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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

#101

Post by cyberferret »

0xfaded wrote: post #95
snowwrestler wrote: post #89

Earlier quoted context omitted.

Sure but now try the same thing with a piece of metal. No one questions whether the Bernoulli and Venturi effects actually exist. But airplanes are heavy and it's pretty obvious that the Bernoulli effect does not produce sufficient lift by itself. As proof that most of the lift comes from deflecting air, I offer the fact that airplanes can fly upside down.

Haha this is a fantastic answer. Also, not most of the effect, all of the effect. Do the same experiment with the paper, but rest the trailing edge on a table. The air can no longer be deflected downwards, so the paper will not rise. Another one to think about, at the air metal boundary the air is stationary on both sides of the wing. So why is there a pressure difference? Bernoulli's law is valid only along flow lin…

Well, I just instantly disproved your hypothesis by holding a piece of paper against the front edge of my desk with it curving up and the trailing edge resting on the flat of the desk, then leant down and blew over the top of it... and the paper lifted at the back. QED.

Not sure why people are looking at the situation as ONE Venturi plane. What I am trying to explain is that there is effectively TWO - and expanding one over the top of the wing leading to a low pressure effect, and a constricting one below the wing leading to a high pressure situation. I wouldn't say that both provide equal amounts of lift, but the paper experiment, and the 747 in the boneyard proves it to a point.

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

#102

Post by rhizome »

billforsternz wrote: post #59
na85 wrote: post #54

Earlier quoted context omitted.

>There is an area of low pressure over the wing where air is taking a longer path than under the wing, but that is only responsible for a small fraction of the lift. The "equal transit time" theory that you appear to be referencing here (air over the top takes a longer path, thus it must go faster and air under the bottom takes a shorter path thus it goes slower) is a complete fallacy. There is no mechanism in physic…

Thanks for this. I read a million explanations of how airfoils worked as a boy and they all said the air had to travel faster over the top surface to catch up. Why does it have to catch up? I would scream internally. I'm stunned to find it was never true.

Probably like the Bohr model in Chemistry, it's an easy way to introduce the concept. Frankly I was under the impression it was true, too, and my dad was a small-plane pilot.

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

#104

Post by [deleted] »

ghshephard wrote: post #96
M_Grey wrote: post #63

Earlier quoted context omitted.

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.

Using that philosophy, then anyone riding a bicycle, even if they aren't going at high-speed on road, should wear a helmet "just in case" there is an accident to protect their skull? There is a balance between annoyance and utility. I personally have no problem wearing a belt for the entire flight, including while sleeping. But I'm not to dismayed by those who leave it off, walk around the cabin, go hang out near the…

[deleted]

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

#105

Post by scott_karana »

Patrick_Devine wrote: post #34
paulannesley wrote: post #8

> one thousand feet above Are the imperial units of measurement an aviation thing, or an American thing, or a bit of both?

Aviation uses feet... and centigrade. The standard lapse rate that pilots use in the troposphere is -2C/1000'.

Is it also called centrigrade, rather than Celsius? Or a mix?

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

#106

Post by hueving »

M_Grey wrote: post #63
lutorm wrote: post #44

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 tri…

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.

What likely happened is that you hit a wind shear at the same time as being struck by lightning. Planes are struck by lightning frequently without passengers even realizing.

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

#107

Post by matsemann »

M_Grey wrote: post #64
taejavu wrote: post #49

Earlier quoted context omitted.

Yeah I'm pretty sure that's the first rule that goes out the window when you're on a private jet.

There's a reason that people with money and power don't always experience good outcomes. Sure, you can do what you like on your jet, and therefore expose yourself to risk that most people never experience. Likewise skiing off-piste or a number of other equally silly activities that you can do, but absolutely shouldn't.

Not sure why you are calling off-piste skiing silly, a rich man sport and something one shouldn't do.

It's an incredible feeling, lots of fun, and if you have to walk up the mountain first it's a nice nature experience as well. Yes, it can be dangerous, but it's a risk you can manage yourself. So it doesn't have to be very dangerous if one follows common advice and also don't ski where there is a high risk of avalanches.

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

#108

Post by sulam »

ghshephard wrote: post #96
M_Grey wrote: post #63

Earlier quoted context omitted.

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.

Using that philosophy, then anyone riding a bicycle, even if they aren't going at high-speed on road, should wear a helmet "just in case" there is an accident to protect their skull? There is a balance between annoyance and utility. I personally have no problem wearing a belt for the entire flight, including while sleeping. But I'm not to dismayed by those who leave it off, walk around the cabin, go hang out near the…

Yes, you absolutely should wear a helmet, just in case -- no quotes required. I have been hit by a car on my bike, and trust me, my helmet absolutely saved my life. No high speed required.

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

#109

Post by sulam »

wfunction wrote: post #56
lutorm wrote: post #44

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 tri…

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.

Surely this entire event is notable because no one had any idea that this might happen. Seat belts or not, 3 or more rolls and a written off airplane is an outcome they would have avoided if they'd known it had even a remote chance of happening.

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

#110

Post by cyberferret »

nether wrote: post #41
Zak wrote: post #39

Earlier quoted context omitted.

Wings generate lift primarily by deflecting air downward. There is an area of low pressure over the wing where air is taking a longer path than under the wing, but that is only responsible for a small fraction of the lift.

"Longer path" has no bearing on reality. A flat plate can generate plenty of lift even with both sides the same. It's also hard to define "path," as the air starts convecting well ahead of the wing in subsonic flow.

Sorry, but I don't subscribe to the 'flat plate' theory. There is a reason that almost every commercial (and most military) aircraft have leading edge slats to generate lift at lower speeds (by making the top of the wing more convex and the bottom of the wing more concave).

If pure 'flat plate' theory was valid, then all those aircraft speeding down the runway with the leading edge of their wings canted downwards 20 or so degrees would result in the airplanes simply being pushed towards the ground and never lifting off...

And Boeing, Airbus et al would build planes with flat slab wings mounted at a 45 degree angle to the airflow, because that would give the maximum lift by the 'flat plate' theory, wouldn't it?

Not that I disbelieve that a flat slab cannot generate lift - but that it is probably a very inefficient way to generate lift compared to the standard aerofoil shape.

[0] - https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Bo...

[1] - https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg

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