Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP Series Airplanes

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Boeing Model 747 series airplanes. The existing AD currently requires repetitive inspections and torque checks of the hanger fittings and strut forward bulkhead of the forward engine mount and adjacent support structure, and corrective actions if necessary. The existing AD also currently requires a terminating action for the repetitive inspections and checks. This new AD requires, among other actions, new repetitive inspections in the existing area and new areas. This new AD also provides for an optional inspection and no longer allows the existing fastener replacement to terminate repetitive inspections. This AD results from new reports of under-torqued or loose fasteners, a cracked bulkhead chord, and a fractured back-up angle after operators accomplished the terminating action required by the existing AD. We are issuing this AD to detect and correct loose fasteners and/or damaged or cracked hanger fittings, back-up angles, and bulkhead of the forward engine mount, which could lead to failure of the hanger fitting and bulkhead and consequent separation of the engine from the airplane.