Airworthiness Directives; Pratt & Whitney Division Engines – Proposed AD for HPC Drum Rotor Disk Assembly

The FAA is proposing a new Airworthiness Directive (AD) targeting specific Pratt & Whitney (PW) turbofan engine models—PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3—commonly used on wide-body commercial aircraft such as the Boeing 747 and 777. The directive was triggered by the identification of a quality escape in manufacturing: certain high-pressure compressor (HPC) drum rotor disk assemblies received incorrect shot peening, a surface treatment process critical to preventing metal fatigue and cracking. The proposed AD mandates a visual inspection of the affected HPC drum rotor disk assemblies to detect incorrect or insufficient shot peen coverage. If an inspection reveals non-conforming coverage, the assembly must be removed and replaced with a part that meets installation eligibility requirements. Additionally, the proposed rule requires proactive removal and replacement of specific HPC drum rotor disk assemblies before they reach defined life limits, regardless of visual inspection results. This is a precautionary measure to ensure structural integrity before fatigue failure could occur. The FAA's primary objective is to prevent potential in-flight engine failure or uncontained engine rotor burst resulting from fatigue cracks in improperly processed disk assemblies, which could pose serious risk to aircraft and passengers. The comment period is open for public and industry input before the AD is finalized.

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