# AD 91-05-04: Engine Fire Extinguishing System

- Type: Airworthiness directive
- Status: Current
- Products: Boeing 747-400 Series
- Effective: March 25, 1991
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-6907
- Docket: 90-NM-153-AD
- Registered aircraft: 38 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/44703431AAAA730B8625696000724320.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/91-05-04

## The airworthiness directive

91-05-04 BOEING: Amendment 39-6907. Docket No. 90-NM-153-AD.

Applicability: Model 747-400 series airplanes, listed in Boeing Service Bulletin 747-26- 2138, Revision 1, dated March 1, 1990, and Boeing Service Bulletin 747-26-2141, Revision 1, dated July 12, 1990, certificated in any category.

Compliance: Required within the next 12 months after the effective date of this AD, unless previously accomplished.

To preclude cross connection of fire extinguishing wiring during maintenance, accomplish the following:

A. For airplanes identified in Boeing Service Bulletin 747-26-2138, Revision 1, dated March 1, 1990: Modify the engine fire extinguishing system in accordance with that service bulletin.

B. For airplanes identified in Boeing Service Bulletin 747-26-2141, Revision 1, dated July 12, 1990: Modify the fire control module in accordance with that service bulletin.

C. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO.

D. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington.

This amendment (39-6907, AD 91-05-04) becomes effective on March 25, 1991.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A20WE](https://openairdocs.org/tcds/A20WE): The Boeing Company; names 1 of 14 models: 747-400 Series

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 38 (38 by airframe model, 0 by engine model)
- Makers: Boeing 38

Models with the most aircraft:

- [Boeing 747-446](https://openairdocs.org/model/boeing-747-446): 10 aircraft (airframe model)
- [Boeing 747-422](https://openairdocs.org/model/boeing-747-422): 8 aircraft (airframe model)
- [Boeing 747-412](https://openairdocs.org/model/boeing-747-412): 5 aircraft (airframe model)
- [Boeing 747-409](https://openairdocs.org/model/boeing-747-409): 4 aircraft (airframe model)
- [Boeing 747-481](https://openairdocs.org/model/boeing-747-481): 3 aircraft (airframe model)
- [Boeing 747-443](https://openairdocs.org/model/boeing-747-443): 2 aircraft (airframe model)
- [Boeing 747-438](https://openairdocs.org/model/boeing-747-438): 2 aircraft (airframe model)
- [Boeing 747-428](https://openairdocs.org/model/boeing-747-428): 2 aircraft (airframe model)
- [Boeing 747-400](https://openairdocs.org/model/boeing-747-400): 1 aircraft (airframe model)
- [Boeing 747-451](https://openairdocs.org/model/boeing-747-451): 1 aircraft (airframe model)

All 10 models: https://openairdocs.org/ad/91-05-04/models.md
Every aircraft: https://openairdocs.org/ad/91-05-04/aircraft.md

Its text cites no advisory circulars or STCs.

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