Airworthiness Directives; The Boeing Company Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model 757 airplanes. This AD was prompted by reports of precoolers that failed due to a wear-out condition, combined with latently failed overheat detection thermal switches. This AD requires an inspection for heat damage on the engine strut structure, repetitive tests of the thermal switch temperature and ground wires, replacement of the precooler on Model 757-300 airplanes, and applicable on-condition actions. The FAA is issuing this AD to address the unsafe condition on these products.