NTSB Identification: CHI02LA044.
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Accident occurred Friday, November 30, 2001 in St Paul, MN
Probable Cause Approval Date: 05/13/2003
Aircraft: Mitsubishi MU-2B-40, registration: N9052Y
Injuries: 4 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The airplane sustained substantial damage on impact with the runway during a hard landing following a coupled autopilot approach. The pilot and three passengers were uninjured. Instrument meteorological conditions prevailed. The pilot reported, "I was using the autopilot to fly the ILS localized timed approach. I was looking for the runway and watching the time. The autopilot inadvertently disengaged, turning the airplane to the left. I righted the airplane just before touchdown. It landed on the mains with the nose slightly high. It came down, and the front wheel and strut broke." During the next flight, a ferry flight for repairs, the accident pilot reported that he engaged the autopilot at 2,500 feet. The pilot reported that when the autopilot was engaged, the airplane pitched down and turned sharply to the right. The pilot reported using opposing control inputs and differential engine power to maintain airplane control. The pilot performed a no flap landing at an en route airport with a 2,497-foot long runway. An examination of the airplane revealed that when the autopilot computer was moved in its shock mount the yoke moved "violently right in roll axis and forward in pitch axis." The MU-2 airplane flight manual's emergency procedures stated, "In case of emergency, the autopilot can be overpowered manually to correct the attitude, but the autopilot must immediately be disengaged. If the autopilot remains engaged, the autopilot will trim the airplane to oppose the pilot's actions. This could result in a severely out of trim condition." The manual stated, "The autopilot can also be disengaged by any of the following methods, "1. Operate trim switch UP or DOWN, 2. Position inverter switch to OFF momentarily and then return, to original position, 3. Turn off the ELECTRIC MASTER SWITCH." The pilot reported 11 hour hours of pilot in command time in the accident airplane make and model.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The autopilot's computer connections arcing and reported disconnection during the localizer approach and the pilot not performing a go around prior to the hard landing. A factor was the pilots lack of total experience in the accident airplane's make and model.

Full narrative available

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