Airworthiness Directives; Boeing Model 757-200, 757-200CB, and 757-200PF Series Airplanes Equipped With Rolls Royce Model RB211 Engines

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Boeing Model 757-200, 757-200CB, and 757- 200PF series airplanes. The existing AD currently requires repetitive detailed inspections to detect horizontal or vertical movement of the shims at the joint of the mid-bulkhead and the upper link fittings, and corrective action if necessary; or certain alternative actions that terminate the requirement for the repetitive inspections. This new AD continues to require those repetitive inspections; decreases the allowable tolerance for shim migration; and adds new repetitive detailed inspections for cracking of the entire mid-bulkhead, and repair if necessary. This new AD also adds additional airplanes to the applicability of the AD. This AD is prompted by reports of cracks in the mid-bulkhead lower vertical flange common to the lower chord and stiffener and reports of cracking at other locations on the mid- bulkhead. We are issuing this AD to detect and correct migration of shims at the joint of the mid-bulkhead and the upper link fittings and cracking of the mid-bulkhead, which could result in cracking of the strut and consequent loss of the strut and engine.