# AD 90-06-04: APU Fire Detection System - Type: Airworthiness directive - Status: Current - Products: Boeing 737-100 Series, 737-200 Series, 737-200C Series, 737-300 Series, 737-400 Series, 737-500 Series, 737-600 Series, 737-700 Series and 737-800 Series - Effective: March 19, 1990 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-6522 - Docket: 90-NM-18-AD - Registered aircraft: 823 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/B5EA5B9D1F4EEC468625695E00720F48.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/90-06-04 ## The airworthiness directive 90-06-04 BOEING: Amendment 39-6522. Docket No. 90-NM-18-AD. Applicability: All Model 737 series airplanes, equipped with Walter Kidde APU fire detection systems that either have not yet had an initial "C" check performed or that have had an APU replaced since performing the last "C" check, certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent an undetected APU fire, accomplish the following: A. Within 3 days after the effective date of this AD, placard the APU as inoperative until the inspection required by paragraph B., below, has been accomplished. B. Within 5 days after installation of the placard required by paragraph A., above, inspect to determine whether a Walter Kidde APU fire detector is installed in the APU compartment. This inspection can be performed by viewing through the APU cooling air exhaust outlet (ref: Model 737 Maintenance Manual 49-11-00). The Walter Kidde element is protected by a perforated shield surrounding the length of the element. If the perforated shield is not seen, open the lower APU shroud and verify that the fire detector element installed is Boeing Part Number 10-61096-316/Walter Kidde part number 894481. NOTE: Boeing Model 737-300 and 737-400 series airplanes inspected in accordance with Boeing Telex M-7272-90-0735, dated January 31, 1990, comply with the inspection requirements of this AD. C. If configuration discrepancies are discovered while accomplishing the inspection required by paragraph B., above, within 5 days, remove and replace the detector with the appropriate Walter Kidde detector that has been approved for installation on the airplane. Upon completion of the inspection required by paragraph B. and this modification, if required, the placard required by paragraph A., above, may be removed. D. Within 10 days after the inspection required by paragraph B., above, if configuration discrepancies are discovered, submit areport of findings to the Manager, Seattle Manufacturing Inspection District Office, ANM-108S, FAA, Transport Airplane Directorate, 7300 Perimeter Road South, Seattle, Washington 98108. The report must include the airplane serial number. E. 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, FAA, Northwest Mountain Region. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment and then send it to the Manager, Seattle Aircraft Certification Office. F. 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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. This amendment (39-6522, AD 90-06-04) becomes effective on March 19, 1990. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A16WE](https://openairdocs.org/tcds/A16WE): The Boeing Company; names 9 of 17 models: 737-500 Series, 737-100 Series, 737-200C Series, 737-800 Series, 737-300 Series, 737-200 Series, 737-700 Series, 737-400 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: 823 (823 by airframe model, 0 by engine model) - Makers: Boeing 823 Models with the most aircraft: - [Boeing 737-823](https://openairdocs.org/model/boeing-737-823): 278 aircraft (airframe model) - [Boeing 737-800](https://openairdocs.org/model/boeing-737-800): 139 aircraft (airframe model) - [Boeing 737-824](https://openairdocs.org/model/boeing-737-824): 135 aircraft (airframe model) - [Boeing 737-832](https://openairdocs.org/model/boeing-737-832): 73 aircraft (airframe model) - [Boeing 737-890](https://openairdocs.org/model/boeing-737-890): 60 aircraft (airframe model) - [Boeing 737-724](https://openairdocs.org/model/boeing-737-724): 36 aircraft (airframe model) - [Boeing 737-790](https://openairdocs.org/model/boeing-737-790): 14 aircraft (airframe model) - [Boeing 737-752](https://openairdocs.org/model/boeing-737-752): 13 aircraft (airframe model) - [Boeing 737-400](https://openairdocs.org/model/boeing-737-400): 8 aircraft (airframe model) - [Boeing 737-852](https://openairdocs.org/model/boeing-737-852): 7 aircraft (airframe model) - [Boeing 737-500](https://openairdocs.org/model/boeing-737-500): 6 aircraft (airframe model) - [Boeing 737-436](https://openairdocs.org/model/boeing-737-436): 6 aircraft (airframe model) - [Boeing 737-700](https://openairdocs.org/model/boeing-737-700): 5 aircraft (airframe model) - [Boeing 737-300](https://openairdocs.org/model/boeing-737-300): 4 aircraft (airframe model) - [Boeing 737-883](https://openairdocs.org/model/boeing-737-883): 4 aircraft (airframe model) - [Boeing 737-205](https://openairdocs.org/model/boeing-737-205): 3 aircraft (airframe model) - [Boeing 737-490](https://openairdocs.org/model/boeing-737-490): 3 aircraft (airframe model) - [Boeing 737-484](https://openairdocs.org/model/boeing-737-484): 3 aircraft (airframe model) - [Boeing 737-732](https://openairdocs.org/model/boeing-737-732): 3 aircraft (airframe model) - [Boeing 737-524](https://openairdocs.org/model/boeing-737-524): 3 aircraft (airframe model) All 40 models: https://openairdocs.org/ad/90-06-04/models.md Every aircraft: https://openairdocs.org/ad/90-06-04/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.