Wake Turbulence from a Paper Airplane (2020) [video] | Hacker News Reader

Wake Turbulence from a Paper Airplane (2020) [video]

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136 pointsthunderbong29 comments

Videos like this reminds me that regular people can do cool and unique stuff. Sometimes I think the internet is just people reposting and copying other people's things. TikTok is one of those places, copies of copies of copies of copies. It also reminds me that I should maybe get more creative in my life and maybe regain some sense of wonder.

The old Bernoulli explanation of how planes fly. As Jef Raskin liked to point out, if this were the case then an upside airplane would accelerate to the ground (just like an upside down VTOL aircraft does) but instead it can fly by just adjusting its angle of attack.

There is indeed a difference in pressure on top and on the bottom of a wing but the main function of the wing is to accelerate the air it passes through towards the ground (like a ceiling fan's blade does). The air goes down, the plane goes up just like Newton intended. The block of air going down is only as wide as the wing - the air to the left and to the right of the wing is not affected. At the transition you are adding a rotation, hence the wingtip vortices.

Any kid who stuck his hand out the window of their moms car and played with the angle of attack knew that the whole airfoil explanation of lift was hogwash. Stick any flat thing out the window and tip it up or down and you instantly feel a corresponding force.

Caution wake turbulence, paper airplane on a 3 foot final.

Super cool video!

A long time ago I did some work for British Airways at Heathrow. The staff car park for Viscount House where I worked was directly under the flightpath and by the end of the south runway.

Minutes after a big jet had landed you would hear the noise of the vortices reaching the ground - they sounded like someone whipping a long stick to and fro.

This was when Concorde was still flying - that would set most of the car alarms off from the engine roar and the dirty brown trail of partially burnt fuel was a sight to behold!

The inner-west of Sydney is crazy for jet-wash effect. Something about the Sydney basin geography means that, when the conditions are right, you can get multiple minutes between a plane going over (at very low altitude) to the weird jet-wash paint smear of sonic cavitation ripping the sky apart.

It's awesome. Apparently there are quite a few calls to various bodies either complaining about or reporting unidentifiable noises in the sky.

It's pretty much the only positive of having a busy international airport so close to the centre of the city (obviously it's been a lot quiter over the last 14-15 months).

A laser sheet generated via a cylindrical, plano convex or Powell lens would be a good way to control the illumination and better visualise the the flow.

A cheap diode laser would get the job done.

That is so impressive that such a small, light, non-powered aircraft can demonstrate the effect so starkly! I had no idea.

How dangerous is wake turbulence from an airplane that is following? Isn't it a major hazard especially in high traffic areas?

Depends. Can be very dangerous when near the ground on takeoff or landing. Heavier, slower aircraft make stronger turbulence. You especially don’t want to be a smaller aircraft behind a larger one. The vortices sink so if you’re following an aircraft and you’re at the same or higher altitude then you’re fine. If you’re lower then watch out, you might be on an intercept course.

> Heavier, slower aircraft make stronger turbulence

Is it the weight of aircraft that contributes to the wake turbulence or the physical size? Presumably these usually correlate pretty well but just asking for clarity…

weight. the wing (plane) is exerting itself on the air and the heavier the plane the stronger the force.

Thanks!

thanks to the A380 it is also dangerous at cruise.

https://www.nbcnews.com/news/world/private-jet-flipped-over-...

This is one of the reasons ATC maintains a certain separation between landing aircraft. For larger airliners which produce more turbulence, this separation needs to be greater. As you can see from the video, wake turbulence migrates downwards over time, so after thirty seconds or so it's no longer an issue for other aircraft on the same glideslope.

The separation between a heavy flight and a small one is 120s. There are many studies to take into account wind (speed and direction) and to have finer table of spacing (often around 85s) taking into account both aircraft types. Near the runway, there is also a ground effect with reflection of the vortex.

All aircraft produce wingtip vortices that create wake turbulence in flight. The vortex strength increases when the aircraft is heavier and when it flies slowly. Thus, the term "heavy" (unlike light, medium and large) is included by heavy-class aircraft in radio transmissions around airports during take-off and landing, incorporated into the call sign, to warn other aircraft that they should leave additional separation to avoid this wake turbulence.

https://en.wikipedia.org/wiki/Heavy_(aeronautics)

I was flipped sideways on short final in a 172 from a 7x7 (can't remember exact plane) that landed ~2 minutes prior on a parallel runway... it happens, though the vortices tend to sink fairly rapidly and are more of a concern for smaller aircraft.

This story is fairly interesting: https://www.nbcnews.com/news/world/private-jet-flipped-over-...

Glad you live to tell the story. Was recovery hard?

Fortunately, not at all. Was able to correct the orientation quickly, and just added power for a go around (about 100' AGL, so had time... but was very much not expecting it up at that altitude given sink rates for vortices)

The tower must have been watching pretty closely because they notified other traffic within about 2 seconds before I called in or gained altitude.

It can definitely be very dangerous. A CRJ (50 seat, common commuter plane) can easily be rolled sideways from a 737-900 or larger. Imagine a biz jet or single-engine piston aircraft being caught in something like that.

Wake turbulence was a factor in the crash of AA587 from JFK back in 2001. The FO flying the take off encountered wake turbulence from a 747 that took off just prior and overused the rudder in response to the point it snapped the tail of the jet, an A300.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587

Very cool! Watch from 3:20 for the results

This explains why certain aircraft have wing tips: https://en.wikipedia.org/wiki/Wing_tip

https://en.wikipedia.org/wiki/Glider_(video_game)

Now I want a fog machine.

Don't let your dreams remain dreams. You can make your own for pennies. You just need heat, water, glycerin, and some kind of structure to keep all those things in the right place.

The description in that article made no sense to me, and it doesn't even have a diagram. When I realized that where they wrote “taping the narrow end” they meant “taping the wide end”, and made some other allowances, it sort of came together. There are other articles on the web with much clearer descriptions.

The same person recently made a video showing how fog interacts with carbon dioxide: https://youtu.be/8kza02WmwuM

It makes me want a fog machine too. My daughter is still a little young to appreciate the science but I bet she’d have fun playing with fog!

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