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Safety Recommendation Details

Safety Recommendation A-79-099
Details
Synopsis: THE NATIONAL TRANSPORTATION SAFETY BOARD HAS COMPLETED ITS DETERMINATION OF PROBABLE CAUSE AND FINAL REPORT ON THE AMERICAN AIRLINES DC-10 ACCIDENT IN CHICAGO ON MAY 25, 1979. THE SAFETY BOARD'S ANALYSIS OF THE EVIDENCE, AND RECOMMENDATIONS SUBMITTED TO THE BOARD BY THE OTHER PARTIES WHO PARTICIPATED IN THE INVESTIGATION AND PUBLIC HEARING, HAVE IDENTIFIED SEVERAL AREAS WHICH WE BELIEVE REQUIRE THE FEDERAL AVIATION ADMINISTRATION'S EARLY ATTENTION.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: INSURE THAT THE DESIGN OF TRANSPORT CATEGORY AIRCRAFT PROVIDES POSITIVE PROTECTION AGAINST ASYMMETRY OF LIFT DEVICES DURING CRITICAL PHASES OF FLIGHT; OR, IF CERTIFICATION IS BASED UPON DEMONSTRATED CONTROLLABILITY OF THE AIRCRAFT UNDER CONDITION OF ASYMMETRY, INSURE THAT ASYMMETRIC WARNING SYSTEMS, STALL WARNING SYSTEMS, OR OTHER CRITICAL SYSTEMS NEEDED TO PROVIDE THE PILOT WITH INFORMATION ESSENTIAL TO SAFE FLIGHT ARE COMPLETELY REDUNDANT.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action
Mode: Aviation
Location: Chicago, IL, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA79AA017
Accident Reports: American Airlines, Inc., DC-10, N110AA
Report #: AAR-79-17
Accident Date: 5/25/1979
Issue Date: 12/21/1979
Date Closed: 12/20/1988
Addressee(s) and Addressee Status: FAA (Closed - Unacceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 12/20/1988
Response: The safety board has reviewed the advisory circular (ac) 25-14 which provides guidance for the certification of flap and slat systems with respect to protection against asymmetry of lift devices. The safety board finds that, while the ac is effective in clarifying the intent of theexisting federal aviation regulations pertaining to safety standards for high lift and drag devices with respect to the redundancy of asymmetry warning and other critical systems as stated in the recommendation. The safety board remains concerned that, since no regulations or guidelinesexist pertaining to the redundancy of critical asymmetry or stall warning systems, similar accidents may yet occur because of multiple systems failures that are not accounted for during the certification process. Ac 25-14 provides guidance for the certification of the flap and slat systems, but is nonbinding. The safety board does not believe the faa response adequately addresses the concerns raised in this letter. Because of the time which has elapsed since issuance, the recommendation has been classified as closed-- unacceptable action.

From: FAA
To: NTSB
Date: 10/27/1988
Response:

From: FAA
To: NTSB
Date: 7/14/1988
Response: ON MAY 4, 1988, THE FEDERAL AVIATION ADMINISTRATION (FAA) ISSUED ADVISORY CIRCULAR (AC) 25-14, HIGH LIFT AND DRAG DEVICES, WHICH PROVIDES GUIDANCE FOR CERTIFICATION OF FLAP AND SLAT SYSTEMS. THIS AC WILL HELP ENSURE THAT THE APPROPRIATE AIRWORTHINESS STANDARDS ARE COMPLIED WITH DURING THE CERTIFICATION PROCESS. I HAVE ENCLOSED A COPY OF THE AC FOR THE BOARD'S INFORMATION.

From: NTSB
To: FAA
Date: 9/23/1987
Response: The safety board has reviewed the draft copy of the ac 25-xx which will provide guidance for the certification of flap and slat systems.The board believes that this ac will help provide protection against asymmetry of lift devices and thus complies with the intent of this recommendation. Pending the issuance of the ac, safety recommendation a-79-99 has been classified as open--acceptable action.

From: FAA
To: NTSB
Date: 7/2/1987
Response: THE FAA IS IN THE FINAL STAGES OF ISSUING AC 25-XX WHICH WILL PROVIDE GUIDANCE FOR CERTIFICATION OF FLAP AND SLAT SYSTEMS. THIS WILL HELP ENSURE THAT THE APPROPRIATE AIR WORTHINESS STANDARDS ARE COMPLIED WITH DURING THE CERTIFICATION PROCESS.

From: NTSB
To: FAA
Date: 5/17/1983
Response: Safety recommendation a-79-99 was intended to require the application of a design criterion to new airplanes so that the need for such safeguards is identified during type certification. Such assurance could be positively attained by incorporating an appropriate requirement into 14 cfr 25.701. We recognize that the faa might interpret the require-ments of 14 cfr 25.1309 and the guidance material contained in ac 25.1309.1 sufficiently broad that the intent of the recommendation could be imposed in certification without further regulatory change. However, in the absence of specificity as to faa policy in this regard, the safety board is unable to evaluate the related certification requirements as they will be applied by the transport category airplane certification directorate duringthe certification of new airplanes. The safety board will maintain safety recommendation a-79-99 in an open- - acceptable action status pending further discussion with faa.

From: FAA
To: NTSB
Date: 10/5/1982
Response: FAA LETTER: IN ADDITION TO THE COMMENTS IN OUR LETTER OF JUNE 10, 1981, ACTION HAS BEEN TAKEN BY FAA TO CONTACT THE PRINCIPAL AIRWORTHINESS INSPECTORS WITH DC-10 RESPONSIBILITY TO DETERMINE THE STATUS OF OPERATOR COMPLIANCE PROGRESS REGARDING AIRWORTHINESS DIRECTIVE (AD) 81-03-03. IN VIEW OF THE INPUT RECEIVED FROM ALL THE OPERTORS THAT THEY WILL MEET THE AD COMPLIANCE DATE OF JANUARY 1983, THE FAA CONSIDERS ACTION COMPLETED.

From: NTSB
To: FAA
Date: 6/7/1982
Response: The safety board closely monitored the slat system modification process which resulted in the issuance of an airworthiness directive (ad) (docket no. 82-nm-03- ad; amdt. 39-4306) on january 21, 1982. This ad modification, consisting of the installation of two balance spring assemblies on the slat control mechanism for the left and right outboard slat control valves, as well as installation of balanced pressure relief valves in hydraulic systems no. 1 and no. 3 slat extend lines of the left and right outboard slat control systems, assures positive protection against asymmetry of lift devices during critical phases of flight. Since this ad action indicates that prudent consideration of service experience is part of the design certification process this recommendation has been classified as open-acceptable action. This recommendation will remain open until information is available regarding compliance efforts.

From: FAA
To: NTSB
Date: 6/10/1981
Response: FAA LTR: DURING FAA POST-ACCIDENT STUDIES, THE QUESTIONS ARTICULATED BY THE BOARD WERE REVIEWED WITH REGARD TO THE DC-10 STALL WARNING AND ASSOCIATED SYSTEMS. AS THE BOARD POINTED OUT, AN ANALYSIS OF THE DETAILED CIRCUMSTANCES LEADING TO THIS ACCIDENT DID SHOW THAT, IN THE SPECIFIC CASE OF THE DC-10, ADDITIONAL REDUNDANCY MIGHT BE APPROPRIATE. AS A MATTER OF LONG STANDING POLICY, FAA ATTEMPTS TO SPECIFY PERFORMANCE STANDARDS, RATHER THAN LAY DOWN STEP-BY-STEP COMPLIANCE REQUIREMENTS, TO ACHIEVE A SAFETY OBJECTIVE. THUS, FOR EXAMPLE, REDUNDANCY IS GENERALLY NOT MANDATED WHEN DISCUSSING GENERAL DESIGN REQUIREMENTS. INSTEAD, A THOROUGH AND COMPLETE ANALYSIS OF FAILURE MODES AND THE RESULTING EFFECTS ON FLIGHT SAFETY IS REQUIRED AND MINIMUM LEVELS OF SAFETY ARE SPECIFIED. SYSTEM REDUNDANCE IS ONE MEANS TO ACHIEVE THAT SPECIFIED LEVEL OF SAFETY, BUT OTHER METHODS ARE ALSO AVAILABLE (DIFFERENT DESIGNS OR HIGHER SYSTEM RELIABILITY ARE TWO EXAMPLES).

From: NTSB
To: FAA
Date: 6/13/1980
Response: The response indicates that faa believes the current regulationsprovide an adequate basis to protect against adverse consequences resultingfrom asymmetric deployment of lift devices. The failure to discuss the merits of redundancy is puzzling in light of the mcdonnell douglas airworthiness directive 79-15-05 (amendment 39- 3515) issued by faa. This ad, applicable to the dc-10, requires installation of a second at/sc computer or modification of the stall warning systemto handle additional inputs from angle of attack and slat position sensors. We would appreciate more specific information regarding the reasons for not including redundancy of warning systems in procedures used to certifi- cate aircraft for lift device asymmetry on the basis of controllability. This recommendation is classified open--unacceptable action.

From: FAA
To: NTSB
Date: 3/20/1980
Response: FAA LTR: CURRENT REGULATIONS CONTAIN A FIRM BASIS TO ASSURE POSITIVE PROTECTION AGAINST ASYMMETRY OF LIFT DEVICES DURING CRITICAL PHASES OF FLIGHT OR THE DEMONSTRATION OF ADEQUATE WARNING AND CONTROLLABILITY OF THE AIRCRAFT DURING CONDITIONS OF ASYMMETRY. FAR 25.671, AS AMENDED BY AMENDMENT 25-23 ON APRIL 8, 1970, REQUIRES DEMONSTRATION OF CONTINUED SAFE FLIGHT AND LANDING AFTER ANY COMBINATION OF FAILURES NOT SHOWN TO BE EXTREMELY IMPROBABLE. FAR 25.1309 PRESENTLY REQUIRES THAT ALL INFORMATION ESSENTIAL TO CONTINUED SAFE FLIGHT AND LANDING BE PROVIDED TO THE PILOT IN ALL CASES OF FAILURES NOT SHOWN TO BE EXTREMELY IMPROBABLE.