Airworthiness Directives; Boeing Model 757 Airplanes

We are adopting a new airworthiness directive (AD) for all Boeing Model 757 airplanes. This AD requires repetitive inspections of the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system for cracks at certain outboard stations of the left and right wings, and corrective action if necessary. This AD also provides optional terminating action for the repetitive inspections. This AD results from reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing TAI system. In one incident, the anchor tab and bulkhead seal assembly had separated because of the cracks. We are issuing this AD to prevent failure of the anchor tab of the bulkhead seal assembly, which in icing conditions could result in insufficient airflow to the wing TAI system, subsequent ice on the wings, and consequent reduced controllability of the airplane.