# Airworthiness Directives; Pratt & Whitney (PW) PW4164, PW4168, and PW4168A Turbofan Engines
> **Rule** · Final rule. · Published 2008-01-03 · Effective 2008-02-07 · 73 FR 394
## Document
- **Document number:** E7-25505
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 73 FR 394
- **Publication date:** 2008-01-03
- **Effective date:** 2008-02-07
- **FAA docket:** Docket No. FAA-2007-27230
## Abstract

The FAA is adopting a new airworthiness directive (AD) for PW PW4164, PW4168, and PW4168A turbofan engines with certain low pressure turbine (LPT) stage 4 disks, part number (P/N) 51N404, installed. This AD requires removing certain LPT stage 4 disks, listed by serial number at the next piece-part exposure or within 7,500 cycles-since-new (CSN). This AD results from a report of improperly manufactured LPT stage 4 disks. We are issuing this AD to prevent an uncontained engine failure due to low-cycle fatigue (LCF), which could result in damage to the airplane.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2008/01/03/E7-25505/airworthiness-directives-pratt-and-whitney-pw-pw4164-pw4168-and-pw4168a-turbofan-engines)
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