What happened
During the terminal descent approximately 6 to 7 miles from the airport, the pilot of the twin turboprop aircraft noticed that the right engine torque meter was reading zero. The pilot noted that this issue had occurred previously and typically resolved by manipulating the throttle.
As the aircraft entered the landing flare, it began to yaw to the right despite the pilot applying corrective left rudder pedal input. The aircraft subsequently made a hard landing, bouncing on the nose twice. This impact resulted in the breaking of the nose wheel strut. Following the impact, the aircraft slid approximately 2,000 feet down the runway, resulting in substantial damage to the airframe.
The investigation
A subsequent ferry flight to a repair facility revealed that the engine power levers were consistently split. To maintain matched engine power parameters, the right power lever had to be positioned approximately 2 inches forward of the left lever. This asymmetrical positional relationship remained constant from flight idle through full power.
Maintenance records were reviewed and showed no record of compliance with Mitsubishi Service Bulletin No. 097/73-001. This bulletin was issued to ensure engine and propeller rigging is adjusted to manufacturer specifications and to prevent degraded flight handling qualities caused by asymmetric or low flight idle power settings.
Findings
- The engine and propeller rigging were not properly adjusted according to manufacturer specifications.
- There was a lack of documented compliance with the relevant Mitsubishi Service Bulletin regarding engine/propeller rigging.