OUCH! This hurts. Neil Is clearly out of his element and has repeated nothing but common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. This video is EXTREMELY disappointing. This is NOT correct.
Great video as always! I’m an aerospace engineering student who just finished Applied Aerodynamics and there is an interesting note bout how wings generate lift. The part where air moves faster on the top surface than on the bottom surface is 100% true, but the part about an air molecule needed to regroup with the other molecules it was near before encountering the wing is actually a myth. There is no requirement for “air molecule neighbors” to remain neighbors after encountering the wing. The only requirement is that air moves faster on the top. A subtle distinction, but still interesting!
There is no requirement for the air to move faster on the top of the wing than the bottom. Bernoulli doesn't make airplanes fly, NEWTON does. The angle of attack accelerates air downward, and the reaction to THAT is LIFT.
@@rsteeb you’re right that accelerating air downward creates lift, but both descriptions are actually describing the same phenomena! That’s why positively-cambered wings at zero angle-of-attack can still create lift.
you are 100% CORRECT! Duncan. There is absolutely NO LAW in physics that stipulates that air needs to "reform" into its original pockets of air. None! Simply put the design promotes lower pressure on top, and higher pressure beneath the wing.
Entertaining as always. A couple of bits of trivia that came to mind as I was listening: 1. Airport runways are designed to align with the most common wind direction in that part of the country. In the middle of the US, they are aligned more north and south. In other parts of the country they are aligned more east and west. 2. Like a lot of early aviators, Lindbergh may gotten his information about wind direction by looking to see which direction the cowherds were pointed
@@StarTalk Thanks. I've watched Star Talk from the beginning and have always found it educational and entertaining - generally covering topics in which I have little knowledge or expertise. So I was delighted to see you discuss something involving my chosen profession of aviation. I thought the impromptu reference to 88 mph takeoff speed was hilarious, especially since it is close to the takeoff speed of a lot of aircraft.
Bernoulli is incidental but not critical in getting an airplane to fly. Some wings (particularly those of acrobatic airplanes) have symmetrical sections - the curve is the same below as it is above, and this is to allow them to fly just as well inverted as they do right side up. Airplanes fly because of the combination between the reaction force generated by the wing and the coanda effect generated by the trailing edge. You can experience the coanda effect by approaching the back of a spoon to a flowing faucet.
Too bad Neil has repeated common misconceptions and made some new ones. He needs to have a *serious* talk with a fluid dynamics expert. Neil is completely out of his element here. This video is EXTREMELY disappointing. Neil is wrong.
According to NASA, the faster air above the wing contributes to a mere 2% of the lift generated. Bernoulli has nothing to do with it because the Bernoulli principle only applies to a closed system. The Coanda effect does add lift forces but the vast majority of majority of lift is from the angle of attack of the wings: air strikes the underside of the wing deflecting it upward. Pilots know to fly angle of attack. Neil de Grasse is not a pilot and does not appear to have studied aerodynamic mechanics
@@judesalles This confuses me. If the air flow above the wing is 2% of the lift, then when the wing "stalls" at high angle of attack it should lose no more than 2% of its lift, as the air flow striking the underside of the wing is still "deflecting" it upward. "Stalling" effects the flow over the wing very much and has almost no effect on the flow under the wing. Why does stalling result in a sudden loss of lots of lift, much more than 2%, when the air is still "striking" the bottom of the wing? Are you sure about this 2% number?
@@judesalles Wrong and NASA doesn't say that. The majority of the pressure difference (which is how lift force manifests) is on the top of the wing (on most airplanes) due to the airfoil design. Most of the deflected air (downwash) is also due to the air flowing over the top surface of the wing.
As a flight instructor I find it fascinating how Tyson explains Lift, and his obvious passion for science. Aerodynamics is a subset of physics, fluid motion to be exact, and vital for us aviators. Edit: as an additional piece of info, most Runways are designed with headings that represent the most frequent average wind directions over the course of a year, for any given location. So the aeroplane has a greater chance of being able to take off into the wind, every time.
Neil is WRONG and completely out of his element! This is probably the worst I've seen ESPECIALLY since Neil is so popular and good at most things he does. NOT THIS ONE!. . Neil has repeated common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. This video is EXTREMELY disappointing.
Please don't refer your students to this video. While many of his points are accurate, he completely misspoke regarding lift at rotation and lift during inverted flight.
Instead, direct them to the book "The Illustrated Guide to Aerodynamics" by Prof. Hubert (HC) Smith. This book is an excellent treatment of conceptual aerodynamics. You can buy the 1st edition used for a low price. It's the very first aerodynamics book I read after I started flying a few decades ago...
@@Observ45er I was also surprised when Neil repeated the Equal Transit Theory to explain lift. I just completed Ground School, where we learned about this common misconception.
I love how you can interpret even a complicated theory to a middle school understanding. You're a helluva teacher! Thanks for offering these classes in this format.
15:10 In WWII all aircraft carriers had a straight deck. The problem with this wasn't relative wind (as you noted, if the wind changes, the carrier would just change heading to put the relative wind down the flight deck), it was that you couldn't have landing operations and takeoff operations going on simultaneously. A landing plane that missed the arrestor wire would plow into aircraft lining up to take off. It was this restriction that contributed to the demise of the Japanese carriers at the battle of Midway because it delayed launching a second strike while recovering the first strike. If the deck used for landing was angled, however, a plane that missed the wire would continue off to the side of the carrier and planes could safely be launched off the bow at the same time. It wasn't until December 1952 that the U.S. started experimenting with an angled deck for landing on the U.S.S. Antietam (CVA-36).
A great video demonstrating the advantage of simultaneous launches and landings can be found on the Growler Jams TH-cam channel: th-cam.com/video/itxCibqCUZw/w-d-xo.html The channel is run by a U.S. Naval Aviator - call sign "PAIL" - and this particular video happens while the carrier is conducting simultaneous launches and landings.
I learned about this when I was eight years old because my dad had been a pilot in WWII and then became an aeronautical engineer. At a point he was designing airplane wings. Sixty + years later I still recall seeing drawings of wings. When Bill O’Reilley did his famous “The tide goes in, the tide goes out, you can’t explain that,” and also mentioned how planes were heavier than air and yet can fly, you can’t explain that, I thought, “I’ve been able to explain that since I was eight years old!”
Do you now understand that Neil's explanation is completely wrong? BOTH about Lift and Bernoulli's Principle? . . And that there are people who DO understand and can explain the fundamental physics?
Getting your brain wrapped around the concept of aerodynamics that allow planes to fly is as difficult as understanding how a battleship with a hull 16 to 20 inches thick can float. It goes against logic.
@@HughButler-lb6zs If you understand Newton's laws and inertia, it's child's play, but so many don't understand those two things and simply repeat words they don't understand continuing the long chain of misconceptions - - as we have in this video.
Me who has studied Aerospace Engineering at undergrad level clicking on this video: Neil deGrasse will probably explain this in a way I have never learnt before
@@heatherwoodley8244 RE H is right. What NDT is positing is commonly known as the "equal transit time" theory. This suggests that two particles that are separated at the leading edge will meet at the trailing edge. And there are two problems with that. The first is that there's no theory by which that should hold true. And the second is that experiments show that it absolutely is not true. It is true that the air flowing over the top of the wing moves faster - but not so that it can meet its partner at the trailing edge. In fact, it can beat its partner to the trailing edge by a healthy margin.
@Rick Cavallaro Interesting. I thought that he was positing the ridiculous ETT theory, but then I told myself that he couldn't possibly be doing so. Strange..
I had an 8 foot piece of paneling about 2 feet wide. As I held it in front of me at arm's length, I spun myself around in circles. I was able to see and feel it rise and fall as I changed the angle of attack. It gave me a lot of insight into lift and drag and flight itself.
That's the true explanation. With your flat board, when it's tilted, the parcels above are flowing MUCH faster than the parcels below. It's also how the Wright brothers flew, by using a sheet of thin canvas, where the upper and lower path-lengths are identical. Dr. Tyson above got it wrong, because the upper flow is far too fast, so the split parcels never rejoin again ...and wing-shape is known to be irrelevant to creating lift. (Wing shape is extremely important in avoiding stall!) If it weren't for the problem of stall, airplane wings would all be flat plates, eh? (Heh, then the fuel tanks would have to be placed next to your luggage.)
@wbeaty I did that experiment years ago. I've been thinking ever since to repeat it but adding different weights to the end of flat plate to get a sense of how much lift is actually generated.
Did something similar as a kid ..l used to hold my hand out of dad's car window with a flat palm ..and tip my hand this way and that to achieve the same effect
@@wbeaty Are the upper and lower path lengths really identical? A '"bubble" of air, or "vortex", stuck in the concave underside of the wing could allow flow to go straight from the leading edge to the trailing edge, making it's path shorter than the upper flow. If wing foil shape is irrelevant to lift creation, then why is "stalling" relevant if it only effects the flow on the upper surface of the wing?
@@jackwickman2403In modern fluids, Circulation and "Kutta Condition" determine the behavior, while path lengths do not. The path-length explanation was a "Lie to Children," like teaching kids that venous blood is bright blue like paint, or that electrons zoom through miles of solid copper at the speed of light, or that the sky is blue because it reflects the ocean. These might sound sensible, yet they're completely wrong. In smoke-pulse videos, the fluids ignore the path lengths, and instead the upper flow vastly outraces the lower flow. It happens because a vortex has been set up, a "chordwise circulation" around the wing, and this circulation is controlled by the angle of the trailing edge. We can eliminate all lift by halting this vortex, yet without changing the wing shape or angle. (Fly slow enough, to where "Kutta Condition" fails, and the circulation halts, so the lift suddenly drops to exactly zero. The wing shape never changed.) "Stall" is an entirely separate issue. Flow-separation is extremely nonlinear, akin to turbulence. When it occurs, the air "thinks" that the top of the wing has been replaced by a giant misshapen lump. Notice that in the simple fluid simulations used to explain how lift is created, no boundary-layers, vortex-shedding, or stalls exist. To understand lift, we don't need to even mention stall.
I live near Tampa International Airport and a smaller airport in Clearwater. Usually the Clearwater Airport hosts smaller air shows. The third airport is MacDill Air Force Base. Which contributes military aircraft to the air shows. They take off and land the military aircraft back at MacDill. The stealth aircraft will participate occasionally. They are probably the weirdest sounding thing I have every heard, they do not roar, they swish the air as they go by until they are well past where you can see them. Then them them go boom. I would love Neil to do a show on them one day.
Actually, as a military history buff, as far as I'm aware, no WWII aircraft carrier had an angled and straight flight deck (runways). Those were developed in the 1950s. One Is for launching aircraft and the other for recovering aircraft ( the ship turns into the wind when it's launching aircraft)
And still the angled deck has nothing to do with landing into the wind. The angled deck simply provides a means for aircraft to take off again if they do not connect with the arresting wires.
14:15 This is incorrect. There are hundreds of airports in the U.S. ALONE that are single, dual, or even triple runways with the same headings. Los Angeles International Airport - KLAX - has FOUR parallel runways only. The one closest to my house - KHEF in Manassas VA - has only two runways and those runways are parallel to each other with one labeled 16L/34R and the other labeled 16R/34L. At Manassas Regional Airport, regardless of the relative wind, you only have ~160 degrees magnetic or the reciprocal ~340 degrees magnetic to choose from when taking off/landing.
The wing tip doesn't produce little turbulent eddys, it produces one big vortex that rotates around the tip. Air above rotates from outside to inside into the downwash that is producing the lift. The winglets manipulate the vortex to get a little less drag.
Actually the principle is correct, with an incorrect base, but the principle still applies. You clearly do not work in aviation. Equal transit time applies to the flow around a body generating no lift, but there is no physical principle that requires equal transit time in cases of bodies generating lift. In fact, theory predicts - and experiments confirm - that the air traverses the top surface of a body experiencing lift in a shorter time than it traverses the bottom surface; the explanation based on equal transit time is false. While the equal-time explanation is false, it is not the Bernoulli principle that is false, because this principle is well established; Bernoulli's equation is used correctly in common mathematical treatments of aerodynamic lift.
I remember when the Australians blew away the competition in the Americas Cup when the put a wing on the keel of their sailboat. It was awesome! It had enough lift to get the hull up and reduce the amount of drag on the water significantly.
I am an airplane model maker. I have been ever since I was 8 years old. I love airplanes so much that each time one is flying over I have to look up. Such wonderful machines.
The downwash at the back of the aero-foil is also a factor. There is an MIT lecture on TH-cam that says this is MORE important than the Bernoulli related pressure differential.
This is the correct response. It's not just more important, downwash is THE explanation for lift. Bernoulli's Principal is a very common misconception.
@@SpiaggiaVita The downwash generates a sliver of the total lift of an airfoil. The test for this is simple to demonstrate in a wind tunnel; it’s actually one of the first uses of wind tunnels I used in aerodynamics for my aeronautical engineering degree. Create a flat plate which spans the width of the test section and the full length of the test section and set to zero angle of attack. Add a curved upper surface at the center of the plate. At zero angle of attack, the plate will generate lift, even though the airstream isn’t deflected down.
@@A_J502 do you have a link to a video demonstrating this? What you described sounds like a closed system, which is where Bernoulli's principle does actually take effect.
@@SpiaggiaVita Closed system only depends on where you draw the system boundaries. Also, the Bernoulli effect isn’t limited to closed systems, so that critique is useless.
I know at my airport in the north central part of the country our wind directions are usually northwest and south. I think that covers the 30 degrees Neil was taking about. Great information.
You do question the Equal Transit Time fallacy. That is. a wrong assumption. The Bernoulli Effect is part of the lift phenomenom, but not as wrongly described here.
@@SpiaggiaVita If the Bernoulli effect doesn’t define lift, why is it almost universally used correctly in design, testing, prediction, and validation of aircraft designs?
@@robertcain3426 You have to blow FASTER on the bottom because the reaction is so weak. Fighter jets show how ineffective deflecting air with symmetrical airfoils is. Fighter jets require much more wing area, speed, and additional control surfaces to produce lift. Curved airfoils are vastly more efficient and effective at producing lift which is exactly why more cambered wings are used in the vast majority of fixed wing and rotary wing aircraft.
@@A_J502 Yes, I was confusing a foiled wing with Bernoulli's principle, since a asymetrically foiled wing is merely an example of Bernoulli's principle. And, rather, asymmetrically foiled wings are an attempt to achieve a level of Bernoulli's principle without an angle of attack. Whereas, flat or symmetrical wings of a jet fighter produce the Bernoulli effect by means of an angle of attack. While lift and diving depends on the Bernoulli principle, level flight does not. Level flight of a flat or symmetrical wing will, having no pressure differential between upper and lower wing surfaces, would, if not for the effect of gravity, fly on an unchanged level path. Thanks for your comment. I find it stimulating.
Hey Neil, Loved how you highlighted the variation of the airplane wing as you move from the fuselage to the tip. In Structural Engineering will call that a structure a CANTILEVER. It experience maximum Bending Moment and Shear Forces at the support i.e. its connection with fuselage and ZERO of them at the tip. All those disturbing forcesmust be less than the strength of the material and joints by a certain margin called Safety Factor.This explains your strength highlight. I'm interested by the DRAG caused by Turbulence.Will research more on this
I so admire - and envy, you folks who are engineers and actually have studied and really understand aeronautics and aviation. I was just today during dinner talking about this subject - how in the heck can the planes + people + fuel + my suitcases (especially on the return trip. 😳 ) become airborne and remain airborne??
Neil, Your explanation of the Bernoulli Principle is exactly the same as my very inspirational 5th grade teacher gave. He was probably a large part of the reason I'm in the 36th + year of a career as an aeronautical engineer. However, as many years ago it still leaves me wondering why does the air passing over the top of the wing "feel" compelled to meet up with the air passing over the bottom of the wing? As other commenters have pointed out,the parcel air moving over the top actually tends to reach the rear of the wing even faster than the parcel of air moving across the bottom. Why is this? The reason is air is incredibly viscous or "sticky" if you will. Have you ever tried to get air off of you? Try running your hand at an angle through water. The air sucks down to fill the void behind your hand. The same thing happens with the curved upper wing surface or even a flat plane traveling at an angle though the air (this is why aircraft can fly upside down) . The air tries to fill the void cause by the upper surface of the wing moving downward and not only speeds up, it also gains a downward momentum. This together with the Bernoulli Principle is what generates lift. If you have ever seen older jet aircraft, that generate soot in the exhaust, in level flight, you can see that the air trailing the aircraft is moving downward. As an aside, it must be nice traveling first class and getting hot meals. It's been many years since those of us in steerage have gotten a hot meal.
It is not the viscosity of the air, it's the mass. Lift is the Newtonian reaction to the accelleration of air downward, which is proportional to the ANGLE of ATTACK. The only reason that aircraft wings have thickness is to acccommodate the spar and maybe some fuel tanks. Bernoulli has very little to do with it!
@@rsteeb Aircraft flying upside down don’t use different laws of physics. For most aircraft, the wings have a positive camber (greater curve across the upper surface relative to a line from the leading edge to the trailing edge). A positive cambered airfoil will need a greater angle of attack when flying upside down than when right side up.
Doctor, Could you please do a video explaining how sail ships could travel "into" the wind. For someone like me, it's mind-boggling that people could sail around the world in any direction regardless of the wind for centuries propelled by the wind caught by a bunch of sails tied to giant wooden masts.
It's impossible to sail directly, head first, straight on, in to the wind. A sail is used to push the boat at an angle offset of the wind direction. The ships captain will take that heading for a bit, then switch to another heading that. And then changes in a bit. More or less zig zapping towards their destination.
To travel directly into the wind is impossible, it's called "being in irons", once you fall off to either side your sails will fill(at different angles depending on the vessel in question), this position is called "close hauled(tight to the centre)". In this position your power from those sails is between 70-90° off dead ahead, this would obviously make you go sideways, except you have a keel in the water and it is performing the opposite effect under water, the combination of these two forces leaves you with a net effect of only forward motion, it's the slowest point of sail due to these confronting forces but at least you can get where you need to go. I hope this helps
Here in 🇳🇿, many years ago, there was a guy in the Bay of Islands somewhere who built a boat with a windmill on it, connected to drive the propeller. He could turn the windmill any which way, so it was always facing into the wind no matter which way the boat was steered. Then the question was asked: could he sail straight up 12 o’clock _into_ the wind, powered only by the wind? And the answer was yes, he could.
I believe aircraft carriers have two runways, not for takeoff options as Neil described here, but because they serve different functions. One is for take off and the ship merely changes course to face the wind for optimal conditions, while the other is for landing while allowing it to point away from the ship in the event of a failed landing.
Small nit-pic about the aircraft carriers, because I work on one (USS Hornet CV-12). The 24 Essex class carriers built during WWII were all built with straight decks, and were all converted to angled deck carriers in the '50's (SCB-125 program), and it was the Forestal class starting in the mid '50's that were the first carries built from scratch with an angled deck. Before the introduction of the angle (a British invention actually), the planes would land in the same direction they took off, and the pilot hoped he hit the arresting wires because, if he missed, there would be a barricade to catch him, and that would hurt (the pilot, and the plane). If he missed that, the only other thing to stop him would be the other planes parked on the front of the deck. By converting to an angled deck, you land on the angle and take off and the straight part up front. That way, if you miss your arresting wire, you can still go around and try again. It has nothing to the wind over the deck. Because the aircraft carrier is a boat, and it's operating in the middle of the ocean, it can always move and make its own wind (30-ish knots), and it doesn't matter in that case what breezes are coming off the ocean. The ship can always turn into the wind if necessary. Another interesting piece of equipment is the catapult on the carries. The older Essex class used hydraulics, the newer super carriers used steam, and the newest Ford Class uses EMALS (electromagnetic). Amazing systems.
A couple of syllabus words we use in pilot training. Rear Horizontal tail wing: elevator - except delta wings (Concorde) Pitch / pitch changes: Angle of attack. Rear vertical wing: vertical rudder Rear vertical wing controls yaw (crosswind) Cruise flight is when Bernoulli law is most effective. Angle of attack AoA (pitch) is directly proportional to minimal takeoff and landing lift performance / airspeed of an aircraft wing design. Have a nice flight ✈️.
Doug, Those details are BIG hints that he's not up to speed elsewhere. In other words: Unfortunately, he also got the whole lift explanation wrong. Too bad Neil has repeated common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. This video is EXTREMELY disappointing. .. If you're going to provide corrections get them right: . There is a "vertical stabilizer" and a rudder (in it's rear). Lift occurs for the same physics at all times. It is NOT changing from "Bernoulli" to something else. To be blunt: Neil is wrong!
Correction needed: AoA and pitch are not the same concept. A wing can stall at any pitch attitude, but only one critical angle of attack. Also, you seem to be confusing the horizontal and vertical stabilizers with the control surfaces mounted on them: elevator (horizontal) and rudder (vertical).
One small correction on aircraft carriers. They have angled decks so planes can be taking off and landing at the same time. The ship always turns into the wind plus makes more wind from the speed of the ship.
To fly, all you need is enough "angle of attack" and enough force. The shape of the plane is just to reduce drag. You could turn a grand piano upside down and make it fly with enough angle and power, since it has has the same "wing loading" (psi) as a 747, if you calculate the weight divided by the lifting area.!
Brute force and ignorance will make a piano fly, but can you keep it flying? Yes planes are shaped to lower drag, but there's much more to the shapes than that. Flying with stability and control involves tiny, subtle manipulations of the air flow that are easily overlooked by the casual observer. Making a plane that goes straight without constant input from the pilot, and then turns on command without going wildly out of control is not a trivial task. The engineers who figure these things out are brilliant. The more you learn about how these things work, the more impressed you'll be.
Aaaahhhh dang it Neil!!! You propagated the stall "speed" myth!!!! An airfoil can stall at ANY airspeed!!! Airspeed is at best indirectly related, and the traditional means of anticipating an aerodynamic stall. An airfoil stalls when the angle of the wind flowing over the airfoil exceeds that airfoil's critical angle of attack. I know, this is meant for the laymen, but this is YOU, Neil! You do stuff right!!!
These are two different things entirely. The Coanda effect is in action when you pour a liquid out of a pitcher, and it sticks to the side rather than flowing freely over the edge of the spout. This fluid redirection is how wings create downwash, which then creates a lifting force on the wing. Bernoulli's Principle is almost completely irrelevant in terms of the amount of lift it generates.
@@SpiaggiaVita What Tyson did with the paper IS the Coanda effect. It has NOTHING to do with Bernoulli. Aurassh is correct (except for the "based on" part. That part is nonsense).
Thanks Neil and Chuck for a great explainer video. I always learn something new each time I watch a new video. Plus I enjoy the process of learning it with the added touch of humor. Happy 2023 to both you and your families. I would love for you to do a explainer video on the stealth technology if you could. Those aircraft are so awesome and, at the same moment, so weird.
Billy Connolly tells of the time he was in the Territorials, as a parachutist. He actually made his first six trips in an aircraft without ever experiencing a landing, because he jumped out every time.
When I was a jet engine mechanic instructor in the Air Force, I used an interesting demonstration of the Bernoulli Principle. Take a spool of thread that has a hole through the spool. Then take a piece of cardboard, I would use one cut out as a disk. Then put a thumbtack in the middle of the disk. Place the disk with the thumbtack facing up into the center of the hole of the spool. Hold the cardboard up to the spool until you start blowing into the hole. Once you start to blow into the spool, you can take your hand away from the disk. No matter how hard you blow into the spool, the disk will stay up against the spool
Love this video guys! The super interesting science, the humour and now I will appreciate flying home for Christmas even more. Maybe I won't even complain about the salad 😁
I would add something that was beaten into my head by my flight instructors. A planes wing will stall at any speed and attitude. Stall occurs when the critical angle of attack to the relative wind is exceeded.
Neil, words from a big admirer and almost 20 years commercial pilot, this is the first time I can fell this is not your area of expertise! Just to add more knowledge to the video. The two effects that generate lift are: Bernoulli effect and downdraft effect. Contrary to intuition, it is not the air “hitting” the wing at an angle that pushes the wing upwards but the deflection of the airmass downwards (action-reaction Newton’s third law). The other part about runways, already partially commented, majority of airports in the world have only one runway tarmac. The motivation of airports behind the construction of two or more runways is just the improved management of traffic flow for improved number of takeoff and landings per minute. Regarding the headwind/tailwind component, a single runway will do just fine since at any wind direction there will always be a headwind vector component for either one direction or the other. Worst case scenario the wind component vector will be fully crossed which is acceptable to a certain specific value for each aircraft. Additionally, airliners can normally accept up to 10-15 kt tailwind component. Finally, as already mentioned by other follower, runways are built based on the predominant statistical wind. This will even be restricted by the local geography that can force runway constructions where the predominant statistical wind will be crosswind. Thanks for the channel, really educational. You are a great science communicator !
I should have read your reply before adding my own. Aerodynamics is complicated. Many factors go into make things 'fly'. The choice of how simple an explanation is offered often depends on the target audience. Personally, I'm a newly converted fan of the Coanda effect--another oversimplification perhaps.
I have always found it hard to accept it’s the Bernoulli, I think its fundamentally the Newtonian(Law 3) that’s why planes can actually fly upside down, otherwise the Bernoulli cannot make that happen.
there are 2 parts to lift. 1 is newton but second parts is preassure differential- But it is not caused by the bernoulli effect but rather because air moving in a curve creates a pressure diff.
One issue... If 2 adjacent air molecules are separated vertically by the leading edge of a wing, there is no reason for them to meet up at the trailing edge. The idea that one must move faster over the wing to cover the longer distance in the same span of time, is flawed, because there's no reason for the 2 molecules to take the same amount of time to reach the trailing edge. The air over the wing moves faster than the air under the wing, due to the shape of the wing, not due to needing to travel farther in the same time. Nothing is forcing them to reach the trailing edge at the same time. The upper flow's time from leading edge to trailing edge is independent from the lower flow's time. Air doesn't "want" anything. It doesn't stay as one parcel when it's disturbed by having a wing pass through it. The wing's shape & angle disturbs the overflow differently than the underflow. If 2 molecules are adjacent at the leading edge and one goes under & the other over, the one that goes over reaches the trailing edge first, because the wing shape speeds it up relative to the air passing under. They don't reunite.
Correct. Air only 'want's to obey Newton's laws. The two parcels that join at the trailing edge started in different locations before the wing arrived. They are" total strangers". .. This actually hurts to listen to. This is still here and it is still WRONG!. This explanation is NOT correct .It is the most common misconception repeated over and over by amateurs. This is EXTREMELY embarrassing. . This story relies on several fallacies, not just one ! This is a long-ago disproved fallacy! . 1- The upper and lower air parcels do not rejoin behind the wing. 2- Path length is irrelevant. A flat or inverted wing uses the same physics. 3- Fast air does not have lower pressure. Blown air is AT atmospheric Pressure. 4- Air speed along a surface is irrelevant to Bernoulli. Bernoulli is about Acceleration. . Neil is clearly out of his element and has repeated nothing but common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. .. Neil's BA in physics has failed completely. This explanation is the worst one of all the other poor ones repeated over and over. To see it all spelled out step-by-step, please see this: . . rxesywwbdscllwpn.quora.com/
The rearward acceleration above the wing is CAUSED BY the lower pressure - just as the decrease in speed below is caused by the higher pressure there. This video is terrible and the absolute worst of the three major misconceptions being spread around by well meaning, but ignorant people. . .. I've outlined the errors in other comments. This is so sad and terrible - he is completely out of his element. In short: The inertia of air approaching the lower surface resists being pushed down which is the CAUSE of the pressure increase. Above the wing, air's inertia has the converse effect because the inertia works against atmospheric pressure, thus reducing the pressure above. People, with good intentions, don't understand and never see inertia as significant and come up with these incorrect explanations. Understanding Aerodynamic lift Correctly: rxesywwbdscllwpn.quora.com/ Neil has another about a month later, about the direction to the sun that is also completely wrong. He's lost it.
Wow, as an engineer in aerospace & RC plane builder, I love this episode. But, I gotta go down the rabbit hole about NdT ROTFL with Nice's "Johnson" remark (after the 7 min. mark). Chuck wasn't aware about the old "My name is Raymond Jay Jonah Johnson Junior" skit, that was part of the short-lived Redd Foxx Variety Show (No, I don't mean "Sanford & Son".) On his show, Redd Foxx introduced to a new generation many old comedians from radio and vaudeville days. (Being seen nationwide revitalized a lot of these actors' careers to go on to other shows and commercials afterwards.) The gag on the show was if someone said "Johnson", comedian Bill Saluga would suddenly show up saying "Ya doesn hav ta call me Johnson..." and go into a non-stop monologe of his full name and all it's permutations. It's funny as heck when I first saw it as a kid, and I still have it memorized! I come for the science, I stay for the off-tangent stuff.
I went to the Navy jet engine mech school in Millington, TN in the '70s, and was authoritatively told to ignore all that: planes fly because the wings push the air down
I think that’s a better explanation. If the shape of wings is what caused most of the lift, then airplanes couldn’t fly upside down, which many airplanes clearly can.
Wings produce lift UPWARDS. The reaction force of the air pushed downwards is nowhere near enough to create the lift measured and verified with the equation of lift which uses Bernoulli equation.
As a kid growing up in the 60's and making paper aeroplanes (Concord style), I'd just like to say that I was the first to discover the turned up or down tip on the end of the wings. The plane flew very straight and level and stayed in the air much much longer than all the others.
Kelsey at 74Gear is a great pilot here on TH-cam that can explain more about this if you are interested. He got a shout out from one of the TH-cam creator's so you know his content is lit.
I saw a paper recently that claimed we are very wrong about where lift comes from. While bernoulli principle is always necessary for lift most of it comes from the force of fast moving air acting on the wing's surface.
Don't forget the upward tilt of the wing relative to the fuselage called the dihedral which also aides in reducing the drag on the wing. Paper airplanes tend to have that dihedral as a part of the folding of the paper. As a kid (60 years ago) I instinctively added a small wiglet at the tips of my model airplanes thinking I was adding the "missing" tail fin not knowing I was adding the turbulence dissipation winglet as well. Also if you watch them in flight many birds have this winglet in their wings when the tip feathers bend upward.
Dihedral counters the effects of the dutch roll. Which as @WarHoover said, improves stability and the tendency of an airplane to return to a wings level attitude when disrupted.
All my paper airplanes were basically delta wing. I don't know how much good winglets would do on a delta wing. Pretty much the only place to fold the wingtip up into a winglet is where the wingtip IS, back by the trailing edge. By the time the air gets that far back, it has already flowed over 90% or more of the wing surface. I'd think that any drag-inducing turbulence would already have been created by the time the air gets that far back on the wing. What do you think?
Alas the explanation is incorrect. Flat plates generate lift with equal distance top and bottom. All you have to do to fly is push air down. Then the air pushes you up. It really is that simple. Anything that is flying is pushing air down. Pressure differences (Bernoulli) are a consequence of that fact. They’re not independent- they’re intimately intertwined.
It might be interesting to note that the Bernoulli principle also applies to the sails of sailboats. It is why shaping the sails with spars (masts and booms) and lines (ropes which stretch the sails) is important in maximizing speed.
Sailboat sails operate over a fantastically wide range of speeds (in percentage terms) from their lowest to highest, a much wider range than aircraft. That many aspects of their design were figured out by trial and error "evolution" before advanced modern aerodynamic theory is truly amazing. The ways that their structure allows their shape to be varied and optimized to such a wide range of speeds and angles is amazingly clever. Low speed aerodynamics is it's own fascinating world.
The air actually moves much faster on the suction surface, and the top parcel reaches the trailing edge much faster than the bottom parcel. Using good old Newtonian mechanics as applied to fluid flow, you can calculate the force the wing creates. Bernoulli effect is just a statement of conservation of energy.
Both descriptions are valid descriptions of the flow field, and from both (once a flow field configuration is established) you can deduce that there's a lift force. But the mechanism that leads to the curved flow field distribution is actually caused by the viscous boundary layer detachment on the trailing edge. Without viscosity there's no such thing as lift (potential flow solution for flow field around airfoil)
Actually I have seen a video on TH-cam of a university professor disproving this. He showed a wind tunnel time lapse of disproving this idea that top parcel of air reaches trailing edge faster than the bottom edge. Overall Bernoulli effect is minimal on flight.
Yeah, nope! There is no magical force pushing the air on the top side of the wing to accelerate back to the trailing edge. On the contrary the air gets shoved more upward than backward as it hits the leading edge. This has been observed in wind tunnels and forms the current models of fluid dynamics.
Mostly about : if I bend the air downwards (over the top) edge of the wing, an equal and opposite force acts on the wing pushing it upwards, and so “lift”. A lot more complicated than this, but Newton is flying the plane, mostly.
Why does the air "want to stay in a single parcel" though? I understand that it gets sped up on top of the wing, but the reason for that speeding up gotta be more feasible than some secret desire of the air.
Bernouilli Effect accounts for ~5% of lift, Angle of Attack 95% (~4% of the axis wing/fuselage), ie Newton's 3rd Law. If not, how to fly inverted? Why do modern fighter jets have almost symmetrical wing profiles? Power/weight ratio so high that BE irrelevant. (Old pilot here).
You fly inverted with a greater angle of attack, which increases the airflow over the wing and increases the pressure differential. Similiar to normal flight.. Inverted flight doesn't violate Bernoulli..
There no such thing as "bernoulli lift". Lift is only caused by deflection. The equal transit time hypothesis is false. A pressure differential doesn't cause lift, but rather IS lift caused by deflection. An upward force doesn't cause another upward force. Only a downward one does.
Actually the bernoulli effect doesn't cause lift. You only get lift by the work of accelerating air downward. This is the only cause. Likewise, you can't accelerate air downward and not get an upward force. You can't lift yourself up by pulling on yourself, you have contact an outside object.
@@Robert-d5l Right. Bernoulli Effect does reduce air pressure above the wing but it's negligible. Just watch a kid fly an RC plane, wings of flat polystyrene sheet, perfect, no BE...
You two, have a wonderful chemistry going on! Thank you for making me laugh! My hubby travelled all over the world, and loves airplanes. I love them too, but am much more anxious than him at takeoff and landing. Your explanations are excellent! I hope more people overcome their fear of flying! I have ❤️
~13:00 Correction - there's not a speed at which a wing stalls, there is an "angle of attack" (AoA - angle that the wing meets the oncoming air) at which it stalls. Having said that, a pilot trying to keep a slowing aeroplane flying at a constant height, will pull back on the control column/joystick further as the 'plane slows, increasing the AoA of the wing in order to maintain the necessary lift (the lift required is the same as the weight of the 'plane). When the wing reaches a critical AoA, (and for a given aeroplane at a set weight this WILL be at a certain airspeed) it will stall, but due to the angle, not the speed. You can actually slow the wing to zero without stalling if you keep it horizontal but you correspondingly don't get any lift! There's an expression we've all heard: "It's not rocket science"... no, rocket science is a LOT easier to explain - (easy to explain, very difficult to do). With a rocket you just chuck a lot of stuff as fast as possible out the back. But the theories of flight?... mankind has been flying for over a century and there are STILL arguments about how! (I say, "theories" rather than "theory" as there is the theory of low speed flight - as discussed here, - the theory of high-speed flight (approaching the speed of sound) AND the theory of supersonic flight, all with their differences.) You've opened a can of worms here, Neil.
@@BLOXKAFELLARECORDS I get your point, but all of us will be forgotten. I'm already forgotten, thankfully, I can disappear at any moment and only the government will care, since they won't get my $$$ anymore. 👍
Startalk is the best! What was up with the most recent episodes intro? Seemed kinda rushed and jumped right into. The introductions and small talk are important too! Love you guys
Class A science lesson/comic relief. Thank you for the enrichment and the enlightenment. You leave us smarter and happier. That bit about you can call me Ray or you can call me Jay was hilarious. May I be a little maternal with you Mr. Tyson. Please take care of your health and give yourself enough sleep and rest, because we all NEED YOU in our world.
Neil, look up attack angle and coanda effect. Air packets don’t have entanglement where they need to catch up with each other if they’ve been bisected.
@@rsteeb literally a 30 second search and read on Wikipedia has the correct answer for wingtip vortices being the result of downwash. If the wing is redirecting air downward, it is easy to see how that would create vortices at the tip of the wing. Pressure has little if anything to do with it.
As a licensed pilot, I can offer that the best direction to fly when taking off or landing is the same as the runway heading.
😉 wise advice.
What if you take off from a 3000m x 3000m field?
@@FrozenLabRat Into the wind is best.
@@FrozenLabRat Fly the direction that doesn't have any deer on it.
And any landing you walk away from is a good landing.
4:18 he literally describes word for word the Equal Transit Theory which has been accepted as wrong.
OUCH! This hurts.
Neil Is clearly out of his element and has repeated nothing but common misconceptions and made some new ones.
He needs to have a serious talk with a fluid dynamics expert.
This video is EXTREMELY disappointing. This is NOT correct.
Actually: REJECTED as it is wrong. . . (;-D)
He’s a nice scientist but he’s very wrong about how a wing develops lift simply stated Newton third law
Great video as always! I’m an aerospace engineering student who just finished Applied Aerodynamics and there is an interesting note bout how wings generate lift. The part where air moves faster on the top surface than on the bottom surface is 100% true, but the part about an air molecule needed to regroup with the other molecules it was near before encountering the wing is actually a myth. There is no requirement for “air molecule neighbors” to remain neighbors after encountering the wing. The only requirement is that air moves faster on the top. A subtle distinction, but still interesting!
Sure you are.
There is no requirement for the air to move faster on the top of the wing than the bottom. Bernoulli doesn't make airplanes fly, NEWTON does. The angle of attack accelerates air downward, and the reaction to THAT is LIFT.
@@rsteeb you’re right that accelerating air downward creates lift, but both descriptions are actually describing the same phenomena! That’s why positively-cambered wings at zero angle-of-attack can still create lift.
Wow! Thank you for this clarification. Keep up the good work!
you are 100% CORRECT! Duncan. There is absolutely NO LAW in physics that stipulates that air needs to "reform" into its original pockets of air. None! Simply put the design promotes lower pressure on top, and higher pressure beneath the wing.
Entertaining as always. A couple of bits of trivia that came to mind as I was listening: 1. Airport runways are designed to align with the most common wind direction in that part of the country. In the middle of the US, they are aligned more north and south. In other parts of the country they are aligned more east and west. 2. Like a lot of early aviators, Lindbergh may gotten his information about wind direction by looking to see which direction the cowherds were pointed
Yo bro. Your not impressing nobody.
Like... I still don't think your smarter than me.
@@BLOXKAFELLARECORDS Not meant to impress, but to entertain.
@@buzbuz33-99 haha 😄 I remember this one. Haha. Discover my music here! Nba highlights... comedy vids.... I got it all.
🔥
We appreciate these bits of trivia! :)
@@StarTalk Thanks. I've watched Star Talk from the beginning and have always found it educational and entertaining - generally covering topics in which I have little knowledge or expertise. So I was delighted to see you discuss something involving my chosen profession of aviation. I thought the impromptu reference to 88 mph takeoff speed was hilarious, especially since it is close to the takeoff speed of a lot of aircraft.
Bernoulli is incidental but not critical in getting an airplane to fly. Some wings (particularly those of acrobatic airplanes) have symmetrical sections - the curve is the same below as it is above, and this is to allow them to fly just as well inverted as they do right side up. Airplanes fly because of the combination between the reaction force generated by the wing and the coanda effect generated by the trailing edge. You can experience the coanda effect by approaching the back of a spoon to a flowing faucet.
Too bad Neil has repeated common misconceptions and made some new ones. He needs to have a *serious* talk with a fluid dynamics expert. Neil is completely out of his element here. This video is EXTREMELY disappointing. Neil is wrong.
According to NASA, the faster air above the wing contributes to a mere 2% of the lift generated. Bernoulli has nothing to do with it because the Bernoulli principle only applies to a closed system. The Coanda effect does add lift forces but the vast majority of majority of lift is from the angle of attack of the wings: air strikes the underside of the wing deflecting it upward. Pilots know to fly angle of attack. Neil de Grasse is not a pilot and does not appear to have studied aerodynamic mechanics
@@judesalles This confuses me. If the air flow above the wing is 2% of the lift, then when the wing "stalls" at high angle of attack it should lose no more than 2% of its lift, as the air flow striking the underside of the wing is still "deflecting" it upward. "Stalling" effects the flow over the wing very much and has almost no effect on the flow under the wing. Why does stalling result in a sudden loss of lots of lift, much more than 2%, when the air is still "striking" the bottom of the wing? Are you sure about this 2% number?
@@judesalles Wrong and NASA doesn't say that. The majority of the pressure difference (which is how lift force manifests) is on the top of the wing (on most airplanes) due to the airfoil design. Most of the deflected air (downwash) is also due to the air flowing over the top surface of the wing.
@@user-vr2rq5hl6l (sic) Thanks. I fixed it.
Chuck is the perfect contrast to Neil's seriousness, the comment "too bad you're not an airplane" cracked me up
i freaking love these guys
As a flight instructor I find it fascinating how Tyson explains Lift, and his obvious passion for science. Aerodynamics is a subset of physics, fluid motion to be exact, and vital for us aviators.
Edit: as an additional piece of info, most Runways are designed with headings that represent the most frequent average wind directions over the course of a year, for any given location. So the aeroplane has a greater chance of being able to take off into the wind, every time.
Neil is WRONG and completely out of his element! This is probably the worst I've seen ESPECIALLY since Neil is so popular and good at most things he does.
NOT THIS ONE!.
.
Neil has repeated common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. This video is EXTREMELY disappointing.
Please don't refer your students to this video. While many of his points are accurate, he completely misspoke regarding lift at rotation and lift during inverted flight.
Instead, direct them to the book "The Illustrated Guide to Aerodynamics" by Prof. Hubert (HC) Smith. This book is an excellent treatment of conceptual aerodynamics. You can buy the 1st edition used for a low price. It's the very first aerodynamics book I read after I started flying a few decades ago...
@@Observ45er I was also surprised when Neil repeated the Equal Transit Theory to explain lift. I just completed Ground School, where we learned about this common misconception.
I find it funny that flat earthers don't understand these concepts they should all be sent to some Island
I love how you can interpret even a complicated theory to a middle school understanding. You're a helluva teacher! Thanks for offering these classes in this format.
Very sorry that you learned from this video
Except the explanation is ALL wrong
15:10 In WWII all aircraft carriers had a straight deck. The problem with this wasn't relative wind (as you noted, if the wind changes, the carrier would just change heading to put the relative wind down the flight deck), it was that you couldn't have landing operations and takeoff operations going on simultaneously. A landing plane that missed the arrestor wire would plow into aircraft lining up to take off. It was this restriction that contributed to the demise of the Japanese carriers at the battle of Midway because it delayed launching a second strike while recovering the first strike. If the deck used for landing was angled, however, a plane that missed the wire would continue off to the side of the carrier and planes could safely be launched off the bow at the same time. It wasn't until December 1952 that the U.S. started experimenting with an angled deck for landing on the U.S.S. Antietam (CVA-36).
A great video demonstrating the advantage of simultaneous launches and landings can be found on the Growler Jams TH-cam channel: th-cam.com/video/itxCibqCUZw/w-d-xo.html The channel is run by a U.S. Naval Aviator - call sign "PAIL" - and this particular video happens while the carrier is conducting simultaneous launches and landings.
Ah, you watched the video.
@@oggyoggy1299 I always try to watch Pail's videos when he releases a new one. He provides great in-the-cockpit instruction. 👍
I learned about this when I was eight years old because my dad had been a pilot in WWII and then became an aeronautical engineer. At a point he was designing airplane wings. Sixty + years later I still recall seeing drawings of wings. When Bill O’Reilley did his famous “The tide goes in, the tide goes out, you can’t explain that,” and also mentioned how planes were heavier than air and yet can fly, you can’t explain that, I thought, “I’ve been able to explain that since I was eight years old!”
Sounds interesting
Do you now understand that Neil's explanation is completely wrong? BOTH about Lift and Bernoulli's Principle?
.
.
And that there are people who DO understand and can explain the fundamental physics?
Getting your brain wrapped around the concept of aerodynamics that allow planes to fly is as difficult as understanding how a battleship with a hull 16 to 20 inches thick can float. It goes against logic.
@@HughButler-lb6zs If you understand Newton's laws and inertia, it's child's play, but so many don't understand those two things and simply repeat words they don't understand continuing the long chain of misconceptions - - as we have in this video.
Me who has studied Aerospace Engineering at undergrad level clicking on this video: Neil deGrasse will probably explain this in a way I have never learnt before
Because it's completely wrong.
@@reh3884 how so? I don’t want to learn faulty info. Share your knowledge please.
@@reh3884 i
I highly doubt that... but I wanna know
@@heatherwoodley8244 RE H is right. What NDT is positing is commonly known as the "equal transit time" theory. This suggests that two particles that are separated at the leading edge will meet at the trailing edge. And there are two problems with that. The first is that there's no theory by which that should hold true. And the second is that experiments show that it absolutely is not true. It is true that the air flowing over the top of the wing moves faster - but not so that it can meet its partner at the trailing edge. In fact, it can beat its partner to the trailing edge by a healthy margin.
@Rick Cavallaro Interesting. I thought that he was positing the ridiculous ETT theory, but then I told myself that he couldn't possibly be doing so. Strange..
I had an 8 foot piece of paneling about 2 feet wide. As I held it in front of me at arm's length, I spun myself around in circles. I was able to see and feel it rise and fall as I changed the angle of attack. It gave me a lot of insight into lift and drag and flight itself.
That's the true explanation. With your flat board, when it's tilted, the parcels above are flowing MUCH faster than the parcels below. It's also how the Wright brothers flew, by using a sheet of thin canvas, where the upper and lower path-lengths are identical. Dr. Tyson above got it wrong, because the upper flow is far too fast, so the split parcels never rejoin again ...and wing-shape is known to be irrelevant to creating lift. (Wing shape is extremely important in avoiding stall!) If it weren't for the problem of stall, airplane wings would all be flat plates, eh? (Heh, then the fuel tanks would have to be placed next to your luggage.)
@wbeaty I did that experiment years ago. I've been thinking ever since to repeat it but adding different weights to the end of flat plate to get a sense of how much lift is actually generated.
Did something similar as a kid ..l used to hold my hand out of dad's car window with a flat palm ..and tip my hand this way and that to achieve the same effect
@@wbeaty Are the upper and lower path lengths really identical? A '"bubble" of air, or "vortex", stuck in the concave underside of the wing could allow flow to go straight from the leading edge to the trailing edge, making it's path shorter than the upper flow. If wing foil shape is irrelevant to lift creation, then why is "stalling" relevant if it only effects the flow on the upper surface of the wing?
@@jackwickman2403In modern fluids, Circulation and "Kutta Condition" determine the behavior, while path lengths do not. The path-length explanation was a "Lie to Children," like teaching kids that venous blood is bright blue like paint, or that electrons zoom through miles of solid copper at the speed of light, or that the sky is blue because it reflects the ocean. These might sound sensible, yet they're completely wrong.
In smoke-pulse videos, the fluids ignore the path lengths, and instead the upper flow vastly outraces the lower flow. It happens because a vortex has been set up, a "chordwise circulation" around the wing, and this circulation is controlled by the angle of the trailing edge. We can eliminate all lift by halting this vortex, yet without changing the wing shape or angle. (Fly slow enough, to where "Kutta Condition" fails, and the circulation halts, so the lift suddenly drops to exactly zero. The wing shape never changed.)
"Stall" is an entirely separate issue. Flow-separation is extremely nonlinear, akin to turbulence. When it occurs, the air "thinks" that the top of the wing has been replaced by a giant misshapen lump.
Notice that in the simple fluid simulations used to explain how lift is created, no boundary-layers, vortex-shedding, or stalls exist. To understand lift, we don't need to even mention stall.
How is this video still up?
I ABSOLUTELY LOVE this subject!!!! We live near PHX airport and I know how it works, but I’m always amazed 🤓😄
I live near Tampa International Airport and a smaller airport in Clearwater. Usually the Clearwater Airport hosts smaller air shows. The third airport is MacDill Air Force Base. Which contributes military aircraft to the air shows. They take off and land the military aircraft back at MacDill. The stealth aircraft will participate occasionally. They are probably the weirdest sounding thing I have every heard, they do not roar, they swish the air as they go by until they are well past where you can see them. Then them them go boom. I would love Neil to do a show on them one day.
Actually, as a military history buff, as far as I'm aware, no WWII aircraft carrier had an angled and straight flight deck (runways). Those were developed in the 1950s. One Is for launching aircraft and the other for recovering aircraft ( the ship turns into the wind when it's launching aircraft)
1953 USS Antietam was the first US carrier to have an angled deck
It also turns into the wind when it is recovering aircraft as well. Carriers will also launch & recover aircraft at the same time.
And still the angled deck has nothing to do with landing into the wind. The angled deck simply provides a means for aircraft to take off again if they do not connect with the arresting wires.
@@jebr055 they call it bolter on a carrier.
14:15 This is incorrect. There are hundreds of airports in the U.S. ALONE that are single, dual, or even triple runways with the same headings. Los Angeles International Airport - KLAX - has FOUR parallel runways only. The one closest to my house - KHEF in Manassas VA - has only two runways and those runways are parallel to each other with one labeled 16L/34R and the other labeled 16R/34L. At Manassas Regional Airport, regardless of the relative wind, you only have ~160 degrees magnetic or the reciprocal ~340 degrees magnetic to choose from when taking off/landing.
The wing tip doesn't produce little turbulent eddys, it produces one big vortex that rotates around the tip. Air above rotates from outside to inside into the downwash that is producing the lift. The winglets manipulate the vortex to get a little less drag.
the explanation with bernoulli and the distances is actually not right
Actually the principle is correct, with an incorrect base, but the principle still applies. You clearly do not work in aviation.
Equal transit time applies to the flow around a body generating no lift, but there is no physical principle that requires equal transit time in cases of bodies generating lift. In fact, theory predicts - and experiments confirm - that the air traverses the top surface of a body experiencing lift in a shorter time than it traverses the bottom surface; the explanation based on equal transit time is false. While the equal-time explanation is false, it is not the Bernoulli principle that is false, because this principle is well established; Bernoulli's equation is used correctly in common mathematical treatments of aerodynamic lift.
I remember when the Australians blew away the competition in the Americas Cup when the put a wing on the keel of their sailboat. It was awesome! It had enough lift to get the hull up and reduce the amount of drag on the water significantly.
I am an airplane model maker. I have been ever since I was 8 years old. I love airplanes so much that each time one is flying over I have to look up. Such wonderful machines.
I get C-130 Hercules planes fly over my house regularly. I’ll run outside every time to see it.
The downwash at the back of the aero-foil is also a factor. There is an MIT lecture on TH-cam that says this is MORE important than the Bernoulli related pressure differential.
This is the correct response. It's not just more important, downwash is THE explanation for lift. Bernoulli's Principal is a very common misconception.
@@SpiaggiaVita yes, aerofoil lift is one of the most misunderstood things in common people and even among teachers
@@SpiaggiaVita
The downwash generates a sliver of the total lift of an airfoil.
The test for this is simple to demonstrate in a wind tunnel; it’s actually one of the first uses of wind tunnels I used in aerodynamics for my aeronautical engineering degree.
Create a flat plate which spans the width of the test section and the full length of the test section and set to zero angle of attack. Add a curved upper surface at the center of the plate. At zero angle of attack, the plate will generate lift, even though the airstream isn’t deflected down.
@@A_J502 do you have a link to a video demonstrating this?
What you described sounds like a closed system, which is where Bernoulli's principle does actually take effect.
@@SpiaggiaVita
Closed system only depends on where you draw the system boundaries. Also, the Bernoulli effect isn’t limited to closed systems, so that critique is useless.
I know at my airport in the north central part of the country our wind directions are usually northwest and south. I think that covers the 30 degrees Neil was taking about. Great information.
I worked at McDonald Douglas as an engineer building airplanes. I still question the Bernoulli Effect.
As you should, it doesn't explain lift.
You do question the Equal Transit Time fallacy. That is. a wrong assumption. The Bernoulli Effect is part of the lift phenomenom, but not as wrongly described here.
@@SpiaggiaVita
If the Bernoulli effect doesn’t define lift, why is it almost universally used correctly in design, testing, prediction, and validation of aircraft designs?
@@robertcain3426
You have to blow FASTER on the bottom because the reaction is so weak.
Fighter jets show how ineffective deflecting air with symmetrical airfoils is.
Fighter jets require much more wing area, speed, and additional control surfaces to produce lift. Curved airfoils are vastly more efficient and effective at producing lift which is exactly why more cambered wings are used in the vast majority of fixed wing and rotary wing aircraft.
@@A_J502 Yes, I was confusing a foiled wing with Bernoulli's principle, since a asymetrically foiled wing is merely an example of Bernoulli's principle. And, rather, asymmetrically foiled wings are an attempt to achieve a level of Bernoulli's principle without an angle of attack. Whereas, flat or symmetrical wings of a jet fighter produce the Bernoulli effect by means of an angle of attack. While lift and diving depends on the Bernoulli principle, level flight does not. Level flight of a flat or symmetrical wing will, having no pressure differential between upper and lower wing surfaces, would, if not for the effect of gravity, fly on an unchanged level path. Thanks for your comment. I find it stimulating.
Hey Neil,
Loved how you highlighted the variation of the airplane wing as you move from the fuselage to the tip.
In Structural Engineering will call that a structure a CANTILEVER. It experience maximum Bending Moment and Shear Forces at the support i.e. its connection with fuselage and ZERO of them at the tip.
All those disturbing forcesmust be less than the strength of the material and joints by a certain margin called Safety Factor.This explains your strength highlight.
I'm interested by the DRAG caused by Turbulence.Will research more on this
I so admire - and envy, you folks who are engineers and actually have studied and really understand aeronautics and aviation. I was just today during dinner talking about this subject - how in the heck can the planes + people + fuel + my suitcases (especially on the return trip. 😳 ) become airborne and remain airborne??
Can you explain Dunning Kruger effect on next video pls?
Does he know enough to???
The issue with the wing-tip vortices is NOT the turbulence.
Neil,
Your explanation of the Bernoulli Principle is exactly the same as my very inspirational 5th grade teacher gave. He was probably a large part of the reason I'm in the 36th + year of a career as an aeronautical engineer. However, as many years ago it still leaves me wondering why does the air passing over the top of the wing "feel" compelled to meet up with the air passing over the bottom of the wing? As other commenters have pointed out,the parcel air moving over the top actually tends to reach the rear of the wing even faster than the parcel of air moving across the bottom. Why is this? The reason is air is incredibly viscous or "sticky" if you will. Have you ever tried to get air off of you? Try running your hand at an angle through water. The air sucks down to fill the void behind your hand. The same thing happens with the curved upper wing surface or even a flat plane traveling at an angle though the air (this is why aircraft can fly upside down) . The air tries to fill the void cause by the upper surface of the wing moving downward and not only speeds up, it also gains a downward momentum. This together with the Bernoulli Principle is what generates lift. If you have ever seen older jet aircraft, that generate soot in the exhaust, in level flight, you can see that the air trailing the aircraft is moving downward. As an aside, it must be nice traveling first class and getting hot meals. It's been many years since those of us in steerage have gotten a hot meal.
It is not the viscosity of the air, it's the mass. Lift is the Newtonian reaction to the accelleration of air downward, which is proportional to the ANGLE of ATTACK. The only reason that aircraft wings have thickness is to acccommodate the spar and maybe some fuel tanks. Bernoulli has very little to do with it!
@@rsteeb
Then why is the Bernoulli effect and derived equations for lift almost always valid?
@@A_J502 Then why do aircraft flying inverted use different "laws of physics"?
@@rsteeb
Aircraft flying upside down don’t use different laws of physics. For most aircraft, the wings have a positive camber (greater curve across the upper surface relative to a line from the leading edge to the trailing edge).
A positive cambered airfoil will need a greater angle of attack when flying upside down than when right side up.
@@A_J502 And the only reason wings have thickness is to accommodate the spar and possibly fuel tanks. Lift is newton's third law in action, full stop.
loved the "adding angle to each other" expression for the runaways.
The parcel staying together is wrong.
When you see the bernulli effect on a wing, an upward force has already occurred caused by a downward one.
Doctor, Could you please do a video explaining how sail ships could travel "into" the wind.
For someone like me, it's mind-boggling that people could sail around the world in any direction regardless of the wind for centuries propelled by the wind caught by a bunch of sails tied to giant wooden masts.
It's impossible to sail directly, head first, straight on, in to the wind. A sail is used to push the boat at an angle offset of the wind direction. The ships captain will take that heading for a bit, then switch to another heading that. And then changes in a bit. More or less zig zapping towards their destination.
To travel directly into the wind is impossible, it's called "being in irons", once you fall off to either side your sails will fill(at different angles depending on the vessel in question), this position is called "close hauled(tight to the centre)". In this position your power from those sails is between 70-90° off dead ahead, this would obviously make you go sideways, except you have a keel in the water and it is performing the opposite effect under water, the combination of these two forces leaves you with a net effect of only forward motion, it's the slowest point of sail due to these confronting forces but at least you can get where you need to go. I hope this helps
Here in 🇳🇿, many years ago, there was a guy in the Bay of Islands somewhere who built a boat with a windmill on it, connected to drive the propeller. He could turn the windmill any which way, so it was always facing into the wind no matter which way the boat was steered.
Then the question was asked: could he sail straight up 12 o’clock _into_ the wind, powered only by the wind?
And the answer was yes, he could.
Modern racing sailboats can sail to approximately 22° apparent wind angle before stalling.
@@rudbeckia885
The Americas are closer to 15° now, it's incredibly really
I always thought Venturi poked holes in the Bernoulli principle! 🛩️
(I’ll see myself out)
Great content as usual!
I believe aircraft carriers have two runways, not for takeoff options as Neil described here, but because they serve different functions. One is for take off and the ship merely changes course to face the wind for optimal conditions, while the other is for landing while allowing it to point away from the ship in the event of a failed landing.
Small nit-pic about the aircraft carriers, because I work on one (USS Hornet CV-12). The 24 Essex class carriers built during WWII were all built with straight decks, and were all converted to angled deck carriers in the '50's (SCB-125 program), and it was the Forestal class starting in the mid '50's that were the first carries built from scratch with an angled deck. Before the introduction of the angle (a British invention actually), the planes would land in the same direction they took off, and the pilot hoped he hit the arresting wires because, if he missed, there would be a barricade to catch him, and that would hurt (the pilot, and the plane). If he missed that, the only other thing to stop him would be the other planes parked on the front of the deck. By converting to an angled deck, you land on the angle and take off and the straight part up front. That way, if you miss your arresting wire, you can still go around and try again. It has nothing to the wind over the deck. Because the aircraft carrier is a boat, and it's operating in the middle of the ocean, it can always move and make its own wind (30-ish knots), and it doesn't matter in that case what breezes are coming off the ocean. The ship can always turn into the wind if necessary.
Another interesting piece of equipment is the catapult on the carries. The older Essex class used hydraulics, the newer super carriers used steam, and the newest Ford Class uses EMALS (electromagnetic). Amazing systems.
A couple of syllabus words we use in pilot training.
Rear Horizontal tail wing: elevator
- except delta wings (Concorde)
Pitch / pitch changes: Angle of attack.
Rear vertical wing: vertical rudder
Rear vertical wing controls yaw (crosswind)
Cruise flight is when Bernoulli law is most effective.
Angle of attack AoA (pitch) is directly proportional to minimal takeoff and landing lift performance / airspeed of an aircraft wing design.
Have a nice flight ✈️.
Delta wings: “elevons” (combination elevator/ailerons).
Ever flown a wingless aeroplane? “Lifting body”.
Doug,
Those details are BIG hints that he's not up to speed elsewhere. In other words: Unfortunately, he also got the whole lift explanation wrong. Too bad Neil has repeated common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert. This video is EXTREMELY disappointing.
..
If you're going to provide corrections get them right:
.
There is a "vertical stabilizer" and a rudder (in it's rear).
Lift occurs for the same physics at all times. It is NOT changing from "Bernoulli" to something else. To be blunt: Neil is wrong!
Correct term is vertical stabilizer for the fixed part and rudder for the moving vertical part.
Correction needed: AoA and pitch are not the same concept. A wing can stall at any pitch attitude, but only one critical angle of attack. Also, you seem to be confusing the horizontal and vertical stabilizers with the control surfaces mounted on them: elevator (horizontal) and rudder (vertical).
Wow. Ace Trucking Company explaining flight.
One small correction on aircraft carriers. They have angled decks so planes can be taking off and landing at the same time. The ship always turns into the wind plus makes more wind from the speed of the ship.
That and safety. An airplane that misses off an angled deck is less likely to hit aircraft parked.
I figured some people would make a comment on this. Thanks!
5:04 I'm sorry but the way Neil's nose props up everytime he blew on that paper keeps cracking me up 😭😭😭
To fly, all you need is enough "angle of attack" and enough force. The shape of the plane is just to reduce drag. You could turn a grand piano upside down and make it fly with enough angle and power, since it has has the same "wing loading" (psi) as a 747, if you calculate the weight divided by the lifting area.!
Also the "rear wing" is upside down. Pushes the tail down to lift the nose. Also the safest seat on the plant!
Got the draG part down
👇
👠📿💃😔
Brute force and ignorance will make a piano fly, but can you keep it flying? Yes planes are shaped to lower drag, but there's much more to the shapes than that. Flying with stability and control involves tiny, subtle manipulations of the air flow that are easily overlooked by the casual observer. Making a plane that goes straight without constant input from the pilot, and then turns on command without going wildly out of control is not a trivial task. The engineers who figure these things out are brilliant. The more you learn about how these things work, the more impressed you'll be.
Arthur Weasley would love this video. 😅😅
Aaaahhhh dang it Neil!!! You propagated the stall "speed" myth!!!! An airfoil can stall at ANY airspeed!!! Airspeed is at best indirectly related, and the traditional means of anticipating an aerodynamic stall. An airfoil stalls when the angle of the wind flowing over the airfoil exceeds that airfoil's critical angle of attack.
I know, this is meant for the laymen, but this is YOU, Neil! You do stuff right!!!
Neil very often gets stuff wrong.
Neil is professor we never had 😢😢 thank you sir for all those learning, totaly free ❤
Neil and chuck do more for humanity than celebrities could ever entertain.
At least for people who want to continue learning throughout their life.
@@GreenAppelPie well said 👍
Except he got this all wrong...Embarrassing.
For starters, the shape of the wing has to angularly accelerate the air around the leading edge.
I learned hard and I laughed hard. God bless Neil and Chuck for all these videos.
I like this natural laughter and the whole video is entertaining while it shares some good knowledge !
As a kid in school I've learn about that, but it was called Coanda Effect (Henri Coanda - Romanian), based on Bernoulli's Principle.
These are two different things entirely. The Coanda effect is in action when you pour a liquid out of a pitcher, and it sticks to the side rather than flowing freely over the edge of the spout. This fluid redirection is how wings create downwash, which then creates a lifting force on the wing. Bernoulli's Principle is almost completely irrelevant in terms of the amount of lift it generates.
@@SpiaggiaVita What Tyson did with the paper IS the Coanda effect. It has NOTHING to do with Bernoulli. Aurassh is correct (except for the "based on" part. That part is nonsense).
You guys are so fun together. You always make me smile. Thanks !!
Thanks Neil and Chuck for a great explainer video. I always learn something new each time I watch a new video. Plus I enjoy the process of learning it with the added touch of humor. Happy 2023 to both you and your families. I would love for you to do a explainer video on the stealth technology if you could. Those aircraft are so awesome and, at the same moment, so weird.
Informative and entertaining. That's a very difficult combination. God bless you Mr. Neil deGrasse Tyson.
88 keys. 88 constellations. 88 mph.. It makes sense.
(I remember that talk
With Dr. NGT, I am always learning something new and 😂 at the same time. Tks doc and Chuck!
I use to work at O'Hare airport for 2 years on the runway.. airplane ✈️ are awesome and so is this video
WHAT WAS THE GLIDER QUESTION??? Absolutely love Star Talk
One basic rule in aviation: Takeoffs are optional - landings are mandatory.
RIP TAKE OFF.
🕊
Billy Connolly tells of the time he was in the Territorials, as a parachutist. He actually made his first six trips in an aircraft without ever experiencing a landing, because he jumped out every time.
When I was a jet engine mechanic instructor in the Air Force, I used an interesting demonstration of the Bernoulli Principle. Take a spool of thread that has a hole through the spool. Then take a piece of cardboard, I would use one cut out as a disk. Then put a thumbtack in the middle of the disk. Place the disk with the thumbtack facing up into the center of the hole of the spool. Hold the cardboard up to the spool until you start blowing into the hole. Once you start to blow into the spool, you can take your hand away from the disk. No matter how hard you blow into the spool, the disk will stay up against the spool
Love this video guys! The super interesting science, the humour and now I will appreciate flying home for Christmas even more. Maybe I won't even complain about the salad 😁
I would add something that was beaten into my head by my flight instructors. A planes wing will stall at any speed and attitude. Stall occurs when the critical angle of attack to the relative wind is exceeded.
Both you guy's are amazing, I always learn so much from the both of you. Keep up the great work, keep safe. Looking forward for the next video.
Neil, words from a big admirer and almost 20 years commercial pilot, this is the first time I can fell this is not your area of expertise! Just to add more knowledge to the video.
The two effects that generate lift are: Bernoulli effect and downdraft effect. Contrary to intuition, it is not the air “hitting” the wing at an angle that pushes the wing upwards but the deflection of the airmass downwards (action-reaction Newton’s third law).
The other part about runways, already partially commented, majority of airports in the world have only one runway tarmac. The motivation of airports behind the construction of two or more runways is just the improved management of traffic flow for improved number of takeoff and landings per minute.
Regarding the headwind/tailwind component, a single runway will do just fine since at any wind direction there will always be a headwind vector component for either one direction or the other. Worst case scenario the wind component vector will be fully crossed which is acceptable to a certain specific value for each aircraft. Additionally, airliners can normally accept up to 10-15 kt tailwind component.
Finally, as already mentioned by other follower, runways are built based on the predominant statistical wind. This will even be restricted by the local geography that can force runway constructions where the predominant statistical wind will be crosswind.
Thanks for the channel, really educational. You are a great science communicator !
I should have read your reply before adding my own.
Aerodynamics is complicated. Many factors go into make things 'fly'. The choice of how simple an explanation is offered often depends on the target audience. Personally, I'm a newly converted fan of the Coanda effect--another oversimplification perhaps.
As an avid flight simmer, this video was pretty informational thank you so much 🧡
Lift is created by the shape of the aircraft creating differences in pressure between the top and bottom surfaces of the aircraft.
Lift is created by asymmetry, which is also controlled by angle of attack.
I have always found it hard to accept it’s the Bernoulli, I think its fundamentally the Newtonian(Law 3) that’s why planes can actually fly upside down, otherwise the Bernoulli cannot make that happen.
Yes that's what he says half way through.
BINGO. Using Bernoulli to explain lift really chaps my hide...
Planes flying upside down still produce lift due to positive angle of attack.
Mainly it’s conservation of momentum: push the air down, the vehicle goes up.
there are 2 parts to lift. 1 is newton but second parts is preassure differential- But it is not caused by the bernoulli effect but rather because air moving in a curve creates a pressure diff.
One issue... If 2 adjacent air molecules are separated vertically by the leading edge of a wing, there is no reason for them to meet up at the trailing edge. The idea that one must move faster over the wing to cover the longer distance in the same span of time, is flawed, because there's no reason for the 2 molecules to take the same amount of time to reach the trailing edge. The air over the wing moves faster than the air under the wing, due to the shape of the wing, not due to needing to travel farther in the same time. Nothing is forcing them to reach the trailing edge at the same time. The upper flow's time from leading edge to trailing edge is independent from the lower flow's time.
Air doesn't "want" anything. It doesn't stay as one parcel when it's disturbed by having a wing pass through it. The wing's shape & angle disturbs the overflow differently than the underflow. If 2 molecules are adjacent at the leading edge and one goes under & the other over, the one that goes over reaches the trailing edge first, because the wing shape speeds it up relative to the air passing under. They don't reunite.
Correct. Air only 'want's to obey Newton's laws.
The two parcels that join at the trailing edge started in different locations before the wing arrived. They are" total strangers".
..
This actually hurts to listen to. This is still here and it is still WRONG!.
This explanation is NOT correct .It is the most common misconception repeated over and over by amateurs. This is EXTREMELY embarrassing.
.
This story relies on several fallacies, not just one ! This is a long-ago disproved fallacy!
.
1- The upper and lower air parcels do not rejoin behind the wing.
2- Path length is irrelevant. A flat or inverted wing uses the same physics.
3- Fast air does not have lower pressure. Blown air is AT atmospheric Pressure.
4- Air speed along a surface is irrelevant to Bernoulli. Bernoulli is about Acceleration.
.
Neil is clearly out of his element and has repeated nothing but common misconceptions and made some new ones. He needs to have a serious talk with a fluid dynamics expert.
..
Neil's BA in physics has failed completely.
This explanation is the worst one of all the other poor ones repeated over and over.
To see it all spelled out step-by-step, please see this:
. . rxesywwbdscllwpn.quora.com/
The rearward acceleration above the wing is CAUSED BY the lower pressure - just as the decrease in speed below is caused by the higher pressure there. This video is terrible and the absolute worst of the three major misconceptions being spread around by well meaning, but ignorant people. .
..
I've outlined the errors in other comments. This is so sad and terrible - he is completely out of his element.
In short: The inertia of air approaching the lower surface resists being pushed down which is the CAUSE of the pressure increase.
Above the wing, air's inertia has the converse effect because the inertia works against atmospheric pressure, thus reducing the pressure above.
People, with good intentions, don't understand and never see inertia as significant and come up with these incorrect explanations.
Understanding Aerodynamic lift Correctly: rxesywwbdscllwpn.quora.com/
Neil has another about a month later, about the direction to the sun that is also completely wrong. He's lost it.
The reason for different runways is NOT so you can take off into the wind!!! It is so you don’t have crosswind.
Or both.
Wow, as an engineer in aerospace & RC plane builder, I love this episode.
But, I gotta go down the rabbit hole about NdT ROTFL with Nice's "Johnson" remark (after the 7 min. mark). Chuck wasn't aware about the old "My name is Raymond Jay Jonah Johnson Junior" skit, that was part of the short-lived Redd Foxx Variety Show (No, I don't mean "Sanford & Son".) On his show, Redd Foxx introduced to a new generation many old comedians from radio and vaudeville days. (Being seen nationwide revitalized a lot of these actors' careers to go on to other shows and commercials afterwards.) The gag on the show was if someone said "Johnson", comedian Bill Saluga would suddenly show up saying "Ya doesn hav ta call me Johnson..." and go into a non-stop monologe of his full name and all it's permutations. It's funny as heck when I first saw it as a kid, and I still have it memorized!
I come for the science, I stay for the off-tangent stuff.
I went to the Navy jet engine mech school in Millington, TN in the '70s, and was authoritatively told to ignore all that: planes fly because the wings push the air down
I think that’s a better explanation. If the shape of wings is what caused most of the lift, then airplanes couldn’t fly upside down, which many airplanes clearly can.
@@truejim Also there are aircraft with flat wings, including paper airplanes.
Precisely,
Wings produce lift UPWARDS. The reaction force of the air pushed downwards is nowhere near enough to create the lift measured and verified with the equation of lift which uses Bernoulli equation.
@@A_J502 What is your explanation as to how wings create lift?
Just awesome 👏🏾👏🏾👏🏾
Stalling is NOT to do with speed, but with AOA.
I have seen many videos that say it is either one effect or the other. This video makes it make so much more sense. Thank you
Yo wud up geeks 🤓
As a kid growing up in the 60's and making paper aeroplanes (Concord style), I'd just like to say that I was the first to discover the turned up or down tip on the end of the wings. The plane flew very straight and level and stayed in the air much much longer than all the others.
Kelsey at 74Gear is a great pilot here on TH-cam that can explain more about this if you are interested.
He got a shout out from one of the TH-cam creator's so you know his content is lit.
Kelsey is great. For the physics, I tend to go to Mentour Pilot - he knows his stuff.
@@ohheyitskevinc oh yeah... He's a great recommendation as well.
Thanks for adding him to the list.
Really awesome explanation! Would appreciate some visuals as well so that we can visualise it correctly.
Is it 100% Wrong! Except the part about lift being the Top-Bottom pressure difference. . .
It is the worst of the common wrong explanations.
Neil deGrasse Tyson: Jack of all trades, master of none.
jack of no trades. master of none.
I saw a paper recently that claimed we are very wrong about where lift comes from. While bernoulli principle is always necessary for lift most of it comes from the force of fast moving air acting on the wing's surface.
Don't forget the upward tilt of the wing relative to the fuselage called the dihedral which also aides in reducing the drag on the wing. Paper airplanes tend to have that dihedral as a part of the folding of the paper. As a kid (60 years ago) I instinctively added a small wiglet at the tips of my model airplanes thinking I was adding the "missing" tail fin not knowing I was adding the turbulence dissipation winglet as well. Also if you watch them in flight many birds have this winglet in their wings when the tip feathers bend upward.
Wing dihedral generally affects aircraft stability. It does not reduce drag.
Dihedral counters the effects of the dutch roll. Which as @WarHoover said, improves stability and the tendency of an airplane to return to a wings level attitude when disrupted.
All my paper airplanes were basically delta wing. I don't know how much good winglets would do on a delta wing. Pretty much the only place to fold the wingtip up into a winglet is where the wingtip IS, back by the trailing edge. By the time the air gets that far back, it has already flowed over 90% or more of the wing surface. I'd think that any drag-inducing turbulence would already have been created by the time the air gets that far back on the wing. What do you think?
There was an article at Ars Technica just recently about paper gliders and their subtleties. Some interesting aerodynamics going on.
That’s not dihedral and not the purpose of dihedral. I think you are confused.
Bringing tonnes of knowledge is one thing- their laughter is another. Amazing you can have so much fun while discussing serious science topics.
Alas the explanation is incorrect. Flat plates generate lift with equal distance top and bottom. All you have to do to fly is push air down. Then the air pushes you up. It really is that simple. Anything that is flying is pushing air down. Pressure differences (Bernoulli) are a consequence of that fact. They’re not independent- they’re intimately intertwined.
It might be interesting to note that the Bernoulli principle also applies to the sails of sailboats. It is why shaping the sails with spars (masts and booms) and lines (ropes which stretch the sails) is important in maximizing speed.
Sailboat sails operate over a fantastically wide range of speeds (in percentage terms) from their lowest to highest, a much wider range than aircraft. That many aspects of their design were figured out by trial and error "evolution" before advanced modern aerodynamic theory is truly amazing. The ways that their structure allows their shape to be varied and optimized to such a wide range of speeds and angles is amazingly clever. Low speed aerodynamics is it's own fascinating world.
The air actually moves much faster on the suction surface, and the top parcel reaches the trailing edge much faster than the bottom parcel. Using good old Newtonian mechanics as applied to fluid flow, you can calculate the force the wing creates. Bernoulli effect is just a statement of conservation of energy.
Both descriptions are valid descriptions of the flow field, and from both (once a flow field configuration is established) you can deduce that there's a lift force.
But the mechanism that leads to the curved flow field distribution is actually caused by the viscous boundary layer detachment on the trailing edge. Without viscosity there's no such thing as lift (potential flow solution for flow field around airfoil)
Actually I have seen a video on TH-cam of a university professor disproving this. He showed a wind tunnel time lapse of disproving this idea that top parcel of air reaches trailing edge faster than the bottom edge. Overall Bernoulli effect is minimal on flight.
Yeah, nope! There is no magical force pushing the air on the top side of the wing to accelerate back to the trailing edge. On the contrary the air gets shoved more upward than backward as it hits the leading edge. This has been observed in wind tunnels and forms the current models of fluid dynamics.
Mostly about : if I bend the air downwards (over the top) edge of the wing, an equal and opposite force acts on the wing pushing it upwards, and so “lift”. A lot more complicated than this, but Newton is flying the plane, mostly.
@@danalex2991
Explain how a wing in which the top and bottom airstreams produce lift if neither is deflected downward.
I love this segment very entertaining and educational
I'd love to see a whole episode about helicopters (an excuse for Neil to talk about Ingenuity and Dragonfly again.)
Why does the air "want to stay in a single parcel" though? I understand that it gets sped up on top of the wing, but the reason for that speeding up gotta be more feasible than some secret desire of the air.
Inertia.
Pls Google Dunning Kruger.
Nice video, very fun and enjoyable :) Thanks very much!
Bernouilli Effect accounts for ~5% of lift, Angle of Attack 95% (~4% of the axis wing/fuselage), ie Newton's 3rd Law. If not, how to fly inverted? Why do modern fighter jets have almost symmetrical wing profiles? Power/weight ratio so high that BE irrelevant. (Old pilot here).
Finally, some common sense.
You fly inverted with a greater angle of attack, which increases the airflow over the wing and increases the pressure differential. Similiar to normal flight.. Inverted flight doesn't violate Bernoulli..
There no such thing as "bernoulli lift". Lift is only caused by deflection. The equal transit time hypothesis is false. A pressure differential doesn't cause lift, but rather IS lift caused by deflection. An upward force doesn't cause another upward force. Only a downward one does.
Actually the bernoulli effect doesn't cause lift. You only get lift by the work of accelerating air downward. This is the only cause. Likewise, you can't accelerate air downward and not get an upward force. You can't lift yourself up by pulling on yourself, you have contact an outside object.
@@Robert-d5l Right. Bernoulli Effect does reduce air pressure above the wing but it's negligible. Just watch a kid fly an RC plane, wings of flat polystyrene sheet, perfect, no BE...
Learned so much in this
You two, have a wonderful chemistry going on! Thank you for making me laugh! My hubby travelled all over the world, and loves airplanes. I love them too, but am much more anxious than him at takeoff and landing. Your explanations are excellent! I hope more people overcome their fear of flying! I have ❤️
~13:00 Correction - there's not a speed at which a wing stalls, there is an "angle of attack" (AoA - angle that the wing meets the oncoming air) at which it stalls. Having said that, a pilot trying to keep a slowing aeroplane flying at a constant height, will pull back on the control column/joystick further as the 'plane slows, increasing the AoA of the wing in order to maintain the necessary lift (the lift required is the same as the weight of the 'plane). When the wing reaches a critical AoA, (and for a given aeroplane at a set weight this WILL be at a certain airspeed) it will stall, but due to the angle, not the speed. You can actually slow the wing to zero without stalling if you keep it horizontal but you correspondingly don't get any lift!
There's an expression we've all heard: "It's not rocket science"... no, rocket science is a LOT easier to explain - (easy to explain, very difficult to do). With a rocket you just chuck a lot of stuff as fast as possible out the back. But the theories of flight?... mankind has been flying for over a century and there are STILL arguments about how! (I say, "theories" rather than "theory" as there is the theory of low speed flight - as discussed here, - the theory of high-speed flight (approaching the speed of sound) AND the theory of supersonic flight, all with their differences.)
You've opened a can of worms here, Neil.
Neil deGrasse Tyson, utilizing every second of his existence.
🤣 So is everyone else who is productive in life. You better get with it too. Or you will be forgotten forever.
@@BLOXKAFELLARECORDS I get your point, but all of us will be forgotten. I'm already forgotten, thankfully, I can disappear at any moment and only the government will care, since they won't get my $$$ anymore. 👍
@@ranonampangom2185 😂😂 right on brother.
I make music so hopefully my songs play 100 years from now.
#johnnyx100
@@BLOXKAFELLARECORDS Nice. By then we'll need music more than ever before.
Dr. Tyson you are a national treasure. Thank you for these videos.
And thank you to you & Chuck for the laughter.
This is my favorite physics principle every time I travel by air! 😃
Startalk is the best! What was up with the most recent episodes intro? Seemed kinda rushed and jumped right into. The introductions and small talk are important too! Love you guys
Class A science lesson/comic relief. Thank you for the enrichment and the enlightenment. You leave us smarter and happier. That bit about you can call me Ray or you can call me Jay was hilarious. May I be a little maternal with you Mr. Tyson. Please take care of your health and give yourself enough sleep and rest, because we all NEED YOU in our world.
Yes! Please talk more about aviation.
Neil, look up attack angle and coanda effect. Air packets don’t have entanglement where they need to catch up with each other if they’ve been bisected.
Yeah, I was kinda surprised to hear this debunked myth explanation from him
Yes, I was hoping he would debunk this long-lived tale. Sadly, it’s perpetuated instead.
This is correct.
IF Coanda effect is important for lift, how do you account for vortex generators on wingtops?
@@rsteeb literally a 30 second search and read on Wikipedia has the correct answer for wingtip vortices being the result of downwash. If the wing is redirecting air downward, it is easy to see how that would create vortices at the tip of the wing. Pressure has little if anything to do with it.
I finally caught up and now I am watching the latest EXPLAINER
Ty Prof Tyson ❤Science is the best 🔥🔥
No, there isn't little turbulent eddys at the wingtip. There is one big wingtip vortex.