AD Would Mandate New Flap Parts on MU-2s

Owners of some 360 U.S.-registered Mitsubishi MU-2s would be required to install newly designed torque-tube joints to prevent possible failure of the flap control system, if a recently proposed AD is adopted. Operators have been required to perform repetitive inspections of the joints under an AD issued in 1988 after “field reports indicating fatigue cracks were found in joint assemblies that had been in service for more than 4,000 hours.” But the FAA said a recent fatal accident investigation revealed that an improper reinstallation of the cotter pins in the torque tube following one of the required inspections resulted in a disconnect in the flap drivetrain and asymmetrical flap deployment. The FAA estimates the cost of labor and parts at $20,960 per airplane.