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A recent in-flight incident concerning a hopelessly jammed stabilizer trim on a K model prompted increased attention to an obscure Mooney Service Instruction (M20-88), and most likely a new Service Bulletin will be released soon. I have written an article that will deal with this subject in more detail in forthcoming issues of the MAPA Log and The Mooney Flyer but wanted to get the word out to the troops sooner so am posting an excerpt here. This problem may occur on K and earlier model Mooneys but here are some generalized procedures you may find useful for stab trim issues in any Mooney. Stabilizer Trim Problem Actions: Jammed Stabilizer—full nose up: The faster the plane goes the more forward elevator pressure will be required, so slow down as much as possible because this force can be considerable. Lower the flaps (takeoff or landing setting as appropriate), fly with the gear up, and use the least power needed… i.e. no need to climb quickly unless you have obstacle or terrain issues. Try to break the jammed trim loose by “shocking” the trim wheel smartly with as much nose down force (front of trim wheel towards the floor) as you can, but don’t forget to fly the plane. Declare an emergency! Pick a suitable airport (a longer runway is better). Configure normally for landing and fly a stabilized approach in the 1.2 to 1.3 VSO speed range. A slightly steeper than normal glideslope will also help. Slowly retard the throttle when landing is assured, flare, and touchdown normally. Jammed Stabilizer—mid position: Not as critical as the full nose up jam previously discussed, but it will still get your attention. It could be caused by a mechanical failure, a foreign object (e.g. rag, pen, flashlight, seat belt) getting lodged in the mechanism, or ice. Turn off Elevator Trim and Autopilot. Apply a moderate amount of manual trim in the direction opposite to that which caused the jam in the first place and consider jostling the plane in an attempt to dislodge foreign objects. (Don’t get overly aggressive—remember the Air Alaska MD-80 that tried to fix a stab trim problem rather than landing.) Land as soon as practical. If the out-of-trim condition is causing problems controlling the aircraft declare an emergency. Consider a no-flap landing (add 10 knots to VREF) if the trim is jammed nose down. Runaway Trim: Grab the trim wheel to stop the motion. The trim motor clutch will slip allowing you to restrain the wheel. Turn off the Elevator Trim switch and disconnect the Autopilot. Some airplanes have a Trim circuit breaker you can pull. Use manual trim. Be sure always to check the trim position prior to takeoff. Improperly set nose trim can make pitch control very challenging. Excess nose down trim will make rotation difficult and can result in porpoising on the runway and a possible prop strike. Excess nose up trim will make it difficult to keep climb attitude and airspeed under control. You can check your Mooney’s trim system yourself to see if it exhibits any tendency to stick at the limits. On the ground, run the trim to the full nose up position and then back slightly to see if there is any tendency to bind at the stop. Then run it to the stop again and give it “a little extra” with the manual trim wheel to see if it exhibits any tendency to stick. Check with your A&P or MSC if you have any concerns about your trim system. Lee Fox