Air Hi Ho

Mitsubishi MU-2 Marquise

The pilot said that after climbing about 500 feet after takeoff, at 120 knots with the gear retracted, the left engine lost power. He feathered the propeller, lowered the nose to the horizon, and began a shallow left turn back to the airport. He left the flaps at 20° and noted a descent of 200 feet to 300 feet per minute in the turn. After clearing trees, the pilot extended the landing gear, banked the aircraft to the right to align it with the runway and lowered flaps to 40°. After touchdown, he applied single engine reversing. The aircraft went off right side of runway and into a ditch, collapsing the right main and nose gear. Examination of the engine revealed the torque sensor housing had failed, resulting in loss of drive to the fuel pump. Metallurgical exam of the housing arm of the torque sensor revealed it had failed from fatigue. On 9/14/79, a service bulletin (SB) was issued for replacement of the torque sensor housing with an improved housing. The manufacturer overhauled the engine on 12/1979, but SB was not complied with. SB indicated a history of resonant vibration causing cracks in the housing arm of original torque sensor and gear assemblies, and that the housing should be replaced, no later than during next part exposure. Investigation revealed pilot did not comply with engine failure procedures and airspeeds. Flight manual cautioned not to use 40° of flaps during single engine landings.

Mitsubishi MU-2 Marquise

Evidence shows copilot called, 'mayday, uncontrolled spin' after aIRCRAFT radar track showed decelERATION from 180 to 120 kNOts over 2 minUTES period while maintaining constant 4,000 feet cruise altitude. Constant altitude consistent with autopilot/autotrim use, particularly in view of reported turbulence/icing. Elevator trim found at approx 13° nose up. No evidence found of preimpact failure or malfunction in aircraft powerplants, structure or systems. Evidence suggests scenario of crew inattention after power reduction with autopilot altitude setting. On power application, aircraft pitched up from slow speed into uncontrolled flight. Duty day at time of mishap approaching 11 hours. All five occupants were killed.