Air safety investigators said today that a United Airlines jet may have skidded off a runway after landing Monday evening at the Jackson Hole Airport because braking system wires were cross-connected.
The National Transportation Safety Board said after its investigators examined the left main landing gear brakes, they determined that the inboard and outboard wheel speed tachometer wires were crossed, a condition that would affect braking capability and the antiskid system.
The Airbus A320 jet, which had flown from Denver International Airport to the Wyoming city as Flight 267, ended up 116 feet past the end of the runway and 140 feet to the right of the runway centerline, NTSB said. The incident occurred about 9:16 p.m.
The plane’s two pilots, four flight attendants and 119 passengers evacuated the plane via emergency slides and no serious injuries occurred, according to the safety board.
NTSB said it also is investigating why one of the emergency slides did not inflate after it deployed.
The agency said it is looking at an event from last October with “similar circumstances” to the Jackson Hole incident when another Airbus A320 operated by United “exited” a runway and hit runway lights after landing at Chicago’s O’Hare International Airport.
In Monday’s incident, investigators found a heavy skid mark on the runway associated with the inboard tire of the left main landing gear, NTSB said. “This tire was found deflated and showed wear consistent with a skid.”
Crossing of the tachometer wires would likely “cause the antiskid system to use the inboard wheel speed to control outboard braking, and vice versa,” NTSB said in its preliminary report.
“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.”
NTSB said an examination of the plane’s maintenance records showed that both main landing gear units on the A320 were replaced in early February.
