# AD 91-03-06: Generator Control Unit - Type: Airworthiness directive - Status: Current - Products: Textron BAe.125 Series 800A, BAe.125 Series 800A (C-29A), BAe.125 Series 800A (U-125), BH.125 Series 400A, BH.125 Series 600A, DH.125 Series 1A, DH.125 Series 1A-522, DH.125 Series 1A/R-522, DH.125 Series 1A/S-522, DH.125 Series 3A, DH.125 Series 3A/R, DH.125 Series 3A/RA and 27 more - Effective: February 11, 1991 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-6868 - Docket: 90-NM-272-AD - Registered aircraft: 110 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/CA811CB16178741186256A09006934ED.0001 - DRS record last changed: January 21, 2026 - Page: https://openairdocs.org/ad/91-03-06 ## The airworthiness directive 91-03-06 BRITISH AEROSPACE: Amendment 39-6868. Docket No. 90-NM-272-AD. Applicability: All Model BAe 125-800A and HS 125-700A series airplanes, pre-Modification 253159; and all pre-Modification 253159 Model DH/HS/BH 125 series airplanes that have been retrofitted with Garrett TFE 731 engines; certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent the overheating of the battery and loss of the pilot's and co-pilot's primary and standby heading and attitude information displays, accomplish the following: A. Within 30 days after the effective date of this AD, perform a visual inspection of the Generator Control Unit (GCU) earth wire, in accordance with British Aerospace Service Bulletin 24-A278, dated July 26, 1990. 1. If no evidence of damage is found, prior to further flight, perform a continuity check of the earth wire between the starter/generator terminal stud "E" and connector pin "F" on the GCU, in accordance with paragraph 2.A.(6) of the Accomplishment Instructions of the service bulletin. If continuity exists, no further action is required. 2. If evidence of damage or lack of continuity is found or suspected, prior to further flight, replace the earth wire in accordance with the service bulletin. 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, Standardization Branch, ANM- 113, FAA, Transport Airplane Directorate. NOTE: The request should be submitted directly to the Manager, Standardization Branch, ANM-113, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Manager, Standardization Branch, ANM-113. 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 British Aerospace, PLC, Librarian for Service Bulletins, P.O. Box 17414, Dulles International Airport, Washington, D.C. 20041. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington. This amendment (39-6868, AD 91-03-06) becomes effective on February 11, 1991. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A3EU](https://openairdocs.org/tcds/A3EU): Textron Aviation Inc.; names 37 of 50 models: HS.125 Series 3B/RB, HS.125 Series 401B, HS.125 Series 600A, HS.125 Series 600B/2, HS.125 Series 403A(C), HS.125 Series 600B/1, HS.125 Series 700A, DH.125 Series 1A/R-522… ## 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: 110 (110 by airframe model, 0 by engine model) - Makers: British Aerospace 80, Hawker Siddeley 11, Corporate Jets 8, Raytheon Corporate Jets 8, Raytheon 3 Models with the most aircraft: - [British Aerospace BAE 125 SERIES 800A](https://openairdocs.org/model/british-aerospace-bae-125-series-800a): 61 aircraft (airframe model) - [British Aerospace HS 125-700A](https://openairdocs.org/model/british-aerospace-hs-125-700a): 14 aircraft (airframe model) - [Corporate Jets BAE 125-800A](https://openairdocs.org/model/corporate-jets-bae-125-800a): 8 aircraft (airframe model) - [Raytheon Corporate Jets BAE 125-800A](https://openairdocs.org/model/raytheon-corporate-jets-bae-125-800a): 8 aircraft (airframe model) - [Hawker Siddeley HS.125 SERIES 700A](https://openairdocs.org/model/hawker-siddeley-hs-125-series-700a): 7 aircraft (airframe model) - [British Aerospace BAE 125-800A](https://openairdocs.org/model/british-aerospace-bae-125-800a): 5 aircraft (airframe model) - [Hawker Siddeley BH.125-400A](https://openairdocs.org/model/hawker-siddeley-bh-125-400a): 2 aircraft (airframe model) - [Hawker Siddeley DH.125-3A/RA](https://openairdocs.org/model/hawker-siddeley-dh-125-3a-ra): 2 aircraft (airframe model) - [Raytheon BAE 125-800A](https://openairdocs.org/model/raytheon-bae-125-800a): 2 aircraft (airframe model) - [Raytheon HS 125-700A](https://openairdocs.org/model/raytheon-hs-125-700a): 1 aircraft (airframe model) All 11 models: https://openairdocs.org/ad/91-03-06/models.md Every aircraft: https://openairdocs.org/ad/91-03-06/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.