# AD 91-25-06: Thrust Reverser Auxiliary Track - Type: Airworthiness directive - Status: Current - Products: Boeing 737-300 Series, 737-400 Series and 737-500 Series - Effective: December 18, 1991 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-8106 - Docket: 91-NM-230-AD - Registered aircraft: 42 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/7034DADF4EC81EB7862569610072E10F.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/91-25-06 ## The airworthiness directive 91-25-06 BOEING: Amendment 39-8106. Docket No. 91-NM-230-AD. Applicability: Model 737-300, 737-400, and 737-500 series airplanes; as listed in Boeing Service Bulletin 737-78-1048, Revision 1, dated February 22, 1990; certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent structural damage to the airplane as a result of separation of the thrust reverser translating sleeve due to worn auxiliary track liners and slider fittings, accomplish the following: (a) Within 14 days after the effective date of this AD, inspect each lower thrust reverser auxiliary track, liner, and slider fittings to determine the ability of the slider to remain in the track, in accordance with the Accomplishment Instructions of Boeing Alert Service Letter Number 737-SL-78-22 (Telex M-7272-91-7201), dated November 6, 1991. Repeat this inspection thereafter at intervals not to exceed 1,500 hours, 750 hours, or 250 hours time-in-service,as determined by percent engagement of the lower auxiliary track slider, and as specified in the service letter. As a result of this inspection, accomplish the following, as applicable: (1) If the slider can be pulled out of the track in both the deployed and stowed position, prior to further flight, replace the track liner and, if applicable, replace or repair the slider fittings and the auxiliary track, in accordance with Boeing Service Bulletin 737-78-1048, Revision 1, dated February 22, 1990. (2) If the slider can be pulled out of the track in only the deployed position, prior to further flight, reinsert the slider in the track and deactivate the thrust reverser in accordance with Chapter 78 of Boeing Document D6-32545, "Boeing 737 Dispatch Deviations Procedures Guide," dated June 14, 1991. (3) If the slider cannot be pulled out of the track in either the deployed or stowed positions, record the percent engagement of the sliders in the lower auxiliary tracks, and repeat the inspection at the specified intervals in accordance with the accomplishment instructions of Boeing Alert Service Letter 737-SL-78-22 (Telex M-7272-91-7201), dated November 6, 1991. (b) Accomplishment of the replacement of the auxiliary track liner and, if applicable, rework or replacement of the slider fittings and the auxiliary tracks, in accordance with Boeing Service Bulletin 737-78-1048, Revision 1, dated February 22, 1990, constitutes terminating action for the inspection requirements of paragraph (a) of this AD. (c) An alternative method 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. The request shall be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, 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. (e) The inspections, repairs, and modifications shall be done in accordance with Boeing Alert Service Letter 737-SL-78-22 (sent to operators as Telex M-7272-91-7201), dated November 6, 1991; and Boeing Service Bulletin 737-78-1048, Revision 1, dated February 22, 1990, which contains the following list of effective pages: Page Number Revision Level Date 1 - 4 1 February 22, 1990 5 - 44 (original) November 22, 1989 The deactivation procedures shall be done in accordance with Chapter 78 of Boeing Document D6-32545, "Boeing 737 Dispatch Deviations Procedures Guide," dated June 14, 1991, which includes the following list of effective pages: PAGE NUMBER DATE 2.78-1.0, June 14, 1991 2.78-1.2, 2.78-2.0, 2.78-3.0, 2.78-4.0, 2.78-6.0, 2.78-7.0 2.78-1.1 May 31, 1990 2.78-5.0 August 17, 1989 This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington, or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, D.C. (f) This amendment (39-8106, AD 91-25-06) becomes effective on December 18, 1991. ## 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 3 of 17 models: 737-500 Series, 737-300 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: 42 (42 by airframe model, 0 by engine model) - Makers: Boeing 42 Models with the most aircraft: - [Boeing 737-400](https://openairdocs.org/model/boeing-737-400): 8 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 737-300](https://openairdocs.org/model/boeing-737-300): 4 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 737-524](https://openairdocs.org/model/boeing-737-524): 3 aircraft (airframe model) - [Boeing 737-505](https://openairdocs.org/model/boeing-737-505): 2 aircraft (airframe model) - [Boeing 737-301](https://openairdocs.org/model/boeing-737-301): 1 aircraft (airframe model) - [Boeing 737-401](https://openairdocs.org/model/boeing-737-401): 1 aircraft (airframe model) - [Boeing 737-306](https://openairdocs.org/model/boeing-737-306): 1 aircraft (airframe model) - [Boeing 737-319](https://openairdocs.org/model/boeing-737-319): 1 aircraft (airframe model) - [Boeing 737-330](https://openairdocs.org/model/boeing-737-330): 1 aircraft (airframe model) - [Boeing 737-405](https://openairdocs.org/model/boeing-737-405): 1 aircraft (airframe model) - [Boeing 737-528](https://openairdocs.org/model/boeing-737-528): 1 aircraft (airframe model) All 15 models: https://openairdocs.org/ad/91-25-06/models.md Every aircraft: https://openairdocs.org/ad/91-25-06/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.