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| Date: | Wednesday 1 May 2002 |
| Time: | 07:29 LT |
| Type: |  Boeing 747-422 |
| Owner/operator: | United Airlines |
| Registration: | N182UA |
| MSN: | 25279/882 |
| Year of manufacture: | 1991 |
| Total airframe hrs: | 48837 hours |
| Engine model: | Pratt & Whitney PW2040 |
| Fatalities: | Fatalities: 0 / Occupants: 290 |
| Aircraft damage: | None |
| Category: | Accident |
| Location: | Pacific Ocean, PO -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Sydney-Kingsford Smith International Airport, NSW (SYD/YSSY) |
| San Francisco International Airport, CA (SFO/KSFO) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight encountered severe turbulence while operating at 31,000 feet msl, and a flight attendant sustained a serious injury. The encounter occurred near position 174 degrees 20 minutes east longitude and 24 degrees 18 minutes south latitude. According to the captain, prior to the turbulence event, the airplane was flying over a flat broken cloud layer with a smooth ride. He reported, in part: "Passing 25 degrees south at FL310 we noticed that the cloud tops were gradually rising. Radar showed very little - a few green returns off to the right. We were in an area of no forecasted turbulence or cumulonimbus buildups. I turned on the seatbelt sign and made a passenger announcement." The seriously injured flight attendant was in the process of securing the duty free cart when she was struck by it during the turbulence encounter. Digital Flight Data Recorder (DFDR) data showed that the airplane experienced a series of oscillating vertical and lateral accelerations that lasted almost 2 minutes. The vertical accelerations (expressed in units of gravity or "g's", 1.0 is normal) ranged from a low of 0.31 to a high of 1.7. The lateral accelerations (a value of zero is normal) ranged from 0.119 left to 0.115 right. During the time frame of the encounter, the airplane's Flight Management Computer reported winds aloft went from 92 knots to 50, then back to 101. The indicated airspeed also varied from a pre-encounter average value of 315 knots to a peak of 344 before returning to the nominal 315 value. Review of the weather portion of the dispatch and flight release package provided to the flight crew noted that in the vicinity of 173 degrees east and 25 degrees south the upper air winds between 31,000 and 35,000 feet were forecast to be from 290 degrees at 102 to 113 knots. The document also noted the possibility of turbulence from longitudes 164 degrees east to 172 degrees east along the planned flight track. The National Weather Service Significant Weather Forecast Chart valid for the flight showed a 120 knot jet stream and the possibility of occasional moderate or lesser clear air turbulence south of the accident location and an area of isolated cumulo nimbus clouds with tops to 40,000 feet to the north. The only SIGMETS in effect for turbulence concerned an area some 900 miles to the west and south of the accident location.
Probable Cause: An in-flight encounter with clear air turbulence and wind shear, which resulted in a serious injury to a flight attendant.
Accident investigation:
 |
|
Sources:
NTSB LAX02LA146
History of this aircraft
Other occurrences involving this aircraft
| 20 October 2013 | N182UA | United Airlines | 0 | Sydney-Kingsford Smith International Airport, NSW (SYD/YSSY) |  |
min |
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 25-Mar-2024 10:47 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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