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Safety Recommendation Details

Safety Recommendation A-81-063
Details
Synopsis: ON JANUARY 31, 1981, NORTHWEST ORIENT AIRLINES FLIGHT 79, WITH 43 PASSENGERS, DEPARTED DULLES INTERNATIONAL AIRPORT FOR SEATTLE, WASHINGTON. WHILE CLIMBING THROUGH 7,000 FEET, THE FLIGHTCREW NOTICED SEVERE VIBRATIONS IN THE NO. 3 ENGINE, FOLLOWED BY A LOUD EXPLOSION. THEY SHUT DOWN THE NO. 3 ENGINE IMMEDIATELY. THERE WAS NO FIRE OR PRIOR REPORT OF ENGINE MALFUNCTION. THE FLIGHT RETURNED TO DULLES AND MADE A SAFE LANDING WITHOUT FURTHER INCIDENT. EXAMINATION OF THE PRATT AND WHITNEY AIRCRAFT JT9D TURBOFAN ENGINE DISCLOSED THAT THE NO. 3 NOSE COWL ASSEMBLY AND FAN CASE HAD SEPARATED FROM THE AIRCRAFT. THE NO. 2 ENGINE HAD INGESTED DEBRIS WHICH RESULTED IN FOREIGN-OBJECT DAMAGE. THE SOURCE OF THE DEBRIS IS STILL UNDER INVESTIGATION.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: ISSUE AN AIRWORTHINESS DIRECTIVE WHICH REQUIRES A VISUAL INSPECTON FOR ARC BURNS BEFORE AND AFTER EACH REWORK OPERATION ON TITANIUM ALLOY FAN BLADES FROM PRATT AND WHITNEY AIRCRAFT JT9D TURBOFAN ENGINES AND REQUIRES REPLACEMENT OF ARC BURN-AFFECTED BLADES. WE FURTHER RECOMMEND THAT A DESCRIPTION OF ARC BURN IN TITANIUM BE INCLUDED IN THE AIRWORTHINESS DIRECTIVE.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Alternate 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: 6/3/1981
Date Closed: 4/5/1982
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Alternate Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 4/5/1982
Response: Since the manufacturer's engine maintenance manual is incorporated in each operator's approved maintenance program, the manual revision requiring removal from service of arc burned blades satisfies the intent of this recommendation. Therefore, A-81-63 has been classified as "Closed--Acceptable Alternate Action."

From: FAA
To: NTSB
Date: 12/21/1981
Response: FAA LTR: THE FAA SHARES THE SAFETY BOARD'S CONCERN AND WE AGREE THAT THE JT9D ENGINE AND MAINTENANCE MANUALS DO NOT ADEQUATELY ADDRESS ARC BURN INSPECTION REQUIREMENTS. ACCORDINGLY, THE FAA ENGINE AND PROPELLER CERTIFICATION DIRECTORATE, IN THE NEW ENGLAND REGION, WORKED CLOSELY WITH THE MANUFACTURER IN REVISING THE APPROPRIATE MANUALS. A REVISION PROVIDES A CAUTION NOTE THAT HIGHLIGHTS THE NEED FOR EXTREME CAUTION WITH ELECTRICAL EQUIPMENT AROUND THE BLADE AND INCLUDES A DESCRIPTION OF SUBSEQUENT DAMAGE THAT COULD RESULT, A DESCRIPTION OF ARC BURN, AND A STATEMENT REQUIRING THE REMOVAL FROM SERVICE OF BLADES THAT HAVE ARC BURN. ALTHOUGH THE STATEMENT REQUIRING BLADE REMOVAL IS UNDERSTOOD TO PROHIBIT THE REPAIR OF ARC BURN BLADES, FURTHER CLARIFICATION TO THE MANUAL WILL BE MADE SPECIFICALLY TO PROHIBIT REPAIR AND TO REQUIRE ARC BURNED FAN BLADES TO BE SCRAPPED.

From: NTSB
To: FAA
Date: 10/20/1981
Response: We are pleased to note that JT9D engines and maintenance manuals have been revised to include a caution note to highlight arc burn inspection. However, we do not agree that this action is sufficient to prevent similar incidents of blade failure. Previous editions of the manuals contained essentially the same information, yet this incident occurred because an arc-burned blade had been reworked and reinstalled instead of being removed from service. Your response does not indicate that a description of arc burn was added to or changed in the manuals. Further, our concern is that operators may be reluctant to replace the expensive blades and may attempt to repair them. We have determined that the blades should be replaced since repaired blades are subject to fatigue cracking. Data Source: NTSB Recommendations to FAA and FAA Responses We will consider the changes to the manuals as acceptable compliance with our recommendation if they include specific statements requiring the replacement of arc- burned blades and prohibiting their repairs. Until the manuals are changed to reflect these requirements, we are maintaining this recommendation in an "Open-- Unacceptable Action" status.

From: FAA
To: NTSB
Date: 8/19/1981
Response: FAA LTR: THE FAA HAS COMPLETED A REVIEW OF THE INCIDENT DATA AND AVAILABLE USER INFORMATION. ACCORDING TO FAA RECORDS, THE NORTHWEST AIRLINES INCIDENT IS THE THIRD BLADE FAILURE RESULTING FROM A MAINTENANCE INDUCED ARC BURN. PREVIOUS INCIDENTS OCCURRED IN 1969 AND 1973. THERE ARE OVER 2300 ENGINES IN OPERATION, EACH CONTAINING 40 TO 48 FAN BLADES, WITH TOTAL ENGINE FLIGHT TIME EXCEEDING 37 MILLION HOURS. FOR THESE REASONS, WE FIND THAT ISSUANCE OF AN AD IS UNNECESSARY. HOWEVER, OUR ACTION IN RESPONSE TO A-81-64 DOES INCLUDE INCREASED EMPHASIS ON THE POSSIBILITY OF ARC BURNS AND INCLUDES A DESCRIPTION OF ARC BURN IN TITANIUM ALLOYS.