# AD 90-01-03: Attitude and Heading Reference System - Type: Airworthiness directive - Status: Current - Products: Bombardier ATR42-300, DHC-8-101, DHC-8-102, DHC-8-103, DHC-8-106, DHC-8-201, DHC-8-202, DHC-8-301, DHC-8-311, DHC-8-315, DHC-8-400, DHC-8-401 and 7 more - Effective: February 5, 1990 - Published: January 4, 1990 - Issued: December 19, 1989 - Superseded by: Nothing supersedes this AD - Product type: Appliance - Amendment: 39-6442 - Docket: 89-NM-98-AD - Registered aircraft: 393 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A01032A6E28CFBFD86256A45004FC009.0001 - DRS record last changed: January 21, 2026 - Page: https://openairdocs.org/ad/90-01-03 ## The airworthiness directive 90-01-03 HONEYWELL, INC., SPERRY COMMERCIAL FLIGHT SYSTEMS GROUP, BUSINESS AND COMMUTER AVIATION SYSTEMS DIVISION (Sperry Corporation): Amendment 39-6442. Docket No. 89-NM-98-AD. Applicability: Honeywell AH-600 Attitude and Heading Reference System (AHRS) Strapdown Attitude and Heading Reference Unit (AHRU), part numbers 7003360-931, -932, -933, -934, -935, and -936, with serial numbers 0100 through 0277. Compliance: Required as indicated, unless previously accomplished. NOTE: These systems are known to be installed in, but not limited to, de Havilland Model DHC-8, British Aerospace Model BAe 125-800, Cessna Model 650, and Aerospatiale Model ATR42-300 series airplanes. To eliminate the possibility of the primary attitude and heading displays on both sides of the instrument panel failing simultaneously, accomplish the following: A. Within 10 days after January 9, 1989 (the effective date of Amendment 39-6093), inspect airplanes with Honeywell AH-600 AHRSinstalled to determine the part number, serial number, and Mod Level of the strapdown AHRU installed in the pilot's (Number 1) AHRS. Prior to further flight after inspection, remove all AHRU part numbers 7003360-931, -932, -933, -934, -935, and -936 with serial numbers 0100 through 0277, without Mod Level "F", from service in the pilot's (Number 1) AHRS. Install the same part number with Mod Level "F" incorporated, or modify the AHRU in accordance with Honeywell Inc., Service Bulletin 7003360-34-32, dated August 2, 1988. NOTE: Serial numbers of the strapdown AHRU are eight digit numbers; the first four are date code and the last four are the individual unit identifier. Serial numbers referred to in this AD are the last four numbers of the serial number. B. Within 60 calendar days after the effective date of this amendment, inspect airplanes with Honeywell AH-600 AHRS installed to determine the part number, serial number, and Mod Level of the strapdown AHRU installed in copilot's (Number 2) AHRS and the auxiliary (Number 3) AHRS. Within 45 days after the inspection, remove all AHRU part numbers 7003360-931, -932, -933, -934, -935, and -936, with serial numbers 0100 through 0277, without Mod Level "F", from service in the copilot's (Number 2) AHRS and the auxiliary (Number 3) AHRS. Install the same part number with Mod Level "F" incorporated, or modify the AHRU in accordance with Honeywell, Inc., Service Bulletin 7003360-34-32, dated August 2, 1988. C. 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, FAA, Northwest Mountain Region. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment, and then send it to the Manager, Los Angeles Aircraft Certification Office. 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. All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Honeywell Inc., Sperry Commercial Flight Systems Group, Business and Commuter Aviation Systems Division, 5353 West Bell Road, Glendale, Arizona 85308. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California. This AD supersedes AD 88-26-05, Amendment 39-6093. This amendment (39-6442, AD 90-01-03) becomes effective on February 5, 1990. ## Affected data sheets (4) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A13NM](https://openairdocs.org/tcds/A13NM): De Havilland Aircraft of Canada Limited; names 12 of 16 models: DHC-8-101, DHC-8-102, DHC-8-103, DHC-8-106, DHC-8-201, DHC-8-202, DHC-8-301, DHC-8-311… - [TCDS A3EU](https://openairdocs.org/tcds/A3EU): Textron Aviation Inc.; names 2 of 50 models: BAe.125 Series 800A (U-125), BAe.125 Series 800B - [TCDS A53EU](https://openairdocs.org/tcds/A53EU): ATR – GIE Avions de Transport Régional; names 1 of 11 models: ATR42-300 - [TCDS A9NM](https://openairdocs.org/tcds/A9NM): Textron Aviation Inc.; names 1 of 1 models: 650 ## 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: 393 (393 by airframe model, 0 by engine model) - Makers: Cessna 201, British Aerospace 66, Bombardier 57, Dehavilland 28, Aerospatiale/Aeritalia 12, Corporate Jets 8, Raytheon Corporate Jets 8, Boeing Of Canada/Dehav Div 6, Boeing 3, Raytheon 2 Models with the most aircraft: - [Cessna 650](https://openairdocs.org/model/cessna-650): 201 aircraft (airframe model) - [British Aerospace BAE 125 SERIES 800A](https://openairdocs.org/model/british-aerospace-bae-125-series-800a): 61 aircraft (airframe model) - [Bombardier DHC-8-402](https://openairdocs.org/model/bombardier-dhc-8-402): 26 aircraft (airframe model) - [Dehavilland DHC-8-202](https://openairdocs.org/model/dehavilland-dhc-8-202): 17 aircraft (airframe model) - [Bombardier DHC-8-315](https://openairdocs.org/model/bombardier-dhc-8-315): 15 aircraft (airframe model) - [Bombardier DHC-8-202](https://openairdocs.org/model/bombardier-dhc-8-202): 14 aircraft (airframe model) - [Aerospatiale/Aeritalia ATR 42-300](https://openairdocs.org/model/aerospatiale-aeritalia-atr-42-300): 12 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) - [British Aerospace BAE 125-800A](https://openairdocs.org/model/british-aerospace-bae-125-800a): 5 aircraft (airframe model) - [Dehavilland DHC-8-106](https://openairdocs.org/model/dehavilland-dhc-8-106): 4 aircraft (airframe model) - [Boeing DHC-8-102](https://openairdocs.org/model/boeing-dhc-8-102): 3 aircraft (airframe model) - [Boeing Of Canada/Dehav Div DHC-8-311](https://openairdocs.org/model/boeing-of-canada-dehav-div-dhc-8-311): 3 aircraft (airframe model) - [Boeing Of Canada/Dehav Div DHC-8-106](https://openairdocs.org/model/boeing-of-canada-dehav-div-dhc-8-106): 2 aircraft (airframe model) - [Bombardier DHC-8-201](https://openairdocs.org/model/bombardier-dhc-8-201): 2 aircraft (airframe model) - [Dehavilland DHC-8-201](https://openairdocs.org/model/dehavilland-dhc-8-201): 2 aircraft (airframe model) - [Dehavilland DHC-8-103](https://openairdocs.org/model/dehavilland-dhc-8-103): 2 aircraft (airframe model) - [Dehavilland DHC-8-315](https://openairdocs.org/model/dehavilland-dhc-8-315): 2 aircraft (airframe model) - [Raytheon BAE 125-800A](https://openairdocs.org/model/raytheon-bae-125-800a): 2 aircraft (airframe model) - [Boeing Of Canada/Dehav Div DHC-8-102](https://openairdocs.org/model/boeing-of-canada-dehav-div-dhc-8-102): 1 aircraft (airframe model) All 24 models: https://openairdocs.org/ad/90-01-03/models.md Every aircraft: https://openairdocs.org/ad/90-01-03/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.