M20C rigging problem

[Matt Hall]

I know this has been posted before but to save myself the countless hours of searching looking for the right information I was hoping someone could give some advice on where to start!

I have a 1962 M20C (no wing leveler) and in cruise it require a slight amount (although annoying) of left rudder pressure to keep ball centered and wings level. If I let off the left rudder pressure the plane immediately starts banking to the right and ball stays relatively in the same position which is what puzzles me. As the controls turn right and the plane banks right it’s almost like it’s flying coordinated by itself but now in a right roll. 
 

This has been an ongoing issue and my mechanic and I have adjusted the amount of turns on the aileron control rod to adjust the deflection which has helped improve the rate of the turn to the right. Additionally I have adjusted the rudder trim tab to the right (to deflect to the left in cruise) not sure if this helped or hindered the situation. 
 

The ailerons looks relatively level using my mark 1 eyeball on the ground and in cruise. When left rudder is released the yoke starts to turn to the right inducing the right roll. When the ball is centered with left rudder pressure the control yoke is relatively center to keep the wings level. 
 

So my question is do you think the root cause is the rudder trim, as in I need more right trim tab deflection so that I can raise my foot off the pedals in straight and level and this will cure the roll because the ailerons and rudder are connected

 

or 

 

is the problem somewhere else in the rigging. 
 

I know this is hard to diagnose over the internet but curious what the group thinks!

[ShuRugal]

It sounds like the bungee springs which cross connect your rudder and airlerons are unbalanced?

Chock your mains and hang a weight on the tail tie down rings to get the nose wheel up. Center the rudder, then set the nose back down so the nose wheel keeps it centered.

What does the yoke want to do? If it doesn't rest in the centered position, your crosslink bungees are unbalanced.

Sent from my Pixel 3a using Tapatalk

[RLCarter]

You’ll need “Travel Boards” to get really close, then slight tweaks once rigged with the boards. Attempting to guess at rigging will slow your plane down. Remember that the rudder trim will change at different power settings, trim it where you fly

[Matt Hall]

Also I have noticed that with the gear down at slower speeds the roll is relatively non existent!

 

 I’ve heard of travel boards but don’t know much more than they’re hard to find. Any insight on how to get a set?

[carusoam]

39 minutes ago, Matt Hall said:

I know this has been posted before but to save myself the countless hours of searching looking for the right information I was hoping someone could give some advice on where to start!

I have a 1962 M20C (no wing leveler) and in cruise it require a slight amount (although annoying) of left rudder pressure to keep ball centered and wings level. If I let off the left rudder pressure the plane immediately starts banking to the right and ball stays relatively in the same position which is what puzzles me. As the controls turn right and the plane banks right it’s almost like it’s flying coordinated by itself but now in a right roll. 
 

This has been an ongoing issue and my mechanic and I have adjusted the amount of turns on the aileron control rod to adjust the deflection which has helped improve the rate of the turn to the right. Additionally I have adjusted the rudder trim tab to the right (to deflect to the left in cruise) not sure if this helped or hindered the situation. 
 

The ailerons looks relatively level using my mark 1 eyeball on the ground and in cruise. When left rudder is released the yoke starts to turn to the right inducing the right roll. When the ball is centered with left rudder pressure the control yoke is relatively center to keep the wings level. 
 

So my question is do you think the root cause is the rudder trim, as in I need more right trim tab deflection so that I can raise my foot off the pedals in straight and level and this will cure the roll because the ailerons and rudder are connected

 

 

is the problem somewhere else in the rigging. 
 

I know this is hard to diagnose over the internet but curious what the group thinks!

I did a search… this is what I found…
 

This is easy to diagnose…

On a good day…

A well rigged Mooney is going to drift left or right…. Resulting in a spiral that tightens over time… depending on the WnB/LR (left/right)

 

This can be balanced using people in the cabin and/or fuel in the wings…

As far as annoying goes…  Mooney sold a ton of wing levelers and autopilots to balance the plane automatically…

 

Does your annoyance get to the level of adding a GFC500?

Work on the known variable balance issues… then go to the rigging issues… then adjust the tail trim…   Without automation this issue changes with fuel balance and people moving about in the cabin… kinda what flying is all about…   
 

Oddly, when fuel is evenly put in the wings… the pilot’s weight is often the cause for an initial drift towards the left… if he is heavier than the pilot that rigged the plane… or to the right if the pilot is on the light side….

Well rigged planes are that  sensitive… increasing dihedral, and putting the wings up high can also remove this effect…

PP thoughts only… My M20C didn’t have an operable wing leveler… (often easy to fix, for a few dollars more)

Or… fly in bumpy weather… it becomes impossible to notice… because you are doing the flying… 

Best regards,

-a-

note: this search has taken a lifetime…. 

[EricJ]

1 hour ago, Matt Hall said:

Also I have noticed that with the gear down at slower speeds the roll is relatively non existent!

 

 I’ve heard of travel boards but don’t know much more than they’re hard to find. Any insight on how to get a set?

Try just lowering the flaps and see if it goes away.   If it does, you may be able to fix it by adjusting the up position on one of the flaps. 

Travel boards aren't necessary for rigging, it's just how some people like to do it.   You can do it with protractors and digital levels as well.

[Sabremech]

2 hours ago, EricJ said:

Try just lowering the flaps and see if it goes away.   If it does, you may be able to fix it by adjusting the up position on one of the flaps. 

Travel boards aren't necessary for rigging, it's just how some people like to do it.   You can do it with protractors and digital levels as well.

I just fixed the stabilizer trim rigging on a J model that had a new autopilot and electric trim installed. Not sure how I would have done it and be assured it was right without the rig board. Not saying it couldn’t be done, just not sure how and how long to be assured it’s in book specs. 
David

[EricJ]

10 minutes ago, Sabremech said:

I just fixed the stabilizer trim rigging on a J model that had a new autopilot and electric trim installed. Not sure how I would have done it and be assured it was right without the rig board. Not saying it couldn’t be done, just not sure how and how long to be assured it’s in book specs. 
David

The rigging board is basically a customized protractor, cut to make it a bit more convenient to use.   A protractor just measures the angle between two surfaces.   Finding zero is fairly straightforward, and then work from there.   The procedures in the SM give the angles to measure, so the boards aren't strictly necessary, just a means to measure the angles.

The boards can be a lot more convenient to use, particularly on the rudder where you can't use a digital level (maybe a compass?), but measuring angles can definitely be done without the boards.   A digital level makes it easy to measure horizontal angle differences, or to use something other than level as the zero reference.   

The only time I've had access to boards was on a Grumman Yankee, and I didn't think in that case it was any easier than using other methods, and not any more accurate, either.   The rudder is a potential exception, because the only other option there is a protractor, which can be done but is just more annoying.

Many shops, including paint shops, that do a lot of rigging don't have boards and manage to get by.

[Guest]

Unlike a Piper Comanche, where the manual provides the angle between the levelling points on the fuselage and the top of the wing flap skin to establish zero,  Mooney needs a travel board to establish zero.  Once established minor tweaking of the zero position can be made without a travel board. Total flap and aileron travel can be set with a digital level etc.

Clarence

[N201MKTurbo]

All that travel board stuff is fine, but you can't fix a heavy wing or a rudder trim issue with travel boards.

If you r mechanic adjusted the aileron links to try to fix a heavy wing, you should have him take the adjustment out. The only thing adjusting the links will do is make your yokes crooked when you are straight and level. 

The only way to fix a rudder trim issue is to bend the trailing edge of the rudder. The only way to fix a heavy wing is to bend the trailing edge of the aileron. or adjust the flap up stop. This is all in the service manual.

[PT20J]

Shoptalk - rigging.pdf

[Sabremech]

2 hours ago, EricJ said:

The rigging board is basically a customized protractor, cut to make it a bit more convenient to use.   A protractor just measures the angle between two surfaces.   Finding zero is fairly straightforward, and then work from there.   The procedures in the SM give the angles to measure, so the boards aren't strictly necessary, just a means to measure the angles.

The boards can be a lot more convenient to use, particularly on the rudder where you can't use a digital level (maybe a compass?), but measuring angles can definitely be done without the boards.   A digital level makes it easy to measure horizontal angle differences, or to use something other than level as the zero reference.   

The only time I've had access to boards was on a Grumman Yankee, and I didn't think in that case it was any easier than using other methods, and not any more accurate, either.   The rudder is a potential exception, because the only other option there is a protractor, which can be done but is just more annoying.

Many shops, including paint shops, that do a lot of rigging don't have boards and manage to get by.

For the stabilizer, you can’t use the top of the horizontal stab with a digital angle finder as it’s not zero. If you look at a rig board, the aluminum angle that is bolted to it is at an angle and not the same as the top of the stab. I’ve used digital angle finders on flaps, ailerons and elevators to check the throw of each, but the stabilizer is different to determine zero like M20Doc states. Since I have access to the rig board, it made sense along with made it easy setting the stab trim per  the maintenance manual.

David

[EricJ]

14 minutes ago, Sabremech said:

For the stabilizer, you can’t use the top of the horizontal stab with a digital angle finder as it’s not zero. If you look at a rig board, the aluminum angle that is bolted to it is at an angle and not the same as the top of the stab. I’ve used digital angle finders on flaps, ailerons and elevators to check the throw of each, but the stabilizer is different to determine zero like M20Doc states. Since I have access to the rig board, it made sense along with made it easy setting the stab trim per  the maintenance manual.

David

He's saying it's an issue on the flaps.   The M20J manual says to align the flaps with the ailerons.

For the stab put the digital level on the top and the bottom and split the difference for the reference.

[Guest]

8 hours ago, Matt Hall said:

I know this has been posted before but to save myself the countless hours of searching looking for the right information I was hoping someone could give some advice on where to start!

I have a 1962 M20C (no wing leveler) and in cruise it require a slight amount (although annoying) of left rudder pressure to keep ball centered and wings level. If I let off the left rudder pressure the plane immediately starts banking to the right and ball stays relatively in the same position which is what puzzles me. As the controls turn right and the plane banks right it’s almost like it’s flying coordinated by itself but now in a right roll. 
 

This has been an ongoing issue and my mechanic and I have adjusted the amount of turns on the aileron control rod to adjust the deflection which has helped improve the rate of the turn to the right. Additionally I have adjusted the rudder trim tab to the right (to deflect to the left in cruise) not sure if this helped or hindered the situation. 
 

The ailerons looks relatively level using my mark 1 eyeball on the ground and in cruise. When left rudder is released the yoke starts to turn to the right inducing the right roll. When the ball is centered with left rudder pressure the control yoke is relatively center to keep the wings level. 
 

So my question is do you think the root cause is the rudder trim, as in I need more right trim tab deflection so that I can raise my foot off the pedals in straight and level and this will cure the roll because the ailerons and rudder are connected

 

or 

 

is the problem somewhere else in the rigging. 
 

I know this is hard to diagnose over the internet but curious what the group thinks!

As you can see from this thread there are as many opinions on rigging as there are maintainers here.  

The manual calls for use of the Mooney travel boards to correctly rig and adjust your flight controls.  Mooney has specific instructions on bending the trailing edge of the ailerons to affect roll trim, do this as a last resort.  Adjusting aileron rods ends changes nothing but the yoke position. Other things to check, raise the plane on jacks and level it laterally, check that the ball is centred, retract the landing gear and make sure that both mains retract fully and the doors are closed against the wing skins.  With a travel board make sure the flaps are set to the same up or zero position.  Flap position can cause a rolling issue.  Rig the aileron control system per the manual, setting the three bellcranks correctly, then adjust the aileron push rods to set the ailerons to the correct zero position, some droop is OK as the ailerons generally lift up at the trailing edge at cruise speed.  I start with one degree of droop.

In correct setting of the elevators can also affect flight, they should also be at the same angle and parallel to each other.

Clarence

[cliffy]

One could make a board and clamp both elevator counter weights even and faired with the fwd stabilizer profile

The board would have a larger notch for the leading edge of the stabilizer and a fine narrow notch for the trailing edge of the elevator in a cutout of the board

The distance between the notches would allow the board to set about half way out on the span of the stabilizer.

If  the top of the board was parallel with the line between the center of the notches then a protractor/level could be 

set on top of the board and IF the airplane as sitting level fore and aft all one needs to do is move the trim wheel to set level on the elevator/stabilizer  

assembly 

One could then add a stub to the board at the aft edge of the stabilizer (not elevator) to maintain the fwd top half of the board parallel to the previous centerline and remove the tail end of the board

THEN one could easily move the trim to 3 1/2 degrees elevator LE down for checking the bungee deflection angles after removing the board assembly by using a Devil Level or other angle finder taking into account the slope of the elevator aft of the hinge line. Throws either way can be divined along with stab  trim settings. 

Shields up!

[Sabremech]

10 hours ago, EricJ said:

He's saying it's an issue on the flaps.   The M20J manual says to align the flaps with the ailerons.

For the stab put the digital level on the top and the bottom and split the difference for the reference.

Hate to disagree with you, but that method is unacceptable to the owner of the aircraft I just worked on. Yes, you might get close, but it is not IAW the maintenance manual. Try to explain that to the investigators after the smoking hole has been created. You have no leg to stand on. 
 

[Matt Hall]

18 hours ago, EricJ said:

Try just lowering the flaps and see if it goes away.   If it does, you may be able to fix it by adjusting the up position on one of the flaps. 

Travel boards aren't necessary for rigging, it's just how some people like to do it.   You can do it with protractors and digital levels as well.

Not sure if this would work because when I let go of left rudder pressure in cruise, the controls still try to turn right, thus starting a right bank. I know the flaps could help but I think the fact that the controls are turning when I let go of rudder and they are interconnected means I need to mess with one of them but it’s hard to figure out which one :-(

[Matt Hall]

15 hours ago, EricJ said:

The rigging board is basically a customized protractor, cut to make it a bit more convenient to use.   A protractor just measures the angle between two surfaces.   Finding zero is fairly straightforward, and then work from there.   The procedures in the SM give the angles to measure, so the boards aren't strictly necessary, just a means to measure the angles.

The boards can be a lot more convenient to use, particularly on the rudder where you can't use a digital level (maybe a compass?), but measuring angles can definitely be done without the boards.   A digital level makes it easy to measure horizontal angle differences, or to use something other than level as the zero reference.   

The only time I've had access to boards was on a Grumman Yankee, and I didn't think in that case it was any easier than using other methods, and not any more accurate, either.   The rudder is a potential exception, because the only other option there is a protractor, which can be done but is just more annoying.

Many shops, including paint shops, that do a lot of rigging don't have boards and manage to get by.

Good idea on paint shops being savvy with balance!

Edited April 4, 2022 by Matt Hall

[Matt Hall]

14 hours ago, N201MKTurbo said:

All that travel board stuff is fine, but you can't fix a heavy wing or a rudder trim issue with travel boards.

If you r mechanic adjusted the aileron links to try to fix a heavy wing, you should have him take the adjustment out. The only thing adjusting the links will do is make your yokes crooked when you are straight and level. 

The only way to fix a rudder trim issue is to bend the trailing edge of the rudder. The only way to fix a heavy wing is to bend the trailing edge of the aileron. or adjust the flap up stop. This is all in the service manual.

We’ve played with the control rods of the ailerons a little bit because they seemed like they were not symmetrical in cruise so at this point it would be hard to take the corrections out because there has been numerous. 
 

Having said that, controls are centered on ground with ailerons in neutral position and in cruise as long as I’m applying left rudder pressure the controls are centered to fly in a straight line…..does that make sense? Make it easier to diagnose whether rudder or aileron is my root cause 

[Matt Hall]

13 hours ago, PT20J said:

Shoptalk - rigging.pdf 79.55 kB · 9 downloads

Wow this was great thanks!!!

[Jcmtl]

what happens to the ball if you take your feet off of the rudder pedals and hold the yoke to keep wings level?

 

[EricJ]

4 hours ago, Sabremech said:

Hate to disagree with you, but that method is unacceptable to the owner of the aircraft I just worked on. Yes, you might get close, but it is not IAW the maintenance manual. Try to explain that to the investigators after the smoking hole has been created. You have no leg to stand on. 
 

The maintenance manual also says repairs to M20J cowls must be done with materials that don't exist any more.   There are plenty of similar examples where deviation from the SM is common due to practicality or necessity.   I doubt there are many maintainers who never deviate from the SM.

When shops don't have, and can't get, travel boards, there are methods that are demonstrably the same, or even more accurate than the travel boards (in my experience).   Likewise it isn't practical for most shops to purchase travel boards for every airplane that comes into their shop.

There's nothing magical about travel boards.   They're great when you have them, but when they're not available it doesn't mean airplanes can't be rigged any more.

[Sabremech]

47 minutes ago, EricJ said:

The maintenance manual also says repairs to M20J cowls must be done with materials that don't exist any more.   There are plenty of similar examples where deviation from the SM is common due to practicality or necessity.   I doubt there are many maintainers who never deviate from the SM.

When shops don't have, and can't get, travel boards, there are methods that are demonstrably the same, or even more accurate than the travel boards (in my experience).   Likewise it isn't practical for most shops to purchase travel boards for every airplane that comes into their shop.

There's nothing magical about travel boards.   They're great when you have them, but when they're not available it doesn't mean airplanes can't be rigged any more.

For cowling repairs you have AC43-13 to reference. 
What will you tell the FAA inspector when rig boards are available and you deviated from the maintenance manual? 
You can talk all around how you can come up with other methods but it won’t get you very far with them. 
 

[Marauder]

For cowling repairs you have AC43-13 to reference. 
What will you tell the FAA inspector when rig boards are available and you deviated from the maintenance manual? 
You can talk all around how you can come up with other methods but it won’t get you very far with them. 
 

I’m living proof of someone who “rigged” my plane without travel boards. They rigged the plane to offset a right turning tendency. The issue that it wasn’t the aileron or flaps that needed to be adjusted. It was the right gear that wasn’t fully retracting. When I got the plane back it flew straight and level but was 5 knots slower.

I took it to an MSC who sorted out the mess. Once they set the control surfaces to the correct position, it got them looking for other causes.

Before I use a non MSC shop I ask them with they have two things. The travel boards and the gear preload tool. If they give me that puzzled look, it’s time to look for another shop.


Sent from my iPhone using Tapatalk Pro

[EricJ]

47 minutes ago, Sabremech said:

For cowling repairs you have AC43-13 to reference. 
What will you tell the FAA inspector when rig boards are available and you deviated from the maintenance manual? 
You can talk all around how you can come up with other methods but it won’t get you very far with them. 
 

Sure when they're available, but usually they're not.   Even the efforts here to duplicate them haven't been very successful in providing options for all models.

Just like when a material specified is no longer available (and AC43.13 doesn't give much guidance on that), when a tool isn't available you may need to do something else.   If you understand geometry and trig and how to make measurements, it's definitely possible to do it without the boards, and lots of shops commonly do and have done for a long time.

In my case I learned the other methods in A&P school, where out of a fleet of more than a dozen different types of airplanes we had boards for one.   So we were taught how to do it with other methods on a bunch of different airplanes.   The one airplane we had boards for was a Grumman Yankee, so I took the time to try three different methods: boards, protractor, and digital level, on that airplane.   The digital level was the most accurate and repeatable.   The boards were actually kinda sloppy in comparison in my opinion, and subject to a lot of positioning errors.  I found I could make the boards say what I wanted within a particular range.

So if I ever get any grief about it I'll point the FAA to my approved A&P school after showing how the other (commonly practiced) measurements can provide a more accurate solution than boards might.   I can probably leverage my 30+ years of engineering experience there, too, for drawings and measurement and tolerance assessment.   It's kinda like how MMO isn't approved to be used anywhere near an airplane, but maintainers have been using it for decades.   This is how "common practice" often gets cited, even by the FAA.   If an airplane crashed that got a cylinder rehabbed with MMO or was running it in their oil or fuel, I doubt the FAA would consider that a cause, since it's been done safely for decades.   Likewise rigging without boards when they're not available.