Emirates A388 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent

Last Update: June 30, 2017 / 17:18:40 GMT/Zulu time

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Incident Facts

Date of incident
Jan 7, 2017

Classification
Accident

Aircraft Registration
A6-EUL

Aircraft Type
Airbus A380-800

ICAO Type Designator
A388

On Jun 22nd 2017 the European Aviation Safety Agency (EASA) released their Safety Information Bulletin 2017-10, the draft of which had already been covered in earlier coverage.

On May 16th 2017 Germany's BFU released their January 2017 Bulletin in German (the interim report covering this occurrence now also available separately in English) reporting that the Challenger (serial number 5464), carrying 6 passengers and 3 crew, got out of control about one minute after it had been overflown by an Airbus A380. The aircraft lost about 9000 feet before the crew was able to regain control. Two passengers received serious, one member of the crew as well as two other passengers minor injuries. The aircraft diverted to Muscat. As the occurrence happened over international waters the BFU is responsible for the investigation assisted by the investigation bodies of Oman, India, United Arab Emirates, Canada, USA and France.

The BFU reported the Challenger had departed Male at 06:52Z, reached cruise flight level 340 at 07:20Z and was enroute along L894 to waypoint KITAL. At 08:18Z the crew reported passing waypoint GOLEM.

An Airbus A380-800, serial number 224, (Editorial note: although the BFU is not permitted by German law to identify aircraft, the narrative is consistent with Emirates A388 A6-EUL) had departed Dubai at 06:55Z for Sydney (Australia). The aircraft was enroute at FL350 in southeasterly direction.

Analysis of flight data of both aircraft showed, that at 08:38:07Z the A380 passed over the Challenger at 1000 feet vertical separation, about one minute later at 08:38:54Z the Challenger, on autopilot, began to rotate to the right around its longitudinal axis despite ailerons deflected to the left and a light vertical acceleration began. Over the next 10 seconds a right bank of 6-8 degrees were recorded, then the right bank increased to 42 degrees within one second despite left aileron deflection of 20 degrees, a vertical acceleration of +1.6G occurred followed by a vertical acceleration of -3.2G one second later. 13 seconds after the begin of the upset the autopilot disconnected and a master warning activated for 7 seconds.

The flight data recorder recorded a loss of altitude of 8700 feet between 08:39:09Z and 08:39:41Z. At 08:39:31Z the airspeed reached 330 KIAS, the left engine's N1 reduced to 40% while the ITT increased to 850 degrees C. The crew shut the left hand engine down.

At 08:56Z the crew declared emergency with India's Air Traffic Control, reported their position and what happened, and advised they were diverting to Muscat via waypoint KITAL.

At 09:15Z the crew restarted the left engine, climbed back to FL250, engaged the autopilot again at 09:56Z and landed at Muscat at 11:05Z.

According to recordings at Omani Air Traffic Control they were informed by India's ATC that the aircraft was at FL230 and was estimated to pass KITAL at 09:37Z. India's ATC reported an engine shut down as cause for the low altitude and advised the crew was diverting to Muscat.

The BFU reported the crew first observed the aircraft above them in opposite direction on their TCAS, the captain subsequently identified an A380 and the airline. The A380 passed them slightly to the left and above. A short time later the aircraft was exposed to wake turbulence, the aircraft rolled to the left uncontrollable (editorial note: this testimony seems to be opposite to the FDR recordings reported above), the autopilot disconnected. Both crew applied right aileron, however the aircraft continued to roll left and made several revolutions, both Inertial Reference Systems, the flight management system and the attitude indicators failed. Both pilots were wearing their lap belts and crotch belts, the first officer was also wearing his shoulder harness. The captain lost his head set, the quick reference manual lifted off in the cockpit and was distributed over the cockpit with single pages around the cockpit. Using external horizont reference the captain identified their attitude and was able to stabilize the aircraft again at FL240, he observed the left hand engine's N1 and N2 separated with the N1 reducing, the ITT reached 1000 degrees C and flashed red, the engine was shut down. Using the memory checklists the crew were able to restore Inertial Reference System (IRS) #1 in ATTITUDE Mode which enabled them to continue the flight towards KITAL, subsequently the crew restarted the left engine using cross bleed from the right hand engine. The crew subsequently restored IRS #2, position and heading were entered into the flight management system, then it was possible to engage the autopilot again.

The flight attendant reported that she was in the middle of the cabin preparing inflight service when the aircraft made three revolutions around the longitudinal axis according to her recollection. At that time 4 passengers were not in their seats, too. During the revolutions the occupants were thrown against ceiling and seats. The flight attendant received minor injuries, the passengers received bleeding wounds.

The BFU reported one passenger received head injuries and a fracture of a rib, another passenger received a vertebral fracture. The flight attendant and the two other injured passengers received bruises respective a nasal fracture.

The BFU reported that following the accident the aircraft flew for more than two hours until landing in Muscat, the cockpit voice recorder therefore was overwritten and the accident sequence no longer available on the CVR.

The BFU reported that Strategic Lateral Offset Procedures had not been permitted on airway L894 used by the Challenger.

The BFU reported that the aircraft sustained no visible damage to fuselage, wings and tailplane including control surfaces. No leakages were observed. The manufacturer however stated, that it was impossible to return the aircraft into airworthy conditions due to accelerations that were beyond the design limits of the aircraft structure. The aircraft was therefore rated substantially damaged.

The BFU reported that ICAO introduced a work group in 2003 to develop safety recommendations to reduce the effects of wake turbulence by A380 aircraft to an acceptable level. The work group focussed on aircraft flying on parallel tracks and advised that wake turbulence could occur as far as 20nm behind and 1000 feet below an A388 or other heavy aircraft (including B744 and A346 specifically being mentioned by the work group). The work group also considered particularly strong wake turbulence behind heavy aircraft climbing or descending. The material quoted by the BFU does not mention aircraft flying in opposite direction.

DONSA waypoint (Coordinates N14.5886 E65.1925) is located 660nm southeast of Muscat Airport.
Incident Facts

Date of incident
Jan 7, 2017

Classification
Accident

Aircraft Registration
A6-EUL

Aircraft Type
Airbus A380-800

ICAO Type Designator
A388

This article is published under license from Avherald.com. © of text by Avherald.com.
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