Airworthiness Directives; Pratt & Whitney Canada Corp. Turbofan Engines

The FAA is superseding Airworthiness Directive (AD) 2004-04- 09, which applied to certain Pratt & Whitney Canada Corp. (P&WC) JT15D- 1, JT15D-1A, and JT15D-1B model turbofan engines. AD 2004-04-09 required a one-time borescope inspection (BSI) of the rear face of certain impellers for evidence of a machined groove or step, and repair or replacement of the impeller if a groove or step is found. Since the FAA issued AD 2004-04-09, the FAA was notified of an uncontained failure of an impeller installed on a P&WC JT15D-1A engine during takeoff and subsequent investigation by the manufacturer that discovered machining marks on the impeller. This AD was prompted by three prior reports of uncontained failure of the impeller, and one additional recent report of an in-service uncontained failure event. This AD requires borescope fluorescent penetrant inspection (FPI) of the rear face of certain impellers for evidence of machining witness lines and, depending on the results of the inspection, replacement of the impeller, as specified in a Transport Canada AD, which is incorporated by reference. The FAA is issuing this AD to address the unsafe condition on these products.