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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

#131

Post by hbk1966 »

ajross wrote: post #77
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.

That's a meaningless correction, and technically not correct. Aircraft are lifted up by air molecules hitting the underside of the rigid body with more force than the top side, by definition. The net integrated instantaneous pressure at the surface of the aircraft IS the lift. The fact that air gets deflected downward is a necessary (c.f. conservation of momentum) effect too. So it's not incorrect to do the analysis…

No, the effect is negligible if it wasn't planes wouldn't be able to fly upside down. It's the pitch of the wing that generates most of the lift. That's why helicopters don't alter the rotor RPM they adjust the pitch of the blades to take a larger bite.

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

#132

Post by bbcbasic »

phumbe wrote: post #7

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. [1] https://www.youtube.com/watch?v=E1ESmvyAmOs [2] https://www.youtube.com/watch?v=dfY5ZQDzC5s…

[7] https://youtu.be/ZJ9uWsvR1l0?t=145

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

#133

Post by JoshTriplett »

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…

> 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?

Having personally done a header over the handlebars onto my helmet, resulting in a dented helmet and an un-dented head: yes, I'd recommend it.

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

#134

Post by peteretep »

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…

    > anyone riding a bicycle, 
    > even if they aren't going at
    > high-speed on road, should 
    > wear a helmet "just in case"
Is this a trick question? The answer is yes. In many places it's a legal requirement.

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

#135

Post by luca_ing »

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.

If you're interested in the topic, maybe you'd like to read

http://www.allstar.fiu.edu/aero/airflylvl3.htm

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

#136

Post by sgustard »

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…

Every once in a while I have to re-realize how amazing this phenomenon is. The only thing in nature that flies are birds which weigh a few ounces. Nothing human-scale flies. Cars don't fly. Yet, the flying machines we decide to build weigh a million pounds and fly simply by going fast until the air lifts them up. That is some ludicrous black magic.

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

#137

Post by cyberferret »

dorfsmay wrote: post #128
cyberferret wrote: post #110

Earlier quoted context omitted.

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…

The shape of the wing makes a huge difference, so a plate or a piece of wood wouldn't make a good wing, but it is still able to fly. Proof? Inverted flight on low power aircraft and gliders.

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 inverted flight at all. The fact that full aerobatic and military jets do, is because they (as I explained earlier) usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing.

To whit, I've had the fortune to fly an old DH Tiger Moth biplane - on that little baby, when you approach the stalling point, you can actually see the the canvas on top of the bottom wing bulge and contort with pressure differential, and you can hear the sucking sounds as the airflow struggles to 'stick' to the wing. There is a little movement on the bottom surface of the top wing too, but not as pronounced.

I'd be interested to see in this thread, who here has actually studied aeronautical engineering, or flown actual aircraft, and who is relying on YT videos or a pure theoretical approach to come up with these theories?

Also interestingly, I believe most of the textbooks I used at flight school were filled with data from NASA and other US military branches with regards to flight dynamics etc., and here on this thread we see articles from NASA (albeit aimed at K-12 audience rather than trainee pilots) basically disproving their earlier academic research.

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

#138

Post by Zombieball »

peteretep wrote: post #134
ghshephard wrote: post #96

Earlier quoted context omitted.

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…

> anyone riding a bicycle, > even if they aren't going at > high-speed on road, should > wear a helmet "just in case" Is this a trick question? The answer is yes. In many places it's a legal requirement.

Thank you!

I'm probably heavily influenced by the fact that I live in one of these places (where helmets are a legal requirement).

All I could think while reading this is "yes, you definitely should always wear a helmet!!"

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

#139

Post by baq »

dorfsmay wrote: post #128
cyberferret wrote: post #110

Earlier quoted context omitted.

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…

The shape of the wing makes a huge difference, so a plate or a piece of wood wouldn't make a good wing, but it is still able to fly. Proof? Inverted flight on low power aircraft and gliders.

Just stick your hand out of the window when you're on a highway. Plenty of lift or downforce depending how you tilt it.

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

#140

Post by sneak »

errantspark wrote: post #13
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?

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. EDIT: ahahaha <3 HN commenters

Containers are also sadly measured in TEU (twenty foot equivalent units) stemming from their American design.

Global, impossible to upgrade standards that mean we are stuck with imperial units for a hundred years yet or more.

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