Airworthiness Directives; Boeing Model 747-100, -200, and 747SP Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, and 747SP series airplanes, that requires repetitive detailed visual and ultrasonic inspections to detect missing, damaged, or broken taperlock bolts in the diagonal brace underwing fittings; and corrective actions, if necessary. This AD also requires eventual replacement of the aft 10 taperlock bolts with new bolts, which constitutes terminating action for the repetitive inspections. This amendment is prompted by reports of damaged, broken, and corroded taperlock bolts of the diagonal brace underwing fittings on the outboard strut due to stress corrosion cracking. The actions specified by this AD are intended to prevent loss of the underwing fitting load path due to missing, damaged, or broken taperlock bolts, which could result in separation of the engine and strut from the airplane.