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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

#361

Post by thisrod »

chakalakasp wrote: post #202
cyberferret wrote: post #36

Earlier quoted context omitted.

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…

BTW the low pressure generating the lift thing is a myth. The lift is caused by the fact that the air is being deflected downward and good ol' Newton's Third Law.

You're both right. When Newton's third law is applied to a wing, the equal and opposite forces are pressure. No one tends to think about the pressure of the wing on the air, but it happens.

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

#362

Post by itsdevlin »

Tangentally 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

Here's a solid article that touches on it w/r/t lift - 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

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

#363

Post by School-Cotton »

davrosthedalek wrote: post #340
School-Cotton wrote: post #266

Earlier quoted context omitted.

Flying 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.

It 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?

Since 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".

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

#364

Post by mannykannot »

vpribish wrote: post #322
chakalakasp wrote: post #202

Earlier quoted context omitted.

BTW the low pressure generating the lift thing is a myth. The lift is caused by the fact that the air is being deflected downward and good ol' Newton's Third Law.

it's not the Bernoulli effect, but it is a pressure difference (from the 3rd law, as you say)

The Bernoulli equation is a valid description of what happens to the airflow pressure and velocity around a wing (at least at speeds well below sonic), but the problem is that it is not much of an explanation - it leaves you with something else to explain, namely the change in velocities. Attempts to do so without invoking calculus have resulted in the propagation of fallacies, such as the 'equal transit time' one mentioned above by tzs.

The "Newton's 3rd. law" explanation treats the wing and its immediate surrounding as a black box: air flows in, and exits deflected downwards, so there has been some downwards-directed acceleration. It does not address details of that process, such as why the above-wing airflow usually generates the larger part of the lift, or even how the deflection occurs, though it is fairly obvious that some sort of deflection will result from driving an inclined plane through the air.

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

#365

Post by pm »

komali2 wrote: post #346
pm wrote: post #190

Earlier quoted context omitted.

I can't say I know anyone who's indulged reiki, but I've got a lot of flak from my brother telling me that cannabis cures cancer, when I told him that I was doing chemoradiotherapy for my Stage 3 rectal cancer. Today I've finished a cycle of six weeks of treatment, and while I'm extremely tired, the signs are good that it's in remission. If I'm lucky, I'll have a full pathological response, i.e., it's gone. Despite t…

I'm not sure about cannabis curing cancer, but there's ample research to support that it can help tremendously with the side effects of chemo. Basically, it can make life more comfortable while you go through treatment.

Yes, there's plenty of evidence for that, I'm not disputing that fact. However, even the most casual search you can find studies testing the effects of cannabinoids in vitro on different cancer types. As I said, the effects are different for each - they respond to different receptors (CB1 and CB2) and have effects ranging from nothing, to halting growth, to promoting cell death and reducing tumour size. The reasons why such differences exist are yet to be researched as far as I can tell though.

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

#366

Post by bartvk »

M_Grey wrote: post #295
School-Cotton wrote: post #268

Earlier quoted context omitted.

Where the fuck are you supposed to ride them, then? Sure I'd love it if cities built separated bike paths everywhere people want to commute, but that's far from reality currently

Boston has bike lanes, so... that would usually work.

Washington DC as well.

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

#367

Post by Zombieball »

mnw21cam wrote: post #218
Zombieball wrote: post #143

Earlier quoted context omitted.

I 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 fr…

Helicopters. Indeed - there is a state known as "settling with power" https://en.wikipedia.org/wiki/Vortex_ring_state where a helicopter is sitting inside its own vortex, and is incapable of climbing straight up with full power.

Super interesting! Never knew this about helicopters. Thanks.

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

#368

Post by Zombieball »

phumbe wrote: post #332
Zombieball wrote: post #142

Earlier quoted context omitted.

Great 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.

Glad 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/

Good visualizations, thanks!

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

#369

Post by jabl »

bipson wrote: post #203
jabl wrote: post #176

Earlier quoted context omitted.

> ... Steve Jobs had not been as wealthy and powerful as they had been, they would also both probably be alive. Steve Jobs got pancreatic cancer, IIRC. Which has a pretty low survival rate, per wikipedia 5% after 5 years from initial diagnosis. So most likely he'd be dead by now no matter what he would have done.

Not all pancreatic cancer is alike. IIRC he had a variant that would have had a ~80% chance of a favorable outcome, given he would have chosen the generally advised treatment

Oh, I didn't know that. Thanks for the correction.

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

#370

Post by scrumper »

gingerbread-man wrote: post #350
scrumper wrote: post #345

Earlier quoted context omitted.

Aha that last point might explain the recent plea bargain I had: a ticket for crossing a double yellow line (points, substantial fine) and I was offered a small fine and no points if I took a seatbelt violation. So did everyone else in court. So I guess that helped the PD get some traffic safety funds?

It's possible, but in my experience the stats NHTSA looked at were compiled by the police department, not the court. (They cared about how many tickets we wrote, not how many convictions were obtained.) A more likely explanation is the severe underfunding and understaffing of prosecutor's offices and state court systems. Most prosecuting attorneys are responsible for carrying hundreds of cases at a time-- they have n…

Ok thanks, and interesting. Understood re tickets written.

(I don't think it alters your point at all because you're still talking about constrained resources and a need to prioritize, but in traffic court in my village the PD is the prosecutor; my negotiation was with a police officer and he in turn represented the results of that negotiation to the judge. Same with everyone else's tickets. Only more serious stuff involved the town prosecutor - he was handling code violations, underage drinking, and a DUI.)

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