# AD 91-21-11: Slat Drive Mechanism Brackets - Type: Airworthiness directive - Status: Historical - Products: McDonnell Douglas DC-9-81, DC-9-82, DC-9-83, DC-9-87 and MD-88 - Effective: October 30, 1991 - Superseded by: [AD 99-21-06](https://openairdocs.org/ad/99-21-06) - Product type: Aircraft, Large airplane - Amendment: 39-8058 - Docket: 91-NM-202-AD - Registered aircraft: 100 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/EA68B46B77EA94D186256A1C0076168D.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/91-21-11 ## The airworthiness directive 91-21-11 MCDONNELL DOUGLAS: Amendment 39-8058. Docket No. 91-NM-202-AD. Applicability: Model DC-9-81, -82, -83, and -87 series airplanes (MD-81, -82, -83, and -87); and Model MD-88 airplanes; certificated in any category. Compliance: Required as indicated, unless previously accomplished within the last 45 days. To prevent inadvertent retraction of the slats during flight, accomplish the following: (a) Prior to the accumulation of 10,000 total landings or within 30 days after the effective date of this AD, whichever occurs later, perform a visual or eddy current inspection to detect cracks of the slat drive mechanism brackets, part numbers 5938886-(any configuration) and 5938887-(any configuration), in accordance with the instructions in McDonnell Douglas MD-80 Alert Service Bulletin A27-322, dated August 22, 1991 (hereinafter referred to as "A27-322"). (b) If no crack is found as a result of the inspections required by paragraph (a) of this AD, repeat the inspections at the following intervals: (1) If the immediately preceding inspection was accomplished using visual means, conduct the next inspection within 1,000 landings. (2) If the immediately preceding inspection was accomplished using eddy current means, conduct the next inspection within 3,000 landings. (c) If a crack is found as a result of the inspections required by paragraph (a) or (b) this AD, prior to further flight, remove and replace the slat drive mechanism with a new part, part numbers 5938887-(any configuration) and 5938886-(any configuration), in accordance with A27-322. (d) After replacement is accomplished in accordance with the provisions of paragraph (c) of this AD, prior to the accumulation of 10,000 additional landings, conduct inspections in accordance with A27-322, and reinspect or replace in accordance with the provisions of paragraph (b) and (c) of this AD. (e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 tooperate airplanes to a base in order to comply with the inspection requirements of this AD. (f) 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, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who may concur or comment and then send it to the Manager, Los Angeles ACO. (g) The inspection and replacement requirements shall be done in accordance with McDonnell Douglas MD-80 Alert Service Bulletin A27-322, dated August 22, 1991. 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 McDonnell Douglas Corporation, Technical Publications-Technical Administrative Support, C1-L5B, 3855 Lakewood Boulevard, Long Beach, California 90846. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. This amendment (39-8058, AD 91-21-11) becomes effective on October 30, 1991. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A6WE](https://openairdocs.org/tcds/A6WE): The Boeing Company; names 5 of 25 models: MD-88, DC-9-81 (MD-81), DC-9-83 (MD-83), DC-9-87 (MD-87), DC-9-82 (MD-82) ## 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: 100 (100 by airframe model, 0 by engine model) - Makers: Mcdonnell Douglas 99, Douglas 1 Models with the most aircraft: - [Mcdonnell Douglas DC-9-83(MD-83)](https://openairdocs.org/model/mcdonnell-douglas-dc-9-83-md-83): 49 aircraft (airframe model) - [Mcdonnell Douglas DC-9-82(MD-82)](https://openairdocs.org/model/mcdonnell-douglas-dc-9-82-md-82): 22 aircraft (airframe model) - [Mcdonnell Douglas MD-88](https://openairdocs.org/model/mcdonnell-douglas-md-88): 14 aircraft (airframe model) - [Mcdonnell Douglas DC-9-87](https://openairdocs.org/model/mcdonnell-douglas-dc-9-87): 13 aircraft (airframe model) - [Douglas DC-9-83](https://openairdocs.org/model/douglas-dc-9-83): 1 aircraft (airframe model) - [Mcdonnell Douglas DC-9-87 (MD-87)](https://openairdocs.org/model/mcdonnell-douglas-dc-9-87-md-87): 1 aircraft (airframe model) All 7 models: https://openairdocs.org/ad/91-21-11/models.md Every aircraft: https://openairdocs.org/ad/91-21-11/aircraft.md ## Related documents - [AD 99-21-06](https://openairdocs.org/ad/99-21-06): Slat Drive Mechanism Assembly Brackets ยท Boeing DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83) and 2 more. Effective Nov 12, 1999. Supersedes this AD 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.