ASN Wikibase Occurrence # 74506
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| Date: | Tuesday 25 May 2010 |
| Time: | 13:05 |
| Type: |  Boeing 777-222ER |
| Owner/operator: | United Airlines |
| Registration: | N794UA |
| MSN: | 26953/105 |
| Year of manufacture: | 1997 |
| Fatalities: | Fatalities: 0 / Occupants: 211 |
| Aircraft damage: | None |
| Category: | Accident |
| Location: | over Atlantic Ocean -
 Canada
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | London Heathrow Airport (LHR/EGLL) |
| Los Angeles, CA (LAX) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight encountered clear air turbulence near the southern tip of Greenland. A review of the weather briefing provided to the accident flight crew by company Flight Dispatch contained relevant SIGMETs along the proposed route of flight. The package was not found to be missing any pertinent published information that could have alerted the flight crew to an enroute encounter with turbulence over Greenland.
Analysis of the calculated winds indicated the airplane encountered a downdraft on the order of 13 feet/sec followed sharply by an updraft of approximately 24 feet/sec. Simulation analysis of the upset
confirmed that the airplane reacted as expected to the calculated wind profile and the recorded control inputs. Based on the simulation study that was performed, the recorded elevator input from the autopilot during the disturbance reduced the magnitude
of the upset.
Analysis of the surrounding atmosphere and GOES-3 satellite photographs indicated the presence of icecap wave instability along the airplane's route of flight that was capable of producing rapidly changing vertical winds on the order of 20 feet per second, which resulted in conditions conducive to severe turbulence.
Probable Cause: An inadvertent encounter with unforecast turbulence in cruise flight.
Sources:
NTSB
http://news.asiaone.com/News/AsiaOne%2BNews/World/Story/A1Story20100526-218424.html
https://flightaware.com/live/flight/UAL935/history/20100525/0915Z/EGLL/CYUL
http://avherald.com/h?article=42bfe842&opt=0
http://news.sympatico.ctv.ca/home/contentposting?feedname=CTV-TOPSTORIES_V3&showbyline=True&date=true&newsitemid=CTVNews%2f20100525%2fturbulence-flight-montreal-100525
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 25-May-2010 23:50 | tatoberry | Added |
| 26-May-2010 00:04 | harro | Updated [Aircraft type, Cn, Location, Departure airport, Destination airport, Source, Embed code, Damage, Narrative] |
| 02-Sep-2010 14:39 | Anon. | Updated [Nature, Embed code] |
| 21-Dec-2016 19:25 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 26-Nov-2017 17:13 | ASN Update Bot | Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative] |
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