# Proposed AD FAA-2012-0071: Pratt & Whitney Canada, Auxiliary Power Units

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2012-18-14
- Products: Pratt & Whitney Canada
- Product type: Appliance
- Action: Notice of proposed rulemaking (NPRM).
- Published: February 27, 2012, 77 FR 11421
- Comments due: April 27, 2012
- Became: [AD 2012-18-14](https://openairdocs.org/ad/2012-18-14)
- Docket: FAA-2012-0071 (https://www.regulations.gov/docket/FAA-2012-0071, where comments are filed)
- Project: 2012-NE-05-AD
- FR document: 2012-4448
- Official PDF: https://openairdocs.org/files/sha256/6e/bf/6ebf3723b2ba924044141f038f4819ad63059abd06bb26a930f48fc28677d8e3 (from https://www.govinfo.gov/content/pkg/FR-2012-02-27/pdf/2012-4448.pdf)
- Federal Register: https://www.federalregister.gov/documents/2012/02/27/2012-4448/airworthiness-directives-pratt-and-whitney-canada-auxiliary-power-units
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/68BF36375B73A60A862579B1004D9E47.0001
- Page: https://openairdocs.org/proposed/FAA-2012-0071

## Summary

We propose to adopt a new airworthiness directive (AD) for certain serial numbers of Pratt & Whitney Canada (P&WC) PW901A auxiliary power units (APUs) approved under Technical Standard Order TSO-C77A and installed on, but not limited to, Boeing 747-400 series airplanes. This proposed AD was prompted by several events of high- pressure turbine blade fracture leading to separation of the rear gas generator case and release of high energy debris. This proposed AD would require modifications of the rear gas generator case, exhaust duct support, and turbine exhaust duct flanges. We are proposing this AD to prevent separation of the rear gas generator case and release of high energy debris, which could result in injury and damage to the airplane.

## Notices in this docket

- Feb 27, 2012: Notice of proposed rulemaking (NPRM). (first notice), FR document 2012-4448, comments due Apr 27, 2012 (https://www.federalregister.gov/documents/2012/02/27/2012-4448/airworthiness-directives-pratt-and-whitney-canada-auxiliary-power-units)

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