# AD 91-03-08: Fluorescent Lighting Systems - Type: Airworthiness directive - Status: Current - Products: Learjet 31, 35, 35A (C-21A), 36, 36A, 55, 55B and 55C - Effective: February 12, 1991 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small/large airplane - Amendment: 39-6876 - Docket: 90-NM-285-AD - Registered aircraft: 293 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/2D9A1D2D09835A0B862569880075FF8F.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/91-03-08 ## The airworthiness directive 91-03-08 LEARJET (FORMERLY GATES LEARJET): Amendment 39-6876. Docket No. 90-NM-285-AD. Applicability: Model 31 series airplanes, Serial Numbers (S/N) 001 through 023; Model 35/35A series airplanes, S/N 001 through 661; Model 36/36A series airplanes, S/N 001 through 059, 062, and 063; and Model 55/55B/55C series airplanes, S/N 001 through 144; equipped with Aerospace Lighting Corporation (ALC) inverters, Part Number (P/N) 18.95(); or Instrument and Flight Research (IFR) inverters, P/N 25-415-3-0L or 250001-240G; or Precision Winding, Incorporated inverters, P/N 6900092 or 6900054-54; certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent electromagnetic interference, and smoke and/or fire in the cabin, accomplish the following: A. Within 25 hours time-in-service after the effective date of this AD, deactivate the cabinet and overhead fluorescent lighting systems, and fabricate and install placards on the deactivated circuit breakers in accordance with the accomplishment instructions specified in the following Learjet Alert Service Bulletins, all dated December 21, 1990: Model Service Bulletin 31 31-33-2A 35, 35A, 36, 36A 35/36-33-5A 55, 55B, 55C 55-33-3A NOTE: This AD applies only to airplanes with the following inverters: ALC inverters, Part Number (P/N) 18.95(); or IFR inverters, P/N 25-415-3-0L or 250001-240G; or Precision Winding, Incorporated inverters, P/N 6900092 or 6900054-54. Inverters having a different part number do not have to be deactivated. B. 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, Wichita Aircraft Certification Office (ACO), ACE-115W, FAA, Central Region, 1801 Airport Road, Room 100, Wichita, Kansas 67209. NOTE: The request should be submitted directly to the Manager, Wichita ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Manager, Wichita ACO. C. 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 Learjet Corporation, Customer Services, P.O. Box 7707, Wichita, Kansas 67277-7707. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or at the FAA, Central Region, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Wichita, Kansas. This amendment (39-6876, AD 91-03-08) becomes effective on February 12, 1991. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A10CE](https://openairdocs.org/tcds/A10CE): Learjet Inc.; names 8 of 29 models: 31, 35, 35A (C-21A), 36, 36A, 55, 55B, 55C ## 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: 293 (293 by airframe model, 0 by engine model) - Makers: Gates Learjet 199, Gates Lear Jet 50, Learjet 44 Models with the most aircraft: - [Gates Learjet 35A](https://openairdocs.org/model/gates-learjet-35a): 135 aircraft (airframe model) - [Gates Learjet 55](https://openairdocs.org/model/gates-learjet-55): 54 aircraft (airframe model) - [Learjet 35A](https://openairdocs.org/model/learjet-35a): 24 aircraft (airframe model) - [Gates Lear Jet 36A](https://openairdocs.org/model/gates-lear-jet-36a): 21 aircraft (airframe model) - [Gates Lear Jet 35](https://openairdocs.org/model/gates-lear-jet-35): 16 aircraft (airframe model) - [Learjet 31](https://openairdocs.org/model/learjet-31): 15 aircraft (airframe model) - [Gates Lear Jet 36](https://openairdocs.org/model/gates-lear-jet-36): 13 aircraft (airframe model) - [Gates Learjet 55C](https://openairdocs.org/model/gates-learjet-55c): 6 aircraft (airframe model) - [Learjet 55](https://openairdocs.org/model/learjet-55): 4 aircraft (airframe model) - [Gates Learjet 55B](https://openairdocs.org/model/gates-learjet-55b): 3 aircraft (airframe model) - [Learjet 35](https://openairdocs.org/model/learjet-35): 1 aircraft (airframe model) - [Gates Learjet 35A (C-21A)](https://openairdocs.org/model/gates-learjet-35a-c-21a): 1 aircraft (airframe model) All 13 models: https://openairdocs.org/ad/91-03-08/models.md Every aircraft: https://openairdocs.org/ad/91-03-08/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.