La Verne, CA, USA
N81MF
Mitsubishi MU-2B-26A
The twin turboprop airplane landed hard collapsing the nose gear, and causing substantial damage to the airframe. The pilot said that about 6-7 miles from the airport, in the terminal descent, he noticed the right engine torque meter read zero. This had occurred before, and the torque would come back if he manipulated the throttle. He continued the normal approach for landing. In the landing flare the airplane yawed right despite his corrective left rudder pedal input. The airplane landed hard, bouncing on the nose twice, breaking the nose wheel strut. It then slid about 2,000 feet down the runway. The ferry pilot, who flew the airplane to the repair facility after the accident, said that the engine power levers were consistently split throughout the entire ferry flight. In order to have the engine power perimeters matched, the right power lever had to be about 2 inches forward of the left one and this positional relationship was constant from flight idle to full power. Maintenance records had no record of compliance to Mitsubishi Service Bulletin No. 097/73-001, which was published "to assure the engine and propeller rigging is adjusted within manufactures specifications and to prevent potential degraded flight handling qualities associated with the flight idle power being set asymmetrically or too low."
On March 27, 2004, at 1216 Pacific standard time, a Mitsubishi MU-2B-26A, N81MF, experienced a hard landing at Brackett Field, La Verne, California. The owner operated the airplane under the provisions of 14 CFR Part 91. The pilot and two passengers were not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and an instrument flight plan had been filed. The personal cross-country flight originated at Lake Havasu, Arizona, at 1225 mountain standard time. The pilot told the National Transportation Safety Board investigator-in-charge (IIC) that about 6-7 miles from the airport, in the terminal descent, he noticed that the right engine torque meter read zero. This had occurred before, and the torque would come back if he manipulated the throttle. He continued the normal approach for landing. In the landing flare the airplane yawed right despite his corrective left rudder pedal input. The airplane landed hard, bouncing on the nose twice and breaking the nose wheel strut. It then slid about 2,000 feet down the runway. In a telephone conversation with the Safety Board IIC the ferry pilot hired to fly the airplane from Brackett Field to Tulsa, Oklahoma, after the accident, said that when airborne there was a significant split between the two engine power levers. The right engine power lever was consistently about 2 inches forward of the left power lever when the left and right engine parameters were matched up. When the ferry pilot was landing the airplane he kept the split between the levers in order to keep the engines producing equal power. Examination of the airframe and right engine maintenance logbook revealed that compliance to Mitsubishi Service Bulletin (SB) No. 097/73-001 had not been entered. The SB was issued "to assure the engine and propeller rigging is adjusted within manufactures specifications and to prevent potential degraded flight handling qualities associated with the flight idle power being set asymmetrically or too low."
the pilot's failure to adequately compensate for an asymmetrical thrust condition and to maintain directional control during the landing flare. The owner/pilot's failure to comply with the applicable service bulletin concerning propeller/power control rigging was a factor.
Source: NTSB Aviation Accident Database
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