Airworthiness Directives; Pratt & Whitney JT9D-7R4 Turbofan Engines

The FAA is superseding an existing airworthiness directive (AD) for Pratt & Whitney (PW) JT9D-7R4 turbofan engines. That AD currently requires inspection of the blade root thickness of 1st stage fan blades identified by part number (P/N) and serial number (SN) in the AD. This AD requires the same actions but corrects 12 P/Ns, adds 10 part SNs, and adds the definition of next fan blade exposure to the compliance section. This AD results from the discovery of inaccurate part quantity, part numbers, and serial numbers used in AD 2005-26-09. We are issuing this AD to prevent 1st stage fan blade fracture and uncontained engine failure, resulting in possible damage to the airplane.