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Safety Recommendation Details

Safety Recommendation A-81-070
Details
Synopsis: ON JANUARY 31, 1981, A NORTHWEST AIRLINES, INC., DC-10-40 DEPARTED DULLES INTERNATIONAL AIRPORT FOR SEATTLE, WASHINGTON. WHILE CLIMBING THROUGH 6,000 FEET, THE FLIGHTCREW HEARD A LOUD NOISE, DETECTED INDICATIONS OF A FAILURE OF THE NO. 3 ENGINE, AND FELT AIRFRAME VIBRATIONS. THE ENGINE WAS SHUT DOWN SUCCESSFULLY, AND THERE WAS NO FIRE. THE FLIGHT RETURNED TO DULLES AND MADE A SAFE LANDING WITHOUT FURTHER INCIDENT.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: REVIEW THE DESIGN OF THE FLANGES AND FASTENERS ON THE FORWARD AND AFT FACES OF THE FAN CASE OF THE JT9D TURBOFAN ENGINE TO INSURE THAT THE INTENT OF AIRWORTHINESS REQUIREMENTS PROVIDED IN 14 CFR 33 AND 14 CFR 25 ARE SATISFIED.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: Chantilly, VA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA81IA008
Accident Reports: Northwest Airlines 79 McDonnell Douglas DC-10-40, N143US
Report #: AAR-81-10
Accident Date: 1/31/1981
Issue Date: 7/10/1981
Date Closed: 9/12/1985
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 9/12/1985
Response: The Safety Board has reviewed the copies of Airworthiness Directive 82-16-10, effective August 16, 1982, and Pratt & Whitney Aircraft service bulletin No. 5335 which accompanied your letter. The Safety Board finds that this Airworthiness Directive, which requires strengthening of the fan case "B" flange, along with the previous action taken by McDonnell-Douglas to modify the fan case "A" flange attachment, complies with the intent of Safety Recommendation A-81-70. Safety Recommendation A-81-70 has been classified as "Closed--Acceptable Action."

From: FAA
To: NTSB
Date: 7/5/1985
Response: FAA LTR: A REVIEW OF OUR FILES DISCLOSED THAT THE BOARD WAS NOT IN RECEIPT OF A COMPLETED REGULATORY ACTION INITIATED BY THE FEDERAL AVIATION ADMINISTRATION. TO COMPLETE THIS ACTION, WE HAVE ENCLOSED FOR THE BOARD'S INFORMATION A COPY OF A FINAL RULE (DOCKET NO. 81-NE-20; AMENDMENT 39-4417) THAT WAS ISSUED ON JUNE 30, 1982, AND BECAME EFFECTIVE AUGUST 16, 1982. THIS AMENDMENT ADOPTED AIRWORTHINESS DIRECTIVE 82-16-10, WHICH REQUIRED INSTALLATION OF REVITED, SEGMENTED STRENGTHENING PLATES AND IMPROVED ATTACHMENT HARDWARE ON THE REAR FACE OF THE FAN EXIT CASE FRONT FLANGE ("B" FLANGE) ON THE JT9D-20 ENGINE INSTALLED IN THE WING POSITION ON THE DC-10-40 AIRCRAFT. THIS ACTION WAS REQUIRED TO PREVENT SEPARATION OF THE FAN CASE ASSEMBLY FROM THE FRONT FAN EXIT CASE, AT THE "B" FLANGE ATTACHMENT AREA, WHICH COULD OCCUR UNDER CERTAIN AERODYNAMIC LOADS FOLLOWING A FAN BLADE FRACTURE.

From: NTSB
To: FAA
Date: 12/7/1981
Response: Thank you for your letter dated November 16, 1981, further responding to National Transportation Safety Board Safety Recommendation A-81-70 issued July 10, 1981. This recommendation stemmed from our investigation of an incident involving a Northwest Airlines DC-10-40 on January 31, 1981. We recommended that the FAA review the design of the flanges and fasteners on the forward and aft faces of the fan case of the JT9D turbofan engine to insure that the intent of airworthiness requirements provided in 14 CFR 33 and 14 CFR 25 are satisfied. We are pleased to be informed that the FAA has completed its analysis and review of the airframe and engine aspects of this incident and is in the process of preparing two separate, but related, Airworthiness Directives (AD) to improve flange capability under adverse conditions. Pending the issuance of these AD's, Safety Recommendation A-81-70 is classified "Open--Acceptable Action."

From: FAA
To: NTSB
Date: 11/16/1981
Response: FAA LTR: AS A RESULT OF THE INVESTIGATION OF THE INCIDENT AND ANALYSIS OF THE DESIGN OF THE FLANGES AND FASTENERS ON THE FORWARD AND AFT FACES, THE NEED TO IMPROVE THE DESIGN IS REQUIRED IN ORDER TO PRECLUDE RECURRENCE. THEREFORE, THE FAA IS IN THE PROCESS OF PREPARING TWO SEPARATE, BUT RELATED, AIRWORTHINESS DIRECTIVES (AD) TO IMPROVE FLANGE CAPABILITY UNDER ADVERSE CONDITIONS. ONE AD ISSUED BY FAA'S NORTHWEST MOUNTAIN REGION, WILL ADDRESS THE "A" FLANGE RELATIVE TO AIRFRAME MOUNTING AND HARDWARE ASPECTS. THE OTHER AD, ISSUED BY FAA'S NEW ENGLAND REGION, WILL ADDRESS ENGINE ASPECTS RELATIVE TO TEAROUT STRENGTHS AND RELATED PROBLEMS. IT IS RECOGNIZED THAT THE APPLICABILITY OF THESE CHANGES AFFECT ONLY JT9D-20 ENGINES INSTALLED ON THE DC-10-40 AIRCRAFT BECAUSE DESIGN OF THE NOSE COWL ATTACHMENT AND ENGINE FORWARD FAN CASE FLANGE IS UNIQUE TO THIS INSTALLATION.

From: NTSB
To: FAA
Date: 9/18/1981
Response: Thank you for your letter of August 24, 1981, responding to National Transportation Safety Board Safety Recommendation A-81-70 issued July 10, 1981. This recommendation stemmed from our investigation of an incident involving a Northwest Airlines DC-10-40 on January 31, 1981. Shortly after takeoff from Dulles International Airport, the No. 3 engine nose cowl assembly and fan case separated from the engine. We recommended that the FAA review the design of the flanges and fasteners on the forward and aft faces of the fan case of the JT9D turbofan engine to insure that the intent of airworthiness requirements provided in 14 CFR 33 and 14 CFR 25 are satisfied. We are pleased to note that this recommendation is being evaluated by the FAA, McDonnell Douglas, and Pratt and Whitney Aircraft. We appreciate the FAA's offer to keep the Safety Board informed of its findings. Pending the FAA's further response, Safety Recommendation A-81-70 will be maintained in an "Open--Acceptable Action" status.

From: FAA
To: NTSB
Date: 8/24/1981
Response: FAA LTR: THE FAA IS CURRENTLY EVALUATING THE STRUCTURAL INTEGRITY, UNDER FAILURE CONDITIONS TYPICAL OF THE DULLES INCIDENT, OF THE AIRCRAFT NOSE COWL ATTACHMENT HARDWARE WHICH INTERFACES WITH THE ENGINE FORWARD "A" FLANGE. A PRELIMINARY DOUGLAS AIRCRAFT SERVICE BULLETIN, DEVELOPED IN COORDINATION WITH PRATT & WHITNEY AIRCRAFT, IS CURRENTLY UDER REVIEW BY OUR NORTHWEST AND NEW ENGLAND REGIONS. MOREOVER, WE HAVE RECEIVED A PRELIMINARY PROPOSAL FROM PRATT & WHITNEY AIRCRAFT TO INCREASE THE STRUCTURAL CAPABILITY OF THE REAR FAN CASE "B" FLANGE BY INCREASING FLANGE SHEAR STRENGTH AND INCORPORATING FLANGE ATTACHMENT BOLTS HAVING GREATER STRAIN ENERGY CAPACITY. FURTHER ANALYSIS AND REVIEW OF THESE PROPOSED AIRCRAFT AND ENGINE MODIFICATIONS IS NECESSARY TO ENSURE COMPATIBILITY OF THESE DESIGN CHANGES WITH BOTH AIRCRAFT AND ENGINE REQUIREMENTS. THIS ADDITIONAL ANALYSIS IS ALSO NECESSARY TO ENSURE ADEQUACY OF THE CHANGES UNDER ENGINE BLADE FAILURE CONDITIONS AND THE FULL RANGE OF AIRCRAFT FLIGHT CONDITIONS AND RESULTANT AERODYNAMIC LOADING.