# Proposed AD 2001-NE-25-AD: Pratt & Whitney 4000 Series Turbofan Engines

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2002-09-01
- Products: Pratt & Whitney
- Product type: Engine
- Action: Notice of proposed rulemaking (NPRM).
- Published: November 23, 2001, 66 FR 58689
- Comments due: January 22, 2002
- Became: [AD 2002-09-01](https://openairdocs.org/ad/2002-09-01)
- Docket: 2001-NE-25-AD
- FR document: 01-29191
- Official PDF: https://openairdocs.org/files/sha256/aa/e8/aae80f05122d589faf40c0a71d514af997680712bcc5ceab66b914e6c30334d9 (from https://www.govinfo.gov/content/pkg/FR-2001-11-23/pdf/01-29191.pdf)
- Federal Register: https://www.federalregister.gov/documents/2001/11/23/01-29191/airworthiness-directives-pratt-and-whitney-4000-series-turbofan-engines
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/EEB2BF61D295219F86256B0D006FC4F8.0001
- Page: https://openairdocs.org/proposed/2001-NE-25-AD

## Summary

The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) PW4090, PW4090-3, PW4074D, PW4077D, PW4090D, and PW4098 turbofan engines with 15th stage high pressure compressor (HPC) disks having certain part numbers (P/N's). This proposal would require initial and repetitive borescope inspections of 15th stage HPC disks for cracks in the knife edges, eddy current inspections (ECI's) of blade loading slots if required, and removal of cracked disks. In addition, this proposal would require the removal from service of these P/N disks, at a new lower cyclic life limit. This proposal is prompted by two reports of 15th stage HPC disks with cracks in the outer rim front rail of the blade loading slots, and in the front forward and middle knife edges. The actions specified by the proposed AD are intended to prevent 15th stage HPC disk failures from cracks, which could result in an uncontained engine failure.

## Notices in this docket

- Nov 23, 2001: Notice of proposed rulemaking (NPRM). (first notice), FR document 01-29191, comments due Jan 22, 2002 (https://www.federalregister.gov/documents/2001/11/23/01-29191/airworthiness-directives-pratt-and-whitney-4000-series-turbofan-engines)

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.