Right Turn Tendency

[SoMooney]

Hey everyone. So I have a '68F. Since we bought the plane we've always had the roll trim on the TC all the way left to get it to fly straight. We always figured this was a PC problem. Well recently we sent the PC system out (the cut off valve and the TC) to Brittain for service. They said the TC was fine, but the valve was busted. So now that thats fixed I can turn off the PC. When I press the button, but dont put any control force on the yoke, she turns right and gets into a 30 degree right bank. Additionally, when flying straight, the ball tends to be a bit right, probably a half to a whole balls width right. 

Any thoughts? Ailerons out of rig? Rudder misaligned?

 

Thanks in advance

Edited July 28, 2016 by SoMooney

[N201MKTurbo]

I would get the aileron rigging fixed first, then add whatever rudder trim you need to get the ball in the middle. The book says to adjust a heavy aileron by bending its trailing edge. Most people don't want to do that and adjust the flap up stops.

[Piloto]

Wrap with tape the PC switch to insure it is disconnected. Fly the plane to level flight and check for roll tendencies, yoke alignment and ailerons alignment with wing tip. Rotate the PC roll knob to insure the PC is disconnected. With minimum power dive the plane to 140kts IAS or higher and check the ball centering. It should be centered. The roll tendency with flaps up is corrected by adjusting the outboard set screw on the outboard flap hinge point. Roll tendency with flaps down is corrected at the inboard link. You will need to perform several flights to have it adjusted right.

José 

[jetdriven]

Follow the service manual but I'd start with making sure the flaps and ailerons. Are both set to zero. Level the plane and mak e sure the ball is actually centered with the airplane confirmed level on the ground.  Clamp the rudder pedals and make sure the rudder is set at 1 degree right.  Make sure all fear doors are closed tightly.  Then go fly. Hold the ball in  the center and note turning tendencies. Then hood wings level with ailerons and note ball position. Adjust flaps, and ailerons and rudder to make it fly straight. 

[BDPetersen]

This very day I addressed the exact opposite issue by adjusting the left flap up position. A likely thing to check with yours. Bringing the right flap down a tad in the up position by backing out the stop bolt on the outboard end would increase lift on the right side and, therefore, increase drag, pushing the ball back to the center. While this is a likely fix, check all other parameters as the others have said.

[jetdriven]

Do you raise the right flap or lower the left? You won't know but the rigging boards can help. A rough guess is the ailerons are at zero when the counterweight is faired.  Fair the flaps to that and it's approximately zero. 

[carusoam]

Going out on a limb...

have you checked the fuel level in each tank.

When making adjustments, do you account for the pilot's weight being off to one side?

My C was fun to fly with its balance so precise.

 

The R has too many things like a wing leveler and rudder trim to notice the precision of side to side balance.

 

With the weight imbalance and no wing leveler on, the bank probably won't stop at 30°... Right?

Iirc, the term spiral is used to describe this.  

 

Best regards,

-a-

[Marauder]

If the flap and aileron leads you to no clue, make sure you don't have a gear hanging a little low.

Sent from my iPad using Tapatalk

[SoMooney]

Thanks everyone!

[SoMooney]

So update on this. My A&P was of the opinion that the ailierons were aligned, so he adjusted the right flap down. I flew it and it helped in the sense that less roll trim left was required to keep it straight, but when i disengage the PC it still turns right, albeit less aggresively. On the ground I took a look at the ailerons and they seem to me to be out of alignment. See the pic below. When I fair the right aileron at the counterweight the left aileron looks like this, it is popped up about 1/2 inch.

 

 

 

[carusoam]

Does the other side look the same?

When your A&P gave you his opinion, did he mention....

There are tools available to determine the set-up for the ailerons. There is a maintenance procedure to follow to get it done correctly...

do a search on rigging boards.  If he has access to a set of these devices, his opinion counts more than if he doesn't.

Rigging doesn't change very much from year to year.  But, once changes have been made, getting it right again can take some extra effort...

It is possible to rent the tools and get the maintenance procedure for your plane.

PP thoughts only, I am not a mechanic.

Best regards,

-a-

[SoMooney]

He didnt use rigging boards, just visual at this point altho eventually we will.

Here is a picture of the other aileron at the very same moment, the coutnerweight is totally even with the wing.(although the flap is now eneven since he adjusted that and it will have to be put back)

 

 

 

[carusoam]

I get the feeling that some surfaces may have been removed for painting..?

part of the paint process is weight and balance of control surfaces.  Rigging properly probably follows that...

search for the rigging boards.  They are giant protractors.  They have settings that are based on experience, not logic based.  Measured in degrees.

It may make sense to check with your local MSC.  This is really Mooney specific experience to get it done with precision without paying somebody to train on your plane..?

Best regards,

-a-

[jetdriven]

Have another person at the other aileron and lift then with quite a bit of force.  That will be where they sit in flight. From what yours looks, they will be about zero in flight. 

[Brian Scranton]

If tweaking the flap helped--have him do one more 1/2 turn on the flap. Baby steps. I had the SAME issue...right turn tendency and we tweaked the flap and it really helped. 

[MyNameIsNobody]

Nevermind.  I thought this was another political thread...

 

(that was a joke)

[Guest]

2 hours ago, MyNameIsNobody said:

Nevermind.  I thought this was another political thread...

 

(that was a joke)

According to news reports people are starting to turn left now that reality is setting in.

Clarence

[ryoder]

Nothing wrong with a tendency to go right.  Now left, you've got a problem there...

[Guest]

12 hours ago, SoMooney said:

So update on this. My A&P was of the opinion that the ailierons were aligned, so he adjusted the right flap down. I flew it and it helped in the sense that less roll trim left was required to keep it straight, but when i disengage the PC it still turns right, albeit less aggresively. On the ground I took a look at the ailerons and they seem to me to be out of alignment. See the pic below. When I fair the right aileron at the counterweight the left aileron looks like this, it is popped up about 1/2 inch.

 

 

 

The ailerons may be rigged from Zero to two degrees drooped meaning the balance weight would be high in the static position.  In my experience I droop the ailerons with a slight droop so that in high speed cruise flight the trailing edge will rise up bringing the balance weight into fair with the wing tip.

Use of travel boards are the best method.

Clarence

[MyNameIsNobody]

3 hours ago, M20Doc said:

According to news reports people are starting to turn left now that reality is setting in.

Clarence

Ha ha...good one.  That was a knee slapper.  You are a funny guy.  Just as Joe P.

Edited August 5, 2016 by MyNameIsNobody

[Guitarmaster]

I had the same problem. Try this.

Clamp the yokes together per the service manual. Rig the ailerons to line up with the wing tips. Maybe droop a little too allow them to fly up to center. Your flaps should match the ailerons in the "fly up" position.

Now flight test.

Hold Your Wings level and your feet on the floor. Don't look at the ball. Does your airplane flat-turn? Note the aileron position.

While keeping the wings level, rudder the airplane until no turn. Look at the ball. If should be centered and the ailerons neutral.

If this is what you have, Check for slop in the rudder system. I had many problems with mine, but one of them that I found was that the back edge of the rudder had been bent very slightly. The service manual allows you a small amount of trimming via that little tab. It does not the take much to make a big difference!

I spent the last year chasing rigging problems. I learned that nearly always, a turn problem is in the rudder system and flaps and ailerons are used as stop gaps. This is assuming no drooping gear like Marauder had.

I gained 9 knots by rigging properly AND the PC system works like a dream now!

Sent from my XT1254 using Tapatalk

[jetdriven]

This is a good article.  Before I bend any trailing edges, make sure the TC skid ball is truly level and that all the gear doors are closed tightly. http://www.knr-inc.com/shoptalk-articles/25-shoptalk/75-201407-control-rigging

Edited August 5, 2016 by jetdriven

[Guitarmaster]

This is a good article.  Before I bend any trailing edges, make sure the TC skid ball is truly level and that all the gear doors are closed tightly. http://www.knr-inc.com/shoptalk-articles/25-shoptalk/75-201407-control-rigging

Excellent article! This is pretty much exactly how I tackled mine.

Just for reference, once everything else was accomplished, it took about a 1/32" bend of the trailing edge to completely eliminate any turning tendency.

Sent from my XT1254 using Tapatalk

[SoMooney]

So update, I had a MSC check the control surfaces and they said that they are all within specification. They thought that when they disengage the PC from the yoke it lets go on the rudder servo but the aileron servos do not and that might have something to do with it. I may just have those servos OH'd to make sure its all working. We just had the TC and the valve that connects to that yoke button OH'd.

Here are notes from a flight test, we also get speeds right to the book

To get level flight the roll trim is set at 10 oclock vs 9 oclock on the last flap adjustment

When wing leveler recovers, from a left turn it goes past level to right by about 5 or 10 degrees and then returns to level in 10 seconds or so.

 

recover to level is much faster from left turn than from right turn

 

Ball is not centered, about 1/3rd outside of line.

 

If we hold the ball center and disengage the PC, it sill turns right

 

 

[Yetti]

There is an adjustment on the Brittian Gyro... Uses a small screw driver to change.  The MSC should know this. Brittian will be able to tell you how to adjust

However, roll trim knob position may vary as much as 90° from center

without indicating a faulty system.

 

http://www.67m20e.com/Manual No. 11990 Mooney PC Operation and Service Instructions.pdf

 

There can be a bit of P factor that requires a bit of right rudder to keep the ball centered at full power