Airworthiness Directives; Boeing Model 777-200, 777-300, and 777-300ER Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 777-200, 777-300, and 777-300ER series airplanes. This AD requires repetitive inspections for discrepancies of the splined components that support the inboard end of the inboard trailing edge flap; related investigative, corrective, and other specified actions if necessary; a one-time modification of the inboard support of the inboard trailing edge flap by installing a new isolation strap and attachment hardware; and repetitive replacement of the torque tube assembly. For certain Boeing Model 777-200 series airplanes, this AD also specifies prior or concurrent accomplishment of one-time inspections of the flap seal panels for cracking and minimum clearances, and of the torque tubes for damage; and related investigative and corrective actions if necessary. This AD also provides a terminating action (modification of the inboard main flap) for the repetitive inspections. This AD results from reports of corrosion on the torque tube and closeout rib fittings that support the inboard end of the inboard trailing edge flap, as well as a structural reassessment of the torque tube joint that revealed the potential for premature fatigue cracking of the torque tube that would not be detected using reasonable inspection methods. We are issuing this AD to detect and correct corrosion or cracking of the torque tube and closeout rib fittings that support the inboard end of the inboard trailing edge flap. Cracking in these components could lead to a fracture, which could result in loss of the inboard trailing edge flap and consequent reduced controllability of the airplane.