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Safety Recommendation Details

Safety Recommendation A-00-104
Details
Synopsis: IN THIS LETTER, THE NATIONAL TRANSPORTATION SAFETY BOARD RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION (FAA) TAKE ACTION TO ADDRESS A SAFETY ISSUE CONCERNING UNCONTAINED ENGINE FAILURES AS A RESULT OF CRACKING AND RUPTURE OF HIGH PRESSURE COMPRESSOR (HPC) STAGE 3-9 SPOOLS IN GENERAL ELECTRIC (GE) CF6-50 AND -80 SERIES ENGINES. THE SAFETY BOARD IDENTIFIED THIS SAFETY ISSUE DURING ITS PARTICIPATION IN THE BRAZILIAN CENTRO DE INVESTIGACAO E PREVENCAO DE ACCIDENTES AERONAUTICOS' (CENIPA) INVESTIGATION OF AN UNCONTAINED ENGINE FAILURE THAT OCCURRED AT SAO PAULO, BRAZIL, ON 6/7/00. ALTHOUGH THE INVESTIGATION IS CONTINUING, INFORMATION GATHERED THUS FAR HAS RAISED SERIOUS CONCERNS THAT WARRANT IMMEDIATE ACTION BY THE FAA .
Recommendation: THE NTSB RECOMMENDS THAT THE FAA: IMMEDIATELY ISSUE AN AIRWORTHINESS DIRECTIVE (AD) TO REQUIRE THE EXPEDITIOUS REMOVAL FROM SERVICE OF CF6-50 AND -80 SERIES ENGINES WITH HIGH PRESSURE COMPRESSOR STAGE 3-9 SPOOLS THAT ARE MOST AT RISK OF RUPTURING AND INSPECT THOSE SPOOLS IN ACCORDANCE WITH AD 99-24-15 AND ENGINE MANUAL INSTRUCTIONS. (URGENT)
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: Sao Paulo, Brazil
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA00RA061
Accident Reports:
Report #: None
Accident Date: 6/7/2000
Issue Date: 8/9/2000
Date Closed: 1/9/2001
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s): Engine,Maintenance

Safety Recommendation History
From: NTSB
To: FAA
Date: 1/9/2001
Response: THE SAFETY BOARD IS PLEASED BY THE PROMPT ACTIONS TAKEN BY THE FAA. BECAUSE THE FAA'S ACTIONS FULLY ADDRESS A-00-104, IT IS CLASSIFIED "CLOSED--ACCEPTABLE ACTION."

From: NTSB
To: FAA
Date: 10/12/2000
Response: Notation 7290: The National Transportation Safety Board has reviewed the Federal Aviation Administration's (FAA) Final Rule, "Airworthiness Directives; General Electric Company CF6-45, -50, -80A, -80e2, and -80El Turbofan Engines," which was published in 65 FR 50623, on August 21, 2000. This final rule, Airworthiness Directive (AD) 2000-16-12, effective September 5, 2000, requires initial ultrasonic and eddy current inspections of certain General Electric (GE) CF6-45, -50, -80A, -80C2, and -80El engine high pressure compressor (HPC) stage 3-9 spools. The Safety Board notes that the FAA issued the AD in response to Safety Recommendation A-OO-104, which requested that the FAA immediately issue an AD to require the expeditious removal from service of CF6-50 and -80 series engines with HPC stage 3-9 spools that are most at risk of rupturing and inspect those spools in accordance with AD 99-24-15 and the engine manual instructions. The Board issued Safety Recommendation A-00-104 following the investigation of a June 7, 2000, uncontained failure of a GE CF6-80C2 engine that was installed on a Boeing 767. The investigation revealed that the stage 3-9 spool ruptured from a dwell time fatigue fracture on the spool's stage 7 web. The investigation further revealed that the fluorescent penetrant inspection that was accomplished on the interior surfaces of the spools at the last shop visit may have been inadequate to detect dwell time fatigue cracks. The AD is intended to remove from service those CF6-45, -50, and -80 series engines with HPC stage 3-9 spools that are most at risk of rupturing so the spool's disk bores, webs, and blade slots can be ultrasonic and eddy current inspected in accordance with AD 99-24-15. The Safety Board is pleased by the FAA's timely response to Safety Recommendation A-OO-I04 an0 supports the final rule. However, because the occurrence of dwell time fatigue in CF6-50 and -80 series engine stage 3-9 spools is extremely unpredictable, the Safety Board will remain concerned about the potential for another spool rupture until all stage 3-9 spools have undergone the initial ultrasonic and eddy current inspection required by AD 99-24-15. The Safety Board appreciates the opportunity to comment on this final rule.

From: FAA
To: NTSB
Date: 9/5/2000
Response: Letter Mail Controlled 09/11/2000 2:39:05 PM MC# 2001254 THE FAA AGREES WITH THIS RECOMMENDATION AND WORKED WITH GENERAL ELECTRIC AIRCRAFT ENGINES TO DEVELOP CORRECTIVE ACTIONS TO ADDRESS THE FINDINGS STEMMING FROM THE RECENT UNCONTAINED ENGINE FAILURE INVOLVING VARIG BRASIL AIRLINES. THE FAA ISSUED AN ALTERNATE MEANS OF COMPLIANCE TO AIRWORTHINESS DIRECTIVE (AD) 99-24-15 ON 8/3/00, TO ALLOW THE USE OF GE SERVICE BULLETINS 72-AO848 AND 72-AO126. THESE BULLETINS WERE REVISED TO REQUIRE THAT WEB INSPECTIONS BE DONE ON ALL CF6-50/80 ENGINES, THAT ARE IN THE SHOP FOR ANY REASON, WITH STAGE 3-9 SPOOLS THAT HAVE ACCUMULATED MORE THAN 7,000 CYCLES-SINCE-NEW. SUBSEQUENTLY, THE FAA ISSUED AD 2000-16-12, ON 8/10/00. I HAVE ENCLOSED A COPY OF THE AD FOR THE BOARD'S INFORMATION. THIS AD WAS STRUCTURED TO CAPTURE THE STAGE 3-9 SPOOL POPULATION THAT IS MOST AT RISK. THIS POPULATION WAS SELECTED BASED ON STRESS LEVELS AND AGE. THE CRITERIA USED TO DEFINE THIS POPULATION INCLUDED HIGH STRESSES AT THE WEB LOCATIONS. AN AGGRESSIVE SCHEDULE WAS ESTABLISHED FOR STAGE 3-9 SPOOLS, WHICH HAVE NOT BEEN BORE-AND/OR WEB-INSPECTED. THE SCHEDULE REQUIRES INITIAL ULTRASONIC AND EDDY CURRENT INSPECTIONS OF SPOOLS WITH 10,500 OR MORE CYCLES-SINCE-NEW WITHIN 500 CYCLES-IN-SERVICE AFTER THE EFFECTIVE DATE OF THE AD, BY THE NEXT ENGINE SHOP VISIT, OR BY 5/31/01, WHICHEVER OCCURS FIRST. AD 2000-16-12 ALSO REQUIRES AN INITIAL INSPECTION OF SPOOLS WITH 7,000 CYCLES-SINCE-NEW TO 10,499 CYCLES-SINCE-NEW WITHIN 1,000 CYCLES-IN-SERVICE AFTER THE EFFECTIVE DATE OF THIS AD, BY THE NEXT SHOP VISIT, OR BY 7/29/01, WHICHEVER OCCURS FIRST. THESE INITIAL INSPECTIONS QUALIFY THE HPC ROTOR STAGE 3-9 SPOOL AS HAVING BEEN PREVIOUSLY INSPECTED WHEN DETERMING THE REPETITIVE INSPECTION SCHEDULES OF AD 99-24-15. THE FAA HAS TAKEN INTO CONSIDERATION THE RISK ASSOCIATED WITH THIS PROGRAM AND THE EXISTING WORLDWIDE INSPECTION CAPACITY OF THE STAGE 3-9 SPOOL AT THE PIECE-PART LEVEL. THE RISK ASSOCIATED WITH THIS INSPECTION PROGRAM'S MILESTONES IS BELOW THE LEVEL ASSOCIATED WITH THE FAA'S CONTINUED AIRWORTHINESS ASSESSMENT METHODOLOGIES. I BELIEVE THAT THE FAA'S ACTION ADDRESSES THE FULL INTENT OF THIS RECOMMENDATION, AND I CONSIDER THE FAA'S ACTION TO BE COMPLETED.