Airworthiness Directives; Pratt & Whitney (PW) Turbofan Engines

We are adopting a new airworthiness directive (AD) for Pratt & Whitney (PW) PW2037, PW2037(M), and PW2040 turbofan engines with certain fan blades with a cutback leading edge, installed. This AD was prompted by reports from PW that fan blade leading edge erosion can result in a fan thrust deterioration mode (FTDM) condition, a condition that cannot be detected by the crew, and that reduces the engine's capability of producing required thrust. This AD requires initial and repetitive maintenance to the leading edge of cutback fan blades or applying performance decrements as specified in the Airplane Flight Manual. We are issuing this AD to correct undetectable fan thrust deterioration on these PW products.