Airworthiness Directives; The Boeing Company Airplanes

We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 757-200, -200PF, and -200CB series airplanes powered by Rolls-Royce engines. That AD currently requires repetitive inspections of the shim installation between the drag brace fitting vertical flange and bulkhead, and repair if necessary; for certain airplanes, an inspection for cracking of the four critical fastener holes in the horizontal flange, and repair if necessary; and, for airplanes without conclusive records of previous inspections, performing the existing actions. This new AD reduces the repetitive inspection interval; adds repetitive detailed inspections for cracking of the bulkhead, and repair if necessary; allows an extension of the repetitive intervals for certain airplanes by also doing repetitive ultrasonic inspections for cracking of the bulkhead, and repair if necessary; and provides an option for a high frequency eddy current inspection for cracking of the critical fastener holes, and repair if necessary. This action also adds a terminating action for certain repetitive inspections. This AD was prompted by reports of loose fasteners and cracks at the joint common to the aft torque bulkhead and strut-to-diagonal brace fitting, and one report of such damage occurring less than 3,000 flight cycles after the last inspection. We are issuing this AD to detect and correct cracks, loose and broken bolts, and shim migration in the joint between the aft torque bulkhead and the strut-to-diagonal brace fitting, which could result in damage to the strut and consequent separation of the strut and engine from the airplane.