Boeing 777 N794UA

Summary

On 25 May 2010 at about 13:05 local time, a Boeing 777 registered N794UA, operated by United Airlines, Inc., was involved in an accident near Southern Tip of Greenland, Denmark. 211 people were on board and 2 were seriously injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 May 2010 at 13:05

Classification

Accident

Location

Southern Tip of Greenland, Denmark

Coordinates

62.0753, -48.2919

Aircraft

Boeing 777

Registration

N794UA

Category

Airplane

Engines

2

Operator

United Airlines, Inc.

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

London → Los Angeles

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

DCA10FA064

2 people were seriously injured.

An inadvertent encounter with unforecast turbulence in cruise flight.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.