On April 17, 2008, at 1830 eastern daylight time, an Eclipse Aviation EA500, N539RM, experienced a stuck rudder trim during a simulated single-engine instrument approach to the Bishop International Airport (FNT), Flint, Michigan. The flight diverted and landed without incident at the Oakland County International Airport (PTK), Pontiac, Michigan, at about 1845 because PTK had more favorable winds for landing. The instructor pilot and the pilot/owner receiving training were not injured. The 14 CFR Part 91 instructional flight departed Detroit City Airport (DET), Detroit, Michigan, about 1815 on a local flight. Visual meteorological conditions prevailed at the time of the incident. An instrument flight plan was filed.

The instructor pilot reported that the pilot receiving training had completed a simulated engine failure of the right engine. Upon completion of the maneuver, he attempted to re-trim the rudder trim since it was set at 58 percent left trim. The rudder trim did not respond. The instructor pilot switched to Alternate trim but without success. The pilots followed the checklist items found in the Quick Reference Handbook (QRH) but without success. The manual trim did not correct the condition with the airspeed at about 200 knots. The instructor pilot proceeded to PTK and executed a precautionary landing without incident. The airplane was shut down. When the airplane was restarted, the condition was corrected and the rudder trim operated normally.

On April 30, 2008, Eclipse Aviation issued a Customer Pilot Communication (CPC) No. 500-2008-007 titled "Rudder Trim Operation." The CPC stated the following:

"There have been several instances of Eclipse 500 operators reporting an inability to actuate the rudder trim following acceleration from a practice single engine event. It was determined that this is caused by trimming rudder for a slow airspeed and then accelerating without removing trim, significantly increasing the trim tab loading and exceeding the trim motor design stalling point. This is considered normal operation, as it is a feature of the design to prevent excessive rudder loads. Eclipse is issuing this CPC to improve operator awareness and provide clarifying guidance."

The CPC stated that the rudder trim actuator is designed with a motor that will stall at a specific load. This is required on the trim actuators to prevent excessive rudder forces for the pilot. Additionally, the trim actuators incorporated a no-back feature to prevent air loads from driving the surface backwards when the trim motor can no longer support the required load. When substantial rudder trim is input at low speeds and the aircraft is then accelerated to significantly higher speeds, the no-back feature will hold the trim surface in position with enough force to match the increased loading on the trim tab. If the increased airspeed creates a high enough load on the trim surface, the rudder trim motor will not be able to overcome the holding force of the no-back due to the designed stall point of the motor.

The CPC further recommended the following guidance to operators:

1. Utilize proper rudder trimming technique by FIRST reducing the yaw with pressure on the appropriate rudder pedal and THEN trimming the rudder to relieve the pedal pressure. This will result in only the appropriate amount of trim necessary for the condition and prevent inputting excessive rudder trim.

2. Following practice single engine events (or any other event where significant rudder trim is input), remove rudder trim once both engines are restored and before accelerating to substantially higher airspeed.

3. If encountering a condition where rudder trim cannot be reduced following acceleration from a lower speed regime, continue to reattempt rudder actuation using the throttle quadrant rudder trim knob while reducing aircraft speed until rudder trim control is restored.

4. Although the use of alternate trim on the MFD is not necessary in this situation, pilots should be aware that any time alternate trim is engaged, normal aileron, elevator, and rudder trim controls will be disabled until alternate trim mode is deactivated on the MFD.

5. If the rudder trim continues to not operate after reducing airspeed through approach and landing, report the issue to Eclipse Customer Care (or your appropriate maintenance support) for maintenance action.

6. Never cycle aircraft power with the engines running, whether on the ground or airborne, in an attempt to circumvent published AFM procedures.

7. It should be noted that Eclipse has flight-tested and certified the aircraft with full rudder trim input during approach and landing. The aircraft has been determined fully controllable throughout landing in this configuration.

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