A380 wake turbulence flips CL604 upside down​

[andypspotter]

A Challenger 604 at FL350 operating from Male-Abu Dhabi passed an A380 opposite direction at FL360, one thousand feet above, about 630nm southeast of Muscat, Oman, over the Arabian Sea.

A short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft into an uncontrolled roll, turning the aircraft around at least 3 times (possibly even 5 times), both engines flamed out, the aircraft lost about 10,000 feet until the crew was able to recover the aircraft, restart the engines and divert to Muscat. The aircraft received damage beyond repair due to the G-forces, and was written off.

An official report is to be published by the German BFU. In the interim, the complete set of circumstances can be read at Aviation Herald.

The current synopsis is copied here:
An Emirates Airbus A380-800, most likely registration A6-EUL performing flight EK-412 from Dubai (United Arab Emirates) to Sydney,NS (Australia), was enroute at FL350 about 630nm southeast of Muscat (Oman) and about 820nm northwest of Male (Maldives) at about 08:40Z when a business jet passed underneath in opposite direction. The A380 continued the flight to Sydney without any apparent incident and landed safely.

The business jet, a MHS Aviation (Munich) Canadair Challenger 604 registration D-AMSC performing flight MHV-604 from Male (Maldives) to Abu Dhabi (United Arab Emirates) with 9 people on board, was enroute over the Arabian Sea when an Airbus A380-800 was observed by the crew passing 1000 feet above. After passing underneath the A380 at about 08:40Z the crew lost control of the aircraft as result of wake turbulence from the A380 and was able to regain control of the aircraft only after losing about 10,000 feet. The airframe experienced very high G-Loads during the upset, a number of occupants received injuries during the upset. After the crew managed to stabilize the aircraft the crew decided to divert to Muscat (Oman), entered Omani Airspace at 14:10L (10:10Z) declaring emergency and reporting injuries on board and continued for a landing in Muscat at 15:14L (11:14Z) without further incident. A number of occupants were taken to a hospital, one occupant was reported with serious injuries. The aircraft received damage beyond repair and was written off.

Oman’s Civil Aviation Authority had told Omani media on Jan 8th 2017, that a private German registered aircraft had performed an emergency landing in Muscat on Jan 7th 2017 declaring emergency at 14:10L (10:10Z) and landing in Muscat at 15:14L (11:14Z). The crew had declared emergency due to injuries on board and problems with an engine (a number of media subsequently reported the right hand engine had failed, another number of media reported the left hand engine had failed).

According to information The Aviation Herald received on March 4th 2017 the CL-604 passed 1000 feet below an Airbus A380-800 while enroute over the Arabian Sea, when a short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft in uncontrolled roll turning the aircraft around at least 3 times (possibly even 5 times), both engines flamed out, the Ram Air Turbine could not deploy possibly as result of G-forces and structural stress, the aircraft lost about 10,000 feet until the crew was able to recover the aircraft exercising raw muscle force, restart the engines and divert to Muscat.

The Aviation Herald is currently unable to substantiate details of the occurrence, no radar data are available for the business jet, it is therefore unclear when the business jet departed from Male and where the actual “rendezvouz” with the A380 took place. Based on the known time of the occurrence at 08:40Z as well as the time when the CL-604 reached Omani Airspace declaring emergency and landed in Muscat, as well as which A380s were enroute over the Arabian Sea around that time The Aviation Herald believes the most likely A380 was EK-412 and the “rendezvouz” took place 630nm southeast of Muscat, which provides the best match of remaining flying time (2.5 hours) and distance for the CL-604 also considering rather strong northwesterly winds (headwind for the CL-604, tailwind for the A380s).

On Jan 7th 2017 there were also other A380-800s crossing the Arabian Sea from northwest to southeast: a Qantas A380-800, registration VH-OQJ performing flight QF-2 from Dubai to Sydney, was enroute at FL330 about 1000nm southeast of Muscat and about 400nm northwest of Male at 08:40Z. An Emirates A380-800 registration A6-EDO performing flight EK-406 from Dubai to Melbourne,VI (Australia) was enroute at FL350 about 470nm southeast of Muscat at 08:40Z. Another Emirates A380-800 registration A6-EUH performing flight EK-424 from Dubai to Perth,WA (Australia), was enroute at FL350 about 350nm southeast of Muscat at 08:40z.

The Aviation Herald received information that Air Traffic Control all around the globe have recently been instructed to exercise particular care with A380s crossing above other aircraft. The Aviation Herald had already reported a number of Wake Turbulence Encounters involving A380s before:

[andypspotter]

German investigators have disclosed that lateral offset procedures were not apparently permitted on the airway being flown by an Airbus A380 and a Bombardier Challenger business jet involved in a serious wake-turbulence upset over the Arabian Sea.

Strategic lateral offset is a technique by which aircraft fly slightly off the centreline of an airway to reduce the risk of a mid-air collision or wake encounter, particularly in regions outside normal air traffic surveillance.

German investigation authority BFU has identified a Sydney-bound Emirates Airbus A380 (A6-EUL) as the aircraft suspected to have triggered the upset to the Challenger 604 on 7 January.

Three crew members and six passengers had been on board the Challenger. Two passengers suffered severe injuries, including broken bones, while two others, and the flight attendant, received either bruising or fractures. Four others, including the two pilots, were unharmed.

The business jet, cruising at 34,000ft, lost 8,700ft in altitude in the space of 32s during the upset, the onset of which occurred less than a minute after the A380 passed overhead, in the opposite direct, at the adjacent cruise level of 35,000ft.

During the descent the aircraft's airframe exceeded the design certification load limits. Although the aircraft landed safely at Muscat, with no apparent external damage, BFU says Bombardier determined the airframe "could not be restored to an airworthy state".

"The aircraft is considered to be damaged substantially," it adds.

BFU confirms that the Challenger – flying from Male in the Maldives to Al-Bateen in the United Arab Emirates – had been operating along airway L894, in the Mumbai flight information region.

India's aeronautical information publication lists 17 routes in the Mumbai FIR on which strategic lateral offset procedures are permitted.

But BFU says airways L894 was "not among them".

The encounter occurred in the vicinity of the DONSA waypoint some 500nm from the nearest land.

BFU says the A380's collision-avoidance system initially detected the Challenger approaching from the opposite direction at a distance of 6nm. The two jets passed one another some 22s later.

Around 48s after the pass, says the inquiry, the Challenger encountered the wake vortex. The A380, by this point, was already 15nm distant to the south-east.

The Challenger initially began to roll to the right, subsequently banking sharply to 42°, and the aircraft experienced strong fluctuations in vertical acceleration and pitch, from 9° nose-up to 20° nose-down, as well as a loss of airspeed from 277kt to 248kt.

Flight-data recorder information captured aileron and rudder deflections to the left, and a roll to 31° left bank. Some 13s after the upset began the aircraft lost the validity of its inertial reference system parameters, and the flight data subsequently recorded zero pitch and roll information.

Testimony from the flight attendant indicates, however, that the aircraft rolled several times during the upset, throwing its occupants against the ceiling.

BFU states that the aircraft's airspeed, which had been around 277kt in the cruise, initially dipped to 248kt before rising to 330kt as the jet descended. Spoilers were extended and then retracted and the left engine, which had been losing thrust, was shut down.

The crew managed to regain control of the aircraft and arrest the descent.

Mumbai air traffic controllers were advised of the occurrence by the crew about 17min after the initial upset, and the pilots declared an emergency, stating that they would divert to Oman. The crew restarted the left engine around 20min later, and the aircraft was flown at 25,000ft. The pilots re-engaged the autopilot about 40min after the engine restart.

BFU says the Challenger landed at Muscat airport around 2h 25min after the wake encounter. The A380 had, in the meantime, continued its flight to Sydney, apparently unaffected by the incident.

Although the German authority has not disclosed the operator of the A380, it has confirmed the airframe involved was MSN224, which Flight Fleets Analyzer confirms as an Emirates aircraft, powered by Engine Alliance GP7200s, which had only been delivered to the Dubai-based carrier less than three weeks earlier.

[andypspotter]

Investigators had no cockpit-voice information, and only limited flight-data recordings, from the Bombardier Challenger 604 involved in an in-flight upset, apparently triggered by wake from an Emirates Airbus A380.

But pilot testimony indicates that the aircraft rolled several times after encountering the wake, injuring five of the Challenger's nine occupants.

The cockpit-voice recorder had already been overwritten by the time the aircraft landed at Muscat, while the jet lost inertial reference system data seconds into the upset and the flight-data recorder did not detail information on the aircraft's attitude, including pitch and roll.

However, the Challenger's captain, who had been flying, told the German-led inquiry that the aircraft had "shook briefly" before rolling heavily to the left. Its autopilot disengaged and the crew had manually attempted to stop the roll with right-bank input.

"But the [aircraft] had continued to roll to the left, thereby completing several rotations," says German investigation authority BFU.

Both pilots fastened their lap belts and the first officer, who additionally wore a shoulder belt, subsequently lost his headset during the roll. The upset also caused pages from the quick-reference handbook to be scattered around the cockpit.

"Since the sky had been blue and the ocean's surface almost the same colour [the captain] had been able to recognise the aircraft's flight attitude with the help of the clouds," says the inquiry, citing the captain's testimony.

The flight attendant told the investigation that she had been standing in the cabin before the upset, and four of the six passengers were also not seated.

"In her recollection the [Challenger] had turned three times around its longitudinal axis, during which the occupants had been thrown against the ceiling and the seats," says BFU. "Several of the passengers suffered injuries, some of which were bleeding. She herself suffered minor injuries."

Inspection of the aircraft after it landed at Muscat showed damage to the seats and panelling, and "traces of blood", the inquiry adds. Armrests on four seats were deformed or fractured and two oxygen masks had fallen from their housing.

One passenger suffered head injuries and a broken rib, while another had fractured a vertebra. Two other passengers and the attendant had injuries including bruising and a fractured nose.

Just after the upset began the left-hand General Electric CF34 engine started to lose thrust and the captain had observed that its interstage turbine temperature had increased to more than 1,000C. The crew shut the engine down.

The aircraft lost almost 9,000ft in altitude before the pilots recovered control at around 24,000ft using aileron control inputs and elevator deflection, according to the crew testimony.

"Based on the memory items the pilots were able to reactivate the [inertial reference system] in attitude mode," says the inquiry, adding that they were able to fly the aircraft towards waypoint KITAL, some 430nm north-east of the location of the upset. This waypoint had previously been on the aircraft's intended course.

The crew subsequently used cross-bleed of the right-hand engine to restart the left.

After restoring the second inertial reference system and eventually re-engaging the autopilot, the crew opted to divert to Muscat.

No warnings of clear-air turbulence had been issued for the Arabian Sea region in which the 7 January upset occurred, reinforcing the suspicion that the A380's wake had been responsible for the event. The inquiry had no available information from the A380's cockpit-voice or flight-data recorders.

BFU states that the Challenger reached airspeeds of 330kt during the descent. It states that the aircraft's maximum operating velocity between 26,570ft and 30,990ft is 318kt.

German business aviation firm MHS Aviation was the operator of the jet (D-AMSC) which suffered an overstressed airframe and was subsequently declared a write-off.