# NTSB DCA10CA032: Boeing 747, N173UA, Anchorage, AK, February 19, 2010 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Data collection · Final report - Date: February 19, 2010, 23:58 UTC - Place: Anchorage, AK - Coordinates: 61.174446, -149.996383 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.1744&lon=-149.9964&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-change of cruise level: Clear air turbulence encounter](https://openairdocs.org/ntsb-events/362) - Highest injury: Serious injuries - Injuries: 1 serious, 25 minor, 236 uninjured - Status: Completed, report February 23, 2017 - Report: Approved by Office Director - NTSB office: Major Investigations Division - NTSB case key (mKey): 75393 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA10CA032 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/75393/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=75393 - Page: https://openairdocs.org/ntsb/DCA10CA032 ## Probable cause an inadvertent encounter with clear air turbulence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Effect on personnel (probable cause); cases with it: [Boeing 747-422, 2 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md?model=1384935), [All aircraft, 78 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-change of cruise level: Clear air turbulence encounter](https://openairdocs.org/ntsb-events/362) (defining event); cases with it: [Boeing 747-422, 1 case](https://openairdocs.org/ntsb-events/362/sequence.md?model=1384935), [All aircraft, 24 cases](https://openairdocs.org/ntsb-events/362/sequence.md) ## Analysis On February 19, 2010, about 1452 Alaska standard time (AKST) (2352 UTC), United Airlines flight 897, a Boeing 747-400, N173UA, encountered severe turbulence during cruise descent between FL310 and FL300 about 100 miles west of Anchorage, Alaska. Of the 243 passengers and 19 crew members on board, 17 passengers and eight flight attendants (FA) received minor injuries and one FA received a serious injury. The airplane received minor damaged. The flight was operating under 14 Code of Federal Regulations (CFR) part 121 as a regularly scheduled international passenger flight from Dulles International Airport (IAD), Washington, DC, to Narita International Airport (NRT), Narita, Japan. Prior to the turbulence encounter, the flight crew received pilot reports (PIREPs) of moderate to severe turbulence above FL340 and that it was less at FL300. According to the flight crew, about one hour late, the flight began to encounter a few "light bumps" or intermittent light "chop." The sky conditions were clear with good visibility. The captain turned on the "fasten seat belt" sign and made a public address (PA) announcement to fasten seat belts. The flight crew requested a descent to FL300 and began to encounter moderate turbulence after starting the descent. The first officer then made a PA announcement directing the flight attendants to "take your seats." The autopilot remained engaged throughout the turbulence encounter, which lasted less than one minute. After encountering the turbulence, the crew assessed airplane damage and checked the number and severity of injuries to passengers and crew. The crew was assisted in assessing passenger and crew injuries by a U.S. Army Special Forces medic who stated that all of the injuries were considered minor. All the FAs indicated that they were able to perform their required emergency duties for the remainder of the flight. After discussing the injuries and the available diversion airports with the FAs, company dispatch and the medic, the flight crew decided to continue on to NRT since there were sufficient diversion airports along the route if the situation worsened. Upon arrival in NRT, 16 passengers and one FA were transported to hospitals for medical evaluation. All were released with only minor injuries, however, the FA was re-evaluated by her personal physician when she returned home with the further diagnosis of a fractured rib. ## Factual narrative On February 19, 2010, about 1452 Alaska standard time (AKST) (2352 UTC), United Airlines flight 897, a Boeing 747-400, N173UA, encountered severe turbulence during cruise descent between FL310 and FL300 about 100 miles west of Anchorage, Alaska. Of the 243 passengers and 19 crew members on board, 17 passengers and eight flight attendants (FA) received minor injuries and one FA received a serious injury. The airplane received minor damaged. The flight was operating under 14 Code of Federal Regulations (CFR) part 121 as a regularly scheduled international passenger flight from Dulles International Airport (IAD), Washington, DC, to Narita International Airport (NRT), Narita, Japan. Prior to the turbulence encounter, the flight crew received pilot reports (PIREPs) of moderate to severe turbulence above FL340 and that it was less at FL300. According to the flight crew, about one hour late, the flight began to encounter a few "light bumps" or intermittent light "chop." The sky conditions were clear with good visibility. The captain turned on the "fasten seat belt" sign and made a public address (PA) announcement to fasten seat belts. The flight crew requested a descent to FL300 and began to encounter moderate turbulence after starting the descent. The first officer then made a PA announcement directing the flight attendants to "take your seats." The autopilot remained engaged throughout the turbulence encounter, which lasted less than one minute. After encountering the turbulence, the crew assessed airplane damage and checked the number and severity of injuries to passengers and crew. The crew was assisted in assessing passenger and crew injuries by a U.S. Army Special Forces medic who stated that all of the injuries were considered minor. All the FAs indicated that they were able to perform their required emergency duties for the remainder of the flight. After discussing the injuries and the available diversion airports with the FAs, company dispatch and the medic, the flight crew decided to continue on to NRT since there were sufficient diversion airports along the route if the situation worsened. Upon arrival in NRT, 16 passengers and one FA were transported to hospitals for medical evaluation. All were released with only minor injuries, however, the FA was re-evaluated by her personal physician when she returned home with the further diagnosis of a fractured rib. ## Aircraft - Registration: [N173UA](https://openairdocs.org/deregistered/N173UA-2012-01-09), registration cancelled 2012-01-09, S/N 24380, built 1989 (OpenAirDocs) - Reported make and model: BOEING 747 (422) - Registry model: [Boeing 747-422](https://openairdocs.org/model/boeing-747-422) (registry code 1384935) (OpenAirDocs) - Registry engine: [Pratt & Whitney PW4000 series](https://openairdocs.org/engine/pratt-whitney-pw4000-series) (registry code 52119, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 24380 - Engines: Pratt and Whitney PW4000 turbo fan; Pratt and Whitney PW4000 turbo fan; Pratt and Whitney PW4000 turbo fan; Pratt and Whitney PW4000 turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: United Air Lines Inc - Registered owner: Wells Fargo Bank Northwest, N.A. - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, January 23, 2010 - Departed: IAD, Dulles, VA - Destination: NRT, Narita - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; injuries: none; airline transport, flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: left; restraint: lap only; flight hours: 15,000 total, 1,732 in this make and model, 100 in the last 90 days, 14 in the last 30 days - Co-pilot; age 52; injuries: none; airline transport, commercial, flight engineer, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review December 18, 2009; seat: right; restraint: lap only; flight hours: 16,500 total, 4,925 in this make and model, 32 in the last 30 days ## Weather - Conditions: Day - Turbulence: Severe ## 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 20100219028409A](https://openairdocs.org/incident/20100219028409A), Feb 19, 2010: Boeing 747-422, Minor damage. Ua 897 iad-nrt encountered severe turbulence in the anchorage fir. The flight was experiencing moderate turbulence and asked for lower altitude due to a… ## Other investigations on N173UA (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 DCA11FA091](https://openairdocs.org/ntsb/DCA11FA091), Jul 29, 2011: Boeing 747-422 (N173UA), Tangshan, China, no damage. Probable cause: an inadvertent encounter with convectively induced turbulence likely due to radar limitations and convective weather developing upwards into the flight path. ## Docket (5 files) The files NTSB released with the investigation on February 23, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=75393. 2.3 MB in all. - Meteorology 5 - Factual Report of Group Chairman (item 1, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40338358&FileExtension=.PDF&FileName=Meteorology%205%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - Meteorology 5 - Attachment 1 Weather Document (item 2, .PDF, 441 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40338361&FileExtension=.PDF&FileName=Meteorology%205%20-%20Attachment%201%20Weather%20Document-Master.PDF - Meteorology 5 - Attachment 2 Flight Crew Statements (item 3, .PDF, 320 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40338362&FileExtension=.PDF&FileName=Meteorology%205%20-%20Attachment%202%20Flight%20Crew%20Statements-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 4, .PDF, 262 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449541&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Operations Factual (item 5, .PDF, 165 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449540&FileExtension=.PDF&FileName=Operations%20Factual-Master.PDF 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.