke right. The annoying thing is that the guys before me "fixed" this by rigging the ailerons to follow suit, so she'd fly straight and level hands-off with the yoke at 10 and 4 o'clock... Check the flap stop bolts first. Are they equal length? And more importantly are your flaps stopping when they butt against these bolts?  They should not stop with the piston and arm assembly. This definitely tells you if you need rigging done.

[PT20J]

2 hours ago, Airways said:

@PT20J this document is very interesting and I'd like to use it in my communication with my maintenance shop.  But could you clarify the source of this document and maybe a reference to this "aeronautical engineering standard" and/or "structural standard that meets the FAA type certificate" ?  I'm not an engineer myself and I need to do a lot of reading on this subject before I can make a sensible argument.

Article was written by Kerry McIntyre at https://www.knr-inc.com

Give him a call, with any questions. He’s very helpful. 

Mooneys come correctly rigged from the factory. Unless damaged, they should stay that way. I’d only have the rigging done at a shop very familiar with Mooney rigging and that has the Mooney travel boards.

Skip

[N201MKTurbo]

There is no adjusting the ailerons that will affect a turning tendency. It will only affect the height of the ailerons and the yoke position. 
 

Adjusting the trailing edge of the aileron will have have the same effect as turning the yoke a bit. Adjusting the flap stop will change the lift of that wing. 
 

I used to bend aileron trailing edges, but for the last few years I’ve started by adjusting the flap stops. It is less traumatic to the plane.

[PT20J]

The correct procedure according to the Mooney Service and Maintenance Manual is to set flaps, ailerons, rudder and elevators properly with travel boards and only then make slight adjustments to the aileron trailing edges to compensate for manufacturing tolerances. It doesn’t take much and it will relieve any aileron control pressure needed to fly level. I did that to mine after wingtip damage done and repaired by the previous owner apparently caused a very slight right turning tendency. But I made sure it was rigged right first. Bending metal is not a cure for incorrect rigging.

Skip

[bmcconnaha]

4 hours ago, PT20J said:

Article was written by Kerry McIntyre at https://www.knr-inc.com

Give him a call, with any questions. He’s very helpful. 

Mooneys come correctly rigged from the factory. Unless damaged, they should stay that way. I’d only have the rigging done at a shop very familiar with Mooney rigging and that has the Mooney travel boards.

Skip

I am headed to his shop this week....

[FlyingDude]

6 hours ago, N201MKTurbo said:

There is no adjusting the ailerons that will affect a turning tendency.

If your plane is rolling to the right and then you raise the right aileron tabs, your right ailerons will go lower. That'll cause a left turn which can compensate for the original right roll. 

Trimming ailerons to compensate for yaw could be done. The yaw would still be there. But it'd be compensated by roll in the opposite direction. You'd be flying in x-controls all the time. 

The other guys already listed the correct sequence as outlined by the manual...

Thanks

[N201MKTurbo]

4 minutes ago, FlyingDude said:

If your plane is rolling to the right and then you raise the right aileron tabs, your right ailerons will go lower. That'll cause a left turn which can compensate for the original right roll. 

Trimming ailerons to compensate for yaw could be done. The yaw would still be there. But it'd be compensated by roll in the opposite direction. You'd be flying in x-controls all the time. 

The other guys already listed the correct sequence as outlined by the manual...

Thanks

You are missing the point.

Re-rigging the ailerons will ever change a heavy wing or turning tendency. You can only affect the average height of the ailerons and the yoke position. It will have no effect on a heavy wing. You can’t rig one up without affecting the other one.

[FlyingDude]

3 hours ago, N201MKTurbo said:

You are missing the point.

Re-rigging the ailerons will ever change a heavy wing or turning tendency. You can only affect the average height of the ailerons and the yoke position. It will have no effect on a heavy wing. You can’t rig one up without affecting the other one.

Sorry, at first I thought it made sense by then  thought this over and I'm not convinced by your explanation. The traditional elevator trim like in a Cessna 172 works by using a small surface to keep the elevator up/down which changes they plane's pitch. Then why doesn't the plane start rolling if aileron trailing edges are bent and one aileron is made to move up and the other down? 

Yes, I agree that the weight discrepancy of 2 wings will not be affected, but by moving the ailerons using these aerodynamic forces in the trailing edges, a discrepancy in lift will be generated (ie roll) that'll counteract the drop of the heavy wing.

Also, the manual mentions bending the trailing edges as a fix for "heavy wing" situation.

[N201MKTurbo]

1 hour ago, FlyingDude said:

Sorry, at first I thought it made sense by then  thought this over and I'm not convinced by your explanation. The traditional elevator trim like in a Cessna 172 works by using a small surface to keep the elevator up/down which changes they plane's pitch. Then why doesn't the plane start rolling if aileron trailing edges are bent and one aileron is made to move up and the other down? 

Yes, I agree that the weight discrepancy of 2 wings will not be affected, but by moving the ailerons using these aerodynamic forces in the trailing edges, a discrepancy in lift will be generated (ie roll) that'll counteract the drop of the heavy wing.

Also, the manual mentions bending the trailing edges as a fix for "heavy wing" situation.

Now you thinking is correct. Bending the trailing edge does act like aileron trim, bending the trailing edge down (the approved direction) will cause that aileron to raise, reducing the lift on that wing, making it heavier. So, if your plane wants to turn left, you would fix it by bending the right trailing edge down. 
 

I would just still put a 1/2 turn counter clockwise on the left flap stop, and 1/2 turn clockwise on the right flap stop, before you bent your airplane.

[PT20J]

I think it is worth understanding why you cannot fix a rolling tendency by adjusting the aileron rigging because I suspect that this is how a lot of airplanes get messed up. In the case of a left wing "heavy" condition the thought might be to droop the left aileron slightly by adjusting it's linkage in order to raise the left wing. But in flight, the aileron will attempt to trail and when it raises the right aileron goes down. The two ailerons will balance aerodynamically and you will be in the same boat as before but the wheel will be off center when the wings are held level.

The two wings are never exactly the same and so some means of trimming out roll due to manufacturing or repair differences must be provided. Some airplanes, such as many high wing Cessnas, have the ability to adjust the incidence of each wing independently. The Mooney wings are not adjustable, being built as a single unit. That's why Mooney uses the trailing edge of the ailerons as a fixed trim tab.

Skip

[FlyingDude]

8 hours ago, N201MKTurbo said:

Now you thinking is correct. Bending the trailing edge does act like aileron trim,

That's what I've been saying since the beginning! Maybe you just got my point...

Anyway, nice discussion. Thanks guys

[FlyingDude]

8 hours ago, PT20J said:

the thought might be to droop the left aileron slightly by adjusting it's linkage in order to raise the left wing.

That's not in the maintenance manual. It would be wrong practice...

[Hank]

5 minutes ago, FlyingDude said:

That's not in the maintenance manual. It would be wrong practice...

And it won't work, as the Dude explained immediately after this cutout quote.

[Airways]

Allright. 

On 9/27/2021 at 12:58 PM, FlyingDude said:

the thought might be to droop the left aileron slightly by adjusting it's linkage in order to raise the left wing.

Shop did this but it didn’t work 100%.  I have the plane re-rigged by a MSC now.  Left bank is still there in full force. So next step would be flap stop or aileron trailing edge bending, right ?

[Ricky_231]

On 4/14/2021 at 5:54 PM, Airways said:

This is a continuation of a similar topic in the Bravo-section, but that one seems dead. 
 

My M20K has a tendency to start and continue a left roll when I let go of the yoke. The yoke stays centered and I have the impression that the ailerons are pretty flush with the wings. 
 

The left turn can be prevented with a little right rudder, so I’m looking at the rudder-aileron interconnect.  Of course a little right rudder makes for a little skid. 
 

Is this fixable ?

 

 

 

 

 

Mine likes to roll to the right. Very slight roll but will deepen if unchecked. I imagine even a small fuel quantity imbalance could cause that, so I don't worry too much about it.

[N201MKTurbo]

On 10/27/2021 at 10:12 AM, Airways said:

Allright. 

Shop did this but it didn’t work 100%.  I have the plane re-rigged by a MSC now.  Left bank is still there in full force. So next step would be flap stop or aileron trailing edge bending, right ?

You should have them un-adjust the aileron first.

[Airways]

30 minutes ago, N201MKTurbo said:

You should have them un-adjust the aileron first.

Yes, that has been done.  Next up: test flight to have a closer look at flap and aileron behaviour.

[Airways]

On 9/26/2021 at 6:51 PM, PT20J said:

The correct procedure according to the Mooney Service and Maintenance Manual is to set flaps, ailerons, rudder and elevators properly with travel boards and only then make slight adjustments to the aileron trailing edges to compensate for manufacturing tolerances. It doesn’t take much and it will relieve any aileron control pressure needed to fly level.

We narrowed it down to adjusting the righthand aileron trim tab.  My question now is: does the aileron trim tab require equal bending over the whole span or do you just bend the outboard part ?  The reason I ask is because it seems hard to bend the whole aileron trim tab at once over the whole span.