NTSB Looking into United Jackson Hole Accident

Air Safety Week, March 17, 2008

The National Transportation Safety Board is investigating an incident in which a United Airlines jetliner veered off the side of a runway at the Jackson Hole (Wyoming) Airport.

On February 25, 2008, an Airbus A320 (N442UA) operated by United Airlines as flight 267, departed the right side of Runway 19 during landing at Jackson Hole Airport.

The captain, first officer, four flight attendants and 119 passengers evacuated the aircraft via the emergency slides. During the evacuation, one of the inflatable slides did not deploy. No serious injuries were reported.

The airplane departed Denver at 1944 MST for Jackson Hole. Visual meteorological conditions prevailed during the nighttime landing. The reported weather at the airport about the time of the incident was wind calm, visibility of 10 miles, and overcast clouds at 3200 feet above the ground.

The airplane came to rest on its landing gear at about a 90 degree angle to the runway in snow about three feet deep. The jetliner ended its flight 116 feet past the end of the runway and 140 feet to the right of the runway centerline.

A heavy skid mark was found on the runway associated with the inboard tire of the left main landing gear. This tire was found deflated and showed wear consistent with a skid. Upon exiting the runway, both engines ingested snow and sustained internal damage. The aircraft itself was not substantially damaged.

Examination of the left main landing gear brakes revealed that the inboard and outboard wheel speed tachometer wires were cross-connected. Such a configuration would be likely to cause the antiskid system to use the inboard wheel speed to control the outboard braking, and vice versa. In such a situation, it would be likely that when the inboard tire began to skid, the antiskid system would release the pressure on the outboard brake instead of the inboard brake.

Examination of maintenance records indicated that both main landing gear units were replaced on the incident airplane in early February 2008.

The Safety Board is also investigating another United A-320 incident with similar circumstances that occurred last October.

On October 9, 2007, an Airbus A320-232, (N431UA) received minor damage when it exited runway 22R (7,500 feet by 150 feet, grooved asphalt) and impacted runway lighting at the O'Hare International Airport (ORD), Chicago, IL. One flight attendant and one passenger reported minor injuries. Flight 628 had departed the Seattle-Tacoma International Airport, Seattle, WA, for ORD.

Investigators are also probing the inoperability of the emergency evacuation slides. The slide at the front left door deployed when the door was opened during the evacuation but did not inflate. The manufacturer of the slide is assisting the NTSB in its investigation of the cause of the failure.

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