LAX05IA312

Shortly after the landing gear handle was positioned to the up position in the initial climb, the flight crew noted an error message on the Electric Centralized Aircraft Monitoring (ECAM) system listing a fault (L/G SHOCK ABSORBER FAULT) message for the nose landing gear (NLG) shock absorber. The gear handle was then moved to the down position and the crew received an error message of a fault for the nose wheel steering (WHEEL N/W STRG FAULT). After determining that the nose landing gear was cocked 90 degrees, the crew landed at an alternate airport, and the NLG tires and both wheels were worn down into the axle. Post incident examination of the nose gear assembly found that two of the four anti-rotation lugs on the NLG upper support assembly fractured and separated due to induced fatigue from the stearing system's programed pre-landing dynamic steering tests that repeatedly cycles pressure to the stearing cylinders. The failed lugs allowed the NLG to deviate from its 0-degree position in the landing gear bay upon gear retraction on takeoff. This resulted in the L/G SHOCK ABSORBER FAULT error message on the ECAM system. When the pilots extended the incident airplane's landing gear, the nose gear achieved the down and locked position 1.5 seconds before the main gear and/or all of the landing gear doors closed. The nose wheel assembly was not centered at this time. The Brake Steering Control Unit (BSCU) detected this off center condition of the NLG and attempted to re-center the nose wheel; however, due to the sequencing of the nose and main landing gear and their respective doors, hydraulic pressure was shut off to the NLG steering valve. This lack of hydraulic power to the servo valve resulted in a lack of position feedback to the BSCU. After a 0.5-second monitoring time period, the BSCU detected this as a fault and deactivated the steering system so that the BSCU could not return the nose wheels to center. Failure of the nosewheels to center initiated a WHEEL N/W STRG FAULT caution message on the ECAM. There were no approved procedures that allowed the flight crew to attempt to reset the BSCU system, which would have re-enabled the hydraulic system and could have resulted in the system recentering the nose wheels.

1.1 History of flight

On September 21, 2005, at 1818 Pacific daylight time, Jet Blue Airways flight 292, an Airbus A320, N536JB, landed at Los Angeles International Airport, Los Angeles, California, with the nose wheels cocked 90 degrees. Jet Blue Airways, Inc., was operating the airplane as a scheduled domestic passenger flight under the provisions of 14 Code of Federal Regulations (CFR) Part 121. The airline transport pilot licensed captain, first officer, 4 flight attendants, and 141 passengers were not injured. The flight departed Burbank, California, at 1531 as a non-stop to JFK Airport, New York, New York. Visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan had been filed.

The first officer (FO) was the pilot flying. He noted no problems during the initial departure, and observed a positive rate of climb. Information from the digital flight data recorder (DFDR) indicated that after liftoff the gear handle was positioned to the up position.

The flight crew noted an error message displayed on the Electric Centralized Aircraft Monitoring (ECAM) system. There was a fault (L/G SHOCK ABSORBER FAULT) message for a nose landing gear (NLG) shock absorber.

The DFDR data then indicated that the gear handle was positioned to the down position. The crew then received an error message of a fault for the nose wheel steering (WHEEL N/W STRG FAULT). There was no master warning so the FO continued flying the airplane while the captain troubleshot the ECAM system.

The FO flew the airplane over Palmdale, California, at 14,000 feet mean sea level (msl) while the captain consulted the flight crew operating manual (FCOM) and maintenance control. The FCOM noted that the nose gear "may be caught at 90 degrees." The captain continued to evaluate the problem to ascertain the systems' status. The flight crew continually updated the cabin crew and passengers.

The flight diverted to Long Beach, California. The captain decided to perform a flyby of the tower for verification on the gear status. The tower, Jet Blue ground personnel, and a local news helicopter advised him that the nose gear was canted 90 degrees to the left. The captain stated that after discussing the situation with company representatives, he decided to divert to LAX because it had optimum field conditions, runway length, and a better emergency/abnormal support services. The crew flew for several hours to burn fuel so that they could land at a lighter weight.

The captain took note of the fuel burn to ensure that the center of gravity stayed within limits. The captain also advised the cabin crew that in the event that the nose gear collapsed, evacuation from the aft doors was not available so everyone would deplane from the forward exits. The flight crew advised the cabin crew to take the emergency procedures up to the point of egress, at which time the captain would advise the method.

Prior to touchdown, the captain announced "brace" and the flight attendants also transmitted "brace" over the public address system.

The captain flew the airplane for the landing. He touched down at 120 knots, and applied normal braking at 90 knots. He held the nose gear off of the ground as long as possible. At 60 knots, the flight crew shut down the engines. They did not use ground spoilers, reverse thrust, or auto braking. During the landing, the forward cabin crew could smell burnt rubber. The cabin crew remained at their stations as previously defined by the captain. The air traffic control tower confirmed that there was no fire, and the captain announced this to the cabin crew. After this notification, the passengers deplaned normally using an air stair.

Upon touchdown, the NLG tires rapidly deflated and tore apart, and both wheels were worn into the axle. During landing, the airplane's trajectory was not affected by the abnormal NLG configuration or subsequent tire destruction, and the airplane stayed on the runway centerline.

Maintenance personnel jacked the airplane up, and removed the damaged wheels. They installed a right nose wheel, and towed the airplane to a maintenance hangar.

1.2 Injuries to persons

No one on board the airplane sustained an injury.

1.3 Damage to aircraft

Damage was limited to the NLG assembly.

1.4 Other damage

There was no damage to any objects other than the airplane.

1.5 Personnel information

1.5.1 Captain

The operator reported that the captain held an airline transport pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane.

The captain held a first-class medical certificate issued on August 12, 2005. It had the limitation that he must wear corrective lenses.

The operator reported that the captain had a total flight time of 10,829 hours. He logged 160 hours in the last 90 days, and 39 in the last 30 days. He had en estimated 2,552 hours in this make and model.

1.5.2 First Officer

The operator reported that the FO held an airline transport pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane.

The FO held a second-class medical certificate issued on April 19, 2005. It had no limitations or waivers.

The operator reported that the FO had a total flight time of 5,732 hours. He logged 254 hours in the last 90 days, and 94 in the last 30 days. He had en estimated 1,284 hours in this make and model.

1.6 Aircraft information

The airplane was an Airbus A320, serial number 1784. The operator reported that the airplane had a total airframe time of 14,227 flight hours and 5,098 landing cycles. It was on a continuous airworthiness inspection program. Maintenance records indicated that Jet Blue maintenance technicians replaced a proximity sensor on the nose wheel prior to the previous flight's departure from New York earlier that day.

1.6.1 Normal operation

The landing gear (L/G) normal extension and retraction system is electrically controlled and hydraulically operated.

The electrical system has a landing gear control lever, two Landing Gear and Control Interface Units (LGCIU), a gear electro-hydraulic selector valve, a door electro-hydraulic selector valve, 32 proximity sensors and their related targets, and a set of indicator lights. The electrical control system has two subsystems; each is governed by a separate LGCIU. At any given time, one LGCIU is in CONTROL and the other is in MONITORING mode (while using the data from the respective proximity sensors).

The hydro-mechanical components include three gear actuating cylinders, three door actuating cylinders, three gear uplocks, three door uplocks, three door by-pass valves (ground opening function for the door), a NLG downlock release actuator, and two MLG lockstay actuating cylinders. For this airplane, the green hydraulic system provides hydraulic power to operate the landing gear.

Upon movement of the L/G control lever, the LGCIU sends a signal to the electro-hydraulic valve assembly. The proximity sensors send signals to the LGCIU, which ensures that the L/G operate in the correct sequence.

The NLG retracts forward into a bay in the fuselage, and centers fore and aft.

When the nose landing gear is in the retracted/uplocked position there is clearance around the wheels. Therefore, if the mechanical centering of the nose wheels fails, the wheels can rotate a certain amount (approximately 20 degrees) until they contact the roof of the NLG bay. Airbus tests have shown that, even with this amount of rotation, the gear will still achieve a free fall, so the gear will not jam in the bay. Following retraction on takeoff, if the nose wheels deviate from their mechanically centered position while in the landing gear bay, a L/G SHOCK ABSORBER FAULT caution light will illuminate.

There are a pair of proximity sensors and targets on the NLG that detect if the gear is ext