high speed cruising

Emirates A380 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent.

An Emirates Airbus A380-800, 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 at FL340 over the Arabian Sea about 630nm southeast of Muscat 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 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.

No radar data are available for the business jet, it is therefore unclear when the business jet departed from Male and where the actual “rendezvous” 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 most likely A380 was EK-412 and the “rendezvous” 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) - this analysis was confirmed on Mar 23rd 2017 by BFU information.

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 enrooted 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 enrooted 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 enrooted at FL350 about 350nm southeast of Muscat at 08:40z.

Air Traffic Control all around the globe have recently been instructed to exercise particular care with A380s crossing above other aircraft.

A number of Wake Turbulence Encounters involving A380s already reported:

Incident: Virgin Australia B738 near Bali on Sep 14th 2012, wake turbulence from A380
Incident: Air France A320 and Emirates A388 near Frankfurt on Oct 14th 2011, wake turbulence
Accident: British Airways A320 and Qantas A388 near Braunschweig on Oct 16th 2011, wake turbulence injures 4
Report: Antonov A124, Singapore A388 and Air France B744 near Frankfurt on Feb 10th 2011, wake turbulence by A388 causes TCAS RA
Report: REX SF34 at Sydney on Nov 3rd 2008, wake turbulence injures one
Incident: Armavia A320 near Tiblisi on Jan 11th 2009, turbulence at cruise level thought to be A380 wake

On Mar 18th 2017 an EASA safety information bulletin released stating:

With the increase of the overall volume of air traffic and enhanced navigation precision, wake turbulence encounters in the en-route phase of flight above 10 000 feet (ft) mean sea level (MSL) have progressively become more frequent in the last few years.

The aim of this SIB is to enhance the awareness of pilots and air traffic controllers of the risks associated with wake turbulence encounters in the en-route phase of flight and provide recommendations with the purpose of mitigating the associated risks.

The draft reasons:

The basic effects of wake turbulence encounter on a following aeroplane are induced roll, vertical acceleration (can be negative) and loss or gain of altitude. The greatest danger is an induced roll that can lead to a loss of control and possible injuries to cabin crew and passengers. The vortices are also most hazardous to following aircraft during the take-off, initial climb, final approach and landing.

However, en-route, the vortices evolves in altitudes at which the rate of decay leads to a typical persistence of 2-3 minutes, with a sink rate of 2-3 metres per second. Wakes will also be transported by wind.

Considering the high operating air speeds in cruise, wake can be encountered up to 25 nautical miles (NM) behind the generating aeroplane, with the most significant encounters reported within a distance of 15 NM. This is larger than in approach or departure phases of flight.

The encounters are mostly reported by pilots as sudden and unexpected events. The awareness of hazardous traffic configuration and risk factors is therefore of particular importance to anticipate, avoid and manage possible wake encounters. The draft issues following recommendations.

As precautionary measures, operators and pilots should be aware that:

- As foreseen in Reg. 965/2012 AMC1 to CAT.OP.MPA.170, the announcement to passengers should include an invitation to keep their seat belts fastened, even when the seat belt sign is off, unless moving around the cabin. This minimises the risk of passenger injury in case of a turbulence encounter en-route (wake or atmospheric).

- As indicated in ICAO PANS-ATM, for aeroplanes in the heavy wake turbulence category or for Airbus A380-800, the word “HEAVY” or “SUPER”, respectively, shall be included immediately after the aeroplane call sign in the initial radiotelephony contact between such aeroplanes and ATS units.

- When possible, contrails should be used to visualise wakes and estimate if their flight path brings them across or in close proximity.

- When flying below the tropopause altitude, the likelihood of wake encounter increases. The tropopause altitude varies (between days, between locations).

- Upwind lateral offset should be used if the risk of a wake encounter is suspected.

- Timely selecting seat belt signs to ‘ON’ and instruct cabin crew to secure themselves constitute precautionary measures in case of likely wake encounters.

In case of a wake encounter, pilots should:

- Be aware that it has been demonstrated during flight tests that if the pilot reacts at the first roll motion, when in the core of the vortex, the roll motion could be amplified by this initial piloting action. The result can be a final bank angle greater than if the pilot would not have moved the controls.

- Be aware that in-flight incidents have demonstrated that pilot inputs may exacerbate the unusual attitude condition with rapid roll control reversals carried out in an “out of phase” manner.

- Be aware that if the autopilot is engaged, intentional disconnection can complicate the scenario, and the autopilot will facilitate the recovery.

- Avoid large rudder deflections that can create important lateral accelerations, which could then generate very large forces on the vertical stabiliser that may exceed the structural resistance. Although some recent aircraft types are protected by fly-by-wire systems, use of the rudder does not reduce the severity of the encounter nor does it improve the ease of recovery.

- Make use of specific guidance available through AOM for their specific type(s)/fleet.

ATS providers and air traffic controllers should:

Enhance their awareness about en-route wake turbulence risk, key factors and possible mitigations, based on the information provided in this document and other relevant material. This could be achieved through flyers, e-learning, and refresher training module.

Possible risk mitigations may consist of:

- Make use of the wake turbulence category (WTC) indication in the surveillance label and/or the flight progress strip (whether electronic or paper), and observe closely separated aeroplanes that are at the opposite extremes of the WTC spectrum;

- As the best practice, provide traffic information, advising “CAUTION WAKE TURBULENCE”, when you identify that a ‘HEAVY’ or ‘SUPER HEAVY’ wake category traffic is climbing or descending within 15 NM of another following traffic;

- Manage en-route traffic crossings such as , when possible while preserving safe tactical management of overall traffic in the sector, avoiding to instruct climb or descend to ‘HEAVY’ or ‘SUPER HEAVY’ traffic within 15 NM distance from another following traffic;

- If at all possible, avoid vectoring an aeroplane (particularly if it is LIGHT or MEDIUM category) through the wake of a HEAVY or SUPER HEAVY aeroplane where wake turbulence may exist.

FORT CARSON, Colo. – Members of the Colorado Army National Guard’s 5th Battalion, 19th Special Forces Group (Airborne) fast-rope from a U.S. Air Force V-22 Osprey aircraft at Butts Army Air Field July 11, 2009. “The operators were conducting special operations training through collaboration with the active duty 10th Special Forces Group (Airborne), and the U.S. Air Force’s 71st Special Operations Squadron out of Albuquerque, New Mexico,” said 5/19th SFG(A) Commander Lt. Col. Ken Chavez. The V-22 is a multi-mission, tiltrotor aircraft designed to perform missions like a conventional helicopter with the long-range, high-speed cruise performance of a turboprop aircraft. (Official U.S. Army photo by Army Pfc. Kristoff Decloedt)