# AD 91-07-01: Electronic Flight Instrument System Symbol Generators - Type: Airworthiness directive - Status: Current - Products: Boeing 737-100 Series, 737-200 Series, 737-200C Series, 737-300 Series, 737-400 Series, 737-500 Series, 737-600 Series, 737-700 Series, 737-800 Series, 757-200 Series, 757-200CB Series, 757-200PF Series and 1 more - Effective: April 3, 1991 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-6945 - Docket: 91-NM-45-AD - Registered aircraft: 1,093 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1C32EA6B8794D1FE862569610072C7AC.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/91-07-01 ## The airworthiness directive 91-07-01 BOEING: Amendment 39-6945. Docket No. 91-NM-45-AD. Applicability: Model 737 series airplanes, line numbers 1975 through 1989; and Model 757 series airplanes, line numbers 338 through 343; equipped with an Electronic Flight Instrument System (EFIS) using symbol generators, part number S242T404-420; certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent blanking of either pilot's EFIS display and loss of one pilot's primary flight instruments, accomplish the following: A. Within 10 days after the effective date of this AD, inspect the EFIS symbol generators installed on the airplane and record the modification status. EFIS symbol generators which do not have Modification 3 implemented, must be removed and modified in accordance with Collins Service Bulletin EFIP-701E-34-03, dated February 1, 1991, prior to further flight. B. Any EFIS Symbol Generators with part number S242T404-420 which do nothave Modification 3 implemented, must be modified in accordance with Collins Service Bulletin EFIP-701E-34-03, dated February 1, 1991, before installation on an airplane. C. An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. NOTE: The request should be forwarded through an FAA Principal Avionics Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. 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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington. This amendment (39-6945, AD 91-07-01) becomes effective on April 3, 1991. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A16WE](https://openairdocs.org/tcds/A16WE): The Boeing Company; names 9 of 17 models: 737-500 Series, 737-100 Series, 737-200C Series, 737-800 Series, 737-300 Series, 737-200 Series, 737-700 Series, 737-400 Series… - [TCDS A2NM](https://openairdocs.org/tcds/A2NM): The Boeing Company; names 4 of 4 models: 757-200CB Series, 757-200PF Series, 757-300 Series, 757-200 Series ## 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: 1,093 (1,093 by airframe model, 0 by engine model) - Makers: Boeing 1,093 Models with the most aircraft: - [Boeing 737-823](https://openairdocs.org/model/boeing-737-823): 278 aircraft (airframe model) - [Boeing 737-800](https://openairdocs.org/model/boeing-737-800): 139 aircraft (airframe model) - [Boeing 737-824](https://openairdocs.org/model/boeing-737-824): 135 aircraft (airframe model) - [Boeing 737-832](https://openairdocs.org/model/boeing-737-832): 73 aircraft (airframe model) - [Boeing 757-232](https://openairdocs.org/model/boeing-757-232): 63 aircraft (airframe model) - [Boeing 737-890](https://openairdocs.org/model/boeing-737-890): 60 aircraft (airframe model) - [Boeing 757-224](https://openairdocs.org/model/boeing-757-224): 40 aircraft (airframe model) - [Boeing 757-222](https://openairdocs.org/model/boeing-757-222): 38 aircraft (airframe model) - [Boeing 737-724](https://openairdocs.org/model/boeing-737-724): 36 aircraft (airframe model) - [Boeing 757-223](https://openairdocs.org/model/boeing-757-223): 23 aircraft (airframe model) - [Boeing 757-236](https://openairdocs.org/model/boeing-757-236): 20 aircraft (airframe model) - [Boeing 757-251](https://openairdocs.org/model/boeing-757-251): 18 aircraft (airframe model) - [Boeing 757-351](https://openairdocs.org/model/boeing-757-351): 16 aircraft (airframe model) - [Boeing 737-790](https://openairdocs.org/model/boeing-737-790): 14 aircraft (airframe model) - [Boeing 737-752](https://openairdocs.org/model/boeing-737-752): 13 aircraft (airframe model) - [Boeing 757-231](https://openairdocs.org/model/boeing-757-231): 13 aircraft (airframe model) - [Boeing 757-324](https://openairdocs.org/model/boeing-757-324): 9 aircraft (airframe model) - [Boeing 737-400](https://openairdocs.org/model/boeing-737-400): 8 aircraft (airframe model) - [Boeing 737-852](https://openairdocs.org/model/boeing-737-852): 7 aircraft (airframe model) - [Boeing 757-200 SERIES](https://openairdocs.org/model/boeing-757-200-series): 7 aircraft (airframe model) All 56 models: https://openairdocs.org/ad/91-07-01/models.md Every aircraft: https://openairdocs.org/ad/91-07-01/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.