Incident Overview
The airplane sustained substantial damage to the nose landing gear after a hard landing on the runway. The incident occurred during a coupled autopilot approach in instrument meteorological conditions. The pilot and three passengers were uninjured.
Pilot Report
The pilot reported using the autopilot to fly an ILS localized timed approach while looking for the runway and monitoring the time. The autopilot inadvertently disengaged, causing the airplane to turn left. The pilot righted the airplane just before touchdown. The airplane landed on the main landing gear with the nose slightly high, then the nose wheel and strut broke upon settling.
Ferry Flight Incident
During a subsequent ferry flight for repairs, the same pilot engaged the autopilot at 2,500 feet. The airplane pitched down and turned sharply to the right. The pilot used opposing control inputs and differential engine power to maintain control. The pilot performed a no-flap landing at an en route airport with a 2,497-foot long runway.
Examination Findings
An examination of the airplane revealed that when the autopilot computer was moved in its shock mount, the control yoke moved "violently right in roll axis and forward in pitch axis."
Aircraft Flight Manual Guidance
The MU-2 airplane flight manual emergency procedures stated that in an emergency, the autopilot can be overpowered manually to correct attitude, but must be immediately disengaged. If the autopilot remains engaged, it will trim the airplane to oppose the pilot's actions, potentially leading to a severely out-of-trim condition. The manual listed methods to disengage the autopilot: operate the trim switch UP or DOWN, momentarily position the inverter switch to OFF and back to original, or turn off the electric master switch.
Pilot Experience
The pilot reported 11 hours of pilot-in-command time in the accident airplane make and model.