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Enroute Airbus A380 wake flips Challenger business jet upside down

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Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#231

Post by dhimes »

votingprawn wrote: post #175
cyberferret wrote: post #137

Earlier quoted context omitted.

And as I have mentioned elsewhere on here - I have flown inverted a few times, and to do so take a tremendous amount of forward pressure on the control stick to even try and attempt to hold altitude while inverted, in order to counteract the wings natural (slight) positive AoA and the tendency for the wing to move towards it upper surface. In fact, most of the aircraft I have flown would not be able to sustain invert…

> I'd be interested to see in this thread, who here has actually studied aeronautical engineering I studied Aerospace Engineering (PhD in Aerodynamics), and I stay out of internet conversations over "how" lift is generated. For me it is one of those topics that is just not worth debating. It seems that people get _really_ attached to their personally preferred theory of lift.

Can you point to a source for those of us who want to know the right answer (like, sailors)?

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#232

Post by LoSboccacc »

nb777 wrote: post #207
phumbe wrote: post #37

Earlier quoted context omitted.

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).

Do you happen to know how arial refueling works then ? E.g. in this image [1] the jet is flying where I would expect a lot of deflected air to be moving to ? Or is it just deflected much more steeply ? [1]: https://upload.wikimedia.org/wikipedia/commons/d/d6/US_Navy_...

the wortex begin as high density high velocity turbolence and expands rearward

http://cfile29.uf.tistory.com/image/145D430D4CFE23D50A5BD0

being close is relatively safe from wortexes - there still is some other turbulence to consider, but the standard turbulent flow caused by drag is chaotic so it'll shake you but will 'even out'

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#233

Post by ndonnellan »

cyberferret wrote: post #36
csours wrote: post #22

Earlier quoted context omitted.

Those wingtip and flap effects on 2 are gnarly! I assume that those occur near dewpoint? or some other atmospheric conditions?

If 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…

Close, but slightly backward. The saturation temperature (dewpoint) is lower at lower pressures. So the lower pressure air reduces the saturation point. The air is not being cooled by the wings. If the sat. point is close to the current air temperature, water vapor will condense.

Similar phenomenon to boiling water at high elevations. Walking up the mountain isn't heating the water, but the boiling point drops as air pressure drops.

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#234

Post by mrkgnao »

paganel wrote: post #228
foliveira wrote: post #165

Good video of the same (similar?) effect on a small plane after taking off after an Antonov-2 http://www.youtube.com/watch?v=KXlv16ETueU

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,…

"It's Russian, hah."

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#235

Post by LoSboccacc »

alkonaut wrote: post #173
goodcanadian wrote: post #26

Earlier quoted context omitted.

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.

The 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?

I 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

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#236

Post by Dylan16807 »

bb611 wrote: post #227
Dylan16807 wrote: post #19

Earlier quoted context omitted.

Though 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.

That'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_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…

> 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.

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#237

Post by gingerbread-man »

burkemw3 wrote: post #226
gingerbread-man wrote: post #216

Earlier quoted context omitted.

Speaking as someone who has actually done seatbelt enforcement, (I worked as a cop for a year after college before getting into software development,) catching people who aren't wearing their seatbelts is really, really hard. Each seatbelt ticket written probably takes ~30 minutes of time for the issuing officer.

I'm interested in hearing the intracacies!

There really aren't any good trick to it-- it's just a matter of finding a good vantage point and watching each driver go by. You're supposed to note the color of the belt (black) and the color of the driver's shirt before pulling the car over. As you'd imagine, fatigue comes quickly-- I never did more than an hour or two at a time. (I still have no idea how the highway patrollmen can it all day, every day without losing their minds.)

NHTSA provides substantial grant funding for traffic-safety enforcement, conditional on the department's enforcement statistics for a particular set of safety-oriented violations, especially seatbelts. The brass encouraged us to take a minimum number of enforcement actions to maximize the chances of having the grant expanded. (It paid a for substantial chunk of our salaries and offered regular 1 1/2 overtime.)

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#239

Post by muninn_ »

elberto34 wrote: post #238

I 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

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.

Re: Enroute Airbus A380 wake flips Challenger business jet upside down

#240

Post by lmm »

tempestn wrote: post #169
ajdlinux wrote: post #116

Earlier quoted context omitted.

That happens to be the justification that my country uses to make bicycle helmets mandatory (though there's significant debate about whether it's actually helped reduce injury rates, and it fairly clearly depresses overall rates of cycling versus other modes of transport). I think the cost of wearing an aircraft seatbelt while you happen to be seated is rather lower than the cost of having to wear a bicycle helmet, t…

What's the cost? Helmets aren't that expensive. Having to carry it around? Could always lock it to the bike. Helmet hair?

Would you be ok with a mandatory helmet law for car drivers and passengers? The risk of a head injury that a helmet would prevent is much higher in a car, and carrying a helmet around in your car is more convenient than on your bike (e.g. it's much less likely to get stolen). Nevertheless, we don't have mandatory helmet laws for people in cars; why is that?
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