Europe's safety authority is proposing checks on the gravity-extension system on Airbus A380 landing-gear following an incident involving an Emirates flight to Dubai.
The aircraft (A6-EDQ), transporting 345 passengers and 27 crew members from London, was forced to land at Dubai without its left-hand main wing gear on 9 November last year.
Its crew had isolated the green hydraulic system, in response to an overheating indication, which meant the undercarriage had to be deployed using free-fall gravity extension, a process which takes around 70s.
But when the landing-gear was deployed at about 4,000ft the cockpit indicators showed that the left-hand wing gear had failed to extend properly. It remained up and locked, although the gear doors had opened.
The crew declared an emergency 4min before landing but managed to bring the aircraft down safely on its remaining landing-gear. It touched down with 12.6t of fuel on board and was towed off the runway.
Investigators from the United Arab Emirates General Civil Aviation Authority found that actuator unlock command wires for both independent free-fall systems of the left wing gear were damaged.
"Damage to the wiring was caused by repetitive movement of the wiring looms induced by wind effects during landing-gear operation due to insufficient support of the looms," the inquiry states.
The wiring was subjected to "flexure endurance fatigue", it adds, the result of aerodynamic forces on the looms during landing-gear operation.
Similar damage was detected on some of the actuator unlock wiring for the right-hand wing gear on the aircraft.
Airbus subsequently issued an operator alert regarding inspection of the actuator system, and the results confirmed that the degradation was only present on the A380's wing gear wiring. It also developed a modification to improve attachments for wiring harnesses connected to the actuators.
For aircraft which have not undergone this modification the European Aviation Safety Agency is proposing repetitive inspections of the wiring as well as tests of the gravity extension system on the wing landing-gear.
If the tests reveal any discrepancy, EASA's proposed airworthiness directive says the operator should carry out corrective measures issued by Airbus before the aircraft's next flight. EASA is taking comments on the directive until 12 July.
Source: Cirium Dashboard
