# AD 77-19-02: Cabin Door Locking Mechanism - Type: Airworthiness directive - Status: Current - Products: Learjet 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25 and 5 more - Effective: July 20, 1978 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-3265 - Registered aircraft: 72 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/60B3A81354E51DC586256E0C006D4B67.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/77-19-02 ## The airworthiness directive 77-19-02 GATES LEARJET: Amendment 39-3040 as amended by Amendment 39- 3265. Applies to all serial numbers of Models 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes certificated in all categories having a 36- inch wide (as opposed to a 24-inch wide) cabin door. COMPLIANCE: Required as indicated in accordance with Compliance Table I set forth in this AD, unless already accomplished. To assure proper locking of the cabin upper door when the inside handle is in the locked position and to prevent possible unwanted door openings that may occur if a pilot disregards the door warning system accomplish the following at the time intervals noted in Table I of this AD: TABLE I COMPLIANCE TIMES I N S P E C T I O N T I M E S Airplane Total Time In Service (Hours) Paragraph "A" Bolt Inspection & Replacement Paragraph "B" Locking Mechanism Inspection Initial Inspection/ Replacement Interval for Repetitive Inspections/ Replacement Initial Inspection Interval for Repetitive Inspections 0 - 2,999 Prior to or upon the accumulation of 3,075 hours' time in service Each 3,000 hours' time in service thereafter In accordance with asterisk (*) paragraph below or upon accumulation of 6,075 hours' time in service, whichever occurs first In accordance with asterisk (*) paragraph below or upon accumulation of each 6,000 hours' time in service after initial inspection 3,000 - 5,999 Within 75 hours' time in service after the effective date of this AD Each 3,000 hours' time in service thereafter In accordance with asterisk (*) paragraph below or upon accumulation of 6,075 hours' time in service, whichever occurs first In accordance with asterisk (*) paragraph below or upon accumulation of each 6,000 hours' time in service after initial inspection 6,000 - up Within 75 hours' time in service after the effective date of this AD Each 3,000 hours' time in servicethereafter Within 75 hours' time in service after the effective date of this AD In accordance with asterisk (*) paragraph below or upon accumulation of each 6,000 hours' time in service after initial inspection * The door locking mechanism inspection must be accomplished any time the bolt inspection required by Paragraph "A" of this AD reveals a cracked, bent, broken or worn bolt. A. Inspect and replace, at the time intervals noted in Table I above, the bolt or pin identified as (5) in Figure I of this AD in accordance with Gates Learjet Service Bulletin SB 23/24/25-280 dated July 15, 1977 or later approved revisions and as summarized below: 1. Remove the bolt, or if applicable, pin from the upper door rod control assembly and visually inspect it for cracks, breaks, bends, or wear. If any of the aforementioned defects are found accomplish the door locking mechanism inspection required by Paragraph "B" of this AD prior to the next flight; and 2. Replace the bolt orpin removed in Paragraph A.1. of this AD with a new Gates Learjet part number 2311490-8 bolt, or a new AN3-21 bolt modified in accordance with the above noted Service Bulletin, and secure using an AN960D10 Washer and either a new MS20365-1032 Nut or AN310-3 Nut and MS24665-132 Cotter Pin. B. Inspect, at the time intervals noted in Table I above, the cabin door locking mechanism in accordance with Gates Learjet Service Bulletin SB 23/24/25-280 dated July 15, 1977 or later approved revisions, and as summarized below: 1. Drill out rivets and remove cabin upper door inner panel. 2. Remove and inspect door locking mechanism for wear and defects in accordance with Learjet Service Manual Inspection Requirements. The maximum allowable diameter (measured in any direction) of the hole in which the (5) bolt is installed is .201 inches. Replace any excessively worn or defective parts prior to the next flight. 3. Reinstall door locking mechanism and using rivets, reinstall the inner panel. 4. Check door locking mechanism for free movement with no binding thru entire operating travel. Correct any binding prior to the next flight. 5. Energize door warning system and check its operation for proper functioning. C. Submit a written report on any cracked, broken, bent or worn (5) (See Figure I of this AD) bolts or pins discovered during inspections required by this AD to the FAA via a letter to FAA, Chief, Engineering and Manufacturing Branch (ACE-210), 601 E. 12th Street, Kansas City, Missouri 64106 or an FAA M or D report (FAA Form 8330-2). The report must include airplane model, serial number, airplane total time-in-service, bolt or pin total time-in-service and statements describing the condition of the bolt and the hole including dimensions of the hole determined in accordance with Paragraph B.2. of this AD. (Reporting approved by the Office of Management and Budget under OMB No. 04-R0174.) D. The actions made mandatory by Paragraphs A, B, and C of this AD are no longer required when Gates Learjet Door Modification Kit AMK 78-2 is installed. E. Airplanes may be flown in accordance with FAR 21.197 to a base where this AD can be accomplished. F. Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. Amendment 39-3040 became effective on September 26, 1977. This amendment 39-3265 becomes effective July 20, 1978. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A10CE](https://openairdocs.org/tcds/A10CE): Learjet Inc.; names 16 of 29 models: 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E… - [TCDS A5CE](https://openairdocs.org/tcds/A5CE): Learjet Inc.; names 1 of 1 models: 23 ## 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: 72 (72 by airframe model, 0 by engine model) - Makers: Gates Lear Jet 27, Learjet 25, Gates Learjet 20 Models with the most aircraft: - [Gates Learjet 25D](https://openairdocs.org/model/gates-learjet-25d): 20 aircraft (airframe model) - [Gates Lear Jet 25B](https://openairdocs.org/model/gates-lear-jet-25b): 12 aircraft (airframe model) - [Learjet 24](https://openairdocs.org/model/learjet-24): 7 aircraft (airframe model) - [Gates Lear Jet 24D](https://openairdocs.org/model/gates-lear-jet-24d): 7 aircraft (airframe model) - [Learjet 23](https://openairdocs.org/model/learjet-23): 6 aircraft (airframe model) - [Learjet 24D](https://openairdocs.org/model/learjet-24d): 4 aircraft (airframe model) - [Gates Lear Jet 24F](https://openairdocs.org/model/gates-lear-jet-24f): 4 aircraft (airframe model) - [Learjet 24B](https://openairdocs.org/model/learjet-24b): 3 aircraft (airframe model) - [Learjet 24A](https://openairdocs.org/model/learjet-24a): 2 aircraft (airframe model) - [Gates Lear Jet 24E](https://openairdocs.org/model/gates-lear-jet-24e): 2 aircraft (airframe model) - [Learjet 25](https://openairdocs.org/model/learjet-25): 2 aircraft (airframe model) - [Gates Lear Jet 25](https://openairdocs.org/model/gates-lear-jet-25): 1 aircraft (airframe model) - [Gates Lear Jet 25C](https://openairdocs.org/model/gates-lear-jet-25c): 1 aircraft (airframe model) - [Learjet 25D](https://openairdocs.org/model/learjet-25d): 1 aircraft (airframe model) All 14 models: https://openairdocs.org/ad/77-19-02/models.md Every aircraft: https://openairdocs.org/ad/77-19-02/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.