Investigation brief · generated 2026-10-09 · source: NTSB public docket and accident database
BOEING 747-422 — Pacific Ocean, A1, 2013-02-19
NTSB number
WPR13LA131
Operator
United Airlines
Registration
N174UA
Highest injury
Serious injury
Regulation
Part 121
Damage
—
Cohort
Part 121 airline
Recorder data
Tier 1 — decoded recorder tables
Every sentence below is taken directly from NTSB records — the accident database, the docket's recorder reports and the Board's findings — with its source noted. Nothing is paraphrased or inferred.
NTSB summary
The flight crew reported that the flight experienced unexpected light-to-moderate turbulence during cruise flight for about 3 hours. The seatbelt sign was illuminated, and the passengers and flight attendants had been seated. A flight attendant, who was on her rest break and was resting in the bunk room, reported that the turbulence had stopped for a while and that she thought she heard a "faint ding" indicating that the seatbelt sign had been turned off, so she went to the lavatory. However, the flight then encountered moderate turbulence, during which the flight attendant sustained a serious injury while walking from her bunk to the lavatory. The flight attendant reported that announcements made over the public address system could not be heard in the bunk room and that it was not always possible to hear when the seatbelt sign was turned on or off. It is likely that, if the flight attendant had a visual indication that the seatbelt sign was on, she would not have attempted to get up until safe movement was assured.
The flight’s encounter with moderate clear air turbulence while en route, which resulted in a serious injury to a flight attendant. Contributing to the accident was the lack of communication equipment in the rest compartment, which, if installed, could have alerted the cabin crewmembers that the seatbelt sign was on.
Verbatim, NTSB determination.
Flight data recorder
· N174UA — 46,801 samples, 23 parameters, 05:40:00.0 to 18:40:00.0.
Parameter
Max
at
Min
at
Final
at
Computed airspeed kts
353.0
05:58:12.0
0.0
05:40:00.0
0.0
18:40:00.0
Pitch attitude deg
14.0
05:51:08.0
-3.0
18:06:00.0
-1.0
18:40:00.0
Roll attitude deg
28.5
18:24:48.0
-16.5
18:18:30.0
-0.4
18:40:00.0
Vertical acceleration g
1.2
17:07:14.0
0.6
14:30:41.0
1.0
18:40:00.0
Computed from the docket's tabular attachment; times as recorded (local or SRN as published).
Sequence of events (FDR factual report)
Time
Event
Page
0540 UTC
Flight departed Sydney (YSSY/SYD), Australia airport on an IFR flight plan
1
1500 UTC
N174UA encountered turbulence during cruise flight over the Pacific Ocean while en route to SFO
1
14:16:00 UTC
FDR data indicated vertical acceleration variations began, ranging between 1.3 g's and 0.65 g's; pressure altitude started at about 37,000 ft
3
14:24:00 UTC
Pressure altitude increased to about 39,000 ft (approximately 8 minutes after 14:16:00 UTC)
3
16:41:40 UTC
Pressure altitude, having remained at about 39,000 ft for approximately 2 hours and 18 minutes, began to decrease
3
16:41:40 to 17:13:30 UTC
Over approximately 31 minutes and 50 seconds, pressure altitude decreased to a minimum of 37,575 ft, then increased to a maximum of approximately 41,000 ft before decreasing and settling at a pressure altitude of about 33,000 feet
3
17:13:30 UTC
Vertical acceleration variations ended
3
18:31:07 UTC
The aircraft landed
3
18:40:00 UTC
End of FDR recording
2
Extracted by claude-sonnet-5; 6 of 9 stated events verified against the raw recorder data.