How Do Airplanes Fly? What Neil deGrasse Tyson got wrong about Bernoulli | StarTalk
Vložit
- čas přidán 9. 05. 2024
- StarTalk is a popular podcast starring Neil deGrasse Tyson and Chuck Nice. When Tyson made a video explaining how a wing generates lift, I was exited. But my high hopes were crushed when he used the "Equal transit time" hypothesis.
StarTalk: "Hoiw do airplanes fly?" • How Do Airplanes Fly? ...
Links to videos about lift:
- This is lift: • Lift explained - Berno...
- Lift formula: • The lift formula expla...
- Forget Bernoulli and Newton: • Forget Bernoulli and N...
- Why are so many pilots wrong about Bernoulli? • Why are so many pilots...
Other links:
- Holger Babinsky: Wind tunnel video. • Wing lift Holger Babinsky
- Holger Babinsky: «Lift” • Lift - Prof. Holger Ba...
- Doug McLean: “Common misconceptions in aerodynamics” • Lift - Prof. Holger Ba...
- Krzysztof Fidkowski: “How planes fly” • Krzysztof Fidkowski | ...
- Khan Academy “What is Bernnoulli’s equation?” www.khanacademy.org/science/p...
- NASA: “What is lift?” www1.grc.nasa.gov/beginners-g...
- NAVY Productions: “Why do aircraft carriers always sail directly into the wind?” • Why Do Aircraft Carrie... - Věda a technologie
Neil gets A LOT of things wrong.
I for one appreciate that he actually got the "lift" concept correct, aside from the speed of the air concept.
But explaining lift is as simple as saying that air *does* push up on the wing because there is a greater concentration of air molecules below than above it on the other side, and the forces aren't equal. AKA "static differential". The wing, being between these two pressure zones, will want to move in the direction of least pressure... generally "up" in a plane.
Bernoulli's principle is virtually a separate "issue" and is only the *cause of the differential* pressure.
Just look at the smoke trail clip. Notice how the smoke is spread out above, and highly concentrated below.
Not sure why this is such a difficult concept for people to grasp. No need to over complicate it until you need to do the actual math.
Lift is cause by action and reaction - molecules been deflected downwards, which cases lift.
The pressure differential is a reaction to the deflection of molecules, not the cause if lift.
R
@@RalphEllisCorrect. F=Ma. The amount of lift is equal to the mass of the air and how much it is accelerated. Maybe not equal but that’s essentially it.
That's what happens when you buy into your own hype.
Are you a creationist?
One of the great challenges in this world, is knowing enough about a subject to think you're right...but not enough about the subject, to know that you're wrong...
Dunning-Kruger effect
@@BritishBeachcomber That-s typical among Scientism adepts. You can find a lot of PhD holders who are dishonest idiots
My favorite example is a PhD in MATHEMATICS who said 10^12 > 10^23 just to slander the target of his hatred
An even greater challenge is knowing when you're being hoodwinked by social manipulators who are actively molesting you and insulting your intelligence by directly appealing to known preconceived notions and preferred (habitually maintained) bias, while making you believe they're "clarifying" something for your intellectual benefit. See my other comment for more details
That's Neil describing his entire career.
That ad drives me crazy.
I went to engineering school with guys like NDT - so eager to teach and or sound smart that they have to sound authoritative in everything, regardless of how little understanding they have of whatever topic they're wandering through at the moment.
As a pilot, listening to Tyson's explanation of lift was like listening to fingernails on a blackboard... Also, anytime anyone says that natural phenomenon "wants" to do something, it's time to change the channel.
Yeah, that was the first obvious error. After all, once the parcel of air has been split by the leading edge of the wing, don't the two halves want to get as far apart as possible, like any recently split couple?
Agree with your annoyance with the use of “wants.” Anthropomorphizing physical phenomena generally conveys lack of competent understanding.
Surely he is using such expressions to resonate more with regular people, that have no physics and technical knowledge about the subject
@@MStoica I disagree. Speaking and writing as if physical phenomena (such as air molecules) have conscious volition _is not_ helpful or instructive to subject-matter novices. Better is to explain in a manner consistent with the know science, yet slowly and carefully and within the audience’s capacity to comprehend. Often, the false attribution of conscious volition is an indication that the speaker himself doesn’t fully understand the subject matter.
@@MStoica If he's purposely spreading falsehoods to build his follower count, that's even worse than his own not understanding the subject in the first place.
Tyson’s greatest work was Cosmos where he was reading from a script written by people who actually knew what they were talking about.
Hes a total fraud.
I thought Tyson wrote it. So I just looked it up. You're right.
There are MANY aerodynamics engineers that get this wrong because it IS what we were taught in college back in the 80s and later years. It wasn't until later that some professors put their videos on youtube to correct the mistake. So that he got it wrong isn't surprising nor does it mean he doesn't know what he is talking about with respect to other subjects just as I posted.
@@FlyingAceAV8B No he isn't, I as an aerospace engineer was taught this too. It wasn't until later that it was corrected.
@@diegom8
>> There are MANY aerodynamics engineers that get this wrong
This is maybe the most basic thing in all of aerodynamics. If an aero engineer today gets this wrong, they have been in a coma for 40 years. This is roughly equivalent to a doctor using blood-letting.
Magnar, well done! I too watched the Neil deGrasse Tyson video (due, in part, to his celebrity status), only to find myself muttering “no, no, no ….”. Thanks for putting together such a well researched, technically correct, exposé of three common misconceptions in aeronautics.
what are the other two?
Except its wrong. His examples were not for straight and level flight. 🤷
@@mrphysics2625 All the examples work the same in level flight.
From the outside, it appears that Mr Tyson's self worth is wrapped around being the smartest person in any room he enters. And it doesn't seem like that meshes well with the final quote in this video.
Lao Tzu - The wise man is one who, knows, what he does not know. And its corollary - Stay in your lane. In short, no one has a good grasp of everything. When one thinks they do, that's precisely when they get into trouble.
The Dunning-Kruger effect. He doesn't know what he doesn't know. But he thinks he knows everything.
dull... he and BO are the dumbbbbbest in any room.
He’s successful because a frustratingly large ratio of ppl respect charisma more than intelligence. Say the thing dramatically and commandingly, and ppl will think there’s substance behind your confidence-but that’s only because most ppl aren’t bold enough to lie that well.
Bravo
Listening to Tyson talk, it boggles the mind how anyone ever took him seriously.
Because he has a PhD in physics and you’re standing on the sidelines with a magnifying glass
As someone with a PhD myself, experience has taught me to tend to count that against someone rather than in their favor.
Years ago before he was exposed as a hack, I listened to him on star talk explaining that elon musk could not accomplish the things he is doing easily today, and that the privatization of space would never happen, and this should always be the governments job. Then went on to explain incorrectly fundamental aspects of rocketry
perception is what matters, learnt it the hard way.
When Tyson passes away, nobody will say "We lost a great scientist today"
"Astrophysicist to the Stars" Neil deGrasse Tyson wanders into the weeds to find a rake. Steps on it.
Haha his explanation about what happens when helicopters loose power was another fo paux
🤣🤣🤣🤣
@@johnlucas2037 . You mean Faux Pas ? Or is a Fo Paux something else...............
I used to like Neil’s science descriptions. Then I saw him give a keynote live at a technical conference in San Francisco. I forgot what topic he was talking about, but the number and level of bombastic arguments and assumptions was counter to what I learned from my scientific mentors. (Three of them are notable enough to have Wikipedia articles.)
But upon watching this (and I’m only at 11:30 ), my level of Picard facepalming has reached a new level. How does he get these cowpies past his fact-checking team?
You’re insufferable
Tyson is NOWHERE as smart as he thinks he is.
I'm just glad he's getting roasted in the comments!
Unfortunately some people take him as a prophet
Most people are not (myself being no exception).
I'm gonna correct one thing - he wants us to think he knows it all. I wish he'd stick to topics he really knows, but he likes the sound of his own voice, so I know he won't stop.
I'd blame the current need of "marketization of the self" nowadays more than him "liking the sound of his own voice".
If you want to stay relevant as a 'product', you need to keep pushing out content, so ppl like deGrasse Tyson push themselves out of their zones of actual knowledge.
Same goes for many of the science communicators on SoMe. Another example is Sabine Hossenfelder, and I'm sure you can find many more that have started within their fields of expertise, but then started reaching outside of that and start getting things wrong.
@@Jarlerus It wouldn't be surprising for mistakes to crop into anyone's work, particularly after making a lot of videos, but are there examples of videos from Hossenfelder where the entire video is wrong or misleading?
@@oliverbatt3559 Videos with outdated, limited, and narrow perspectives. Often around more politicized topics. Still, it shows a lack of actual expertise in subjects. Just like the Tyson video referenced here; The explanation is simplified, parts of it (f.ex. how Bernoulli's is explained) might be correct, but the whole lacks a lot.
What topics does he really know? I've watch him botch history, biology, medicine -- even basic physics and astronomy!
@@HopDavid If you can do a better job, you should give it a go. We need more people advocating science for people too lazy to put in the work themselves.
On another explainer, Tyson said that airplanes taxi in the air above the airport, and not on the ground. Chuck Nice was visibly disturbed by Tyson's explanation, because even Chuck knew that aircraft taxi on the ground….on taxi ways.
Can’t they also be referring to holding patterns and go arounds etc?
High time you all start paying real taxi's. Then everybody can go to excellent public schools and that will avoid having so many people losing contact with mother earth. Educate like everybody, like it was like centuries like ago. Like. Duh.
@@marquisdelafayette1929 Yes, and he uses exactly the WRONG word for that. Besides, that word taxi is ridiculous, anyway. Who invented that, deserves spanking on his taxi area's.
Unless you are Harrison Ford. Then you just land wherever, taxi-ways, golf courses, and so on, lol!
I think he was confusing that with holding patterns
DeGrasse isn't just in the wrong lane here, he's on the wrong highway!
Wrong runway
He always pontificates on subjects that are not his field
and not just on this topic. Never has a "scientist" fallen so deep as NdGT
He is not much better with the subjects is supposed to be an expert in.
Does anybody ask the question WHY? I bet he never did actual calculations on aerodynamics all by himself. Sure he CAN, but this video only leaves the impression, Tyson did not go into detail, here. Mind you, there is a whole lot more to know about wings and planes. The first supersonic planes went down like a brick, trying to kill the pilot. It took a while before it was clear what caused such problems. And that is just one example. See? It is even difficult explaining how wings work, before you know it, you are marketing an out dated theory.
And these weird tit for tat comments here, well, it doesn't make me happy, either.
What really scares me is that I have never taken a single class in aerodynamics... yet I still knew many of the things he said were wrong. Particularly the part about all airports and aircraft carriers have more than one runway are they are never at 90 degrees... you know... because I have eyes.
Neil DeGrasse Tyson, and most others, also forget that you can build a plane with thin flat wings and it will still fly. Inefficient, yes, but I build balsa models like that for fun.
Some acrobatic airplanes have symmetrical (top-to-bottom) wings that fly upside down, just as well as they fly upright. And people sometimes fly upside down (at -1G) using wings that are optimized for upright flying.
I knew that from childhood because a paper aeroplane would fly. Many of the balsa wood toy planes from my childhood also had wings cut from a flat sheet of wood which was curved slightly by the attachment to the "fuselage". They would also fly perfectly well.
it flies because when titled upwards the air has to move a greater distance and this causes a negative pressure on top
I was also going to mention exactly this... thanks.
It is not necessarily inefficient. As we get into super and hypersonic speeds, a thin, flat wing is very much desired, aerodynamically.
Tyson ain't no Sagan, that's for sure...
Be careful....you will be called a racist because of this comment.
But I agree with you.
Sagan was scientifically sound.
@@christopheryellman533he made his own mistakes too. There was a whole segment in the original Cosmos about the burning of the Library of Alexandria and the middle ages which is entirely misinformation for example. Everyone has their blindspots.
@@AdamBrusselback A friend of mine was an undergraduate at Cornell, and one of his classmates worked in Sagan's lab. He said when he went in there to visit him, there were clouds of smoke from the good weed.
@@christopheryellman533LOL. I believe it.
As noted by others - if “Equal transit time” were correct then inverted flight would be impossible, as would flat high-speed wings that have no curvature. Holding angled cardboard out a car window forces it upward.
Even more importantly would be the fact that you'd be able to get the lift essentially for free without the annoyance of induced drag.
I was told flying inverted was just because the airplane had much more power to overcome the drag
That's a misconception. Inverted flight wouldn't work if equal transit time were the ONLY way to create lift. AoA can create lift AND the airfoil shape and resulting different velocities ALSO create lift.
Claiming that Bernoulli lift makes inverted flight impossible is like saying that the existence of pizza makes hamburgers impossible. BOTH exist.
Then you have explanations based on air flowing downward long after the wing has passed by. Such as mentioned early in this video. But that explanation violates the law of causation - the air going down later can't push the wing up earlier. Cause always comes BEFORE effect. The cause can't come AFTER the effect. The air flowing downward AFTER it has left the wing is a result, an effect, of lift - it can't be the cause.
@@thomasward4505 Put most simply, wings generate lift via momentum transfer. The airfoil redirects the flow of air downward (provided there is AoA or camber) and this results in a reaction force on the wing that both produces lift and drag. Conventional wings will produce lift inverted provided there is sufficient angle of attack. Symmetric airfoils will also generate lift in both orientations, but require that there is always some angle of attack or no lift will be generated as the airflow will be unperturbed. Conventional wings like those on an airliner are designed to generate lift even in the absence of AoA so that the plane can fly level during cruise to reduce drag. There is a lot more to it, such as the wing being “high performance” capable of generating large quantities of lift even at relatively slow speeds. This also comes with proportional amounts of drag (which is a lot) which is one reason jets have such large powerful turbofans.
@@thomasward4505 And fwiw flying inverted will generally require more power since the wing is not optimized for negative angles of attack unless it’s specifically designed for it. But most of the time inverted flight is impossible due to the design of the fuel and lubrication systems since they are gravity fed. The fluids will collect on the opposite side and expose the sump to air. I believe in fighter jets there are reserve lubrication and fuel tanks designed specifically for negative g’s that allow for brief periods of flight inverted. Also the famous “vomit comet” used for low-g training gets around this by having specific minimum requirements for the quantity of fuel onboard so that the pickups remain submerged even in near zero g.
NDT is evolving into Cliff Clavin from Cheers.
Neil seems to be getting careless. Air does not "want" anything. It is a group of molecules under pressure due to gravity. I assure you, air does not want anything, just as water does not "seek its own level". It is water. Water seeks nothing. Words matter, Neil. 🙂
Yes, what you describe is somewhat of a problem these days. It's not just Neil tending to anthropomorphize like that while trying to explain some aspect of Physics.
@@jokerace8227 This anthropomorphic mindset has reached insane levels in IT. Ascribing aspirations, dreams and goals to elections and transistors is a deep form of bullshit, but seems to a big part of many AI discussions. Malicious programming and programmers, perhaps, but many seem to believe that a device can have a mission, dreams and goals outside of its program and programmers.
somewhat water wants to do something. it is not completely wrong.
read my post!
Physicist do this all the time, it’s not their fault if you bone heads can‘t comprehend a metaphor
He has the difficult job of making science understandable to those who have insufficient instruction in science. The U.S. has been falling behind in that since the 80's.
I respect Dr. Tyson, but it surprised me when he stated that a helicopter cannot glide if its only engine stops. I fly single-engine airplanes and helicopters, and I'd rather be in the latter when the engine quits.
Interesting. Do you chalk that up yo your autorotation skills, or are you saying autorotation has better odds than gliding, period? If the latter, care to elaborate please?
@@--SPQR-- I'd prefer to be able to glide so I have better choices where to land, instead of having to land on whatever's directly below me (roughly).
@@--SPQR--i guess autorotation allows you to land where you choose in a small area; a plane still needs a nice flat field or similar. though bush planes can land pretty easily in a small space
He represents the worst kind of 'know-it-all'.
Thanks for confirming what I have known as a pilot for years. Interesting to note, I still, on occasion have to correct certified flight instructors during bi-annual reviews, that bernoulli alone is not sufficient. In fact, there are still manuals out there that still teach it incorrectly.
And none that explain it correctly!
Angle of attack.
@@codetech5598 Sure, angle of attack certainly affects lift (and drag) but why?
a Bernoulli based configuration, does not even generate lift!
@@RationalDiscourse A higher AOA moves more air downward, like a variable pitch prop pulls more when the pitch angle increases.
Your shirt is indeed cooler! More people should see this video.
The primary purpose of an aircraft carrier's angled deck is to allow landings and launches simultaneously.
I was working on my pilot licenses while in college pursuing my civil engineering degree. My hydraulics professor was the first engineer I had heard who was so perplexed at how many otherwise credible people had the flawed "understanding" of Bernoulli and lift. To this day, from the FAA publications down, that misunderstanding continues. It's hard to understand why it has not been corrected after having been explained by so many sophisticated aerodynamic experts like those Magnar refers to at the end of his video.
Yea, I was gonna say the same thing: it's hard to blame Neil about Bernoulli when he's basically saying the same thing the FAA taught me while getting my pilot certificate....
How do you explain stall without Bernoulli? “Negative pressure gradient” triggers warnings in x-foil .
How would you summarize lift in words in terms of reconciling some of the inconsistencies? I believe there are even some inconsistencies in some of the referenced sources expert sources.
@@chiefcrash1 I think that's a reasonable statement. There is a lot of historical legacy in all the confusion.
@@ArneChristianRosenfeldt Stall is about excessive abruptness in the flow path contour. Something like a lot of race cars all with too much speed for a particular turn.
Dunning-Kruger would be proud of their theory!
It's undefeated. Unlike Neil deGrasse Tyson.
It is an observed phenomenon, not a theory. Just to be a bit pedantic.
I love it when you can ‘see’ the low pressure envelope above a wing when planes are close to landing in wet humid conditions. That cloud above the wing.... now you see me, now you don’t. The same conditions also show the powerful vortices coming from the outboard tips of the trailing edge flaps. When lift and wake air turbulence become visible.
I heard the bit about the air going a longer distance and wanting to "catch up" 50 years ago when I was 12. Seemed wrong to me even back then. Thanks for finally setting the record straight.
Same.
read my post!
Yeah, that smoke demo showing the top air getting back FASTER was a revelation!
The explanation needs a bit of adjustment. While equal transit time is wrong, Bernoulli is not wrong just because equal transit time is wrong.
Bernoulli requires that transit time is fast, fast enough for momentum of the lateral flow to be conserved. Experimentally this is seen as faster than equal transit time, because the mass density is less and it is mass times velocity that is a constant according the fundamental law of conservation of momentum.
@@rsteeb It does show that Bernoulli is indeed an essential concept.
Several years ago I was looking through a graduate level aeronautics textbook where the author was discussing lift via Bernoulli & upper/lower path length. He concluded that a Cessna 182 would have to accelerate to over 400MPH to lift its own weight if this were the mechanism that enabled a wing to generate lift. It is amazing that this myth is still being taught by the FAA and was a multiple choice answer on the airman 3rd class written test.
When taking those silly FAA written exams, I studied normally to learn the stuff, sure, but then a couple days before the test just start going through the list of all the FAA questions that they publish (do they still?) that has every question and every answer and memorizing--and there was always at least one question where the book warns "the FAA wants you to answer B even though that's wrong". Sure makes it go quicker when you recognize the question and don't have to read it and can just pick B or D or whatever without any work. I finished the instrument 3 hour test in about 25 minutes. Proctor asked "are you giving up?" "No, I'm done". 98/100. Dunno what I missed and that still haunts me.
A simple experiment I was shown in the 1960s, long before I gained my humble private pilots license, involved 2 pieces of paper. Take a sheet of, let’s say, copy paper and hold it horizontally, like a mouth organ, but just under your bottom lip. If you blow across that paper, even quite gently, the sagging sheet will lift to be horizontal in both directions, left to right and front to back. A more dramatic experiment is to hold 2 sheets of paper vertically, close together and up against your lips. When you blow between them, fairly hard, you will be rewarded with the noisy report of the 2 sheets flapping wildly against each other. These are but 2 examples of Daniel Bernoulli’s principle at work. Oh. another example, I experience it every morning, is the way a shower curtain is drawn inwards by the water rushing past it, same principle. Smart man that Dutch born Swiss mathematician/physicist! The other factor keeping aircraft airborne is that the wings push the air down, via the angle of attack, not unlike a water skier’s skis. This is well illustrated by the slight drop in altitude noticed when an aircraft moves out of ground effect immediately after it leaves the end of the flight deck of an aircraft carrier. This is more pronounced with lower powered planes.
My father was a pilot and owned a cessna 150. You definitely learn about ground effect when landing! It's said that it has an effect within 1/2 of the wingspan from the ground. One trick for short field over obstacle grass runway takeoffs he would use was to wind up the engine, release the brakes, lift off the ground early long before normal rotation speed was reached, by using ground effect, then level our a foot or two above the runway, thus using ground effect, to remove the rolling resistance of the wheels to "run like hell" gaining momentum until he could "pop" it up just over the trees then level off again to gain speed back to establish normal climb rate. Bush pilot's trick. Flying is about energy management. I know of a "gotta go!" fatal plane crash of a plane from a short slush covered runway that failed to clear an obstacle because this wasn't followed. The slush slowed the acceleration and they knew this would be a factor. It's usually against policy but as soon as you are commited to the takeoff in this situation, and the plane will fly in ground effect lift up a couple feet, retract the gear to reduce drag and "run like hell!" Gradually gaining a few more feet to prevent a tail strike if needed get all the speed you can, and trade energy for required altitude, then unload the airplane to gain back climbing speed. Instead, they lied to the airplane, stayed on the runway, trying to get to normal rotation speed, failed, and then just kept hauling back on the stick, willing it to fly, gained a mabey 50 ft and stalled. "You can lie to your friends and family, but if you lie to your airplane, it will kill you!"
If Bernuoulli effect is dominant in producing lift, then upside down flight would be impossible.
no, Bernoulli always plays part when air velocities are different on both sides of the airfoil, you always can calculate lift knowing the distribution of velocities, upside down has nothing to do with it
As always captain, you correct misled people. Being always looking for the truth and do research is key to good pilots. Thank you for your wisdom 🙏
*misled
I recently saw him talk about landing the space shuttle. He claimed that NASA discovered that putting linear grooves in the runway would straighten out the shuttle when it landed. The Dept. of Transportation had been putting grooves in the highways and freeways before NASA even existed. They do this to help the road shed water when it rains to avoid hydroplaning. I've driven on these surfaces for almost 50 years and I can tell you that a grooved surface does NOTHING to keep a vehicle going straight.
A grooved road surface and ribbed tires make for a squirrelly motorcycle ride!😬
I suppose then he thinks they are "self driving roads" just set your cruise control, let go of the wheel and begin watching Tyson DeGrasse vids for a few miles, no worries mate! Grooves would help tires skidding sideways in a crosswind to some degree essentially "steering" it. The shuttle landed at a high angle of attack and spent a long time with the main gear on the runway holding the nose up, letting it settle slowly. The load on the mains is very low for a while because of ground effect and the high angle of attack. every time the pilot inputs a rudder command to keep the shuttle straight in a crosswind, it causes a sideways force on the main gear trying to rotate the nose in the opposite direction. This is because they can't bank it to counter it while the wheels are on the ground. Applying the rudder without banking when flying is called "skidding" you do this to point your nose more into a crosswind to fly a straight course, using a portion of your thrust to counter the crosswind. This creates drag. In a small, slow, plane and a large crosswind, I have actually flown a course forwards by looking out the side window! That's fun when using a compass to navigate since you have to make a correction because the plane rotated under the dial. You are doing the same thing in a plane in a crosswind landing, you are "drifting" the aircraft. You can also use the engine to pull you back over the runway. The shuttle is a glider, this means they can't go around, and can't power it back over the runway if things get out of hand. It's actually an amazing piece of flying to make an "engine out" landing every time! The sooner you stop the skid the better because when the mains finally "bite" at a high angle to your line of travel they throw you to the side, and you can begin fishtailing.
To accomplish this the grooves run DOWN the runway or road. They do help with skidding. Concrete is very smooth, therefore hydroplaning is more of an issue because water has a harder time getting out from under your tires. Groves help with this especially cross grooves.
As a sailing instructor I sometimes had studends who knew all about Benoulli's theorem. When I pointed out that a sailboat's sail has no thickness, I was met with disbelief. "How dare you question Benoulli!"
Newton's law of motion explain airfoil lift nicely. Those infatuated with Benoulli have to resort to Newton when challenged on the inconsistencies.
You are100% correct to question the use of Bernoulli's theorem in sailing. But whose explanation do you use? Marchaj? Gentry? Fossati?, North Sails? ...?
Coandă effect
There are many principles at play with an airfoil.
Newtonian physics is the ultimate explanation, because lift or any aerodynamic force is due to an equal and opposite reaction to an air mass being accelerated. Air mass is accelerated (deflected) Either by a moving surface at an inclined angle of attack, or by another deflected surface attached to a primary surface which is moving at zero angle to the relative wind.
The how and the why of this air bending is explained by Bernoulli, Coandă, et. al.
@@RationalDiscourse As I said, an angle of attack deflects the airstream in one direction which results in the equal and opposite force in the other direction. Newton.
@@jj4791 Without an angle of attack there can be no lift. Your "zero angel to the relative wind" idea is not correct. If the airfoil is producing lift, it has an angle of attack. The fact that the bottom edge of an airfoil is parallel to the wind direction does not mean that the airfoil has a zero angle of attack. Tha angle is defined by the cord of the angle of the two sufaces of the airfoil have at its trailing edge which results in a downward deflection of the airstream.
Thank you for this video. I am appalled at the number of amateurs who are putting out misinformation about aerodynamics on CZcams! I never realized how mystifying the topic is to non-aviators. Videos like yours help set the record straight. I fear it is only fellow aviators who watch them, though. 👍🛫✈🛩
The FAA gets this stuff wrong, and requires all pilots also be wrong to pass the test.
A perfectly flat panel, with no curvature, generates lift. Small wooden children's toy airplanes use flat sheets for wings, and they fly just fine. Properly curved airfoils can increase lift efficiency. Cantilevered wing tips can help with reducing vortices, thereby reducing stall speed. There are optimal designs for these also. Long thin wings are more efficient than short fat wings at generating lift, but long thin wings are more susceptible to turbulence. Each blade in a jet engine is a type of wing.
Tyson is a science _popularizer,_ just like Carl Sagan was. Nothing more.
Carl backed his talk with something more than Neil does.
Except too much of what he spouts is NOT science, so in reality, he's a pseudoscience populariser.
He's never appealed to me, maybe it was his self-assured smuggness which is not a great characteristic of a scientist.
Thank you for your clarification on this issue. Good Job.
as a kid in elementary school, one day an airline pilot came to the school to teach the class about how planes work. She used the equal transit time explanation to show how lift works, and unfortunately by the time I had learned that that wasn't entirely accurate, I had already been sharing that incorrect information for years.
It's actually a little bizarre that NDT got this so wrong. I mean if he thought for a moment and recalled - for example - that many airplanes regularly fly inverted (and that most airfoils don't look like his example and many are close to symmetrical about the chord line) he'd have to realize that his explanation was flawed. And don't even get me started by the "up the flaps on the tail wing" part. Sigh. Thanks for the video Magnar!
I watch occasionally videos from NDT. Sometimes I don't have enough knowledge of the topic to call him false but this time about airplanes and airport configurations he hit right at one of my best topic. He was pathetic the less I can say.
- NDT "Airplane must always take off facing the wind" FALSE
- NDT "pilote raise the tail flaps to raise the nose up" WRONG it's aileron. There's no flaps there and flaps on wings have a complete opposite purpose
- NDT "Airports always have two runways and are never in a 90° cross over to give more possibilities of taking off up wind" FALSE and FALSE
- NDT "When the plane accelerate it comes a momentum where the plane pop up suddenly to the sky. It's not something happening smoothly and progressively" FALSE bullshit
and of course the Bernoulli explanation...
Like someone else wrote here, if NDT can be so wrong about a topic I perfectly know, how much bullshit he can say on topics I don't know enough to call bullshit?
Finally! someone else who knows about the Babinski principle.
Another great video Captain. Well done
Great video explaining most important aspects
There is one other thing Coranda effect . The tendency of a fluid to stay attached to a convex surface
Coanda Effect (as beloved of the Dyson company).
Thank you for this wonderful explanation
As an engineer and a pilot, I went so so so so many times into this discussion with "the public in general" and with other pilots...
Honestly I was allowing myself to be desappointed already before watching your video, as a way to avoid an even bigger deception.
It ended up working in reverse: how happy I am to finally see a pilot going through the real scientific relevant aspects of lift in a correct way...
Thank you so much for this fresh air of clarity! It would be really nice if science communicators would do a little home work before addressing such huge audience as they have.....
What is the role of Navier-Stokes in describing bodies moving through fluids which air is ultimately?
those wrong explanations are the official academic science. most scientists and engineers do not know better
The character Sheldon Cooper on the Big Bang Theory is smarter than Neil.
All the characters on Big Bang Theory are smarter than Neil. So are most of the actors.
Neil will always be a space cadet. Best description of lift I have seen yet. Never thought of it as a hybrid principle between Bernoulli and Newton.
So glad to have found your channel.
And this is why he needs to stay in his lane. My home airport of Plant City Municipal Airport(KPCM) only has one strip and 2 runways. There are airports that can have 2 strips and only 3 runway, not 4 like you would think, because one end is not used for takeoff or landing due to obstacles(but usually due to rich people). Also, where I used to work at Igor Sikorsky Memorial Airport(KBDR) has 2 strips and 4 runways(used to have 3 strips and 6 runways), and the two remaining strips are RWY 6-24 and RWY 11-29.
KCPM is 10-28 right?
Brilliant video !
Bravo, for your excellent work another time.
FYI Magnar, I was subscribed and clicked 'like' before the spider :-)
I look forward to your videos, thank you for the effort.
It is interesting that two of the world's leading astrophysicists, Tyson and Kraus, rockstars of their field, think they can bang on about everything. I especially dislike their hubris, the emphatic way they pronounce their opinions. A real scientist is careful and uncertain - because science is a set of hypotheses which are only correct until we find something better. In consequence, I have no time for such people - because if they are wrong about a subject I do understand, they might well be wrong about everything.
It is a stretch to call Tyson an astrophysicist, much less one of the world's leading astrophysicists.
His C.V. is easy to find online. Five 1st author papers, all from the 80s and 90s. In 2008 his name appears very late in long lists of authors for the COSMOS review papers.
Were those five 1st author papers during his college years outstanding? No. Harvard turned him down for post grad. At University of Texas they dissolved his doctoral committee, essentially flunking him. His advisors correctly told him he had no aptitude for astrophysics.
Most of Tyson's career has been flashy and often inaccurate pop science.
Nobody is omniscient but that doesn’t make them wrong about everything. Tyson gets people interested in science and we need a hell of a lot more people like him because way too many people treat science like another religion these days. You take what knowledge you can from people but verify what you’re being told and don’t just blindly trust the cult of personality. On the flip side, whenever a smart guy gets something wrong, there’ll be a long line of people gleefully piling on to stroke their own ego.
@@Danimalpm1 Does Tyson inspire a deep interest? If so why is it his fans usually don't notice his errors?
His bad math and science is merely annoying. I do not care if he tells his pseudo nerd fans that there are more transcendental numbers than irrationals. Or that the James Webb Space Telescope is parked at the sun-earth-l2 point in earth's shadow.
What makes me angry is when he uses his wrong history to underscore his talking points regarding politics and history. Using falsehoods to push a narrative is a serious offense,
@@HopDavid Snake in DeGrasse Tyson is an establishment guy. Science is what the government _tells_ him it is: he re-packages their politics, dressing them up as science and then spews propaganda on behalf of Big Pharma and the ICC.
@@Danimalpm1yep, and they're making themselves known with their vitriol and hysteria.
NDT needs to turn off his ego and watch this vid.
It has no OFF switch.
I took aviation mechanics in the late 80s and what Mr Tyson stated was exactly what was taught. The instructor even used dots to show the path taken by the air flow and the dots aways met up. Its been decades but I can remember plotting airfoils using stick pins and string.
My instructor was a licensed pilot with the following ratings; instrumentation, multi-engine, instructor and was a licensed A/P mechanic. He never stated how many, but he spoke about the times he assisted in a crash investigation and a local kit plane producer in addressing undesired flight characteristics.
Neither pilots nor mechanics need to understand the physics of flight. They are practical disciplines. As a physicist, NdGT ought to be able to look deeper into the matter, but that doesn't seem to be his objective. He has become an entertainer, not an educator.
8:51 it’s meant to be drag, but in the wind tunnel experiment earlier the angle of attack of the wing was not flat. i always think it seems like a lot of it is the change of angle of the air rather than pressure change
Neil DeGrasse Tyson gets many things wrong outside of his own field of expertise. A typical example of the Dunning-Kruger effect.
He even gets many things wrong when it comes to basic physics and astronomy.
Unless you call his area of expertise hype and self promotion.
You should have stopped after "wrong".
It gets things wrong about biology too.
@@av_oid Biology, medicine, history. Even basic physics and astronomy.
Neil's field of expertise would be hype and self promotion.
Can you show me where he got basic physics wrong @@HopDavid
Neil dG ... a lot of warm air. And he keeps talking and talking...
Instead of just saying : I don't know a damn thing about flying. Hillarious.
Thank you, Magnar! ✈
Using the definition of NASA: "Lift is a *mechanical* force. It is generated by the interaction and contact of a solid body with a fluid (liquid or gas)" then, in a *strictly mechanical sense* only the lower part of the wing is able to generate lift in steady horizontal flight.
By definition, no force is able to get a "grip" on the upper part of the wing (the outside surface which is in contact with surrounding air) and *pull* the upper part of the wing upwards. There is no pulling force on the upper part of the wing. However, because of the angle of attack and the fact that the wing is not moving through a vaccum but through pressurized air, the upper part of the wing is able to decrease the ambient static air pressure exercised by Earth's atmosphere, therefore less air molecules are hitting against the upper side of the wing pushing it downwards, but this is not lift as lift would be directed upward, not downward. So at all times, air is only pushing against the upper part of the wing pushing the wing down and that's why those diagrams here: 8:56 are wrong as they depict force vectors pulling the upper side of the wing upwards.
There is no mechanical force pulling the upper part of the wing upwards. However, there is a force resulting from static air pressure pushing at all times against the upper AND lower part of the wing. So the lower part of the wing is able to push the wing upwards as the upper side of the wing it is no longer pushed down as much because of aerodynamic effects (angle of attack, wing shape, air speed and so on). The wing moves upwards because of the aerodynamically created influence on the effect the surrounding static air pressure has on the wing (greater on the lower part) + the aerodynamically generated force of lift on the lower part. On the upper part, there cannot be any aerodynamically generated force of lift, only an *aerodynamically generated local reduction of the effect of static air pressure pushing downwards against the wing* (because of Bernoulli) therefore diminishing the downward push of the static pressure on the upper part of the wing. Therefore not every surface on the wing produces lift, but every bit of the surface influences how air moves around the wing and how the airflow is bend.
Also, in case you don't understand this argument: if you buy a vaccum suction cup holder, once installed on a window pane, it actually does not suck on the window to stay put. The part facing the window pane can be compared to the upper wing, the part facing you can be compared to the lower wing.
So the "vaccum suction cup holder" remains put because static air pushes it against the window pane (that would be lift) the only difference is, in order to create it, there is no need for airflow because the surface facing the window is hermetically sealed of and the lower static pressure is permanently maintained so there is no need for dynamic airflow over a curved surface at an angle of attack in order to create a local reduction of static air pressure hitting the wing.
Now, it would be foolish to say the inner part of that suction cup holder created "more lift than the outer part" - as no force is pulling the inner surface against the window pane, only the outside static air pressure is pushing the suction cup against it.
We had a Designated Pilot Examiner that would get very upset with applicants that would claim the air particles would meet back up. I get it. But it's also what most people are taught because visually, it's easy for most people to picture. I feel like there's some "gotcha" and micromanaging going on with this subject. Like ok...cool. Just correct people. It's not a huge deal. Some people in here are probably not very fun at parties.
Runway directions are chosen by monitoring wind conditions for a period before aerodrome construction which @gcpgrey did a video on. They aren't at 90 due to laziness . Nzch has it because wind commonly goes north south (02/20) but occasionally off the mountains (27/11).but klas doesn't have 90 diff. This is because analysis shows common wind directions.
Right. Ideally, the runways will be situated so that most of the time, one will be aligned with the wind. If the wind is mostly from a narrow range of the compass, they might build runways that cross at a narrow angle. Although a lot of airports have to contend with geographic constraints and can't have ideal runways. The busiest airports have parallel runways with no crossings because that's the best way to serve many planes in quick succession. Modern transport category aircraft can handle huge crosswind components, so they don't always have to perfectly align with the wind.
@@bbgun061 and unfortunately it sounded like mr nordal was saying they're always 90 which I don't think is right either. Although what's kden about :p
@@mickster04 Denver (KDEN) is what you get with almost unlimited land to build on lol...
I caught that video by NDGTyson. I am a physicist and a pilot, and I was shocked also about how badly he botched that explanation. Not sure if he just didn't do his homework, or was trying too hard to dumb it down for his audience. But it was surprising to see. I have been trying to figure out where that air moving faster over the top explanation came about in the first place. I can only surmise that a simplified explanation somewhere in the past got lost in translation. If one is going to try to simplify using that line of "explanation " it would be more intuitive to say that the angle of attack slows down the air on the bottom, so that the air on the top is moving faster relative to the average air on the bottom. That way there is no magical speed up of air on the top.
I was not shocked, 20 years ago
The problem with any "air moving faster over the top explanation" is wrong is because the air doesn't move faster over the top than the undisturbed air. It may move faster than the air below, but that's because, as you can see in Babinsky's video, the air below the wing decelerates. There is not a scrap of evidence that the air above the wing accelerates - and acceleration is what is required for Bernoulli to apply. Sure the air above the wing is at a lower pressure than the undisturbed air, but that is not caused by the air accelerating over the wing. It's something quite different, which not many people have realised yet.
@@RationalDiscourse...ya.. didn't I just say that? The explanation has always been Newton's laws and momentum transfer.
Not surprising, Tyson is a fraud
@@IanDSouza Nope, you didn't. You did agree that the air over the top is not going faster than the undisturbed air, but you have not made any connection between "the air on the top is moving faster relative to the average air on the bottom" and "Newton's laws and momentum transfer" as if that explained it all. The mechanics of momentum change do not generate anywhere nearly enough force to overcome the gravitational force of the mass of the airplane. Show me the maths.
The angled deck carrier only has CAT in the forward deck for launching planes, angled aft deck only has trap for retrieving planes. It's an operation consideration.
uh.. you might want to research that
‘71, ‘72, I worked on the flight deck of the USS Ranger Cv61. You are most assuredly wrong sir!
This is completely wrong. The forward part of the angled deck has launch capability also.
Such a great video, even pilots often get this wrong, since I guess it's just easier to teach an oversimplified explanation to someone who won't ever actually have to design a wing, but great to see a pilot who really gets it!!!
Wel, holding your hand out of your car window is still a good analogy for a wing. A poorly designed wing but a wing none the less. You do not need an airfoil shape to achieve flight. A cinder block will fly and be controlled with enough thrust. The airfoil shape is more efficient at creating this effect of being sucked up like a noodle by the lower pressure air as this air is sucked down into the upper shape or surface of the airfoil. It's bernulis principle. It's a half Venturi shape layed on a flat surface instead of bent into a circle. A ram air engine of sorts. Sucks its way up and pushes that air downward. It's some wormhole stuff.
A cube can fly, just vector the thrust to apply all of the lift. Nobody cares about flying, everybody cares about flying with thrust that is much smaller than your weight.
I had not listened ot Tyson's explanation previously, but it sounds like a simplified Physics class that ignores the complications of the real world. It reminded me of the joke told to me by one of my Physics professors in college to stress that point: "Physics is the study of frictionless elephants whose mass can be neglected". The forces on the air do indeed act to "keep it at one parcel", but real-world forces like friction and the energy imparted as the wing moves through it prevent this from happening. Terms get complicated depending on the frame of reference that is being used (ie. whether the wing acts on the air, is with an aircraft, or the air acts on the wing, as in a wind tunnel).
At least Tyson discussed angle of attack and its effect on lift. Some drawings used to explain lift show the airfoil at an angle of attack that produces either no lift or sometimes even a net downward "lift".
I've seen many experienced pilots and others describe the equal transit time theory. Starting in jr high school when I did a science project on Bernouli's principle. The upper wing actually forms a venturi between the wing upper surface and the air above. But not all wings are flat on the bottom and curved on top. Some are nearly symmetrical. Such as the laminar flow airfoil on the P-51.
Beautiful explanation. So the form of the wing throws tne air generating a sort of centrifugal force and accelerating the air above the wing. At higher speed lower pressure.
Again the dilemma, its not the air thats moving around the wing, because it is usualy static. Its the wing moving through the air. The low pressure over the wing is created because the underside is pushing a small portion of the air FWD and downward. The air over the wing is trying to rush in to equilize the low pressure. Thats what makes the lower pressure. And it works the same on all subsonic wing types.
The math is the same whether the wing is moving, or the air is moving. It's all relative.
Motion is relative. There is no difference between the air moving around the wing or the wing moving through the air. If there was a difference, wind tunnels would be useless.
@@bbgun061 If the air is moving the energy is in the moving air. If the wing is moving the energy is in the wing. The result will not be exactly the same but close.
@@jonnyueland7790 From the wing's perspective, the air is moving. From the air's perspective, the wing is moving. From an observer on the ground, both are moving. (There is always wind aloft.) The math says the result is the same, no matter what way you look at it.
Yes, absolutely! Looking at the wing moving through undisturbed air is the way to go. The wing pushing the air forward and down is generating the high pressure below the wing. The wing pulling the air from above and behind (into the "void" generated by the wing) is generating the low pressure above the wing.
Tyson is perhaps the most annoying explainer on CZcams and I am not alone in my observation
You do NOT talk about daddy Tyson like that. What is wrooOONG WITH YOUUU???
Excellent, clear explanation. Thanks!
Excellent video. Although, as to the effect of air hitting the bottom of the wing after rotation, I will have to dig deeper (and re-watch your video). I still believe in my gut that some upward force is generated from tha direct impact with the bottom of the angled wing…yes, much is a vector opposite the plane’s direction…but some surely must be a vector 90 degrees to the chord? And some part of that vector is 90 degrees to the ground? Would an angled barn door experience any upward force?
Arrogance and ignorance are never far apart.
I know it's going to be a good day when I start with The Grass getting disproven.
I just love this stuff. As a kid, i watched the smoke lines move around the upper and lower surfaces of the airfoil and understood how lift is generated, i just couldn’t understand the math. LOL.
Looking at Tyson's quote and based on things I have heard him say, his days must be filled with new learning experiences.
Honestly, as a huge fan of Carl Sagan, Neil deGrasse Tyson is regular disappointment.
He states the air just "wants to" reach the same air particle on the other side - but doesn't question by which mechanic this air particle can do this. Thank you Magnar for being a great teacher.
Captain you are very experienced and you are right. This guy has always been misleading people in physics and he has absolutely no idea about aerodynamic.
His explanation of the rocket equation was horrible. He tells Chuck Nice that rocket propellant goes exponentially with payload mass. When it is delta V that drives the exponent in the rocket equation. Larger rockets with larger payloads are actually a more efficient use of propellant.
Yet the vast majority of his CZcams commenters will be praising him for his wonderful explanation that brings complicated subjects down to earth so the common person can understand them.
There are many examples of this. It drives me up the wall.
NdeGT is one of those people who think they're so smart they never need to check with actual experts to see if they're right. Thanks for setting him straight, Magnar.
Aïe !!! at 9:05, green AND blue are low pressure.
Above AND below wings, there is LOW pressure. The deficit of pressure above is more important than the deficit below, so the summation gives lift.
On the diagram at 9:05, green AND blue are low pressure (don't look at the arrows). The size of green (above) is bigger than the size of blue, so there is lift.
Tyson keeps disappointing me.
I stopped listening to Neil when he said when you wake up in the morning you can decide which gender to be. I hope I can reverse the years of damage to my brain from listening to him for a decade. He gives science a bad name.
Praise Jesus
Agree with most of the other posters however the statement about all airports having two runways is correct. For instance at our home grass strip has a single strip of land runway 9 and runway 27 which you would announce to other aircraft so they know which way you are taking off or landing.
I was all ready to complain about this video, but no - this is all correct. So many people get aerodynamics and lift wrong because it's complicated. Great video! Earned a sub from me.
The point of this video and some other ones I’ve watched is to basically bash and discredit Neil. They don’t take in account that the guy is just trying to provide basic understanding of a complex subject without having to resort to graphs, or videos or formulas that most people do not know about. It’s a podcast! Is not a class! Also you said that Neil said “air particle”, which he didn’t. He said “a parcel of air”, which is quite different. I know that a lot of people don’t like Neil just because he is black, but the guy is a brilliant disseminator of knowledge. He may not be 100% precise because no one is perfect, but trying to criticize him with some kind of mockery is just pathetic.
It has nothing to do with race. Really, you went there. No, it’s because he pontificates on subjects holding himself out as an expert on every subject.
1. We're not racist for having opinions about what he said.
2. He did not mock him. You can critique without mocking.
2. You can explain this in the more correct fashion without getting too complicated. What's complicated is dispelling the myths that are often shared...
3. There's a big difference between being wrong about some small things versus painting the entire topic in an incorrect way. He may not be teaching a class, but he still expresses himself as an educator. He should educate.
I love Neil's enthusiasm, even when he misses the mark a bit.
Airports also consider prevailing wind directions. So runways at a 30° angle may be the best if the winds almost never are at 90° from the first runway.
The Kutta-Jukovski circulation equation demonstrates that, when the upper stream and the lower stream depart the leading edge simultaneously and arrive at the trailing edge simultaneously, the nett lift is zero.
DeGrasse is a clown.
Tyson is a DEI poster boy
Lets simplify the previous post---if all lift was from Bernouli effect, a flat plate will not fly, but most 10 year olds have learnt that it does, and sometimes quite well!
Actually the streamlines over a flat plate form an aerofoil (one of the reasons flat plates are lousy from a drag perspective). Delta wings form vortexes over the wing too further increasing the velocity over the top surface of the wing and increasing lift further. Thats how bumblebee’s fly - vortex lift.
Aerodynamics is “complicated”.
When my high school science teacher said "the air on the top of the wing needs to move faster to meet back up with the air under the wing," I remember asking why it needed to meet back up at all (e.g., what if the airfoil never ended and there was no trailing end?). Her answer, which wasn't an answer alt all, was that 'because physics demanded it'.
Quantum entanglement I guess?!?!
How much did tyson pay for his degree, ive quetioned a lot of his stuff and reserached that he has been wrong on many,many subjects. One or two mistakes can be forgiven but not on many.
Neil's doctoral committee at University of Texas had the guts and integrity to flunk him and show him the door. And to this day they are being called ignorant and racist.
Makes me wonder about QUOTAS
Thanks for the debrief!
The reason they’re less than 90 sometimes is because of the land configuration, there could be housing, a golf course, a freeway, or a river that prevents them from going 90. Also they can sometimes get a LONGER runway that they need by going diagonal instead of cross-cross. There are two angles on an aircraft carrier for one and only one reason. Sim planes can land on one and take off from the other, simultaneously and without interfering with each other. Tyson Dunning Krueger says what?
Tyson is a total joke.
Thank you. Common misconception, unfortunately.
If winds were random, a 90 degree separation with crossing runways would be optimal. I think airport planning considers local prevailing winds. IAH in Houston for example has runways at about 330 & 270 degrees. SLC in Salt Lake City has only about 350 & 360 degrees. It's a trade-off of local conditions, land use, and other things affecting flight patterns. Aircraft can operate with crosswinds but it's not optimal & can increase risk.
As a paraglider (ridge soaring) we use the air flow over hills to gain lift. It's quite odd, because it's been described to me as being the same thing that happens in the first 1/3 of a wing chord. However the "upward" deflection of the airflow over the mountain creates a much high band of lift just in front of the summit. The upwards vector of the air there can extend hundreds of feet above the hill, even without any thermic effects.
The danger is what happens on the "back side" of the hill. Being there in a paraglider would be no less dangerous than going through a river rapids in a childs blow up dingy. You can't see air. However you can visualise it as water. The front side of the hill has an accelerating laminar flow. The back side is tumbling crashing waves of down draughts and the resulting rotors. When I asked my instructor, "So how bad is it if you got blown over the back?". His answer was short. "Back breaking."
Flat top mountains are a lot more fun. As long as you don't go too far back, you can land in the laminar zone, so it's really smooth.
Before watching the video. Lift has to do with air mass and the speed of travel. You create a vacuum area on a wing which makes it move into the void. Which isn't a void but less atmospheric pressure
??