For anyone interested, there are several great youtube videos[1-4] that show the wakes (the wingtip vortices in particular) created by various aircraft.
This incident brings the Reduced Vertical Separation Minima (RVSM)[5] into question. Strategic Lateral Offset Procedure (SLOP)[6] can be used used to avoid such incidents.
> In addition to mitigating en route midair collision hazard, SLOP is used to reduce the probability of high-altitude wake turbulence encounters. During periods of low wind velocity aloft, aircraft which are spaced 1000 feet vertically but pass directly overhead in opposite directions can generate wake turbulence which may cause either injury to passengers/crew or undue structural airframe stress. This hazard is an unintended consequence of RVSM vertical spacing reductions which are designed to increase allowable air traffic density. Rates of closure for typical jet aircraft at cruise speed routinely exceed 900 knots.
Seriously, "unintended consequence"? It seems quite obvious in retrospect.
This is a reminder that the announcement that you should "keep your seat belt fastened at all times when you're in your seat" isn't just something someone made up. It's a small price to pay in case you ever encounter severe turbulence en route, but it might be one of these things that most people don't realize until it happens to them. Hitting your head against the cabin ceiling can seriously put a damper on your trip.
Or, as with cars, just be in the bigger car. Another a380 would probably have shaken off this encounter. Size, and the flex that comes with size, flattens out these things.
True.I would think this would be more of a problem for people from US states where wearing a seatbelt is not mandatory.
In other parts of the world (with more sense) such as Europe, Australia, we're conditioned to always using it due to strict enforcement and as such it's not such a novelty.
When I was in single digits, my mother and I were coming home from an international flight and the plane was struck by lightning. We lost a bit of altitude (felt like a TON of altitude subjectively), and yeah... it was a damned good thing we'd all been told to keep those seatbelts on. It was literally the difference between seconds of terror, and someone being seriously injured.
While I agree with the general sentiment, to be honest there are easier solutions here. They could've just turned on the sign as soon as they saw the A380 so that people could fasten their seatbelts then. And then turned off the sign when the threat was gone. You don't need a cannon to kill a fly.
Had to google around to understand wake turbulence. If I read the wiki correctly, it's basically a horizontal tornado that emanates from the wings. That would explain the rolling that the aircraft encountered.
On another note, I fly every week for work, can't imagine rolling five times and engines losing power with a drop of 10k feet. That's absolutely insane. I've had engines lose power before, but it was quickly regained such that the drop was more moderate.
It's helpful to think of an aircraft's wake in two parts.
The wing is deflecting air downward to provide lift; this creates a volume of downward-moving air behind the aircraft.
There's higher pressure under the wing and lower pressure on top, so air from below tries to get above the wing at the wingtips. This causes circulatory motion, yielding wingtip vortices (see my top-level comment for some visualizations).
This is quite interesting. I've been living underneath a flight plan for the last few years, and every now and then I've noticed a strange noise that seems to come from the air a few seconds after a plane has passed overhead on approach. The best way I can describe it is as a tearing noise, somewhat like a long stretched version of a tear in paper, or fabric. I've long suspected that it may be due to turbulence, and this article certainly suggests that the turbulence for some aircraft is much more powerful than I'd suspected.
That's likely the sound of jetwash striking (nearly) stationary air as it exits the engine.
I'm familiar with the roar of jets taking off. Some years back I happened to be biking past an airport, at the end of the runway, just as a passenger jet was lining up for takeoff, headed away from me. I thought I'd pause to watch.
Only as the engines spooled up did I think, "hrm, this could get loud".
It didn't.
Instead, what I heard was ... the engines spooling up. Loud, yes, but not a roar, just an increasing pitch, until the airplane started accelerating down the runway.
It wasn't until some 15-20 seconds later that I heard the familiar roar, echoing off of hills five or so miles away. That's when I realised that the whine was the sound of the turbines, but the roar was the sound of exhaust gas, streaming out of the engines, hitting stationary air and generating intense turbulence, and radiating outward in a perpendicular line to that jetwash. So I didn't hear it directly (it was moving away from me), only the reflection (as that wall of noise, now reflected off the hills, was directed back toward me.
I doubt the vortex would make any particularly loud sound, though you might hear the rushing of air. Speeds are in the tens of miles per hour rather than hundreds as with jetwash.
Big problem is the use of autopilot navigation locked to the GPS route.. this pretty much guarantees that you will fly right below the wake of the above plane on the same route! (Before GPS it will be very odd to flight exactly the same path) ..
Eh. e.g. the north atlantic tracks have been around since the 1960s. GPS wasn't available to the public until Korean Air Lines Flight 007 in the 1980s.
I was looking at FlightRadar24 and listening to ATC while an A380 took off from Dulles near DC. Not only did they warn for wake turbulence when the plane was already well away, they held other aircraft for a runway inspection after the plane took off. I'd imagine that kind of wake could kick up some significant debris on the ground as well.
To be clear, that crash in Queens was 100% pilot error (and the plane allowing insane inputs). There was a little turbulence, but it was the extreme rudder movement that threw the plane around and tore off the tail.
The physics of this are insane. Then again, by my calculation the A380 displaces roughly 11 million cubic feet of air per second at the max landing weight.
EDIT: this is the net downward displacement of air sufficient to equal the A380 850,984lb max landing weight assuming a ballpark air density of ~0.075 lb/ft^3. The aircraft displaces much more air via its engines, fuselage and secondary effects, but the above number seems most relevant to the Challenger 604 ~1,000 feet beneath the aircraft :).
I just love An-2 planes. They can take off and land almost everywhere, they're one of the slowest and lowest flying planes that I've ever seen (which I find cool), plus the propeller/engine has a special sound. There's a couple of them stationed just outside my parents' village in Eastern Europe, if you look on the GMaps link that thing close to them it's actually a sheepfold (https://www.google.ro/maps/@44.2288052,27.5250523,386m/data=...).
I've been on a widebody caught in an A380 wake before. Some seriously violent turbulence for a few seconds, and the pilot came on afterwards to tell us what happened.
Holy smokes that must have been terrifying. Glad nobody died. I hate flying as it is (not that I'm likely to ever find myself in a private jet anytime soon).
Wow. Uncontrolled roll at least 3 times, maybe 5. G-loads severe enough to damage the airframe beyond repair. And this was a 9-passenger bizjet, not a tiny light single.
Pilots should be aware of wake turbulence and wingtip vortices in particular, and should be aware that being at a lower altitude than the generating aircraft is the most dangerous position (the vortex pattern is denser than the surrounding air and therefore descends).
Also, an invisible vortex is no less turbulent for its invisibility.
Landing at O'Hare in a smaller bombardier 2x2 (crj 700 I think) jet following a jumbo was an interesting (white knuckle) ride I had in recent memory. The plane turned over lake michigan east of the city and felt like it went completely 90deg to the ground losing a good amount of altitude which I do not believe was the pilots intention. I definitely heard a few gasps, the stewardess curse and my wife grip my hand hard. Followed by 10 minutes of bumps, drops, and wing waggling and a landing that felt like we simply dropped 10 feet on to the tarmac.
Those little jets man... they're fine most of the time but what a spooky experience that was.
Tangentally related - We deal with this a lot in Wingsuit BASE jumping (well, in wingsuit skydiving as well, but wake vortices and turbulence (aka 'burbles') have killed more than a few extremely talented pilots in the last year).
It's fucking wild how small of a wing can put off a sizable wake. With wingsuits, if you fly behind and slightly above a buddy, you're going to hit his burble and you're going to immediately lose lift and possibly start spinning. There's a clip floating around of a bunch of us on a training jump in race suits and one of the guys hits a burble from the group and just gets dropped a few hundred feet damn near immediately.
Right now, the vertical separation minima for aircraft worldwide are not conditional on size. At altitudes above 28,000ft MSL, the minimum vertical separation is 1000ft, even for superjumbos. It is probably a rare event that two aircraft come so close both vertically and horizontally, but I wonder if there will be a rule change because of this incident nonetheless.
By contrast, the horizontal separation minima vary dramatically based on the size of the leading aircraft.
It's fairly standard practice, as long as the aircraft involved are certified for it and flying on autopilot. Given that the planes involved were flying at FL350-60, they probably were (altitudes above a certain threshold - FL290 in the US) are restricted to aircraft operating under rules allowing 1000ft vertical separation.
By law, 5 (nautical) miles horizontal separation or 1000 feet vertical separation is required. When aircraft were smaller, that was probably more than sufficient. The A380 is another beast entirely, though.
Mostly an aviation thing but descended from the fact that many early airplanes were American/British. IIRC only China, Russia and the DPRK use metric units.
Aviation. 500 & 1000 ft intervals are very convenient discrete altitude levels for coordinating traffic, and that's probably a key reason why it's held up universally. In meters, the interval will either awkward and hard to communicate numbers or spaced too widely to be efficient.
Under normal flight conditions, the aircraft's engine supplies hydraulic power to the flight controls (flaps, ailerons, elevator), like power steering in your car. Very necessary for big/fast aircraft, as the plane is heavy and the force of the air resisting the movement of those control surfaces is very high.
If the engines fail, you still need to be able to control the plane, so there is something called a ram air turbine[1] which can be deployed out of the side of the aircraft. It is basically just a little propeller which spins in the breeze, which powers a pump, which supplies the hydraulic pressure to control the plane. So if the power goes out, you can still deploy that thing and have "power" assistance in controlling the plane.
The article says the ram air turbine did not deploy, possibly because the g-forces were holding it in, or perhaps because the g-forces or aerodynamic stresses were flexing the body of the plane so much that the turbine was held in place by the bending. So the pilots did not have "power steering" on the plane, and had to pull on the controls with "raw muscle force".
There is probably some mechanical advantage, probably both from the leverage afforded by the mechanics of actuation, and from the aerodynamics of the wing, that allow a single human to move the whole plane around. But it would still be very, very hard to control the plane without power assist, especially under such extreme conditions.
(Any pilots/aerospace engineers feel free to chime in/correct mistakes here).
If both engines went out, then that means hydraulic power was lost, and that all of the aerodynamic forces on the control surfaces were transmitted directly to the stick. This is exactly the same as trying to steer a car with the engine turned off - you can do it, but it takes much more effort than when the power steering is working.
It appears that there is a section of air between 29,000ft and 41,000ft, where flights are allowed to be closer than is normally allowed. Instead of 2,000ft apart, they are allowed to fly 1,000ft apart. In order to operate continually in this airspace, a plane must be "RVSM approved". Otherwise they have to either request special permission or make a continuous climb through said airspace while complying with their usual 2,000ft requirements.
The article mentions that the A380 and Challenger 604 were 1,000ft apart. So, I would assume they were both RVSM approved. This event could call the RVSM into question.
When an airframe is stressed beyond its design limits it can't be put back into service. It's conceivable that it could be put through a "C-check" type process of disassembly and inspection, but given the age and residual value of the plane that might not have been cost effective.
Planes are very fragile and are not meant to be able to sustain loss of control at high speeds. Sudden disintegration does happen mid air following a loss of control.
I am always impressed at how they look like a big chunk of metal from the outside, but they are in fact mostly made out of air and very thin and light materials.
As an uneducated guess, the wing mounts (aluminum?) and surrounding fuselage have stretched way beyond tolerance and are no longer capable of supporting nominal load. The metal has fatigued and must be replaced, which would require new wings and nearby fuselage -- at no small cost.
I'd imagine it's less a case of the plane being damaged heavily and more a case of there's just not enough value gained by keeping it in service to offset the potentially disastrous cost if something were to go wrong.
The article said the plane had been subject to very intense g forces, so I would imagine substantial structural damage. They should feel lucky that it didn't fall apart.
Some comments were deferred for faster rendering.
phumbe|9 years ago
This incident brings the Reduced Vertical Separation Minima (RVSM)[5] into question. Strategic Lateral Offset Procedure (SLOP)[6] can be used used to avoid such incidents.
[1] https://www.youtube.com/watch?v=E1ESmvyAmOs
[2] https://www.youtube.com/watch?v=dfY5ZQDzC5s
[3] https://www.youtube.com/watch?v=uy0hgG2pkUs
[4] https://www.youtube.com/watch?v=KXlv16ETueU
[5] https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...
[6] https://en.wikipedia.org/wiki/Strategic_lateral_offset_proce...
ryguytilidie|9 years ago
csours|9 years ago
mcguire|9 years ago
smarx007|9 years ago
bglazer|9 years ago
bbcbasic|9 years ago
mirimir|9 years ago
> In addition to mitigating en route midair collision hazard, SLOP is used to reduce the probability of high-altitude wake turbulence encounters. During periods of low wind velocity aloft, aircraft which are spaced 1000 feet vertically but pass directly overhead in opposite directions can generate wake turbulence which may cause either injury to passengers/crew or undue structural airframe stress. This hazard is an unintended consequence of RVSM vertical spacing reductions which are designed to increase allowable air traffic density. Rates of closure for typical jet aircraft at cruise speed routinely exceed 900 knots.
Seriously, "unintended consequence"? It seems quite obvious in retrospect.
lutorm|9 years ago
taejavu|9 years ago
wallace_f|9 years ago
sandworm101|9 years ago
sundvor|9 years ago
In other parts of the world (with more sense) such as Europe, Australia, we're conditioned to always using it due to strict enforcement and as such it's not such a novelty.
M_Grey|9 years ago
wfunction|9 years ago
uptownfunk|9 years ago
On another note, I fly every week for work, can't imagine rolling five times and engines losing power with a drop of 10k feet. That's absolutely insane. I've had engines lose power before, but it was quickly regained such that the drop was more moderate.
phumbe|9 years ago
The wing is deflecting air downward to provide lift; this creates a volume of downward-moving air behind the aircraft.
There's higher pressure under the wing and lower pressure on top, so air from below tries to get above the wing at the wingtips. This causes circulatory motion, yielding wingtip vortices (see my top-level comment for some visualizations).
unknown|9 years ago
[deleted]
rurban|9 years ago
jmts|9 years ago
dredmorbius|9 years ago
I'm familiar with the roar of jets taking off. Some years back I happened to be biking past an airport, at the end of the runway, just as a passenger jet was lining up for takeoff, headed away from me. I thought I'd pause to watch.
Only as the engines spooled up did I think, "hrm, this could get loud".
It didn't.
Instead, what I heard was ... the engines spooling up. Loud, yes, but not a roar, just an increasing pitch, until the airplane started accelerating down the runway.
It wasn't until some 15-20 seconds later that I heard the familiar roar, echoing off of hills five or so miles away. That's when I realised that the whine was the sound of the turbines, but the roar was the sound of exhaust gas, streaming out of the engines, hitting stationary air and generating intense turbulence, and radiating outward in a perpendicular line to that jetwash. So I didn't hear it directly (it was moving away from me), only the reflection (as that wall of noise, now reflected off the hills, was directed back toward me.
I doubt the vortex would make any particularly loud sound, though you might hear the rushing of air. Speeds are in the tens of miles per hour rather than hundreds as with jetwash.
clueless123|9 years ago
antubbs|9 years ago
flashman|9 years ago
clueless123|9 years ago
jacquesm|9 years ago
https://en.wikipedia.org/wiki/American_Airlines_Flight_587
Is another example (though pilot error likely made a bad situation worse in that particular incident).
cr4ig_|9 years ago
unknown|9 years ago
[deleted]
TillE|9 years ago
jseip|9 years ago
Dylan16807|9 years ago
rjurney|9 years ago
jseip|9 years ago
foliveira|9 years ago
http://www.youtube.com/watch?v=KXlv16ETueU
paganel|9 years ago
JshWright|9 years ago
peteretep|9 years ago
gigatexal|9 years ago
Animats|9 years ago
xaldir|9 years ago
lutusp|9 years ago
Also, an invisible vortex is no less turbulent for its invisibility.
bfrog|9 years ago
Those little jets man... they're fine most of the time but what a spooky experience that was.
dbalan|9 years ago
itsdevlin|9 years ago
It's fucking wild how small of a wing can put off a sizable wake. With wingsuits, if you fly behind and slightly above a buddy, you're going to hit his burble and you're going to immediately lose lift and possibly start spinning. There's a clip floating around of a bunch of us on a training jump in race suits and one of the guys hits a burble from the group and just gets dropped a few hundred feet damn near immediately.
EDIT: Found it - http://giphy.com/gifs/cBP3YE9hf9oVa
Here's a solid article that touches on it w/r/t lift - http://base-book.com/speed-to-fly
...and here's one that's a bit more applied that has to do with how burbles affect canopy deployments - http://base-book.com/some-thoughts-on-wingsuit-openings
gingerbread-man|9 years ago
By contrast, the horizontal separation minima vary dramatically based on the size of the leading aircraft.
theWatcher37|9 years ago
nsgoetz|9 years ago
ddinh|9 years ago
https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...
goodcanadian|9 years ago
paulannesley|9 years ago
Are the imperial units of measurement an aviation thing, or an American thing, or a bit of both?
errantspark|9 years ago
EDIT: ahahaha <3 HN commenters
NikolaNovak|9 years ago
You'll hear them referred to as Flight Levels or Angels as well (Angel 15 == 15,000feet).
dorfsmay|9 years ago
khuey|9 years ago
Patrick_Devine|9 years ago
arnarbi|9 years ago
JamilD|9 years ago
masor|9 years ago
EGreg|9 years ago
Any more info on that??
tbabb|9 years ago
If the engines fail, you still need to be able to control the plane, so there is something called a ram air turbine[1] which can be deployed out of the side of the aircraft. It is basically just a little propeller which spins in the breeze, which powers a pump, which supplies the hydraulic pressure to control the plane. So if the power goes out, you can still deploy that thing and have "power" assistance in controlling the plane.
The article says the ram air turbine did not deploy, possibly because the g-forces were holding it in, or perhaps because the g-forces or aerodynamic stresses were flexing the body of the plane so much that the turbine was held in place by the bending. So the pilots did not have "power steering" on the plane, and had to pull on the controls with "raw muscle force".
There is probably some mechanical advantage, probably both from the leverage afforded by the mechanics of actuation, and from the aerodynamics of the wing, that allow a single human to move the whole plane around. But it would still be very, very hard to control the plane without power assist, especially under such extreme conditions.
(Any pilots/aerospace engineers feel free to chime in/correct mistakes here).
[1] https://en.wikipedia.org/wiki/Ram_air_turbine
avhon1|9 years ago
nunez|9 years ago
A380s are HUGE, so this isn't surprising. wake turbulence is a killer
wwalser|9 years ago
It appears that there is a section of air between 29,000ft and 41,000ft, where flights are allowed to be closer than is normally allowed. Instead of 2,000ft apart, they are allowed to fly 1,000ft apart. In order to operate continually in this airspace, a plane must be "RVSM approved". Otherwise they have to either request special permission or make a continuous climb through said airspace while complying with their usual 2,000ft requirements.
The article mentions that the A380 and Challenger 604 were 1,000ft apart. So, I would assume they were both RVSM approved. This event could call the RVSM into question.
xapata|9 years ago
gadders|9 years ago
elberto34|9 years ago
CPLX|9 years ago
Coincoin|9 years ago
I am always impressed at how they look like a big chunk of metal from the outside, but they are in fact mostly made out of air and very thin and light materials.
randcraw|9 years ago
FussyZeus|9 years ago
muninn_|9 years ago
arrty88|9 years ago
jseip|9 years ago
[deleted]
peteretep|9 years ago
[deleted]
sctb|9 years ago
koliber|9 years ago
ebcode|9 years ago
unknown|9 years ago
[deleted]