# Proposed AD 99-NM-350-AD: Boeing Model 747-400, 747-400F, 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F Series Airplanes

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2001-11-08
- Action: Notice of proposed rulemaking (NPRM).
- Published: June 15, 2000, 65 FR 37494
- Comments due: July 31, 2000
- Became: [AD 2001-11-08](https://openairdocs.org/ad/2001-11-08)
- Docket: 99-NM-350-AD
- FR document: 00-15189
- Official PDF: https://openairdocs.org/files/sha256/4c/45/4c456a36301abd5beab4f74f39f17621ecf44df3b8bdcca2eb6a25f471d6d11f (from https://www.govinfo.gov/content/pkg/FR-2000-06-15/pdf/00-15189.pdf)
- Federal Register: https://www.federalregister.gov/documents/2000/06/15/00-15189/airworthiness-directives-boeing-model-747-400-747-400f-757-200-757-200cb-757-200pf-767-200-767-300
- Page: https://openairdocs.org/proposed/99-NM-350-AD

## Summary

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747- 400, 757-200, 767-200, and 767-300 series airplanes. That AD currently requires repetitive checks to detect certain failures in the warning electronic unit (WEU) or modular avionic warning electronic assembly (MAWEA); repetitive tests to detect any failure of tactile, visual, or aural alerts generated by the WEU or MAWEA; and corrective action, if necessary. This action would make these requirements applicable to other airplanes on which the defective power supplies may be installed, eliminate the repetitive tests for certain airplanes, and increase the interval for the repetitive tests for certain other airplanes. This action also would require replacement of the existing power supplies in the WEU or MAWEA with modified, new, or serviceable power supplies. The actions specified by the proposed AD are intended to prevent failure of the WEU or MAWEA power supplies, which could result in loss of visual, aural, and tactile alerts to the flightcrew. Absence of such alerts could result in the flightcrew being unaware that an immediate or appropriate action should be taken in the event of an unsafe condition.

## Notices in this docket

- Jun 15, 2000: Notice of proposed rulemaking (NPRM). (first notice), FR document 00-15189, comments due Jul 31, 2000 (https://www.federalregister.gov/documents/2000/06/15/00-15189/airworthiness-directives-boeing-model-747-400-747-400f-757-200-757-200cb-757-200pf-767-200-767-300)

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