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Enroute Airbus A380 wake flips Challenger business jet upside down
- jseip 10y agoThe 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.
- rjurney 10y agoWhy does the landing weight effect the air it displaces?
- thrill 10y agoNot displacement (volume), but pressure from velocity: lift. The amount of lift by definition has to equal the weight of the aircraft at 1G.
- vpribish 10y ago... and the force of that lift on the plane has an equal and opposite on the air. A Heavier plane disturbs the air more.
- deleted 10y ago[deleted]
- ars 10y agoWeight of airplane = mass of air displaced per second * velocity of air. The weight of the airplane is a force downward, the air must match that force, either by throwing a lot of air with little velocity, or a less air, faster.
- Dylan16807 10y agoThough note that a box around a cruising A380 at 827 feet per second * 79 feet tall * 262 feet wide is itself 17 million cubic feet.
- bb611 10y agoThat's a pretty poor approximation, and I think the result discounts the meaning of the original point. The A380 is a lot more like 3 boxes (based on A380-800: http://www.airbus.com/fileadmin/media_gallery/files/tech_data/AC/Airbus-AC-A380-Jan16.pdf http://www.airbus.com/fileadmin/media_gallery/files/tech_dat...): 1) A fueselage box with a cross section of 2067 ft^2 2) A wing box of ~1200 ft^2 (a very broad approximation because of engines, the actual wing box - the part of the plane where the wings meet the fueselage - and the curve of the wings), 3) A tail box with a cross section of 144 ft^2 So a total cross section of ~3411 ft^3 * 827 fps = ~3 million ft^3 Point being, the plane isn't moving 11 million cubic feet just to move forward, it pushes on a little more than a quarter of that directly. These wake effects happen because it's disrupting so much air outside of the zone it actually travels in, mostly below and behind it.
- Dylan16807 10y ago> That's a pretty poor approximation It's not an approximation. I'm giving a sense of scale, not saying how much volume the plane has. The point is that while 11 million cubic feet sounds like a lot, if you put it in a big box next to the plane then they would be on the same scale. > the plane isn't moving 11 million cubic feet just to move forward, it pushes on a little more than a quarter of that directly That's jseip's post's problem, not mine.
- jseip 10y agoEDIT: 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 :).
- jseip 10y agoThe 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.
- jacquesm 10y agoThe wakes of large aircraft are such that even big passenger planes make sure to keep plenty of separation. https://en.wikipedia.org/wiki/American_Airlines_Flight_587 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_ 10y agoI 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.
- jacquesm 10y agoThe same would happen with any widebody, the displacement is enormous and it's one very good reason to nail down everything close to the ground in the path of these planes very well.
- lohi 10y agoWhich is also why, as you might know, they explicitly call them heavy and super respectively. https://en.wikipedia.org/wiki/Heavy_(aeronautics) https://en.wikipedia.org/wiki/Heavy_(aeronautics) https://www.youtube.com/watch?v=iI6avay9w4g https://www.youtube.com/watch?v=iI6avay9w4g
- Zombieball 10y agoI believe warning of wake turbulence is very common after take off of any large and heavy aircraft. Wingtip vorticies can sit over a runway (or even drift over to parallel runways) for minutes after a takeoff. They are very dangerous to smaller aircrafts. The key to avoiding vorticies is to take off at a point earlier than the previous aircraft and to climb at a steeper angle (vorticies travel behind and downwards from the aircraft that made them). Example: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/avoid-wake-turbulence-during-takeoff-and-landing/takeoff-profile.jpg http://www.boldmethod.com/images/learn-to-fly/aerodynamics/a... Helicopters can also produce serious turbulence as well!
- phumbe 10y agoFor 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. [1] https://www.youtube.com/watch?v=E1ESmvyAmOs https://www.youtube.com/watch?v=E1ESmvyAmOs [2] https://www.youtube.com/watch?v=dfY5ZQDzC5s https://www.youtube.com/watch?v=dfY5ZQDzC5s [3] https://www.youtube.com/watch?v=uy0hgG2pkUs https://www.youtube.com/watch?v=uy0hgG2pkUs [4] https://www.youtube.com/watch?v=KXlv16ETueU https://www.youtube.com/watch?v=KXlv16ETueU [5] https://en.wikipedia.org/wiki/Reduced_vertical_separation_minima https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi... [6] https://en.wikipedia.org/wiki/Strategic_lateral_offset_procedure https://en.wikipedia.org/wiki/Strategic_lateral_offset_proce...
- csours 10y agoThose wingtip and flap effects on 2 are gnarly! I assume that those occur near dewpoint? or some other atmospheric conditions?
- jacquesm 10y agoThey always occur. It's just that around the dewpoint you can visualize them. But they're all the more deadly for normally being invisible.
- phumbe 10y agoTo add to jacquesm's response, the footage in [2] is definitely from a humid day. That makes condensation happen very readily. If I remember correctly, the trails from the outboard edges of the flaps are just like wingtip vortices. The airfoil's geometry suddenly changes, acting like a wingtip and creating a vortex.
- cyberferret 10y agoIf you recall Boyle's Law from high school physics - Temperature is proportional to pressure. Aircraft wings generate an intense area of low pressure over the top of the wing (which is what essentially generates the lift). This low pressure area is magnified when flaps and slats are deployed. On a humid day, the lowering of the pressure over the wings can basically force the air temperature at that point to lower and reach dew point temperature, essentially forming temporary clouds that are whipped around by the moving air vortices. Once the aircraft has passed that point, the temperature generally stabilises and conforms to surrounding air temperature, which usually dissipates the temporary condensation. The 'twirly' bits on the wingtips is basically spillover from the high pressure under the wings to the low pressure above the wings, creating that mini tornado vortex. This is also the reason that many modern aircraft have those 'winglets' on the wingtips, to try and minimise these spillover vortices which can cause problems for trailing aircraft, as well as induce extra drag on the source aircraft.
- paulannesley 10y ago> one thousand feet above Are the imperial units of measurement an aviation thing, or an American thing, or a bit of both?
- arnarbi 10y agoIt's an aviation thing.
- khuey 10y agoAn aviation thing. Flight levels are measured in feet across the vast majority of the world.
- NikolaNovak 10y agoAviation thing (unfortunately, but it is what it is). You'll hear them referred to as Flight Levels or Angels as well (Angel 15 == 15,000feet).
- goodcanadian 10y agoTechnically, the lowest flight level is FL200 or 20000'. Below that, altitudes are reported in feet. I'm not really familiar with the "angels" thing. I suspect that is specifically military. EDIT: there was a reply (since deleted) that indicated I may not be completely correct on stating FL200 as the lowest number used. I contend that I am still basically correct for North America, but there is some subtlety: https://en.m.wikipedia.org/wiki/Flight_level https://en.m.wikipedia.org/wiki/Flight_level
- deleted 10y ago[deleted]
- ajross 10y agoTechnically, a flight level isn't a distance measurement at all. It's defined by atmospheric pressure, so that all planes use the same "ground" barometer by definition. The feet are expressed nominally relative to a standard sea level pressure.
- clueless123 10y agoBig 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) ..
- clueless123 10y agoFew years ago, an embraer actually cut another's plane wing off for the exact same reason. (They were flying at the wrong altitude though)
- phumbe 10y agoThat's Gol Transportes Aéreos Flight 1907 -- https://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Flight_1907 https://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Fl... There's also an episode ("Phantom Strike") of the TV series Mayday about the incident; it's probably on youtube.
- sneak 10y agoAhh, I see you are one of those kinds of wikipedia readers as well. I've spent many a late night reading about the minutae of air disasters. Hello, friend. May I also recommend strong radiation source mishandling accidents?
- davidwihl 10y agoThey were not flying at the wrong altitude - ATC cleared both aircraft to the same altitude on a collision course.
- flashman 10y agoIt's a big sky until you're using the same road as everybody else...
- antubbs 10y agoEh. 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.
- nsgoetz 10y agoI don't know much about aviation, but 1000ft seems kinda close to pass another aircraft. How normal is that distance?
- ddinh 10y agoIt'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. https://en.wikipedia.org/wiki/Reduced_vertical_separation_minima https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...
- goodcanadian 10y agoBy 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.
- alkonaut 10y agoThe question is then - are there any systems that can ensure that two airraft aren't passing eachother at just 1000 feet if one of them is a behemoth? Will the corridors magically widen when an A380 enters it? Will nearby aircraft be warned when crossing right under an A380 that they are basically on a collision course, while had it been a small aircraft it wouldn't be a problem?
- LoSboccacc 10y agoI never understood why corridors at opposing directions aren't by default offseted both in altitude and lateral separation - there have been quite many collision already because navigation aid reduced the positional error within a corridor to few meters
- uptownfunk 10y agoHad 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.
- deleted 10y ago[deleted]
- phumbe 10y agoIt'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).
- Zombieball 10y agoGreat explanation! I think it's also interesting to point out this is also the explanation for the trend of adding winglets to the tip of the wings. They help reduce the wingtip vorticies, and in turn, reduce parasitic drag and improve fuel efficiencies.
- phumbe 10y agoGlad you brought up winglets. My favorite example are those on the new 737 MAX. Boeing's page[1] about them is top-notch. [1] http://www.boeing.com/commercial/737max/737-max-winglets/ http://www.boeing.com/commercial/737max/737-max-winglets/
- Zombieball 10y agoGood visualizations, thanks!
- peteretep 10y agoI'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.
- deleted 10y ago[deleted]
- lutorm 10y agoThis 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.
- taejavu 10y agoYeah I'm pretty sure that's the first rule that goes out the window when you're on a private jet.
- danaliv 10y agoAnd it's the number one way you're going to get injured. Keep your seatbelt buckled, even when the sign is off.
- umanwizard 10y agoFlying is already so incredibly torturously uncomfortable for me that the very slight risk of injury or death is worse it for the increased comfort of not having a seatbelt on.
- davrosthedalek 10y agoIt is worth the risk for the persons next to you or the row over when you get thrown through the plane and hit them in the head?
- umanwizard 10y agoSince I don't get upset when other people do things for their own comfort that make me extremely slightly less safe to a similar extent, the Golden Rule school of ethics suggests: "yes".
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- jmts 10y agoThis 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.
- dredmorbius 10y agoThat'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.
- nunez 10y agoI thought controllers space aircraft based on their takeoff weight for this reason. Is this true? A380s are HUGE, so this isn't surprising. wake turbulence is a killer
- xapata 10y agoI don't think it's the only reason.
- wwalser 10y agoThe (current) top thread in the comments section references the reduced vertical separation minima (RVSM): https://en.wikipedia.org/wiki/Reduced_vertical_separation_minima https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi... 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.
- Animats 10y agoWow. 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.
- xaldir 10y agoCompared to an A-380 a 9-passengers bizjet is a tiny feather.
- gigatexal 10y agoHoly 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).
- EGreg 10y ago"until the crew was able to recover the aircraft exercising raw muscle force" Any more info on that??
- tbabb 10y agoUnder 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). [1] https://en.wikipedia.org/wiki/Ram_air_turbine https://en.wikipedia.org/wiki/Ram_air_turbine
- Tarq0n 10y agoAre there standards of strength that pilots have to meet for situations like these? What about female pilots?
- gingerbread-man 10y agoCessna pilot here-- I've never flown an aircraft with hydraulic controls. (Small planes use pushrods or cables to actuate the controls. It's all muscle power for us.) The physics of flight produce a very useful convenience: the amount of force needed to effect a particular degree of attitude change (e.g. a 10 degree bank) remains the same, regardless of speed. Planes up to the size of small jets (the Cessna Mustang, for instance) use fully manual controls with no power assistance. The Challenger is a bit bigger, but even after the remaining pressure in the hydraulic system completely dissipated, I doubt more than 30lbs of pressure would have been required to actuate the controls. And the rotational inertia of the turbines should have provided at least some assistance on top of that. (I have no idea what would have happened if an airliner lost both engines simultaneously in a stall.)
- lutusp 10y agoPilots 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.
- peteretep 10y ago> It's an incredible feeling, > lots of fun > Yes, it can be dangerous, > but it's a risk you can > manage yourself Try meth!
- koliber 10y agoThis comment thread quickly deteriorated from civil discussion to absurdist comparisons.
- peteretep 10y agoI guess I could have said "Just because something is great fun, and you think you're in total control of inherent risks, doesn't mean it's a good idea, or that you're capable of making good risk assessments". But I'm British, and we communicate in specific ways.
- untog 10y agoNot really. Exaggeration for comic effect is a useful and entertaining tool when applied properly. I don't think anyone considered it an actual comparison of off-piste skiing and meth.
- M_Grey 10y agoExcept that it's not. In the UK you can go to prison for pot, which is less dangerous than (for example) horseback riding. Its the situation which is absurd, not the comparison.
- ebcode 10y agoThis is hilarious. But for the sake of the internet, I just have to say, no, really, don't actually try meth.
- dbalan 10y agoIMO this has slightly better info: https://avherald.com/h?article=4a5e80f3&opt=0 https://avherald.com/h?article=4a5e80f3&opt=0
- foliveira 10y agoGood video of the same (similar?) effect on a small plane after taking off after an Antonov-2 http://www.youtube.com/watch?v=KXlv16ETueU http://www.youtube.com/watch?v=KXlv16ETueU
- paganel 10y agoI 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=!3m1!1e3?hl=en https://www.google.ro/maps/@44.2288052,27.5250523,386m/data=...).
- mrkgnao 10y ago"It's Russian, hah."
- JshWright 10y agoThe rapid left/right pan of the music on that video is _super_ obnoxious if you're wearing headphones.
- gadders 10y agoThat was some flying by the Challenger pilots (to my layman's eyes at least). I'm glad I wasn't on that flight.
- elberto34 10y agoI wonder the private plane had to be written off...was the damage that bad? It's like the plane broke apart ..maybe the probems were mostly internal
- muninn_ 10y agoThe 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.
- Coincoin 10y agoPlanes 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.
- CPLX 10y agoWhen 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.
- FussyZeus 10y agoI'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.
- randcraw 10y agoAs 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.
- gingerbread-man 10y agoRight 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.
- theWatcher37 10y agoThe way the FAA tends to run things is rules are either written in blood or incident reports.
- bfrog 10y agoLanding 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.
- arrty88 10y agothis is horrifying. does anyone have a sketch of how many flips the jet underwent before regaining control?
- itsdevlin 10y agoTangentally 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. EDIT: Found it - http://giphy.com/gifs/cBP3YE9hf9oVa 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 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 http://base-book.com/some-thoughts-on-wingsuit-openings