# NTSB ANC99LA099: Boeing 747-269B, N707CK, Anchorage, AK, July 29, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 29, 1999, 15:00 local (23:00 UTC) - Place: Anchorage, AK - Coordinates: 61.159626, -149.990966 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.1596&lon=-149.9910&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 5 uninjured - Status: Completed, report July 10, 2001 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - ADs cited in the narratives: [AD 96-25-10](https://openairdocs.org/ad/96-25-10) (OpenAirDocs) - NTSB case key (mKey): 46872 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC99LA099 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46872/pdf - Page: https://openairdocs.org/ntsb/ANC99LA099 ## Probable cause The failure of a turbine blade, and subsequent penetration of the shroud (containment ring). A factor associated with the accident was the FAA's insufficient design standards/requirements addressed in an FAA Air Worthiness Directive, which called for a strengthened containment ring. The failed containment ring was in compliance with the Air Worthiness Directive. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, climb - to cruise - turbine assembly,turbine blade - failure (cause) - turbine assembly,shroud - penetrated (cause) - insufficient standards/requirements,aircraft, faa(organization) (contributing factor) ## Analysis During climbout, the Boeing 747 crew noted a loud 'thump,' followed by a change in the number three engine instrument indications. One crewmember noted there was a fist-sized hole in the side of the engine cowling. The captain shut down the number three engine, returned to the departure airport, and landed without further incident. A postlanding inspection revealed that the inboard aileron sustained substantial damage. Disassembly of the engine revealed that there were eleven 2nd stage turbine blades that were fractured in the midspan area, and one other 2nd stage turbine blade that was elongated and necked down in the midspan area with most of the shroud tip rubbed off. The turbine exhaust case had a 16 1/2-inch long hole between the case front flange and the front mount rail. Engine service records revealed that when the turbine exhaust case was overhauled, Airworthiness Directive (AD) 96-25-10 was complied with by incorporating Chromalloy Anniston Division's, Supplemental Type Certificate (STC) SE00047AT-D. The intent of STC SE00047AT-D is to comply with FAA Airworthiness Directive (AD) 96-25-10 by increasing the wall thickness of the turbine exhaust case, thus providing enhanced containment capabilities in the event of an internal engine failure. A portion of the turbine exhaust case was sent to the NTSB Materials Laboratory for examination. A Safety Board metallurgist confirmed that both the hardness and microstructure were consistent with design specifications stipulated in Chromally Anniston Division's STC. ## Factual narrative On July 29, 1999, about 1500 Alaska daylight time, a Boeing 747-269B airplane, N707CK, had an uncontained engine failure during climb-out from the Anchorage International Airport, Anchorage, Alaska. The flight was being conducted under Title 14, CFR Part 121, as a nonscheduled international cargo flight, operated by Kitty Hawk International, Inc., as Flight 11281. There were no injuries to the five crewmembers aboard. Visual meteorological conditions prevailed at the time of departure from Anchorage, and an instrument flight plan had been filed for the flight to Bangkok, Thailand. During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge on July 30, a company quality assurance official stated that about 20 minutes after departure, the crew noted a loud "thump," followed by a change in the number three engine instrument indications. He said that one of the crewmembers went to the back of the airplane to visually check the status of the engine, and noted there was a "fist-sized hole in the side of the engine cowling." The quality assurance official stated that the captain shut down the number three engine, returned to Anchorage International Airport, and landed without further incident. A postaccident inspection revealed that the inboard aileron sustained substantial damage. On July 30, 1999, the airplane was three-engine ferried from Anchorage to the operator's maintenance base in Oscoda, Michigan, where the engine was removed. The engine was subsequently shipped to a maintenance facility in Tel Avia, Israel, for disassembly and examination. On September 7, 1999, the engine was disassembled under the direction of an NTSB Powerplant Group Chairman, and in the presence of the parties to the investigation. The disassembly revealed that there were eleven 2nd stage turbine blades that were fractured in the midspan area, and one other 2nd stage turbine blade that was elongated and necked down in the midspan area, with most of the shroud tip rubbed off. The turbine exhaust case had a 16 1/2-inch long hole between the case front flange and the front mount rail. The Powerplants Group completed its examination of the engine on September 8. A copy of the Group Chairman's report is included in this report. An examination of the engine maintenance records revealed the engine was removed from service due to a cracked diffuser case on August 1, 1998, at 43,946 hours total time, and 11,629 cycles. During this maintenance procedure, an overhauled turbine exhaust case was installed. The engine records revealed that when the turbine exhaust case was overhauled, FAA Airworthiness Directive (AD) 96-25-10 was complied with by incorporating Chromalloy Anniston Division's, Supplemental Type Certificate (STC) SE00047AT-D. The intent of STC SE00047AT-D is to comply with FAA Airworthiness Directive (AD) 96-25-10 by increasing the wall thickness of the turbine exhaust case, thus providing enhanced containment capabilities in the event of an internal engine failure. A portion of the turbine exhaust case was sent to the National Transportation Safety Board's Materials Laboratory for examination. A Safety Board metallurgist confirmed that both the hardness and microstructure were consistent with design specifications stipulated in Chromally Anniston Division's STC. A copy of the NTSB materials laboratory factual report is included in this report. ## Aircraft - Registration: [N707CK](https://openairdocs.org/deregistered/N707CK-2014-12-11), registration cancelled 2014-12-11, S/N 21681 (OpenAirDocs) - Reported make and model: Boeing 747-269B - Registry model: [Boeing 747-246F](https://openairdocs.org/model/boeing-747-246f) (registry code 1384850) (OpenAirDocs) - Category: Airplane - Serial number: 21541 - Airframe hours: 59727 - Engines: P&W JT9D-7J 48650 lbs thrust turbo fan - Damage: Substantial damage - Flight: Part 121 - Registered owner: Kitty Hawk International, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, July 19, 1999, 268 hours before - Departed: ANC, ANCHORAGE, AK - Destination: VTBD, BANGKOK - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 11,000 total ## Weather - Conditions: Visual (VMC), Day - Visibility: 100 statute miles - Temperature: 14 °F - Altimeter: 29.00 inHg ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19990729017619A](https://openairdocs.org/incident/19990729017619A), Jul 29, 1999: Boeing 747269B, Anchorage, AK, Substantial damage. (.19) On July 29, 1999, about 1500 Alaska daylight time, a Boeing 747-268B airplane, N707CK, had an uncontained engine failure during climb-out from the… ## Other investigations on N707CK (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB CHI97IA096](https://openairdocs.org/ntsb/CHI97IA096), Mar 22, 1997: Boeing 747-269B (N707CK), Manaus, Brazil, incident, minor damage. Probable cause: the pilot-in-command's (non-flying pilot) improper flare. Related factors were inadequate crew/coordination, haze and sunglare. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- 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.