# Proposed AD 99-NM-66-AD: Boeing Model 747-400 Series Airplanes Equipped With Pratt & Whitney PW4000 Series Engines

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2000-12-21
- Action: Notice of proposed rulemaking (NPRM).
- Published: December 28, 1999, 64 FR 72579
- Comments due: February 11, 2000
- Became: [AD 2000-12-21](https://openairdocs.org/ad/2000-12-21)
- Docket: 99-NM-66-AD
- FR document: 99-33569
- Official PDF: https://openairdocs.org/files/sha256/3d/25/3d251f9a4e8dd1421491eb1788582bd83943c2430fba2712e8a8909a40a801f1 (from https://www.govinfo.gov/content/pkg/FR-1999-12-28/pdf/99-33569.pdf)
- Federal Register: https://www.federalregister.gov/documents/1999/12/28/99-33569/airworthiness-directives-boeing-model-747-400-series-airplanes-equipped-with-pratt-and-whitney
- Page: https://openairdocs.org/proposed/99-NM-66-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-400 series airplanes. This proposal would require installation of a modification of the thrust reverser control and indication system and wiring on each engine; and repetitive functional tests of that installation to detect discrepancies, and repair, if necessary. This proposal is prompted by the results of a safety review, which revealed that in-flight deployment of a thrust reverser could result in a significant reduction in airplane controllability. The actions specified by the proposed AD are intended to ensure the integrity of the fail-safe features of the thrust reverser system by preventing possible failure modes, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane.

## Notices in this docket

- Dec 28, 1999: Notice of proposed rulemaking (NPRM). (first notice), FR document 99-33569, comments due Feb 11, 2000 (https://www.federalregister.gov/documents/1999/12/28/99-33569/airworthiness-directives-boeing-model-747-400-series-airplanes-equipped-with-pratt-and-whitney)

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