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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

#271
post #77

Earlier quoted context omitted.

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…

Air does not behave like a bunch of bullets hitting a wing. It's a fluid with velocity and pressure everywhere, not simply in the vicinity of aircraft surfaces. A wing is a pump that sets up circulation in the airflow, upward of the leading edge and downward off the trailing edge. The downward momentum of the air flowing off the trailing edge produces an equal and opposite reaction by Newton's third law which is the…

> Air does not behave like a bunch of bullets hitting a wing

Yes it does. And those bullet impacts are the very definition of pressure.

The aerodynamics snobbery that you're trying to invoke is that those bullets also hit each other, so you can't make ideal gas assumptions and must model the whole system as a giant system of differential equations (c.f Bernoulli) if you want numbers out.

That doesn't change the fact that air pressure at the surface of the body is what causes the force on the body. That busybodies feel the need to argue against this bleedingly obvious point says some very bad things about the way the aviation community has tried to teach aerodynamics.

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

#272

Earlier quoted context omitted.

So according to this answer[1], ~1.7MM fly/day. Making a quick guess that from '80-'08, Americans average 1MM flights/day, then odds of serious injury are ~1 in 95,000. Odds of death are 1 in 9,333,333. Assuming the possibility of taking 3 'average' flights/day, then you'd need to board flights non-stop for 8,523 years to die, on average. 88 years to be injured. [1] - https://www.quora.com/How-many-people-fly-domesti…

Of course, general aviation is much more dangerous. As a general rule, the smaller the plane, the riskier it is, partially due to the corresponding increase in regulatory scrutiny as the size of the aircraft grows. Private pilots need a minimum of ~50 hours for their license. Most newly-hired jet pilots, private and commercial, have at least 1500 hours, and many have more than that.

Larger airplanes are also much more capable (better instruments, things like anti-icing systems, ability to fly above weather), far better maintained on average, fly into better airports, have better flight planning resources, and more.

Note that when looking at airline safety, you'll get misleading numbers if you go back too far. Safety has improved remarkably in the past couple of decades. In the 80s and 90s, a couple hundred fatalities per year was about typical in the US. In the last decade, the typical number is zero. There hasn't been a fatal crash involving an American airliner for over eight years, and you have to go all the way back to 2001 (November, not September) to find one involving a major American airline. Even if you include foreign airlines operating in the US, that only adds one fatal crash and three deaths to the recent total.

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

#273
post #240

Earlier quoted context omitted.

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?

> The risk of a head injury that a helmet would prevent is much higher in a car What is this based on? My own intuition is that the risk is many times higher on a bike.

I don't remember the source, take that as you will. Cars go faster which means a higher risk of collisions (less time to react etc.), and also a higher risk of head injury per collision.

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

#274

Right now, the vertical separation minima for aircraft worldwide are not conditional on size. At altitudes above 28,000ft MSL, the minimum vertical separation is 1000ft, even for superjumbos. It is probably a rare event that two aircraft come so close both vertically and horizontally, but I wonder if there will be a rule change because of this incident nonetheless. By contrast, the horizontal separation minima vary d…

The way the FAA tends to run things is rules are either written in blood or incident reports.

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

#275
post #273

Earlier quoted context omitted.

> The risk of a head injury that a helmet would prevent is much higher in a car What is this based on? My own intuition is that the risk is many times higher on a bike.

I don't remember the source, take that as you will. Cars go faster which means a higher risk of collisions (less time to react etc.), and also a higher risk of head injury per collision.

Maybe I'm just a shitty cyclist but I've wiped out way, way more times on a bike than in a car. You can crash without it being a "collision".

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

#276
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…

Can we talk about this in terms of actual statistics? How dangerous is flying without a seatbelt relative to say, driving without one?

> How dangerous is flying without a seatbelt relative to say, driving without one?

I guess it depends on (the size of) your aircraft.

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

#277
post #201
post #177

Earlier quoted context omitted.

And the pitch of the wing causes one side of the wing to be hit harder by air molecules than the other, just like GP said. Maybe you hit reply on the wrong post?

The 'air molecules impinging on the airfoil' theory of lift is not wrong, but does not account for a large fraction of the lift generated either. In a dense enough medium such as air at normal flight altitudes, you have to take into account how those air molecules interact with other air molecules and not only the airfoil. Sum up all those interactions, and you get fluid dynamics rather than a molecule hitting a surf…

Fluid dynamics is a useful, but simplistic model. It's not actually true, but can accurately model truth.

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

#278

Earlier quoted context omitted.

Can we talk about this in terms of actual statistics? How dangerous is flying without a seatbelt relative to say, driving without one?

Per the FAA ( https://www.faa.gov/passengers/fly_safe/turbulence/ ): - Each year, approximately 58 people in the United States are injured by turbulence while not wearing their seat belts. - From 1980 through 2008, U.S. air carriers had 234 turbulence accidents, resulting in 298 serious injuries and three fatalities. - Of the 298 serious injuries, 184 involved flight attendants and 114 involved passengers. - At least…

Maybe it's safer /not/ to wear a seatbelt.

It was hard to find good stats with quick googling, but this old source[1] suggests that blood clots during flights are the greater risk, killing at least 2,000 people in the UK per year. I suspect that keeping a seatbelt off while cruising lets you shift around more mid flight and would give a small decrease in the frequency of clots.

[1] http://news.bbc.co.uk/2/hi/health/1109406.stm

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

#279
post #240

Earlier quoted context omitted.

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?

> The risk of a head injury that a helmet would prevent is much higher in a car What is this based on? My own intuition is that the risk is many times higher on a bike.

There are were 42000 brain injury-related hospitalizations for motor vehicle occupants per year, though this data is from before 2001.

https://stacks.cdc.gov/view/cdc/13379/cdc_13379_DS1.pdf (Table 10)

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

#280
post #94
post #86

Earlier quoted context omitted.

I don't know about that. I think mostly it has to do with having the power to pick and choose critical service providers, bully them, etc. If Michael Jackson and Steve Jobs had not been as wealthy and powerful as they had been, they would also both probably be alive. Neither has much to do with being risk-takers, although you might be right that a higher arousal threshold desensitized them to risk. It may also be tha…

I feel like Steve Jobs is an odd choice... He turned down treatment I thought?

He was a fruitarian, and that much fructose is pretty toxic for your pancreas.
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