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.
Nope, definitely a vortex. Lens flares don't curl like that. But it's not smoke, it's condensation caused by the reduced air pressure in the vortex. You can see similar condensation happening for the same reason (but without a vortex) behind the tire.
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 reach dew point temperature, essentially forming temporary clouds that are whipped around by the moving air vortices.
Once the aircraft has passed that point, the temperature generally stabilises and conforms to surrounding air temperature, which usually dissipates the temporary condensation.
The 'twirly' bits on the wingtips is basically spillover from the high pressure under the wings to the low pressure above the wings, creating that mini tornado vortex. This is also the reason that many modern aircraft have those 'winglets' on the wingtips, to try and minimise these spillover vortices which can cause problems for trailing aircraft, as well as induce extra drag on the source aircraft.
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.
A lightweight paragliding set can be as light as 3 kg these days, and experienced pilots can travel 200+ kilometers regularly with a tiny bit heavier set (say 8 kg).
Paragliding requires ascending currents to maintain or gain altitude, IOW you're always going downwards relative to the surrounding air mass. Birds don't (although they obviously do know how to use it for the cheap).
I think maybe the GP is more amazed about the (self-) generated lift and assorted scale. Seems like humans have a thing for hurling self-propelled heavy metal boxes at ridiculous speeds, whether on ground, in the air, or in a vacuum.
Close, but slightly backward. The saturation temperature (dewpoint) is lower at lower pressures. So the lower pressure air reduces the saturation point. The air is not being cooled by the wings. If the sat. point is close to the current air temperature, water vapor will condense.
Similar phenomenon to boiling water at high elevations. Walking up the mountain isn't heating the water, but the boiling point drops as air pressure drops.
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 that way. But it's absolutely wrong to correct someone saying that "lift is pressure" with "lift is actually deflected air".
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 lift.
This is clearly demonstrated by this incident. Many tons of air deflected downwards by the A380's wings had enough force to flip the unfortunate plane below several times.
> 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.
Yeah, that site is indeed one of the worst offenders. Try a fluid dynamics textbook. I genuinely don't think you understand what I'm saying. Air isn't magic fairy dust that pushes on airfoils from a distance. Pressure is impact.
If you hit a slice shot in tennis, the ball will travel considerably further because the backspin produces circulation which generates lift. If air was a bunch of bullets, the effect wouldn't happen at all. If you raise a spoiler on a Grob's wing, its lift-producing capabilities drop considerably because the spoiler interferes with the circulation. If air was a bunch of bullets, a spoiler wouldn't do anything.
> Air isn't magic fairy dust that pushes on airfoils from a distance.
No. Like I said, it's a fluid that has pressure and velocity everywhere. At low enough Reynolds numbers, like for model gliders, you can even get away with treating it as a non-compressible fluid with decent results.
> Pressure is impact.
And contact between two objects is really about Pauli exclusion surfaces at the atomic level. So what?
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.
The poster wasn't talking about the 'curved upper surface' myth. You can understand the lift to be a consequence of the pressure differential, and that is not inconsistent with planes flying upside down.
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 surface in vacuum.
Better for what? Fluid dynamics is actually great for a huge number of stations. For pure realism you can use Quantum Mechanics, but good luck simulating that for a protean let alone a 747.
My point was you can still find a lot real world issues for example wing icing. So, that you need to be aware of what you are and are not simulating.
No, the correction is valid. The main component of lift is an upwards reactive force produced by pushing a mass of fluid downwards, in accordance with Newton's third law.
That is the only component of lift --- unless you think that Newtin's laws can be violated on a macro scale. But owing to the way that pressure is defined, the same phenomenon can also he understood in terms of a pressure differential.
this is just an argument in whether you want to explain the phenomenon mechanically or in terms of thermodynamics.
pushing a mass of fluid downward is equivalent to creating a net downward pressure. its the same thing, just expressed in different terms. the unit of pressure is force per square inch, for you americans. by integrating over all the area, you get the force that you are talking about.
The Coanda [or "coma daily" as my iPad helpfully autocorrects] Effect also contributes to lift.
The air "sticks" to the surface of the wing and leaves the trailing edge in a partially downward direction i.e the air is deflected downward by the top of the wing not just the bottom.
For a quick demo of this, hold the bowl of a spoon
under a running faucet and see how it pulls the spoon into the stream.
>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 physics that requires the air to "meet up" at the trailing edge of the wing.
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.
The Bohr model at least has simplicity going for it, and it's close enough to explain most things that are relevant to chemistry.
For aircraft lift, "equal transit time" is not easier to understand than "an angled wing pushes air down, because of conservation of momentum that pushes the aircraft up".
"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.
While you're on point about flat wings, in wind tunnel tests on profiled wings, you do in fact see a velocity difference between top flowing and bottom flowing streams. It's not enough of a difference, however, to cause coincident streams on the leading edge to line back up at the trailing edge.
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.
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.
> I'd be interested to see in this thread, who here has actually studied aeronautical engineering
I studied Aerospace Engineering (PhD in Aerodynamics), and I stay out of internet conversations over "how" lift is generated. For me it is one of those topics that is just not worth debating. It seems that people get _really_ attached to their personally preferred theory of lift.
Seconded. Masters in ASE, written my own vortex lattice code from scratch.
"Wings generate lift by changing the velocity of the flow around them" seems general and correct but the why part is pretty tricky without notions of continuity and conservation laws. And vorticity helps a lot, too.
You should write a blog entry on current theory, and post "I'm an expert, here are the current theory(ies), I will not debate about it", or point to a wikipedia page that is accurate in your opinion.
Flight is a complex system, there are multiple variables effecting it. And yet half the responses here are regurgitated from grade school without references.
Its a somewhat common joke in our office that if you ask 3 researchers "What is lift?" you'll get 5 answers (and probably a bit of an argument).
I think "It's complicated" and "Why do you need to know?" are often the only appropriate answers, as context is important. I've read some "aerodynamics for pilots" type books that from a research point of view I considered to be, to some degree, wrong. But ultimately they were _right_ in that they taught the pilot exactly what they needed to know.
In a way it reminds me of electricity. I know enough to design and make simple circuitry, but I know electrical engineers and physicists that could run rings around me at both the circuit design level and the "That's not how electricity works, you idiot!" level.
> 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.
I don't think that is right. The tail wing has a different angle of attack than the main wing. On the order of one degree I think. This is so to give a self stabilizing effekt. When flying upside down you have to compensate heavily to avoid what would be a destabilizing effect.
The horizontal stabilizer of most aircraft has a negative angle of attack and produces downforce, not lift in straight and level flight. This allows the center of gravity to be forward of the wing's center of lift by moving the overall center of lift forward. The result is a tendency to pitch down if airspeed decreases without other control inputs, countering the reduced airspeed.
Flying inverted in a relatively stable aircraft requires a lot of forward pressure because for the inverted aircraft's wing to have a positive angle of attack, the horizontal stabilizer has an even larger positive angle of attack. The pilot must counter this with the elevator to establish a stable ratio of lift to downforce.
As an aside, modern aerobatic aircraft are often rigged 0,0,0 (wing incidence, tail incidence, dihedral), so level flight will need equal elevator deflection in the appropriate direction.
Less efficient - but makes for symmetrical performance.
> The fact that full aerobatic and military jets do, is because they usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing.
Fair enough, it is symmetrical, but still has a lot of shape to it - only time I've been inverted was in a grob 103, and was a passenger for that part of the flight, here's the cross section of it's little sister which is also fully aerobatic:
Agreed, that's why I said it'd still work. But the shape does contribute to its efficiency, otherwise manufacturers wouldn't spend money trying out different shapes, adding winglet etc...
A bit late to reply, but I had to think of your post while spending some hours idly staring at at the top of an airliner wing today. Slats (and non-flat airfoils in general, I suspect) are there to allow a harder angle of attack ("amount of pointing up relative to the direction of movement") without stalling.
You can push the air hard on the underside, but on the top side, you have to gently accelerate the flow downwards, or else it forms vortices and you suddenly lose a significant fraction of the amount of air you would otherwise deflect downwards.
If I remember right the "longer path" thing was in Encarta, there was a guy that used Encarta to prove to me that the theory is right and I believed it m it made sense I am wrong and not the encyclopedia.
Additionally, the paths don't meet up/join at the trailing edge of the wing. There's no reason air above and below needs to separate and meet up into the same flow.
Well, the same Venturi principle applies if you look at it in terms of laminar airflow over the wing. The top of the wing (via curvature and downward deflection) is essentially creating a widening venturi tube, whereas the bottom of the wing is creating a closing venturi tube. (Oh, ok, it is planar rather than a tube, but the principle is essentially the same).
Hence the high pressure under the wing and the low pressure on top of the wing. The very act of 'deflecting' millions of cubic metres of airflow generates high/low pressure points. Hence at the end of the day, we could argue that the pressure differential is what is causing the lift?
Disclaimer: Not an aeronautical engineer, just a former commercial pilot.
Yes to pressure part and no to the venturi part. Well, it's not enough. You still have to generate a downdraft to conserve momentum and the venturi idea doesn't explain that.
Or we can just go to the demonstration that our flight instructor did in the first 5 minutes of our Aerodynamics 101 lectures.
Get a piece of A4 or Letter sized paper and try this experiment with it [0]. For best effect, hold both the edges closest to you in each hand and twist the front edge downwards to keep it straight and prevent the paper twisting which could inadvertently straighten it. (i.e. Not with one hand like he is doing in the video).
The Bernoulli principle with postulates the Venturi effect is about the only theory that can explain why the trailing edge of the paper moves UPWARDS when you blow across the top of the curved paper.
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 lines and is a consequence pressure difference required to accelerate (or decelerate) a fluid. Since in the laminar situation flow does not occur from the top surface to the bottom (minus around the tips), direct application is nonsensical. If you integrated all flow lines from all surfaces however, you would get the correct answer.
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.
Well, scale up the wind according to the weight of the metal (and the overall surface area of the metal) and it can happen, as evidenced by this 747 in a boneyard 'rotating' under heavy gusty winds [0] (taking into account the massive weight and CoG difference without the engines on).
Extend the flaps and slats on that aircraft and I am sure the effect will be all the more pronounced.
And yes I've flown aircraft inverted too - it take a tremendous amount of forward stick to try and maintain level flight in that config to counteract the wings natural tendency to move towards the top surface.
People have pointed out the "Thunderbirds" F-16s flying in the "mirror" formation [1] and not displaying much difference in AoA between the upright and inverted aircraft, but supersonic fighter usually have a straighter, almost trapezoidal shaped wing cross section rather than a curved 'fish' shape. I am willing to bet the inverted pilot has a fair bit of forward stick on though.
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.
The common explanation of lift for laypersons contains a number of non-sequiturs and even falsehoods, but this is not one of them. Newton's laws applied to the situation play out in complicated fluid dynamics, and result in a pressure difference over the wing, with a reduction above. That difference, summed over the wing, is the lift (and also the source of the induced drag, I believe, but that is a step beyond.)
Fun fact: One of the weirdest things about heavier-than-air flight is that upon posting any explanation for it online, several people will tell you you're wrong. Each of them will also disagree with one another. All will have sources.
Yes, but by making the air move you introduce a low pressure where it moved from, and a high pressure where it moved to. They are interconnected, just like how you can determine speeds through conservation of momentum or conservation of energy.
There are myths related to low pressure (such as the infamous "equal transit time" theory), but low pressure generating lift is not one of them.
The pressure explanations and the Newton's Third Law explanations are not different theories of lift. They are just different ways of looking at the same thing underlying thing.
The motion of a wing through a fluid has to conserve mass, energy, and momentum. If you analyze lift by focusing on conservation of momentum, you get the Newton's Third viewpoint. If you analyze by focusing on conservation of energy, you get a pressure viewpoint.
It's just another way of framing the same phenomenon (albeit one that makes much more sense to me than high school fluid dynamics). What gets left out of the pressure explanation is what pressure is, which is a statistical representation of Newton's third law applied over huge numbers of tiny things moving in random directions in a given frame of reference
The NASA article discusses a deliberately simplistic model that does not consider the deflection of airflow over the top of the wing, but it would be easy to overlook the caveat if you don't already know the answer. Further down the page there is a link to a correct Newtonian flow-turning model.
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.
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.
To add to jacquesm's response, the footage in [2] is definitely from a humid day. That makes condensation happen very readily.
If I remember correctly, the trails from the outboard edges of the flaps are just like wingtip vortices. The airfoil's geometry suddenly changes, acting like a wingtip and creating a vortex.
> In addition to mitigating en route midair collision hazard, SLOP is used to reduce the probability of high-altitude wake turbulence encounters. During periods of low wind velocity aloft, aircraft which are spaced 1000 feet vertically but pass directly overhead in opposite directions can generate wake turbulence which may cause either injury to passengers/crew or undue structural airframe stress. This hazard is an unintended consequence of RVSM vertical spacing reductions which are designed to increase allowable air traffic density. Rates of closure for typical jet aircraft at cruise speed routinely exceed 900 knots.
Seriously, "unintended consequence"? It seems quite obvious in retrospect.
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 trip.
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.
Probably they have a different idea about risk management than more risk-averse people. Worrying a lot about very low probability events is not compatible with the risk-taking typically required to make a lot of money. After all millionaires are largely a "survivor club" filtered from high risk appetite workaholics.
Pedantic, but. Families with $1m net worth are largely late-middle-aged (newly retired) salary workers with paid-off mortgages on their median-priced houses in suburban flyover country, plus ~40 years of 401k contributions and capital gains.
They drive Toyotas and fly economy for their 1-2 yearly vacations because that's what left when the 15% 401k contribution, mortgage on 3bd house, children's educations, and groceries are paid for.
Think teachers, bureaucrats, journalists (pre-internet), scientists, engineers, doctors, and lawyers, in roughly ascending order. What you'd call the upper middle class.
There are about 8 million millionaire households in the US as of 2016 [0].
Private jets are more a feature of the Fortune 500 CEO Davos-going class. $1 million in income maybe, very different from $1m net worth. It's not generally useful to conflate these wildly different wealth levels under the same terminology.
You're taking the term "millionaire" too literally. There was a time when a million dollars really was well beyond the reach of a salary worker, but a century of inflation took care of that. The term is still used as a synonym for "really really rich". Last time I heard the true threshold for really rich was about $100 million.
The internet personal finance community rallies behind The Millionaire Next Door, which talks about the habits of the people I'm describing as if they were the same rich elite that flies on private jets.
As a result, I try to call out abuse of the term millionaire whenever I see it.
I see your point, but "abuse" is in the eye of the beholder. It might be time to retire the word Millionaire, but unfortunately nothing has arisen to replace it.
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 that people used to winning, on some level, expect to keep winning. Either way, we're not just talking about Fortune 500 C-levels here, plenty of people with loads of money and power did nothing to get it, and have no special qualities associated with that ability to get it.
Anecdotal but I notice in my circles only less financially well off people endulge in quackery. The latest is that you do not need treatment for anything if you do enough marijuana and reiki (not to mention a lot of poor people burn their last money on reiki training....) especially not doing chemo when they sbould is hard to witness.
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 the number of people who go through cancer, it's rarely brought up in polite conversation. It wasn't until I got it myself that all manner of people came out of the woodwork to talk about how someone they knew had gone through the same thing. Many of them have been using concentrated cannabis oil (which my brother also said I should do). After reading a couple of studies, it does have a positive effect on cancers, but the level depends on the type of cancer. In the case of colorectal cancers, it seems to stop the cancer but not kill it, most likely due to the CB1 receptors in the tumour being hypermethylated (as in, the gene isn't being expressed). The level of evidence isn't that of a systematic review, but it's enough for me to give it a go and certainly enough for further research. Unfortunately, the two sides of the argument seem to think that it either doesn't do anything (there's not enough evidence) or that the medical establishment is just a ruse and that cannabis cures all cancer. I prefer to use my critical thinking skills and get the best of both worlds.
I can understand why people might indulge in quackery - I've got surgeons telling me they need to cut out my rectum and part of my lower intestine, even with a full pathological response. Possible side effects are shitting 3 times a day (not so bad) and erectile dysfunction (worse). This has been the gold standard of care for 15+ years now, and the surgeons don't give a fuck about my quality of life, they just want to cut. There's mounting evidence to show this might be overtreating the problem, and that you can get away with a heavier dose of chemo with the radiotherapy. Frankly, I don't want anyone cutting anything out of me unless it's absolutely necessary, but it's hard finding an advocate who would be willing to tell the surgeons to fuck off.
I'm lucky, in this sense: I understand the research and I have access to upcoming studies (I used to work at an institute that did systematic reviews of evidence). Most people won't have such advantages, so they just sit there and do what the surgeons tell them to do, as if they don't have any options other than no treatment. If that's all the choice I got, I'd be wary of the medical establishment too.
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.
I would advocate, for many reasons, taking regular treatment and cannabis at the same time, but refusing regular treatment because cannabis will do it is a bit over the top. I am a cancer survivor so people tend to talk to me about it.
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.
Which more likely has absolutely nothing to do with him being rich. His quackery behavior was very high on the scale before he was rich post Apple IPO.
> ... 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
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.
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".
I wonder if your head would actually hit the cabin ceiling though because of the centrifugal force. The plane might have flipped too quickly for that to happen
IIRC, the Chapecoense flight was done by a private charter company which provided services to football teams. That was not a private jet incident at all.
Ah, right. Like a weekly maid versus a live-in maid.
Still, as far as I know, the safety of standard commercial airlines is much better than both charters and private planes. Without the regulators to monitor the maintenance and pilots, it turns out people take more risks.
It's not even a rule on airliners, merely a suggestion. I'm sure silly people on private jets will keep their seat belt off when seated, but plenty of silly people do that on airliners too.
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.
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.
The challenge with measuring the safety of general aviation is that it is much more behavior-dependant. All of the US airlines use the same standards for deciding when to fly/ not fly for weather, have similar maintenance programs, training requirements, etc... When it comes to private air travel, it's all up to the pilot and the insurance company.
I imagine GA follows something like a Pareto distribution, with 10% of the pilots involved in 90% of the incidents. That 10% would get retrained or weeded out in the airlines, and the rest get much more consistency on all the rest of the stuff you mention.
So yeah, there really isn't any one "the safety of general aviation." It's a huge spectrum.
Another challenge is reporting. The FAA knows exactly how many flights and how many hours the airlines did last year, but GA activity is much harder to gauge. It's hard to figure out what safety looks like when you don't have a good figure for the denominator.
From my limited experience working with them, the general aviation insurance industry seems ripe for startups. Data science is a huge deal in insurance, but the companies insuring Cessnas and Pipers don't seem to have fully caught on.
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.
You don't need to wear it tight (like you do with a car seat belt), we're not talking about tens of G accelerations like in a car crash. All you need is for it to prevent you from flying up out of your seat.
I'm not saying the risk is particularly large, at least in a large aircraft. However, the inconvenience of buckling your seat belt is practically nil, so the value proposition is pretty clear to me.
Or, as with cars, just be in the bigger car. Another a380 would probably have shaken off this encounter. Size, and the flex that comes with size, flattens out these things.
True.I would think this would be more of a problem for people from US states where wearing a seatbelt is not mandatory.
In other parts of the world (with more sense) such as Europe, Australia, we're conditioned to always using it due to strict enforcement and as such it's not such a novelty.
Speaking as someone who has actually done seatbelt enforcement, (I worked as a cop for a year after college before getting into software development,) catching people who aren't wearing their seatbelts is really, really hard. Each seatbelt ticket written probably takes ~30 minutes of time for the issuing officer.
There really aren't any good trick to it-- it's just a matter of finding a good vantage point and watching each driver go by. You're supposed to note the color of the belt (black) and the color of the driver's shirt before pulling the car over. As you'd imagine, fatigue comes quickly-- I never did more than an hour or two at a time. (I still have no idea how the highway patrollmen can it all day, every day without losing their minds.)
NHTSA provides substantial grant funding for traffic-safety enforcement, conditional on the department's enforcement statistics for a particular set of safety-oriented violations, especially seatbelts. The brass encouraged us to take a minimum number of enforcement actions to maximize the chances of having the grant expanded. (It paid a for substantial chunk of our salaries and offered regular 1 1/2 overtime.)
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 no choice but to prioritize, aggressively.
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.)
I'm actually really curious about the officer handling the DUI on his own. Those cases are often simple, but are also often very complex and involve defense counsel and evidentiary disputes. Which state do you live in?
I live in NY but just to be clear this wasn't a DUI - I don't drink and drive! My ticket was for crossing a double yellow line, the offense in NY is called "Disobeying a Traffic Control Device".
The town prosecutor was handling the only DUI that day. (A town PD officer handled the lesser offenses, including mine.)
I'm surprised. At least here in Indiana, as best as I recall, drivers cannot be pulled over for seatbelt violations, only if some other offense occurs.
It varies based on state law. The federal DOT can't pass its own traffic laws or regulations for constitutional reasons, so they incentivise states to implement what they think is a good idea by offering them financial incentives. The best example of this is the 21-year-old drinking age. (They threatened to cut off all highway funding for states that didn't raise it from 18 to 21.)
Pretty much every traffic officer I know could find at least 5 reasons to pull over any car, no matter how scrupulous the driver.
The better way to make people wear their seatbelts would be to standardize a really annoying seatbelt alarm in every car. I have a Subaru Forrester, and if I unbuckle my belt for 10s in my driveway, it goes crazy.
Fun fact: At the police department, we actually had the seatbelt alarms for all of our cruisers disconnected. Being able to get quickly in and out without the seatbelts snagging on our gear was the priority at low speed. Most officers are trained to unbuckle and be ready to exit the vehicle before coming to a full stop (technically illegal.)
The truly cool application of technology to traffic enforcement is the speed camera lottery in Stockholm. I have very mixed feelings on automatic license plate readers: rules for what can and can't be done with the data they produce don't really exist, and that's a real problem.
I think it would be a very hard problem. Take a look at some pictures of cars in traffic-- the seatbelt is extremely hard to see. If it were doable, it would probably take more optics engineers than ML scientists; glare and lack of contrast look like the biggest problems.
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.
I flew into Dallas during a storm once, plane was struck by lightning many, many times. It was pretty spooky, but that was all. The lightning simply passes through the exterior of the plane. However if there is a gap in the exterior, then damage could occur.
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 cocktail lounge in business class, etc...
Yes, you should absolutely wear a helmet when riding a bicycle at low speeds.
Your skull is vulnerable to impacts at speeds that are relatively low compared to full-speed cycling.
On a few occasions I've witnessed a cyclist panic and wobble after being passed far too closely by a car traveling far too fast for such a manoeuvre. This has caused such cyclists to wobble, inadvertently clip the curb and mount the pavement, fall off sideways and subsequently strike their head on a nearby wall whilst falling.
The resulting injury can be very harmful.
Another example of slow-speed head injury: off-road biking down a very steep incline with a loose surface. I've seen people fall and tumble at almost stationary speeds.
To be clear - any cyclist crazy enough to ride a bicycle on the same road as cars definitely needs all the protection they can get, I think that goes without saying. But now you've moved from the "extraordinary low risk of accident" that comes from cycling to the "Probably one of the most dangerous things I can do" risk factor.
And, pretty much 100% of the time I go snowboarding, I wear a helmet.
What I'm trying to surface (apparently poorly) is that life, to some degree, is about managing risks. And we often respond carte blanche scenarios with exactly the same response, regardless of whether it's proportionally required.
Cycling - on road, moving fast, around anything else moving fast, at all treacherous conditions - sure, yes wear a helmet. But, casual cycling on a nice day, protected path - probably not required.
Another area of proportional risk response - portable devices on planes. At one time, end of the world if you had one on during takeout (seriously, other passengers would freak out if they thought yours was on) - and then, all of a sudden - every airport/airline in the United States lets you read your kindle, play games on your phone. People realized their responses were not proportionate to the risk.
Huh? Over here at least, people (me included) cycle on the same road as cars all the time. Not freeways, of course, but normal city roads with a speed limit of up to 50 km/h. It's actually illegal to cycle on the sidewalk unless there's an explicit traffic sign allowing bicycles.
You could not pay me to rid a bicycle on the road here in Singapore. Or in many places in Northern California. I can't tell you about Dubai, because I've never seen a cyclist on the road there. My "Risk Mitigation" strategy in these scenarios is to say, "No, Hell No."
Regarding the law - it's illegal in Redwood City to ride on the sidewalk, but almost 100% of "Utility" cyclists (that is, people taking short trips who aren't decked out in "cyclist" gear) almost always ride on the sidewalk; and the police certainly did not make it a priority to ticket them - and given the density of police cars in Redwood City, any given cyclist traveling a few kilometers was likely to be seen by one, if not more police officers.
When I lived in Boston, it was certainly legal to ride bicycles in the road (and illegal to ride them on many sidewalks), but cyclists still got hit by cars all the time. Riding with cars (whether in your own "lane" sandwiched between parked cars and moving cars, or in the same lane as the cars that want to bolt ahead at 40 mph whenever they have the chance) is the only legal option to get around by bike, but is absolutely not safe. It's one of the places where I think our legal code is absolutely bats--t crazy.
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
Netherlands doesn't count, it's a place where cars respect bikes and vice versa. Try riding a bicycle in a country where there's hostility between the two.
> the "extraordinary low risk of accident" that comes from cycling
No, bicycling is fairly high-risk in general, like skiing, or any other sport that involves a human body travelling faster than the average set of legs can walk it around. Even just going around the block a few times there's always the chance of some random events leading to an unfortunate encounter with a tree.
Of course, it's not skydiving either. And life is a series of risks, I'm not saying don't do it.
Yours are anecdotal evidence of an extremely low risk. There are some bike accidents, which are already rare; Very few involve the head; and even fewer would be saved by a helmet. Whereas, requiring a helmet is a sufficient disincentive to biking that studies have shown that it increases the number of deaths in countries that made it mandatory, by making people drive instead and later die from cardiac diseases and obesity.
So yes you should wear a helmet while biking, but we should not make it mandatory.
In other counter-intuitive statistics about biking, passing at the red light is good for you.
> 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.
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.
Out of curiosity, is cycling a common mode of transportation where you are from?
I recall seeing studies showing that helmet-laws generally coincided with low use of bicycles. Places where cycling is extremely common (like Denmark and Holland) never seem to have them, and it's uncommon to see cyclists using them unless they're doing something particularly dangerous (riding in traffic, off-road, etc).
That happens to be the justification that my country uses to make bicycle helmets mandatory (though there's significant debate about whether it's actually helped reduce injury rates, and it fairly clearly depresses overall rates of cycling versus other modes of transport).
I think the cost of wearing an aircraft seatbelt while you happen to be seated is rather lower than the cost of having to wear a bicycle helmet, though.
Mandatory helmets protect cyclists from injury - but make cycling less popular. Fewer people cycling means they get less exercise and increase other health risks. On average it's a health benefit to cycle without a helmet, compared to driving - and of course people are still welcome to add helmets if they don't mind them.
It's actually the reason why I don't use the bike share program, even though I have a station right next to my apartment building. I could ride it to/from the train station or the grocery store, but I'm paranoid about not wearing a helmet, and hauling the bulky thing around all day is a massive inconvenience.
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?
Sure but you have to normalize it somehow. Americans drive way more than they bike. I imagine if you calculated this per-time or per-distance, driving would still come out much safer for the brain than cycling without a helmet.
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.
Did you hit your head though? Even "low" speed for a car can be 20mph; you can hit a stationary object and be thrown around pretty severely.
That said yeah if you're "wiping out" more than like once every few years you're doing something seriously wrong (or at least taking an unnecessary risk). I've only once had any kind of incident on my cycling commute.
The hardest I've wiped out on a bike was where a bike trail intersected a road. Everything was super wet and slick from rain. Despite bikes having right of way and my bright bike light being on, a truck with no headlights barreled across it without stopping.
Once I saw it, I had to slam on the brakes so hard my rear brake cable popped out of the handlebar, disabling the rear brake completely and I was putting full pressure on the front brake. I didn't have time to react and avoid going over the handlebars, and I hit my helmet on the pavement. (Thankfully, I did stop in time to avoid the truck hitting me).
Was I doing something seriously wrong? Yes -- I was riding a bike without a properly adjusted rear brake cable. However, this sort of mechanical issue (and any number of others) could happen to any riders who aren't much more hyper-diligent about maintenance than average.
Who knows if we'd even be having this conversation had I not been wearing a helmet that night.
From a public health perspective, evidence suggests making helmets mandatory is counter-productive, and so I don't support those laws. However, I still maintain that anyone who cycles without a helmet is fucking stupid.
Cycling in the rain is a risk. Cycling in the dark is a risk. Cycling across badly-designed intersections (and if it put you as a cyclist in the kind of danger it wouldn't have put a car in, it's a badly-designed intersection) is a risk. Being on the road without a helmet - indeed doing anything in your life without a helmet - is a risk. In all of these cases one weighs up the risk of doing it against the inconvenience of not doing it.
Maybe we're all "fucking stupid", but by the stats someone cycling without a helmet is less stupid than someone driving, at all. There's this weird, disproportionate cultural obsession with helmets for cyclists and cyclists only.
Locking it to the bike isn't a good solution if you live in a place where it rains or snows a lot. So you end up having to carry it with you on errands. If you bike a lot, those small inconveniences add up.
I can't imagine fashion sense is much of a reason, that seems like a strawman argument commonly conjured up by helmet laws advocates.
I always thought the statistic that mandatory helmets reduced cycling was a bit pathetic myself. It really isn't that hard. Yes, I have come off my bike and hit my head, while wearing a helmet. Unfortunately, I landed on a tooth rather than my helmet, which wasn't a lot of fun.
Regarding helmet hair, I had a colleague who had the most amazing hair spikes (think coffee cup sized), who would very carefully put a cycle helmet on every day before cycling home.
Keeping the safety belt on protects other passengers too. A person weighing 80kg has surprisingly high amount of kinetic energy when the plane trashes around.
Kinetic energy is also the reason why the flight attendants try to lock as much as possible of the loose items to the overhead bins or under the chairs.
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?
Speed only makes a difference if your head hits something whilst moving at that speed. Or you can just fall off at a walking pace, and the acceleration between the top of your head to the ground is enough to kill you. Happened to a guy on the local trail a few years ago, as happens elsewhere as well.
I think the bicycle helmet comparison is valid here - one big point is, that the typical bicycle helmets are not protecting your head well, you would need a motorcycle helmet for good protection.
I don't think one needs to be confined to the seat for the whole flight duration, but when sitting down, there is no good reason not to wear a belt either.
Bicycle helmets are a compromise of course; a heavier helmet would give better protection but would be very cumbersome. But even light helmets give a lot of protection against very simple, silly accidents, like not noticing a bump on the road, or failing to unclip when slowing down.
And there are ofcourse better or worse bicycle helmets around. And the way you wear them is also important. I have helped a large number of kids around my block put them on correctly after seeing them mostly hanging on the back because the parents don't know how to set the length and angle of the strap...
There is a pretty good statistical argument for wearing a helmet anytime one is near roads, sidewalks, moving walkways, bike lanes, or anywhere else objects are moving more than 0.5m/s, whether you are moving or not. You can even die relatively simply from falling from an otherwise motionless standing position and hitting your head on the paved ground. The brain is remarkably fragile.
I kind of want the helmet-in-public fashion trend to kick in.
Here in Australia, where they're mandatory, us 'hipster' types get around this by wearing helmets that look like the sort of 'crash hat' that skateboarders wear: very dome-like, skull-shaped things rather than the traditional swept-back-vents-all-over helmets that your racing cyclist would wear.
Hotter in summer, but they look cooler. ;-)
FWIW, I thought it was weird at first having to wear a helmet. I'm from the UK. Now, though, it just seems bizarre that I wouldn't. It's my skull! My brain is in there. It only takes one idiot, and knocking my head off concrete from 6ft up at even 10km/h sounds like a terrible idea. Anything that cushions the blow, even if that blow is unlikely, now seems like the most obvious idea in the world.
But a skateboard helmet doesn't work as well as a bicycle helmet when bicyckling. They are made for different falling types. They are better than nothing but not as good as the better bicycle helmets.
Sorry, thought about it at the time but didn't write it - they are actual bicycle helmets styled like skateboard helmets. They're fully rated for bike riding.
If the cops stop you (which they do, occasionally) and you are actually wearing a skate helmet, not rated for bike riding, that doesn't count as 'wearing a helmet' and you'll be fined.
(I'm sure the idea of being fined for wearing the wrong helmet will horrify some people but remember, that's the law here. The law also says you need a bell on your bike. It's rare, but the bike police do random stops and if you don't have a bell, strictly speaking, you'll be fined. Never happened to me, but it can.)
((Which, by the way - and sorry for the errata with the double-brackets - I actually support. I ride through central Melbourne. Pedestrians are a nightmare. Having a working bell is actually important. They cost $5. The law is a public service which, in this case, works. Get a bell.))
Indeed. I feel naked if I start to cycle without a helmet (even though they are not strictly mandatory here, the law says you should wear one but there are no penalties for not wearing it.)
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.
> They could've just turned on the sign as soon as they saw the A380 so that people could fasten their seatbelts then
In a car you usually fasten your seatbelt all the time so that you don't have to guess when the risk is going to occur. In a plane there's no reason not to act the same way.
> In a car you usually fasten your seatbelt all the time so that you don't have to guess when the risk is going to occur. In a plane there's no reason not to act the same way.
Sure there is. The chances of dying in a car accident are around 1% whereas the same in an air accident is, like, 100x less likely?
It's like how you wear a helmet when you're in a construction zone but you don't wear a helmet when walking around the city despite the nonzero chance that something might fall on your head. (Or do you?)
We are not only talking about dying in accidents, hitting your head on the ceiling can still hurt a lot. The risk does not only come from meeting planes, it can also be natural turbulence that you get no warning for.
The reasons there are less accidents in the planes is not because they are inherently more safe (ever read up how helicopters work?), it comes from the rigorous rules around everything flying. The rules exists mostly because something happened and the industry set rules to make it not happen again.
You wear helmets on construction sites because the risk of something falling on your head is so much higher when people are working with loose tools in high altitudes, hanging from ropes or whatever. (And the company is responsible for your safety so will protect their asses from getting sued.)
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.
You'd think so, but from now on do you think planes are going to stop flying under each other or try to maneuver out of the way when this happens inadvertently? I really wish they do, but that's not the impression I got from the article. All I saw was "ATC all around the globe have recently been instructed to exercise particular care with A380s crossing above other aircraft. The Aviation Herald had already reported a number of Wake Turbulence Encounters involving A380s before", which is kind of vague and doesn't quite give me the impression they're necessarily (literally) going to go out of their ways for this if it has a chance of happening.
If you are flying in controlled airspace then you fly where ATC tell you, not where you happen to think would be a good idea. If you want to change course for any reason you ask ATC. The only exception would be to avoid an imminent collision.
Does not work for Clear Air Turbulence, which can be severe enough to make people fly out of their seats, too. I've been in planes where the CAT was severe enough to have lifted me out of my seat if I hadn't been buckled in, and it happened with no warning.
In the 1-2 minutes between this thing booming past them, and being sent into a spin... you want them telling people to buckle up? That doesn't seem like the easier solution; it mostly sounds like a way to have people still hurrying in the aisles when it's too late.
Even half a minute minute is a hell of a lot of time and overwhelmingly better than no notice. Currently airplanes sometimes only turn on the sign after the turbulence has already started.
Also, it's not like they never have no idea which airplanes are around them until they visually see the airplane. They could turn on the sign earlier if they know earlier.
I mean you say that, but wasn't this an accident predicated on not being aware of the positions of other planes? You're basically saying that we should plan for accidents, because wearing a seatbelt is somehow... what? Cumbersome?
If your neurological integrity isn't worth some hours in a seat, I guess that's your choice to make though.
"According to information The Aviation Herald received on March 4th 2017 the CL-604 passed 1000 feet below an Airbus A380-800 while enroute over the Arabian Sea, when a short time later (1-2 minutes)"
They saw the plane, and 1-2 minutes later... bang. We already went over this.
> They saw the plane, and 1-2 minutes later... bang. We already went over this.
We did, that's why it made zero sense that you said this was predicated on not being aware of the positions of other planes. They were aware of this a full 1-2 minutes earlier at least. They could've turned on the sign. The solution was totally implementable.
I think we've reached that point at which I'd be happy to buckle my seatbelt and let you walk around the cabin to your heart's content. I am not your parent.
When I sit in the same cabin, and I'm buckled up, the previous poster (or his body parts) will be bouncing all over the seats of the same cabin, which is a danger to me. So I still prefer that he also buckles up.
As do I, but he's a poster on HN and not on a flight with me, and I have considerations for the value of my time and the integrity of my sanity when dealing with people who think that "intentionally obtuse" is a position in argument.
In my experience (particularly on Emirates) they generally turn the seatbelt sign on before the turbulence because they can generally predict it on radar.
It is a little annoying when you have 20-30 minute seatbelt periods with barely any actual turbulence but there you go.
Had to google around to understand wake turbulence. If I read the wiki correctly, it's basically a horizontal tornado that emanates from the wings. That would explain the rolling that the aircraft encountered.
On another note, I fly every week for work, can't imagine rolling five times and engines losing power with a drop of 10k feet. That's absolutely insane. I've had engines lose power before, but it was quickly regained such that the drop was more moderate.
It's helpful to think of an aircraft's wake in two parts.
The wing is deflecting air downward to provide lift; this creates a volume of downward-moving air behind the aircraft.
There's higher pressure under the wing and lower pressure on top, so air from below tries to get above the wing at the wingtips. This causes circulatory motion, yielding wingtip vortices (see my top-level comment for some visualizations).
Do you happen to know how arial refueling works then ? E.g. in this image [1] the jet is flying where I would expect a lot of deflected air to be moving to ? Or is it just deflected much more steeply ?
The other two replies covered your questions well, so I'll just add that wakes don't descend particularly fast. According to the FAA's Pilot's Handbook of Aeronautical Knowledge[1] (page 14-28), "Tests have also shown that the vortices sink at a rate of several hundred feet per minute, slowing their descent and diminishing in strength with time and distance behind the generating aircraft."
Considering the Challenger's encounter with the A380's wake, it took 1-2 minutes for the Challenger to hit the wake, so the wake probably had 1-3 minutes to make the 1000-foot descent. That very roughly fits the expected "several hundred feet per minute" descent rate.
Considering the case of refueling, the wake's motion downward is much slower than the aircrafts' horizontal motion, so it wouldn't have descended much by the time it's left behind entirely.
being close is relatively safe from wortexes - there still is some other turbulence to consider, but the standard turbulent flow caused by drag is chaotic so it'll shake you but will 'even out'
This is quite interesting. I've been living underneath a flight plan for the last few years, and every now and then I've noticed a strange noise that seems to come from the air a few seconds after a plane has passed overhead on approach. The best way I can describe it is as a tearing noise, somewhat like a long stretched version of a tear in paper, or fabric. I've long suspected that it may be due to turbulence, and this article certainly suggests that the turbulence for some aircraft is much more powerful than I'd suspected.
That's likely the sound of jetwash striking (nearly) stationary air as it exits the engine.
I'm familiar with the roar of jets taking off. Some years back I happened to be biking past an airport, at the end of the runway, just as a passenger jet was lining up for takeoff, headed away from me. I thought I'd pause to watch.
Only as the engines spooled up did I think, "hrm, this could get loud".
It didn't.
Instead, what I heard was ... the engines spooling up. Loud, yes, but not a roar, just an increasing pitch, until the airplane started accelerating down the runway.
It wasn't until some 15-20 seconds later that I heard the familiar roar, echoing off of hills five or so miles away. That's when I realised that the whine was the sound of the turbines, but the roar was the sound of exhaust gas, streaming out of the engines, hitting stationary air and generating intense turbulence, and radiating outward in a perpendicular line to that jetwash. So I didn't hear it directly (it was moving away from me), only the reflection (as that wall of noise, now reflected off the hills, was directed back toward me.
I doubt the vortex would make any particularly loud sound, though you might hear the rushing of air. Speeds are in the tens of miles per hour rather than hundreds as with jetwash.
Big problem is the use of autopilot navigation locked to the GPS route.. this pretty much guarantees that you will fly right below the wake of the above plane on the same route! (Before GPS it will be very odd to flight exactly the same path) ..
Eh. e.g. the north atlantic tracks have been around since the 1960s. GPS wasn't available to the public until Korean Air Lines Flight 007 in the 1980s.
The OP means that satnav ensures that two aircraft on a reciprocal or identical track will now pass over one another, whereas there used to be navigational slop that would give some unintentional but useful lateral displacement.
Ironic that you should use the term 'slop', since that's exactly how they avoid flying the same route across the Atlantic tracks for example (Strategic Lateral Offset Procedure).
Also worth noting for the transatlantic paths is the direction of traffic. When it's morning in North America, traffic is predominately westbound. When it's night, traffic is predominately eastbound.
Right now, it's the middle of the day (12:50p Central). There's a bit of a mix[1], but it's still predominately westbound.
The consequence of this is that most traffic will be separated by at least 2000 feet. Eastbound traffic will (generally) be at odd Flight Levels (so 29000 feet, 31000 feet, etc.) while Westbound traffic will be at even FLs (30000 feet, etc)[2]. This assumes RVSM airspace.
Ahh, I see you are one of those kinds of wikipedia readers as well. I've spent many a late night reading about the minutae of air disasters. Hello, friend.
May I also recommend strong radiation source mishandling accidents?
I was looking at FlightRadar24 and listening to ATC while an A380 took off from Dulles near DC. Not only did they warn for wake turbulence when the plane was already well away, they held other aircraft for a runway inspection after the plane took off. I'd imagine that kind of wake could kick up some significant debris on the ground as well.
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 from the aircraft that made them).
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.
Another point related to its size: the 747 has thrust reversers on all four engines. The A380 only has them on the two innermost engines, because the wingspan is so wide those engines aren't always over the runway and have a higher chance of kicking up debris with reverse thrust.
The same would happen with any widebody, the displacement is enormous and it's one very good reason to nail down everything close to the ground in the path of these planes very well.
To be clear, that crash in Queens was 100% pilot error (and the plane allowing insane inputs). There was a little turbulence, but it was the extreme rudder movement that threw the plane around and tore off the tail.
The physics of this are insane. Then again, by my calculation the A380 displaces roughly 11 million cubic feet of air per second at the max landing weight.
1) A fueselage box with a cross section of 2067 ft^2
2) A wing box of ~1200 ft^2 (a very broad approximation because of engines, the actual wing box - the part of the plane where the wings meet the fueselage - and the curve of the wings),
3) A tail box with a cross section of 144 ft^2
So a total cross section of ~3411 ft^3 * 827 fps = ~3 million ft^3
Point being, the plane isn't moving 11 million cubic feet just to move forward, it pushes on a little more than a quarter of that directly. These wake effects happen because it's disrupting so much air outside of the zone it actually travels in, mostly below and behind it.
It's not an approximation. I'm giving a sense of scale, not saying how much volume the plane has. The point is that while 11 million cubic feet sounds like a lot, if you put it in a big box next to the plane then they would be on the same scale.
> the plane isn't moving 11 million cubic feet just to move forward, it pushes on a little more than a quarter of that directly
Weight of airplane = mass of air displaced per second * velocity of air.
The weight of the airplane is a force downward, the air must match that force, either by throwing a lot of air with little velocity, or a less air, faster.
EDIT: this is the net downward displacement of air sufficient to equal the A380 850,984lb max landing weight assuming a ballpark air density of ~0.075 lb/ft^3. The aircraft displaces much more air via its engines, fuselage and secondary effects, but the above number seems most relevant to the Challenger 604 ~1,000 feet beneath the aircraft :).
I just love An-2 planes. They can take off and land almost everywhere, they're one of the slowest and lowest flying planes that I've ever seen (which I find cool), plus the propeller/engine has a special sound. There's a couple of them stationed just outside my parents' village in Eastern Europe, if you look on the GMaps link that thing close to them it's actually a sheepfold (https://www.google.ro/maps/@44.2288052,27.5250523,386m/data=...).
I've been on a widebody caught in an A380 wake before. Some seriously violent turbulence for a few seconds, and the pilot came on afterwards to tell us what happened.
Holy smokes that must have been terrifying. Glad nobody died. I hate flying as it is (not that I'm likely to ever find myself in a private jet anytime soon).
Wow. Uncontrolled roll at least 3 times, maybe 5. G-loads severe enough to damage the airframe beyond repair. And this was a 9-passenger bizjet, not a tiny light single.
Pilots should be aware of wake turbulence and wingtip vortices in particular, and should be aware that being at a lower altitude than the generating aircraft is the most dangerous position (the vortex pattern is denser than the surrounding air and therefore descends).
Also, an invisible vortex is no less turbulent for its invisibility.
Landing at O'Hare in a smaller bombardier 2x2 (crj 700 I think) jet following a jumbo was an interesting (white knuckle) ride I had in recent memory. The plane turned over lake michigan east of the city and felt like it went completely 90deg to the ground losing a good amount of altitude which I do not believe was the pilots intention. I definitely heard a few gasps, the stewardess curse and my wife grip my hand hard. Followed by 10 minutes of bumps, drops, and wing waggling and a landing that felt like we simply dropped 10 feet on to the tarmac.
Those little jets man... they're fine most of the time but what a spooky experience that was.
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.
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 dramatically based on the size of the leading aircraft.
It's fairly standard practice, as long as the aircraft involved are certified for it and flying on autopilot. Given that the planes involved were flying at FL350-60, they probably were (altitudes above a certain threshold - FL290 in the US) are restricted to aircraft operating under rules allowing 1000ft vertical separation.
By law, 5 (nautical) miles horizontal separation or 1000 feet vertical separation is required. When aircraft were smaller, that was probably more than sufficient. The A380 is another beast entirely, though.
The question is then - are there any systems that can ensure that two airraft aren't passing eachother at just 1000 feet if one of them is a behemoth? Will the corridors magically widen when an A380 enters it?
Will nearby aircraft be warned when crossing right under an A380 that they are basically on a collision course, while had it been a small aircraft it wouldn't be a problem?
I never understood why corridors at opposing directions aren't by default offseted both in altitude and lateral separation - there have been quite many collision already because navigation aid reduced the positional error within a corridor to few meters
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.
Technically, the lowest flight level is FL200 or 20000'. Below that, altitudes are reported in feet. I'm not really familiar with the "angels" thing. I suspect that is specifically military.
EDIT: there was a reply (since deleted) that indicated I may not be completely correct on stating FL200 as the lowest number used. I contend that I am still basically correct for North America, but there is some subtlety:
Technically, a flight level isn't a distance measurement at all. It's defined by atmospheric pressure, so that all planes use the same "ground" barometer by definition. The feet are expressed nominally relative to a standard sea level pressure.
That is absolutely correct. I thought about mentioning it, but did not. Flight levels are definitely expressed as "pressure altitudes" rather than absolute altitudes. The air pressure (or rather density) is the more important number when it comes to keeping an aircraft in the air, anyway.
Generally, you'll use flight levels until either you hit the transition level specified in the approach plate or ATC clears you beneath that level, at which point they'll switch to using feet and give you the QNH (atmospheric pressure at sea level) to calibrate your altimeter.
Depending on conditions, FL180 could be below the transition altitude at 18000'. I doubt, therefore, that you would ever be given anything below FL200. That is the subtlety to which I'm referring (well that and the fact that different transition altitudes are used in other countries). I'll admit that this is stretching my knowledge. Prior to this thread, I merely "had it on good authority" that FL200 was the minimum.
1. The nautical mile is an SI derived unit, now fixed at 1852 meters.
2. It's a more useful unit than the kilometer for long-distance navigation due to its historical definition in terms of arc along a line of latitude making it easy to work with on charts.
Aviation. 500 & 1000 ft intervals are very convenient discrete altitude levels for coordinating traffic, and that's probably a key reason why it's held up universally. In meters, the interval will either awkward and hard to communicate numbers or spaced too widely to be efficient.
Under normal flight conditions, the aircraft's engine supplies hydraulic power to the flight controls (flaps, ailerons, elevator), like power steering in your car. Very necessary for big/fast aircraft, as the plane is heavy and the force of the air resisting the movement of those control surfaces is very high.
If the engines fail, you still need to be able to control the plane, so there is something called a ram air turbine[1] which can be deployed out of the side of the aircraft. It is basically just a little propeller which spins in the breeze, which powers a pump, which supplies the hydraulic pressure to control the plane. So if the power goes out, you can still deploy that thing and have "power" assistance in controlling the plane.
The article says the ram air turbine did not deploy, possibly because the g-forces were holding it in, or perhaps because the g-forces or aerodynamic stresses were flexing the body of the plane so much that the turbine was held in place by the bending. So the pilots did not have "power steering" on the plane, and had to pull on the controls with "raw muscle force".
There is probably some mechanical advantage, probably both from the leverage afforded by the mechanics of actuation, and from the aerodynamics of the wing, that allow a single human to move the whole plane around. But it would still be very, very hard to control the plane without power assist, especially under such extreme conditions.
(Any pilots/aerospace engineers feel free to chime in/correct mistakes here).
Cessna pilot here-- I've never flown an aircraft with hydraulic controls. (Small planes use pushrods or cables to actuate the controls. It's all muscle power for us.)
The physics of flight produce a very useful convenience: the amount of force needed to effect a particular degree of attitude change (e.g. a 10 degree bank) remains the same, regardless of speed. Planes up to the size of small jets (the Cessna Mustang, for instance) use fully manual controls with no power assistance. The Challenger is a bit bigger, but even after the remaining pressure in the hydraulic system completely dissipated, I doubt more than 30lbs of pressure would have been required to actuate the controls. And the rotational inertia of the turbines should have provided at least some assistance on top of that. (I have no idea what would have happened if an airliner lost both engines simultaneously in a stall.)
If both engines went out, then that means hydraulic power was lost, and that all of the aerodynamic forces on the control surfaces were transmitted directly to the stick. This is exactly the same as trying to steer a car with the engine turned off - you can do it, but it takes much more effort than when the power steering is working.
It appears that there is a section of air between 29,000ft and 41,000ft, where flights are allowed to be closer than is normally allowed. Instead of 2,000ft apart, they are allowed to fly 1,000ft apart. In order to operate continually in this airspace, a plane must be "RVSM approved". Otherwise they have to either request special permission or make a continuous climb through said airspace while complying with their usual 2,000ft requirements.
The article mentions that the A380 and Challenger 604 were 1,000ft apart. So, I would assume they were both RVSM approved. This event could call the RVSM into question.
When an airframe is stressed beyond its design limits it can't be put back into service. It's conceivable that it could be put through a "C-check" type process of disassembly and inspection, but given the age and residual value of the plane that might not have been cost effective.
Planes are very fragile and are not meant to be able to sustain loss of control at high speeds. Sudden disintegration does happen mid air following a loss of control.
I am always impressed at how they look like a big chunk of metal from the outside, but they are in fact mostly made out of air and very thin and light materials.
As an uneducated guess, the wing mounts (aluminum?) and surrounding fuselage have stretched way beyond tolerance and are no longer capable of supporting nominal load. The metal has fatigued and must be replaced, which would require new wings and nearby fuselage -- at no small cost.
I'd imagine it's less a case of the plane being damaged heavily and more a case of there's just not enough value gained by keeping it in service to offset the potentially disastrous cost if something were to go wrong.
The article said the plane had been subject to very intense g forces, so I would imagine substantial structural damage. They should feel lucky that it didn't fall apart.
I guess I could have said "Just because something is great fun, and you think you're in total control of inherent risks, doesn't mean it's a good idea, or that you're capable of making good risk assessments".
But I'm British, and we communicate in specific ways.
Not really. Exaggeration for comic effect is a useful and entertaining tool when applied properly. I don't think anyone considered it an actual comparison of off-piste skiing and meth.
Except that it's not. In the UK you can go to prison for pot, which is less dangerous than (for example) horseback riding. Its the situation which is absurd, not the comparison.
Well, both Allies and Axis used methedrine during WWII. In recent decades, US military has shifted to modafinil. But I'm certain that W enjoyed his methedrine, back in the day :)
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
[3] https://www.youtube.com/watch?v=uy0hgG2pkUs
[4] https://www.youtube.com/watch?v=KXlv16ETueU
[5] https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...
[6] https://en.wikipedia.org/wiki/Strategic_lateral_offset_proce...