In this month's Shoptalk, I will explain to pilots and owners my procedures for properly rigging the flight controls of your Mooney aircraft. I know there have been several articles in the Log concerning flight control rigging, but this one is going to explain systematically what you need to consider and why. You will be able to recognize any incorrect settings. Perhaps no other maintenance procedure requires the pilot's input as much as rigging the flight controls of an aircraft. Many mechanics are not pilots and probably no one knows your aircraft as you do. Knowledge will help make rigging your aircraft a cooperative venture between you and your mechanic. I might suggest that you discuss this article with him or her prior to beginning the project. Following these steps should be an easier way than following the service manual. Most of what is in the service manual are contained here, and it must be used as a cross-reference. At the end of this procedure, I will go into detail about the final flight tests and adjustments. This procedure applies to all metal Mooney airplanes.

Before starting, you must have the following as well as standard tools:

• A set of appropriate jacks.
• The service manual for your aircraft.
• A digital protractor.
• The travel boards for your aircraft.
• Patience

Read this article to the end and understand the entire procedure. Heed the hints mentioned at the end of the steps.
STEP #

1. Place airplane on jacks.
2. Remove belly panels exposing aileron/rudder inter-connecting springs and mechanism.
3. Level A/C on jacks. See your service manual for this procedure.
4. On the turn and bank indicator, make sure the ball is centered between the hash marks. Reset the turn and bank indicator in the panel if this ball is not centered. If the ball cannot be properly centered by adjusting the instrument then replace the instrument panel shock mounts. These rubber mounts are probably sagging or broken. Do not go to step 5 until the ball is centered between the hash marks when the aircraft is properly leveled.
5. Clamp the pilot's rudder pedals together. Be sure they are even. Install a straight bar across both control yokes to hold the yokes centered and together.
6. Measure the aileron interconnect springs for their length. Most are stretched about 4.9" long, but the important consideration here is that they are exactly the same length when the rudder pedals and control wheels are clamped together evenly. See your service manual for the exact spring length and readjust the springs until they are at this length. Do not go on to step 7 until this is completed.
7. Verify that the rudder is aligned straight and not deflected from the vertical fin centerline. If your airplane has rudder trim make sure it is set correctly as per your service manual before checking the rudder. On the TLS, the indicator is one notch to the left of the centerline when the rudder is actually straight.
8. Readjust your rudder to centerline with rudder pedals clamped together.
9. Install the aileron/flap travel board on the wing. See the service manual for the exact location of the travel board.
10. Set both ailerons for 2° droop as measured on the travel board when the control wheels are clamped together and level.
11. Set outboard flap limit bolts to 0° on the travel board for both flaps. Angles are the same for both flaps using a digital protractor and is the same as the inboard angle on each flap. Often, I find that they are not the same. If this is the case, then adjust the flap actuating rods to obtain the same angle inboard as outboard. This is very important; it is not discussed in any Mooney service manual I have ever seen. If the outboard angle is 15° but the inboard angle is 17° then the flap will cause extra lift on that wing and you will never get the airplane to fly straight. Do not go to step 12 until all four angles match within 1/2 degree.
12. Remove aileron and rudder pedal locks and clamps.
13. Using a wooden clamp, align and secure one side of the elevator with the horizontal stabilizer and verify that the other elevator is at the same angle using a digital protractor. This is the other area I frequently see out of rig. If one elevator is up 2° when the other is level, then the plane will want to roll because of the twist in the tail.
14. Using the aileron travel board, verify that the ailerons actually travel up and down the full and correct amount and that they hit the stops on each bell crank in each wing. Once you have set the stops properly and the ailerons are rigged at 2° droop (each aileron) you will find that the control yoke will turn the same amount from left to right.
15. Verify that the flaps go down the proper amount using the flap travel board. Refer to the service manual again to determine the degrees of travel.
16. Verify that the stabilizer trim travels the correct amount in the nose up and nose down positions using the correct travel board and figures from your particular service manual. This is critical on the TLS model. Verify the trim indicator is set properly for the tail position.
17. Adjust the nose gear stop bolts for the correct rudder travel. Frequently these bolts are bottomed out and will not touch the stops. With the new style nose gear truss the bolts are, in fact, the rudder stops. The clamps and brackets in the tail are no longer utilized for this purpose. If there is a rudder position indicator, make sure it represents the position of the rudder.
18. Verify that the elevator stops are set for the proper elevator travel. Readjust the clamps and brackets in the tail if there is insufficient elevator travel in either direction.
19. Re-bend all rudder and aileron trailing edges to straight. Sight along the length of the trailing edge. Carefully bend the tabs or the trailing edge until completely straight.
20. Verify on TLS models that the elevator tabs are bent down 7°. It is amazing how much extra nose up authority this little tab on the elevator gives the airplane. On all aircraft be sure left and right elevator tabs are the same. If different, a little roll force would be produced but worse, torsional stress would be induced in flight between left and right elevators.
21. Now is a good time to adjust the nose gear steering. Check the steering horn for excessive play and that it is adequately greased. Steering horns that are worn (I out and/or improperly shimmed are common problems. This has become a very expensive part of all Mooneys but it is important, so make sure that it is correct before going on to step 23. You can readjust the linkage between the steering horn and the rudder pedal torque tubes and some adjustments may necessary once the aircraft is back on its wheels.
22. Retract the landing gear and check the gear doors and fairings. Always take the opportunity when the aircraft is on jacks to observe a landing gear cycle. Misaligned gear doors cause excessive drag and can affect aircraft trim.
23. These two items must be performed in the correct order. Lower the gear and remove the airplane from the jacks. Fuel tanks should be balanced. Testing time! Be sure to take notes while taxiing and in flight.
24. Do some taxi tests. If the aircraft won't track straight with zero rudder deflection, you will experience excessive nose wheel tire wear and some directional control problems during landing. Crosswinds from one side will be more difficult to handle than from the other side (no, don't adjust the steering for your prevailing winds).
25. At normal cruise power, 65 to 75%, in calm conditions, level the airplane out and allow the airspeed to stabilize. Level the wings with the autopilot or P/C system off. Put your feet flat on the floor and verify the tum and bank ball is centered. If it is centered, skip to STEP 27.
26. Be sure the rudder trim is centered. If you must push the left rudder pedal to center the ball (remember "Step on the ball!"), the trailing edge of the rudder will have to be bent to the right. Remember to bend the tab from the NAV light all the way to the top of the rudder evenly. When the plane will fly with the ball centered, feet flat on the floor when the wings are level you can move on to step 27.
27. Again; normal cruise power, calm conditions, P/C system or autopilot off, rudder trim centered. With feet flat on the floor verify that the ball is centered. Level the wings and release the control yoke. Observe the position of the ailerons with respect to the flaps. Take notes. If one aileron rides higher then the other, equalize them by doing the following. On the low aileron, bend the trailing edge down. That will raise that aileron. Typically, both ailerons should ride slightly above the flaps. The aircraft at this point should fly straight and level. Recheck the ball. Step 26 and then this step may have to be repeated for fine-tuning the trim.

 

Some hints on bending the tabs: A little bend of 2 to 3 degrees goes a long way. Bend evenly the entire length of the trailing edge of the control surface. If you have an aftermarket Aerotrim system installed make sure the indicator pointer is centered and the trim tab is straight (faired).
If the aircraft flies straight with autopilot or P/C systems off, don't re-rig the airplane. If when you engage the P/C system, the plane rolls (with the P/C knob centered) then check the P/C servo rubber cups. Replace the cups as necessary and try again.
If the aircraft has a retractable step, have someone observe that the step retracts completely when the engine is running. If it does not retract, then the servo cup is not getting enough vacuum pressure or the cup is bad.
Again, be patient. After some additional flights, you may want to revisit steps 25, 26, and 27.

In conclusion, I will say that about every third airplane that comes into my shop is out of rig. When I ask an owner about it, a typical response would be, "It has always flown that way." That does not need to be. A little time, money and effort can put you back on the straight and level. Better fuel efficiency will offset the money spent. One final item: Is the engine properly shimmed in the engine mount? The Lycoming-engined Mooneys have two thicknesses of shims installed between the rubber engine mounts and the engine itself. An incorrectly shimmed engine will have an improper angle of thrust in relationship with the centerline of the fuselage. This is a very difficult item to resolve because every airplane was shimmed differently at the factory. Remember, all these planes are hand-built and no two are exactly alike. When referencing the Parts Book or Service Manual for the engine shim part number or location, you will only find, "AR" (as required). That's because Mooney uses an engine jig that is mounted on the firewall and the engine is shimmed to match the jig.

If you have questions about this or any other ShopTalk article, please e-mail me at shoptalk@knr-inc,com or call me at my aircraft repair shop, 307-789-6866. All ShopTalk articles can be read here at www.knr‑inc.com. Until next time, enjoy flying your Mooney.