Airworthiness Directives; Pratt & Whitney Division Turbofan Engines

The FAA is adopting a new airworthiness directive (AD) for certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines. This AD was prompted by several reports of low-pressure turbine (LPT) 4th- stage vane cluster assemblies leaning back and notching into the rotating LPT 4th-stage blades, causing some blades to fracture and release. This AD requires initial and repetitive replacements of the LPT 4th-stage air sealing ring segment assemblies with parts eligible for installation. This AD also requires initial and repetitive dimensional inspections of the LPT case for bulging and, depending on the results of the dimensional inspections, repair or replacement of the LPT case. The FAA is issuing this AD to address the unsafe condition on these products.