I knew that wake turbulence could pose a hazard to aircraft in their approach to airports before landing. However, courtesy of a link over at Earthbound Misfit's place, I was surprised to learn that it's also a danger during flight along air corridors. The Aviation Herald reports:
The business jet, a ... Challenger 604 ... 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.
. . .
According to information The Aviation Herald received on March 4th 2017 the CL-604 ... 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.
There's much more information at the link.
What's more, the article lists at least six other encounters where wake turbulence affected (and sometimes damaged) other aircraft. A seventh was reported by the pilot of a Boeing 777 over the Atlantic in 2013, again caused by an Airbus A380, the largest airliner in service today. The two aircraft were much further apart, so the effect was less (and much less damaging), but it was still enough to be alarming.
I trotted into the first-class galley. As I began to pour, the airplane experienced a rapid succession of intense turbulence. We began a pronounced roll to the left. The very pleasant and seasoned flight attendant I had engaged in conversation grabbed the nearest stationary piece of galley equipment for support. Her smile was replaced by a wide-eyed expression.
The seatbelt sign soon illuminated. Within moments, the intercom phone chimed. The flight attendant reached for the handset. My copilot was calling. He was commanding all flight attendants to be seated. Imagine that.
By the sharpness of the bumps and the definitive bank of the airplane, I had a good idea that we had not encountered your garden-variety clear-air turbulence. I stumbled my way to the interphone and called my copilot, indicating an urgent desire to return to the cockpit.
I hopped back into the left seat only to be greeted by another bout of turbulence. Suspecting foul play, I glanced at the traffic symbol on the TCAS display. Sure enough, another airplane cruised directly ahead of us at FL 400. I immediately pushed the heading select button on the eyebrow of the glareshield and turned us 30 degrees to the right.
In spectacular fashion, I watched as a wispy spiraling circle rocketed back toward us. It was a wingtip vortex. Never in my career had I actually seen one in its entirety at cruise altitude. The vortex once again appeared, buffeting the airplane. I instructed my copilot to ask Gander Center for an immediate altitude change to FL 400. I pressed the vertical-speed button on the glareshield eyebrow and rotated the dial to a 500 fpm rate of climb. I wasn’t going to wait for the next encounter. Within moments, another wispy spiral sped its way back toward our position. Only this time, we missed its wrath.
Again, more at the link.
I think the passengers and crew of that business jet over the Indian Ocean were extremely lucky to survive the encounter, considering that their aircraft was less than one-twentieth the size and mass of the huge A380. The difference between them in wake vortex strength and duration is so great as to be almost unimaginable. I'm surprised this incident hasn't been more widely reported. It's a hazard confronting almost every aircraft in the sky, so I'd imagine every pilot would be interested in learning how to minimize such dangers.
Aviation Herald concludes its article with the draft of a proposed EASA safety bulletin, advocating greater vertical and horizontal separation between aircraft on air routes. I hope they promulgate it soon!
Peter
8 comments:
There is no way to control a CL600 series aircraft by sheer muscle force. The controls are linked by steel (or carbon fibre/kevlar) cables to hydraulic PCUs (Power Control Units) at each control surface. The cables only move a valve, (2 valves in the case of the aileron PCU) to port hydraulic fluid to one side or the other of the PCU piston. Without hydraulic pressure there is no possibility of control. Fortunately even with both engines flamed out they will windmill at about 17% in a glide giving a bare minimum of flow on the engine driven pumps.
They were really lucky that the 604 didn't pitch up into a deep stall from which there is no recovery. I would love to hear the CVR tape from this incident. I would guess the pilots were well trained.
Regarding the EASA report, for the past 20 years the industry has been trying to squeeze airplanes together tighter via RVSM (Reduced Vertical Separation Minimum) and WAAS (Wide Area Augmentation System) which basically creates three electronic lanes in the sky, 10 miles apart.
Al_in_Ottawa
Al beat me to it. WAAS is about the ONLY fix, other than wider spacing horizontally between acft, or some degradation model of wake turbulence (both vertical and horizontal dispersion) that attaches to the acft bug for the controllers.
Sort of makes one wonder about the GA crashes that occur between Flagstaff and Phoenix, that are usually written off as "pilot error". Airliners coming from the Midwest make their descents through that area.
Ed_Mc
(more than meets the eye)
I'm already scared enough to fly thank you very much. Yikes.
Not sure what y'all are so bothered about. I wouldn't mind if the right people were on the trailing aircraft. Of course, that's unfortunately not likely to be the case with commercial air.
When I first saw the proposal for RVSM I didn't think it was a good idea. I realize they are trying to squeeze more traffic into the transatlantic lanes, but it's simply dangerous. I went through wake turbulence coming out of Atlanta a few years back and it wasn't fun. We were crossing someone's wake and the shock made me worry a bit.
Wake Turbulence is nothing to play with.
Given that the wake turbulence was enough to total out an aircraft and send the passengers and crew to the hospital, one with serious injuries, I'd advocate grounding all airbus size aircraft until a fix can be found.
Its not about "airbus size aircraft", and the article wrongly leaned towards A380 types as the problem. Its mostly anything and even similar sized aircraft can give you a ride.
RVSM has us at 1000' vertical seperation. Vortices trail and descend behind the aircraft, so being behind and slightly lower is the problem area. We are allowed to offset laterally in oceanic airspace up to 2 miles right. Of course that doesnt help anything if everybody is 2 miles right of course. If I can see the passing aircraft I will generally try to offset laterally for a little while until it is farther ahed to miss the votices.
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