Emirates A6-EDQ

A warning during the London to Dubai flight

Emirates flight EK002 left London Heathrow for Dubai at 1405 UTC on 9 November 2016. The Airbus A380-861, registered A6-EDQ, carried 345 passengers, two flight crewmembers and 25 cabin crewmembers. Its departure and initial cruise were uneventful. The commander was flying and the copilot was monitoring. Both pilots were qualified for the flight, and the investigation found that they had been well rested.

About three hours and 20 minutes into the flight, the electronic centralized aircraft monitoring system indicated that the green hydraulic system temperature had risen above its normal operating range. A further message indicated an overheat. Following the flight crew operating manual, the pilots isolated the green hydraulic system and began preparing for the limitations that would affect the rest of the flight.

The A380 had two independent hydraulic systems, green and yellow. The green system normally supplied the nose and wing landing gear extension mechanisms, nose wheel steering and wing gear brakes, among other services. With that system isolated, the nose and wing landing gear had to be lowered through the emergency gravity extension system. The loss also slowed flap extension and increased landing distance because half the ground spoilers would be unavailable.

Preparing for the approach

The pilots discussed the hydraulic problem with Emirates maintenance control. The commander asked whether the isolated system could be restored to extend the landing gear, and was advised that restoration was impossible in flight. He requested a long approach at Dubai and towing support after landing. Air traffic control provided a 20 mile final approach and assigned a stand near the expected runway exit. The senior cabin crewmember was briefed about the hydraulic problem and the anticipated tow.

Fuel consumption was a particular concern. The operating manual allowed for an increase of up to 10 percent after loss of the green system if outer ailerons deflected upwards. Once all the landing gear was extended, consumption could increase by as much as 100 percent. The emergency extension system left the gear doors open, and the isolated green system prevented retraction. A go-around would therefore leave the aircraft flying with the extended gear and its additional drag.

An initial calculation gave expected landing fuel below 7,000 kg, including a required reserve of 4,600 kg. The pilots discussed declaring a minimum fuel state if necessary and sought to avoid a hold. A revised calculation, accounting for lower consumption in descent, gave more than 10,000 kg at landing. About an hour before arrival, the crew had established the sequence for configuring the aircraft for approach, landing and subsequent movement on the ground.

The left wing gear fails to extend

At about 4,000 feet, approximately eight minutes before landing, the pilots selected the landing gear down. The A380 had a nose gear, two body gear assemblies and two wing gear assemblies. Gravity extension used electrically powered emergency unlock actuators to release the uplocks, allowing the gear to fall into position. Two dedicated control modules provided independent electrical channels for the emergency release.

The indications showed the other landing gear down and locked, but the left wing gear failed to reach that state. Its doors were open. The crew declared an emergency approximately four minutes before touchdown and advised that the aircraft would need a tow from the runway. The operating manual contained a procedure for landing with one abnormal wing or body gear, including manual braking and avoidance of the autobrake system.

The commander elected to continue. The investigation found that the fuel remaining and the increase in consumption with the gear extended were the deciding considerations. Its analysis said that, as the new gear problem emerged late in the approach, the time available to obtain and process further information was diminishing and the commander focused on his earlier decision to land. The findings recorded 13,300 kg of fuel on approach when the emergency was declared.

Landing and recovery to the terminal

The A380 landed uneventfully at 2022 UTC with 12,600 kg of fuel. It came to a stop beside taxiway K6. The pilots felt a slight lean to the left during the landing roll and decided to remain on the runway. Smoke was seen near the landing gear brakes, but the fire commander established that there was no fire. The commander reported that the brake temperatures were within limits.

Ground staff approached with a tug. The commander assumed that the person arranging an inspection was an Emirates maintenance engineer. In fact, no company engineer had been dispatched to the runway. Emirates network control had arranged support for the earlier hydraulic problem but had not learned of the emergency declared on the air traffic control frequency shortly before landing. Its engineer was waiting at the stand to troubleshoot the hydraulic defect.

The aircraft was towed slowly via K6 to stand F20 with its passengers aboard. No landing gear safety pins had been fitted. The investigation found unclear communication and confirmation bias: the commander believed a company engineer was managing the tow, while the ground personnel believed they were carrying out his request. The investigation found that nobody competent was in charge of assessing whether the aircraft was safe to move.

Dubai Airports recovery procedures called for a team involving airside operations, the airline engineer, a tug operator and a headset mechanic. The engineer was responsible for establishing whether the aircraft could safely be towed. Emirates engineering procedures also required a walk around inspection and fitting landing gear safety pins before towing, with a technical logbook entry controlling their fitment. That procedure did not cover recovery with passengers and cargo aboard. The headset mechanic and tug operator said they followed the airside controller's instructions.

At the stand, engineers confirmed that the left wing gear was still fully retracted. Fuel was transferred from the left wing tank to the right to level the aircraft before passengers disembarked in controlled groups through the forward left main deck door. All 372 occupants escaped injury. The aircraft, property and environment were undamaged. The investigation found no operational pressure on the ground crew to clear the runway.

Testing reveals two separate technical defects

Airbus supplied a technical adaptation document with instructions and limitations for moving the empty aircraft to a maintenance hangar. Troubleshooting began the next day with AAIS investigators present. Initial visual checks revealed no damage. With the aircraft raised on jacks and the weight on wheels systems reset, the left wing gear extended successfully. More detailed inspections then found broken wires in the harnesses feeding both emergency unlock channels.

Examination of the left wing wiring identified fractures in the three command wires of each channel. Deformation of the wire strands indicated repeated mechanical loading, and investigators found evidence of arcing between broken ends. Tomographic examination confirmed flexure endurance fatigue. The final report attributed the failed release to fatigue damage in the two independent command wire channels, caused by aerodynamic effects on inadequately secured wiring looms during gear operation.

Both free fall control modules passed tests in the hangar and at the vendor facility. The uplock worked satisfactorily after the wires were repaired, although results of additional vendor tests were unavailable when the report was issued. Investigators also found similar damage on the right wing gear channel B wires. The damaged left wing wires were repaired, the uplock assembly and control modules were replaced, and a subsequent gravity extension test succeeded.

The green hydraulic temperature sensor was separately examined in France. Tests found a failed sensing element that produced unreliable values and indications. Some resistance measurements were absent, while measurements below ambient temperature were higher than expected and produced readings above actual system temperatures. The investigation thus documented the sensor defect alongside the wiring damage that prevented emergency extension.

Fleet findings and safety changes

The aircraft had passed an operational emergency extension test on 20 July 2015. The maintenance programme called for free fall tests every 24 months or 3,000 flight hours, whichever came first, including an electrical wiring check and a functional extension test. After the incident, Airbus issued Alert Operator Transmission A32R009-16 on 22 November 2016. It recommended a gravity extension test within one month and inspection of all 24 emergency unlock actuator positions, followed by another extension test, within two months. Initial responses from 75 aircraft inspections identified 37 aircraft with damaged wires.

The final inspection results recorded wire damage on 73 aircraft out of 195 inspections. Relevant damage affected the left and right wing gear unlock systems and appeared unrelated to aircraft age or loom length. Airbus flight tests used cameras to observe the mechanisms and wiring during gear movement. They confirmed aerodynamic movement at the wing gear positions, with minimal or no movement at the body and nose gear positions.

On 26 December 2016, the AAIS issued two prompt recommendations to EASA covering mandatory fleet inspections, investigation of the fatigue mechanism and a design improvement. Airbus subsequently published service bulletin A380-92-8103 and production modification 77381 on 5 May 2017. The final report identified no additional contributing factors to the gear extension failure.

The final report, issued on 14 June 2017, also addressed recovery procedures. The Airbus recovery manual excluded occupied aircraft and the maintenance manual prohibited towing with passengers aboard. Emirates procedures did not cover recovery in these conditions. Recommendations to Emirates called for safe towing instructions and improved monitoring of declared emergencies. Recommendations to Airbus called for consistent flight manual guidance about anticipated towing and detailed instructions for pilots, engineers and ground staff handling similar recoveries.