DCA10CA032

NTSB accident investigation · Boeing 747 · Anchorage, AK · February 19, 2010

Accident · Serious injuriesData collectionFinal report
Date
February 19, 2010, 23:58 UTC
Place
Anchorage, AK
Injuries
1 serious, 25 minor, 236 uninjured
Damage
Minor damage
Phase of flight
Enroute
Aircraft
N173UABoeing 747
Defining event
Enroute-change of cruise level: Clear air turbulence encounter
Weather
Day
Status
Completed · report February 23, 2017
Report
Approved by Office Director
NTSB office
Major Investigations Division
FAA report
20100219028409A
Case key
75393

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

an inadvertent encounter with clear air turbulence.

Findings · 1

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Turbulence: clear air turbulenceEnvironmental issues › Conditions/weather/phenomena · Effect on personnelBoeing 747-422: 2 casesAll aircraft: 78 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

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
Reported as
Boeing 747 (422)
Category
Airplane
Serial number
24380
Engines
Pratt and Whitney PW4000, turbo fanPratt and Whitney PW4000, turbo fanPratt and Whitney PW4000, turbo fanPratt 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

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew · 2

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
59
Injuries
None
Certificates
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
Role
Co-pilot
Age
52
Injuries
None
Certificates
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

Docket · 5

The files NTSB released with the investigation on February 23, 2017, on NTSB’s docket system: statements, records, photos and specialists’ reports. 2.3 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.

Other investigations on N173UA · 1

Matched to the same aircraft by N-number and date.