Emirates A388 near Dubai on Nov 9th 2016, hydraulic overheat leads to unsafe main gear on landing

Last Update: June 28, 2017 / 14:07:44 GMT/Zulu time

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Photo of Emirates Airlines A6-EDQ, Airbus A380-800 — Emirates Airlines A6-EDQ, Airbus A380-800 (Photo credit: DeepWater90 / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Nov 9, 2016

Classification
Incident

Airline
Emirates Airlines

Flight number
EK-2

Departure
London Heathrow, United Kingdom

Destination
Dubai, United Arab Emirates

Aircraft Registration
A6-EDQ

Aircraft Type
Airbus A380-800

ICAO Type Designator
A388

An Emirates Airbus A380-800, registration A6-EDQ performing flight EK-2 from London Heathrow,EN (UK) to Dubai (United Arab Emirates) with 345 passengers and 27 crew, was enroute when the crew received an ECAM message "HYD G SYS TEMP" followed by "HYD G SYS OVHT". The crew performed the related checklist actions isolating the green hydraulic system. On approach to Dubai the crew performed an alternate gear extension which resulted in an unsafe indication for the left hand wing (main) gear, on final approach the ground proximity warning system activated warning that the left hand wing gear was not down. The crew performed a safe landing on runway 30L according to FCOM procedures for landing with one abnormal wing or body gear.

The United Arab Emirates GCAA rated the occurrence a serious incident and opened an investigation.

On Jun 28th 2017 the GCAA released their final report concluding the probable causes of the incident were:

The AAIS determines that the cause of the failure of the emergency unlock actuators to release the left wing landing gear was the flexure endurance fatigue damage to the independent channel A and channel B emergency unlock actuator (EUA) command wires.

The flexure endurance fatigue was induced by aerodynamic effects acting on the inadequately secured wiring loom during landing gear operation.

The GCAA summarized the sequence of events:

The departure and initial flight in cruise continued normally until 3 hours 20 minutes into the flight, when the flight crew received an electronic centralized aircraft monitoring (ECAM) message, indicating that the green hydraulic system had exceeded the normal operating temperature. A further message was received shortly after advising the crew that the green hydraulic system had overheated. The flight crew followed the flight crew operating manual (FCOM) instructions and isolated the green hydraulic system.

The isolation of the green hydraulic system resulted in the loss of hydraulic pressure for the wing landing gear extension. The flight crew reviewed the procedures to lower the landing gear using the emergency gear extension method. The loss of the green system hydraulic pressure also resulted in restricted use of the nose gear steering, slow flap and slat retraction, and limited brake function.

The flight crew discussed the situation with the Operator’s maintenance control center (MCC), which is part of the Operator’s network control center (NCC). The flight crew asked the MCC to inform air traffic control (ATC) in Dubai that they requested a long approach and a tow from the nearest taxiway after landing.

On the final approach, at about 4,000 feet and approximately eight minutes prior to landing, the landing gear was selected down. The landing gear indication showed that the landing gear was down and locked, except for the left wing gear. While the landing gear doors indicated open, the gear indicated that it was not down and locked. As a result, the flight crew declared an emergency four minutes prior to the landing.

In a situation where the green hydraulic system is isolated inflight, landing gear retraction is inhibited and the landing gear doors remain open. This results in a significant increase in drag and then in fuel consumption. With the fuel remaining as a consideration, the Commander elected to continue the approach and land.

The landing at 2022 UTC was uneventful and the Aircraft came to a stop on the runway adjacent to taxiway K6. The flight crew communicated with ground staff and, after an inspection, it was decided to tow the Aircraft to the assigned stand F20, which was the closest to the exit taxiway. On arrival at the stand, it was noticed that the left wing gear had not extended and was still in its bay.

Due to the retracted wing landing gear, the Aircraft was leaning slightly to the left, and after arriving at the stand, fuel was transferred from the left wing tank to the right wing tank to level the Aircraft. The passengers were disembarked in controlled groups through the forward left door on the main deck.

The GCAA reported in their analysis that the damage to the wires were found on many A380s globally:

An overheat indication of the green hydraulic system required the flight crew to isolate the system and to comply with a number of restrictions for the completion of the flight. One of these restrictions is the utilization of the emergency landing gear free fall system.
The failure of both of the independent channel A and channel B emergency unlock actuators on the left wing landing gear uplock assembly was caused by damage to all six command wires in the vicinity of the two unlock actuator connectors.

The examination and analysis identified that the independent and dedicated channel A and channel B EUA command wires were most likely damaged by repetitive aerodynamic loads as a result of the installation design, which provided insufficient support for the wiring looms when they were exposed to aerodynamic effects during gear extension and retraction.

An A380 fleet inspection initiated by the Aircraft manufacturer identified many aircraft with similarly damaged EUA wires.

The GCAA analysed crew decision making:

One of the Commander’s main concerns, during the preparation for landing, was the anticipated increase in fuel consumption due to the loss of the green hydraulic system and possible aileron deflections. An initial fuel calculation resulted in landing fuel of less than 7,000 kg, which included the required 4,600 kg reserve. The Commander was concerned that being sent to the hold could further reduce the landing fuel, therefore the crew discussed declaring a minimum fuel state, if required. A second calculation resulted in more than 10,000 kg of landing fuel.

The flight crew used the time available to them to prepare for the remainder of the flight, and considered the expected system limitations. At approximately one hour to landing, they had established the sequence for the Aircraft configuration for approach, landing, and taxiing.

At an altitude of 2,600 feet, and 4 minutes 36 seconds before landing, the Commander decided against a go-around due to fuel quantity remaining reasons. The Commander intended to avoid entering the hold prior to encountering the wing landing gear fault. When the problem became apparent, and an emergency was declared, time was running out to access and process more information causing the Commander to focus on his first decision which was to continue the approach and land. The Aircraft landed with 12,600 kg of fuel onboard.