# Proposed AD 2000-NE-25-AD: Pratt & Whitney PW4000 Series Turbofan Engines

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2001-20-02
- Action: Notice of proposed rulemaking (NPRM).
- Published: December 27, 2000, 65 FR 81780
- Comments due: February 26, 2001
- Became: [AD 2001-20-02](https://openairdocs.org/ad/2001-20-02)
- Docket: 2000-NE-25-AD
- FR document: 00-32879
- Official PDF: https://openairdocs.org/files/sha256/51/70/51709fa8d31998f68c9b9e1fa73ede1aa79f5aaaba910c045637d5f8e1300af2 (from https://www.govinfo.gov/content/pkg/FR-2000-12-27/pdf/00-32879.pdf)
- Federal Register: https://www.federalregister.gov/documents/2000/12/27/00-32879/airworthiness-directives-pratt-and-whitney-pw4000-series-turbofan-engines
- Page: https://openairdocs.org/proposed/2000-NE-25-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) PW4000 series turbofan engines with 2nd stage high pressure turbine (HPT) air seal assembly part number (P/N) 50L976 or P/N 50L960 installed. This proposal would require operators to recalculate 2nd stage HPT air seal assembly cycles-in-service, based on flight hour-to-cycle ratio usage. This proposal would also require upon recalculation, initial and repetitive on-wing borescope inspections of 2nd stage HPT air seal assemblies for cracks based on the newly calculated service life. This proposal would also require the removal from service of any cracked seal assemblies, and the removal of seal assemblies at or before newly calculated service life limits. This proposal is prompted by reports that thirteen 2nd stage HPT air seal assemblies have been found cracked in the rim area. The actions specified by the proposed AD are intended to prevent 2nd stage HPT air seal assembly fracture that could result in an uncontained engine failure.

## Notices in this docket

- Dec 27, 2000: Notice of proposed rulemaking (NPRM). (first notice), FR document 00-32879, comments due Feb 26, 2001 (https://www.federalregister.gov/documents/2000/12/27/00-32879/airworthiness-directives-pratt-and-whitney-pw4000-series-turbofan-engines)

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