Beechcraft Model 58 Baron
Overheated Pitch Servo
The pitch servo overheated, causing smoke in the cockpit. Investigation revealed the current-limiting resistor had melted. The pilot reported that the aircraft had experienced some minor porpoising prior to the smoke. This is the third time this aircraft has experienced this problem and the third s/n with the same problem.
Part total time: Unknown
Beechcraft Model 300LW King Air
Uncommanded Pitch Inputs
Autopilot made uncommanded momentary pitch inputs at FL230 and then again at 4000 feet msl. Found elevator trim servo clutch out of tolerance and slipping. Adjusted the servo clutch to maintenance manual specs.
Part total time: 921.0 hours
Beechcraft Model B300 King Air
Intermittent Pitch Trim
Elevator trim annunciation took a long time to extinguish after engine start. Elevator trim in cruise flight was binding and immovable with autopilot on. A sudden nose-down pitch excursion was experienced but stabilized a few seconds after. Landing was uneventful. Maintenance replaced the elevator pitch trim servo (p/n 8221168003).
Part total time: 393.0 hours
Beechcraft Model 400A Beechjet
Intermittent Yaw Dampener
Aircraft experienced an intermittent yaw dampener fault—the autopilot would trip off while in turbulence. Troubleshooting found the rudder servo (p/n 622-6717-104) to be weak. The unit was removed from service and replaced with an overhauled item.
Part total time: Unknown
Cessna Model 172F Skyhawk
Binding Autopilot Servos
Elevator and aileron servos (p/n 8100064) stuck in flight. Owner/pilot cleared with force. Removed old unit and replaced with manufacturer’s new replacement part. Returned aircraft to service after complete test per manufacturer’s recommendations. Elevator servo had previously been changed for the same issue.
Part total time: Unknown
Cessna S550 Citation II
Porpoising Autopilot
At FL400, the autopilot started porpoising and was turned off. Afterward, the aircraft would not trim properly. The crew diverted; it was difficult to keep it pitched down while descending. During the final phase of flight, the yoke was very difficult to input pitch changes, but was okay in the roll axis. After landing, troubleshooting duplicated the problem. Elevator servo (p/n 4006719914) was replaced with serviceable unit.
Part total time: Unknown
