WASHINGTON -- There have been at least seven cases in which the front wheels on Airbus A320s became stuck in a sideways position, forcing pilots to make emergency landings.
No one was hurt in any of the landings, the latest of which occurred Wednesday night in front of a national television audience when a JetBlue plane touched down in Los Angeles amid smoke and sparks as the front tires disintegrated.
The incidents, while unnerving, are considered anomalies and have not prompted federal authorities to take action beyond ordering airlines to follow Airbus instructions for replacing rubber seals on the gear.
With about 2,500 Airbus A320s in operation worldwide, the number of incidents involving jammed nose gear is not significant, Federal Aviation Administration spokesman Greg Martin said yesterday.
''It's a safe aircraft," he said.
Wednesday's emergency started soon after takeoff from Burbank, Calif., when the JetBlue A320 pilot noticed a caution light indicating a problem with the landing gear. He circled past the Long Beach Airport's control tower, where flight controllers saw that the nose wheel hadn't retracted and was twisted out of alignment.
The plane flew in circles for three hours to burn off fuel, then landed safely at Los Angeles International Airport, balancing on its rear wheels as it rolled down the center of the runway.
Passengers on board JetBlue Flight 292 watched news reports about their own flight as they prepared for an emergency landing.
Some of those aboard said later that they appreciated seeing news reports on what was happening. Others were horrified.
''It was absolutely terrifying, actually. Seeing the events broadcast made it completely surreal and detached me from the event," said Zachary Mastoon, a musician heading home on the Burbank-to-New York flight. ''It became this television show I was inextricably linked to. . . . It only exacerbated the situation and my fear."
The A320 family, which includes the A318, A319, and A321, has a somewhat unusual landing gear that rotates before retracting into the fuselage.
''It's definitely not the most common way," said Chuck Eastlake, a aerospace engineering professor at Embry-Riddle Aeronautical University in Daytona Beach, Fla. ''The reason is that the ability of the nose wheel to rotate 90 degrees introduces the possibility of failure, exactly like what we saw."
The A320 landing gear is moved through hydraulic pressure, with fluid pumped into a valve, which moves a piston. Rubber seals called O-rings are used to prevent the hydraulic fluid from leaking. If the hydraulic fluid leaks, the piston won't work right, Eastlake said.
That's what happened in at least two previous incidents. Airbus said the landing gear got stuck because of problems with the seals, and told airlines they should replace the seals on A320 and A321 aircraft.