The sweep angle in wings of modern sub-sonic planes has little to nothing to do with supersonic flow. It's the there to avoid aeroelastic divergence. In summary, lift will cause bending and torsion on the wing. As the torsion increases the angle of attack, it increases lift, and that can cause a feedback loop where the wing deforms increasing lift, thus increasing deformation and so on until breaking. Back-swept wings result in negative coupling between bending and torsion on the wing, and so the bending of the wing counteracts the increasing torsion, keeping the angle of attack at safe values. The opposite happens with forward-swept angles, so you would need much stiffer wings to avoid divergence.
You are right, a back-swept wing avoids divergence however I wouldn't say it is the primary reason for it. Divergence is not a big problem as much as flutter and control reversal which occur at lower speeds (before divergence) and a positive sweep angle (back-swept) has a negative impact on control reversal speed.
Lets give credit accordingly. The Germans invented the first Jet fighter called Messerschmitt Me 262 in 1942. They were the ones who discovered the wing design that allowed airplanes to fly faster. I don't have any admiration for Nazi German but many inventions were appropriated by allies engineers that later took credit by things that the Germans developed. It is sad but war is the motivation for technological advance still today.
+Yousef Zidane actually there are many cases where messerschmitts, spitfires and other aircrafts broke the sound barrier during dives, or almost near mach 1. the thing was to still have control of your aircraft during the dive.
The British had the first fighter in the gloster meteor. Germans had first front line fighter . The meteor was slower but could turn , roll and accelerate faster.
Same principles apply on a forward swept wing, only the sideways moving air in front of the wing is somewhat decreased, which increases the efficiency. However, on a forward swept wing there is a lot of stress on the outer tip of the wing (especially on the front of the outer tip) which demands foe strengthening that part, which is quite difficult, because that part of the wing is the weakest part of the wing on a normal swept wing. The Germans actually tried out forward swept wings in 1944 on one of the arados which resuktet in a weird upward-bending wingtip. Of cource there are modern jets that have forward swept wings, but somehow they don't perform as good as the others.
This really is an incredible video for engineering students in the field of aeronautics. Its so quick and succinct while bringing forth some critical concepts in an easy to understand method.
This isn't how swept wings work. Spanwise flow is undesirable in any wing--of which straight wings certainly are subject to. Look at all of the aircraft--both straight wing & swept wing--that use wing fences, vortilons, dog toothed leading edges, and other devices to PREVENT spanwise flow. What a swept wing does is allow you to make a thinner effective airfoil (because the airflow is going over the wing in the direction of the undisturbed air--rather than perpendicular to the wing) without the structural challenges of making a thin airfoil.
Bartonovich, That is the way I learned it also. I do not know if you have seen the Mach effect on a wing in flight. It appears as a shadow on the wing at the thickest area. The sun has to be at the correct angle. The Mach shock wave causes the shadow. On a B707 this starts about .82 Mach. The aircraft has Mach trim to counteract the nose down that would occur as that lift is forward of The CG.
1:20 , i think the lift is reduced on the tail wing (elevator) due to a downwash decrease caused by the center of pressure and shockwaves moving backward (Mack Tuck)
+Michael Beverly My thought exactly, but I just read the 262 had swept wings to accommodate heavier-than-anticipated engines, which required a shift in CoG. This was made by sweeping the wings, but the Germans had also unwittingly improved aerodynamic performance at high speed too :)
+piloteer Not unwittingly, in the sense that they knew that adding sweep should also improve performance. The high-speed versions HG2 / HG3 had much larger sweep angles of 35 / 45 degrees only for aerodynamic reasons.
Ah okay - I read that on the initial model, the sweep was purely to alter the CoG and didn't achieve any significant performance otherwise, as it may have done on subsequent models. That's just what Wikipedia says :)
You seem to have done a lot to ignore non-American advances in high speed flight. For example a little mention that "it was based on a German prototype" ignores the huge, massive advances Germany made during WW2 to culminate in swept wing planes in production and in combat during the war. The Bell X1 I could forgive you for, as people seem to constantly recite the American suggestion that it was America breaking the pattern. The reality is that the vast majority of the science and technology behind breaking the speed of sound came from Britain who were conducting similar tests. The British gave that data to the Americans on the promise that America would fund the tests (everyone else who participated in WW2 was incredibly poor at the time) and that America would use the mass of British technology in those tests, break the sound barrier, and give Britain the technology discovered by the X-1 tests. Well the X-1 broke the sound barrier and America said "thanks, bye" essentially. The irony being Britain was so close to breaking the sound barrier at the time, and the biggest and most important keys America lacked in breaking the sound barrier were discovered by Britain a long time ago, comparatively speaking. So yes America broke the sound barrier, but Britain discovered how it was done, invented the use of the all-moving tail surface with regards to Mach 1 speeds, and generally gave America an absolute shit load of help in breaking that magic number. So sure, America has done a lot to advance flight technology after the 50s, but please don't ignore the advances made by everyone else. This was a triumph of all of mankind's ingenuity, not of America alone. And truth be told, America was stuck in a rut regarding all of its military technology in the 50s. Air, land, and though admittedly they were doing great as far as naval was going that too was beginning to stagnate mid 50's. Its up for debate why, possibly because the people in power were all too old and resistant to change, I personally believe its because the rest of the world was at war and improvement was a necessity. This is all too evident when Russia is concerned who completely revolutionised the ground war in response to German attacks, and quite frankly a large part of what they learnt is still in use today, at least in the broad strokes.
The Су-47 Беркут says: "fuck that i'm gonna have forward swept wings." Also your videos are great. Are you going to be focused mainly on aerospace engineering in your videos? Because i like that.
That's cool, thanks. Subscribed. I learned a lot of interesting stuff about aviation through flight simulators like IL sturmovik 1946 and the DCS modules. The P-38 control surface lock during transonic speeds was one of them. Keep it up.
That does make me wonder. Obviously there are both real-world and fictional examples of planes with forward swept wings, but they are rare. (even more so than pusher prop aircraft) The question arises though, what are the upsides and downsides of a forward swept wing, and why are they not used much? (Is there an obvious downside, or is it just not fashionable?)
The tips of a forward-swept wing can twist upwards, increasing the angle at which the tips hit the air and twisting it even more up to the point of structural failure. I'd recommend you do your own research and take my words with a grain of salt, as i'm not exactly an aerospace engineer.
The Gemans' were the first to use swept back wing. When a Scientist noticed the angle that the water came off the stern of a ferry . He used everyday to go to school when he was a child . He used this angle to help to solve the problem of highspeed flight . Messerschmitt Me 163 being one of the first to it.
I like this channel and watched your videos with great interest. Unfortunatly this design wasn't developed by Americans but by Germans who reached +1000 km/h in 1944 with the Me 163. The engineer of this plane was Alexander Lippisch who was brought to the States and helped the USAF to develope its inmature technical unnderstanding of avionics close to the sound barriere. The german engineers where aware of these effects since at least 1934, this is why the Ju 87 already had a dive break to reduce speed and avoid the effect of shockwaves.
+Smartuy +Smartuy I am praying to every deity conceived by humanity that you are a troll... "the Me-262 did not have swept wings"? You have to be joking... Also, do consider a name change.
The 262s wings were only angled to change the centre of lift to compensate for the change in centre of gravity due to the installation of heavier engines. The DC-3 was similarly modified--in 1935.
Nice informative video. Although not related to swept wings, one key invention that made the Bell X-1 controllable was the all moving stabilizer. These are now standard on every aircraft that flies near or above Mach speeds.
+Real Engineering Would be awesome if you also made a video about the pros and cons of swept forward wing designs as well (SU 47 Berkut, Grumman X 29, etc.)
+Real Engineering Please make more videos. Your research and information is so informative and intersting. Thank you for making such a channel and putting time into it for us :D
No it goes slightly further back than that. One of the first documented inventors of the swept wing was a fellow Irish man called William Dunne, but he invented it for different reasons. He invented it for longitudinal stability
Yes, but the video does not explain why the passenger planes, which fly at normal subsonic speed, need those wings Today the planes are needed these wings to be efficient, but it is interesting as it has developed historically
Passenger planes still fly pretty close to 400 knots (about 800kph) which is way faster than the p38 lightning. Also they reduce drag and are generally more efficient.
All modern passenger jets fly at transonic speeds, in other words, above their critical mach number. Part of the airflow over the wing is supersonic and therefore a shockwave does exist. Sometimes you can even see the wave as a weird refraction of light just above the wing if you are lucky and sitting in a window seat near the wing. I've seen it on Airbus A330. Swept wing not only delays the onset of the shock wave (= increases critical mach number) but also makes the shockwave less severe, allowing the aircraft to be accelerated further into the transonic speed range without suffering too much drag or other undesirable effects of the shockwave.
You might want to do some research... Look up "transonic" in Wikipedia. The oversimplified explanations of the challenges of high speed flight have led a lot of people (including many professional pilots) to believe that the critical Mach is something so "critical" that you must not ever reach it... without realising that we fly above it all the time. Actually we almost never cruise below it! The whole foundation of the design of modern jets is flying safely and effectively in the transonic speed range.
What? Who? How? What do you mean? Now I'm confused. :D But I'm not confusing the speed concepts. IAS has nothing to do with this, what matters is the Mach number.
00PiggyCosmonaut I'm pretty sure the video was clear on how the American engineers learned the swept wing from the captured German planes. So what do you mean by "same way?"
teitake Well first the Germans studied in wind tunnel tests, and that's how they figured it out. Then the Americans found out about it. They used wind tunnel tests to figure out WHY it helped. He kind of explains that in the video, but not to much.
00PiggyCosmonaut It's typical of Discovery Channel but it's too America-centric to me. The important research had been done in German with regard to the topic of the video but they just skimmed over. Very disappointing.
In the mid 80s I had a field trip to a nearby Air Force base where I asked one of the airmen why some planes have straighter wings and some have very angled wings. Airman: _"You know how when you're running down the hall with your arms out straight, then you put your arms back and you go faster?"_ Me: _"No 🤨"_ . I'm starting to suspect he didn't actually know...
+methanbreather Makes you wonder why the Americans took so many German engineers and all the German research into swept wings? Why would the US need it if they knew everything already?
+methanbreather Makes you wonder why the Americans took so many German engineers and all the German research into swept wings? Why would the US need it if they knew everything already?
They did - but not because of any transonic or supersonic requirements. With the 262 it was in order to maintain the centre of lift and gravity of the aircraft within tolerable bounds. The 163 was tailless, so needed sweepback to retain longtitudinal stability. Just because an aeroplane has swept back wings does not imply that the sweepback has been put there to enable it to go faster than sound. The De Havilland Tiger Moth also has swept back wings.
Where the hell is the me 262 from Germany on this list? They had used the swept wing design because it allowed the plane to go faster and solved the issues you stated just a lot sooner than you spoke of in the video.
They did not. The wing was swept on the 262 for the same reason it was swept on the piston engined DC-3 a decade earlier... to move the centre of lift closer to the centre of gravity because of design changes (developing the DC-3 from the DC-2... and installing heavier engines on the 262).
the captured german design is Me. p1101 prototype, 80% complete while captured; it was to be fitted with Hes011 turbojet engine; the Bell X-5 was based on this design.
A good video explaining the mechanics of the swept wing design, but you got your history wrong. During WWII the German engineers were aware of the need and were designing swept wind aircraft during the 40's up to the end of the war. The most famous being the Messerschmitt Me 262, the first practical jet that, while very deadly to Allied bombers, were manufactured in too few a number and too late to affect the outcome of the war.
Just discovered your channel (you are shared by a french new technologies website), and I couldn't stop before watching all your videos, incredible quality here, looking forward to your next contents! Thanks man.
General stability of Dunne's plane design was so good it flew as a pair of swept back wings, only.... no tail at all. It would also allow for totally hands-off flying, which was considered amazing at the time (1912) en.wikipedia.org/wiki/Dunne_D.8 JW Dunne was more famous for his book "An Experiment with Time" which was first published in 1927. It has remained popular, and has never been out of print.
for those of you that dont have time. normal straight wings gives higher lift but more drag (slower) angled wings gives less drag but has lower lift (worse when going slow)
There are so many Irish accents and his 'troo-la-loo-la-le' accent is just silly, I bet probably pronounces Donegal as (Don-A-Gul) instead of the Irish way.
The engineer who worked at the development of the swept-back wing and other features of high subsonic as well as supersonic wings was Adolf Busemann. It was on his calculations that the wings of the Me 262 were based. Imho he would have deserved some mention.
The AN-225s tail is interesting since it’s a swept back but not tapered at all. The non tapered swept back tail is compensated by large rudders/vertical stabilizers that function kinda like huge winglets.
well, actually the wing doesnt just develop lift due to the faster flowing air on the upper side. There is also a waaaay more important thing called circular stream around the wing. The direcion of flow matches on the upper side, wich accelerate the air and goes counterways on the bottom side. This circular stream produces a whirl kinda thing behind the wing, wich actually develops the lift of an airplane. Can u pls correct this? the theory was found out watching planes start in the rain, u could see the whirls behind the wing with bare eyes. This theory is totally approved by now and the basic thing for developing new profiles
That turbulence produced behind the wing is called wake turbulence in a normal plane. For planes like concorde or other planes with delta wing, this vortex is captured and used for lift, but for the average commercial planes, this vortex only adds to the drag, and not lift, which is why devices like winglets and raked wingtips are developed to avoid this vortex.
Circulation is a modeling tool, not a theory of flight. Bernoulli's theorem still explains the physics of flying; circulation reduces a 3D flow calculation to a 2D approximation, so models can be developed & compared MUCH more quickly than CFD or FEA methods.
Thank you for producing this informative video! I'm slightly confused however, about modern jet airlines, which don't fly at supersonic speeds-- are their wings swept back because they still add efficiencies add enough stability even in subsonic flight?
+Victor Chen That is what I explained at 0:50. The plane can develop areas of supersonic flow while travelling at subsonic speeds because the air accelerates over parts of the plane.
You can go supersonic with straight wings. Witness the first plane to break the sound barrier - the Bell X-1. The Lockheed Starfighter famously had pretty straight wings - and was capable of Mach 2. The first rule of making a supersonic wing is make it thin. Sweepback does, of course, help - a lot.
Real Engineering Dude, don't worry about it. Just keep pushing ahead. Little shit like that doesn't diminish your intelligence or ability to grasp larger concepts that a lot of people grapple with. Keep on kicking ass! Subbed.
You should have consulted an aerodynamicist first. Planes haven't flown transonic speeds in decades. THE REAL reason they still sweep the wings back is so they can be much lighter. In a sudden gust or pulling out of a dive, a straight wing, any wing, bends up about the line which is along the centers of lift. This is 1/4 the way back from the leading edge. No matter how much stronger the spar is than the skin, there's always the tendency to twist the wing while it is bending up. On a straight wing, the twist is such as to make the tips twist with increasing alpha; that is more lift than the root. If the plane is above the maneuvering speed, more twist comes with more lift which comes with more twist and so on until one or the other wing breaks off. Below the maneuvering speed, it won't rip the wing off, but one tip will stall before the other and the plane will go out of control. But when the wing is swept back as the wing bends up, the twist is such as to unload the wing. A swept back wing doesn't have to be as strong so it can be allowed to bend 20 feet or more. A straight wing must be made very rigid so it won't even think about twisting. This was discovered way after the transonic advantage the video was about.
+Walter Clark Before you get too pleased with yourself in calling out how "wrong" this video is, let me remind you that *all* jet airliners today cruise at around Mach 0.8-0.9, which is well within the transonic regime. In fact, for classical aerofoil profiles designed with classical incompressible flow theory in mind, the critical Mach number can be as low as 0.6-0.7. Modern wing design manages compressibility effects and its associated drag with a combination of wing sweep and supercritical aerofoil design. *Drag reduction is the primary driver of wing sweep.* The effect that you've written about certainly is true, referring to what is known in the aeronautical engineering field as "static aeroelastic stability". Sweep-back does entail an inherent increase in this form of stability, but this is largely serendipitous. In practice, modern wings are designed far more elegantly by taking advantage of the anisotropic material properties of fibre reinforced plastic composites. This allows the aerodynamicist to concentrate on his work of minimizing drag, while leaving it to the structural and aeroelastics engineers to ensure that the wing is structurally sound.
If you have not already done so, please consider explaning why the canard wing set up (the first to fly under power) has never been adopted for large commercial aircraft in great numbers. Also perhaps comparing it's advantages n disadvantages.
You lost me at "The air over the top of the airfoil accelerates; this is how the wing generates lift"... which is NOT how a wing generates lift. If it was, then you would be able to stand underneath a rotary wing aircraft (ie. helicopter) and there would be almost no air movement. Clearly the lift is generated by pushing the air mass downwards (ie. Newton's Third Law of Motion) and not from any Bernoulli Effect.
Air accelerating over the top of the wing is one way the wing generates lift. It isn't the only way. The way you mentioned is the primary source of lift.
It would be more correct to say it generates a 'trivial amount of lift' - it may as well be zero. But you didn't say that. You said, "This is how the wing generates lift" further extending this daft notion that Bernoulli's Principle is why wings work. :-/
Depending on the airfoil, the Bernoulli effect can generate 5 degrees of angle of attack worth of lift. That is not trivial or daft in any sense. I simplify these videos down to allow them to flow and teach the specific point I am trying to make. Teaching the principles of lift entirely will be saved for another video.
The debate about which of the "effects" "creates" the lift misses the point completely and shows a lack of understanding of physics. Lift is a complicated process and all of the laws of physics apply to all parts of it all the time. You can't cherrypick one of the laws and claim that this law alone is the "explanation". Because lift is so complicated, the best you can do if trying to explain it in simple terms is describe some aspects of it to give at least a rudimentary intuitive understanding of what is going on. In this sense focusing on Newton's 3rd is a lot more meaningful exercise than the ridiculous Bernoulli effect "explanation" which is complete nonsense. Wing pushes the air down, air pushes the wing up. Of course this doesn't explain the how and why it pushes the air down but going into such detail is not possible without having a rather advanced level understanding of physics. There absolute is NOT several "effects" or "ways" in which the wing generates lift. There is only ONE process that cannot be cut into pieces. Newton's 3rd, pressure distribution, speed of the airflow, circulation... these are all aspects of the one and only lift-creating process.
It is true that pressure differentials must be present for lift to happen. However, saying that pressure differentials "cause" lift is just as incorrect (or correct) as saying that the wing pushing air downwards causes lift. It is not meaningful to say that any single aspect of this process "causes" lift. All aspects are integral parts of the process. Actually, it would probably be more meaningful to say that lift causes the pressure differentials! ;-) Imagine two guys fighting over what makes a car move. One claiming that it is the engine, other insisting that it is the tires. Who is right?
I recommend you read "The Simple Science of Flight" by Hendrik Tennekes. You'll find that the Bernoulli effect accounts for only a small percentage of a plane's lift! The vast majority is simply conservation of linear momentum from the wings pushing air downwards while not stalling the airflow (a principle which leads to Bernoulli's effect with some assumptions)
Wing sweep isn't the only factor, aerofoil thickness also plays its part. Those the F-105 was able to fly supersonic with unswept, but tapering wings. Sweep is usually measured not on the leading edge, but on the quarter chord line.
Šimon Hubatka That's what I mean - the traditional explanation doesn't stand up to analysis. A wing can only generate lift by directing part of the airflow downwards = reaction force. Thus it's the angle of attack that generates lift.
Šimon Hubatka Actually I once saw a video of aerodynamicist who explained that the pressure difference is caused by deflection of air. The pressure difference then causes the speed difference in airstream above and below the wing. So the speed difference doesn't actually cause pressure differences, it's the other way around.
Pressure difference and deflection of air are just two ways of describing the same thing. Both are accurate, they're just two different descriptions of the same stuff.
@@S0umin When I was in engineering school studying fluid mechanics we were explicitly told that Bernoulli's principle is an outdated explanation for the cause of lift, and that a reaction force caused from the deflection of air on the lift surface is a more complete explanation. OP seems to understand more than you do......
+Sean Sun Well I hope it helps with the understanding! I have a master's degree in aeronautical engineering. Stability and control subjects are so interesting and a lot more understandable when explained visually.
if you read chuck yeagers book they certainly didn't solve the problems by moving the elevators higher on the tail he almost died due to pitch control failure and was only saved by his training and quick wit when he compensated with manual pitch trim control. the bell xs-1 later corrected those problems.
You forgot like the biggest advantage with the swept wing. They created more stability, making it posible to reduce the size if the rudder, or decrese the minimum landing speed.
Let's not forget Microsoft and the US government. Japan had a vastly superior OS under works, US government went in and threatened the developers via the Japanese government. Development was stopped. Now Americans are going around saying "we invented everything".
There used to be one called the concorde. Technically i guess that you're right because the concorde is no longer in use but there was at one point a passenger jet flying at mach 1+. He has a video on it.
then , though it isn't a civilian machine, the Avro Vulcan was interesting because its wing had varying degrees of sweep depending on the thickness of the wing at any given point...
Why are these important things? Motor cars have devastated the World. There must be more peaceable inventions that are important, like electricity, penicillin, television, fertilisers, vaccination, the pill, computers, the Internet etc.
Amazing content. Just found your channel today and i already watched all your videos, keep up the great work man, and thanks for getting me excited about going into engineering this upcoming year
This may be apocryphal, but I thought the ME 262 had a swept wing because the engines were so big that they needed to move them back to give the pilot a better field of view, unintentionally improving the aircraft's aerodynamic performance in the process.
To be fair, the Me 262 wing sweep had nothing to do with critical Mach or shock waves, but simply with re-positioning the center of lift to accommodate heavier than anticipated engines.
It's interesting that some aeroplanes have swept wings that are very much not super-sonic eg Tiger Moths! (the wings for my 1/6th scale one are propped beside my desk as I type) I don't understand the aerodynamics very well (but I try!) but I understand swept wings simulate dihedral and so add stability to slower aircraft. It seems that is applied to biplanes because the modern Pitts aerobatic biplane has the upper wing slightly swept so that its root can be in front of the cockpit (for pilot upward visibility) whilst the bottom wing has a degree or two of dihedral. So perhaps swept wings weren't discovered after all only when supersonic flight problems were being solved. Thanks for your excellent series of videos
Not a bad video on engineering and aerodynamics trivia. I think it would work even better as an educational video if you addressed, however briefly, the following questions: Why does the air above the wing accelerate? Why does that produce lower pressure and therefore creating lift? What are shockwaves and why do they form at the locations of supersonic flow? Why do shockwaves reduce lift and increase the drag of the wing? Why does airflow separate from the wing at supersonic rather than transsonic speed and why does the shockwave move towards the rear as the speed increases? Why does air in straight wing design only flow parallel to the chord? Why does the span-wise component of the airflow not accelerate? Alas, if your videos are aimed at aviation engineers and physicists who already do understand these concepts, then I guess it's fine. :)
amazing videos and chanel, you made freaking easy to understand very complex things in a such way that even one person wiht no idea about aerodynamics can understand, not anybody can do that you had a unique talent for this, keep going
The F-14 Tomcat has wings that can retract in flight, thus reducing the drag and increasing speed. I used to work on these jets when I was in the Navy.
Thanks to Real engineering ,you certainly contribute to the development of knowledge. Hi Jerry , of course you can get angry but those are the facts. Maybe you did not know that the Mustang P-51, among other aero engineers, constructed also a German who was not a Nazi, because in the United States came as a little child ... you can use google if you want.
There is another reason for swept wing: Stall recovery. With the AOA highest near the body, that part of hte wing will stall first, which leaves the remaining lift further back at the tips of the wings. This causes the nose to drop and the plane to recover from the stall.
This is also why birds, will actually make their wings smaller when diving through the air. You'll notice this if you observe a seagull, or some sort of bird of prey diving through the air at high speed. Their wings are never fully out, they are slightly tucked in, so they have greater flight control at higher speeds.
The Boeing 747 takes advantage of this wing design and the newest version of the 747, the 747-8i flew 12 km/h below the sound barrier on it's test flight. Of course, it used extra powerful engines, but the wing design helped the plane not to be ripped apart at that speed.
Great video, small note: a .50 caliber bullet (not round) can be of many different weights (grains) 655 grain - 800grain. which are identical in diameter but different in length. I wonder exactly which bullet the Bell X-1 was modelled after.
The reason why the Bell X=1 could maintain stable supersonic speed was its variable position horizontal stabilizer originally developed by Miles aircraft M52
There is also a pretty interesting story behind the US development of supersonic control surfaces. If I am remembering correctly, US engineers approached British engineers to have an information swap on supersonic technology. After the British gave their info to the US engineers, the US engineers pulled out of the deal. Pretty messed up.
I believe those flaps in the P-38 you were referring to are called dive flaps or air breaks. I am familiar with glider air breaks which is where I got the name. Not sure if it is the same.
I try to base my videos around a story, rather than just the raw engineering. You have an suggestions there? Why did the forward swept wing come into existence?
Better maneuverability was the reason for a forward swept wing, but it has engineering challenges, under high loads the wing tips bend up causing greater and great lift, carbon fiber fixed greatly alleviated this issue. A Blanik glider uses a forward swept wing, the engineering reason was to help with CG balance issue with a two place glider with one pilot, the forward swept wing moves the CG forward which helps.
Actually wings have different angles at different parts, the wing is twisted and gets straighter towards the plane. This increases speed, efficiency and safety.
Birds sweep their wings backwards when they are facing strong relative windspeed (in wind gusts and/or when diving) or when plunging into the sea. In all cases this is to reduce frontal wing area to minimize drag.
So, if the air traveling over the top going faster is what generates lift, explain symmetric wings. It's the downward flow of air that provides lift, not the flow going over the top of it, in line with Newton's Third Law. If you ever look at the wings of a plane they are angled so that the trailing edge is lower than the leading edge.
Great Work man!! I love your way of laying out the secrets of the craft in such a plain and smooth way, ( I am a fellow Aerospace Engineer), and currently I do teach in an Aviation Academy. I really want you to make a video about the Variable Camber concept, which is achieved in the B-787 through a VCTU (Variable Camber Trim Unit) Thank you.
Actually there is another reason for swept wings. The airplane is more direction-stable, because when it is flying sideways, there is more drag on the wing which is turned to the front, which turns the airplane back in straight flight. It's a bit hard for me to explain because I'm not a native speaker.
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The sweep angle in wings of modern sub-sonic planes has little to nothing to do with supersonic flow. It's the there to avoid aeroelastic divergence. In summary, lift will cause bending and torsion on the wing. As the torsion increases the angle of attack, it increases lift, and that can cause a feedback loop where the wing deforms increasing lift, thus increasing deformation and so on until breaking. Back-swept wings result in negative coupling between bending and torsion on the wing, and so the bending of the wing counteracts the increasing torsion, keeping the angle of attack at safe values. The opposite happens with forward-swept angles, so you would need much stiffer wings to avoid divergence.
That’s also why delta wings are popular. They’re really durable.
You are right, a back-swept wing avoids divergence however I wouldn't say it is the primary reason for it. Divergence is not a big problem as much as flutter and control reversal which occur at lower speeds (before divergence) and a positive sweep angle (back-swept) has a negative impact on control reversal speed.
Wow! So detailed. What did you read Sir, I want to understand this a bit more like you.
Lets give credit accordingly. The Germans invented the first Jet fighter called Messerschmitt Me 262 in 1942. They were the ones who discovered the wing design that allowed airplanes to fly faster. I don't have any admiration for Nazi German but many inventions were appropriated by allies engineers that later took credit by things that the Germans developed. It is sad but war is the motivation for technological advance still today.
the me 262 didn't break the sound barrier though
+Yousef Zidane actually there are many cases where messerschmitts, spitfires and other aircrafts broke the sound barrier during dives, or almost near mach 1. the thing was to still have control of your aircraft during the dive.
Marcos Allendes yeah but i meant not in level flight so the wings being swept back couldnt have been to help with higher speeds
The flying wing was developed by Jack Northrop--among others--well before WWII
The British had the first fighter in the gloster meteor. Germans had first front line fighter . The meteor was slower but could turn , roll and accelerate faster.
What about Forward-swept wings? can you make a video?
Same principles apply on a forward swept wing, only the sideways moving air in front of the wing is somewhat decreased, which increases the efficiency. However, on a forward swept wing there is a lot of stress on the outer tip of the wing (especially on the front of the outer tip) which demands foe strengthening that part, which is quite difficult, because that part of the wing is the weakest part of the wing on a normal swept wing. The Germans actually tried out forward swept wings in 1944 on one of the arados which resuktet in a weird upward-bending wingtip. Of cource there are modern jets that have forward swept wings, but somehow they don't perform as good as the others.
+St0RM33 Emm, that would give the plane more manuvarbiliy *IF* it the wings are at the correct spot for the center of mass.
+St0RM33 This is why fighter jets *normally* place their wings more at the front/center-of-mass
The x-29 is an example of forward swept wings
*Cough* Su-47 *Cough*
This really is an incredible video for engineering students in the field of aeronautics. Its so quick and succinct while bringing forth some critical concepts in an easy to understand method.
This isn't how swept wings work. Spanwise flow is undesirable in any wing--of which straight wings certainly are subject to. Look at all of the aircraft--both straight wing & swept wing--that use wing fences, vortilons, dog toothed leading edges, and other devices to PREVENT spanwise flow.
What a swept wing does is allow you to make a thinner effective airfoil (because the airflow is going over the wing in the direction of the undisturbed air--rather than perpendicular to the wing) without the structural challenges of making a thin airfoil.
Bartonovich, That is the way I learned it also. I do not know if you have seen the Mach effect on a wing in flight. It appears as a shadow on the wing at the thickest area. The sun has to be at the correct angle. The Mach shock wave causes the shadow. On a B707 this starts about .82 Mach. The aircraft has Mach trim to counteract the nose down that would occur as that lift is forward of The CG.
Great explanation
1:20 , i think the lift is reduced on the tail wing (elevator) due to a downwash decrease caused by the center of pressure and shockwaves moving backward (Mack Tuck)
Your videos are highly educational and can deliver information in a very detailed way. Thanks!
You skipped by the first swept wing Jet the ME 262...
Don't be silly, America discovered everything. Have you never watched a Hollywood film?
+Michael Beverly I skipped a lot more than that! Bell X-5 was the best teaching tool.
+Michael Beverly My thought exactly, but I just read the 262 had swept wings to accommodate heavier-than-anticipated engines, which required a shift in CoG. This was made by sweeping the wings, but the Germans had also unwittingly improved aerodynamic performance at high speed too :)
+piloteer Not unwittingly, in the sense that they knew that adding sweep should also improve performance. The high-speed versions HG2 / HG3 had much larger sweep angles of 35 / 45 degrees only for aerodynamic reasons.
Ah okay - I read that on the initial model, the sweep was purely to alter the CoG and didn't achieve any significant performance otherwise, as it may have done on subsequent models. That's just what Wikipedia says :)
You seem to have done a lot to ignore non-American advances in high speed flight. For example a little mention that "it was based on a German prototype" ignores the huge, massive advances Germany made during WW2 to culminate in swept wing planes in production and in combat during the war. The Bell X1 I could forgive you for, as people seem to constantly recite the American suggestion that it was America breaking the pattern.
The reality is that the vast majority of the science and technology behind breaking the speed of sound came from Britain who were conducting similar tests. The British gave that data to the Americans on the promise that America would fund the tests (everyone else who participated in WW2 was incredibly poor at the time) and that America would use the mass of British technology in those tests, break the sound barrier, and give Britain the technology discovered by the X-1 tests.
Well the X-1 broke the sound barrier and America said "thanks, bye" essentially. The irony being Britain was so close to breaking the sound barrier at the time, and the biggest and most important keys America lacked in breaking the sound barrier were discovered by Britain a long time ago, comparatively speaking. So yes America broke the sound barrier, but Britain discovered how it was done, invented the use of the all-moving tail surface with regards to Mach 1 speeds, and generally gave America an absolute shit load of help in breaking that magic number.
So sure, America has done a lot to advance flight technology after the 50s, but please don't ignore the advances made by everyone else. This was a triumph of all of mankind's ingenuity, not of America alone.
And truth be told, America was stuck in a rut regarding all of its military technology in the 50s. Air, land, and though admittedly they were doing great as far as naval was going that too was beginning to stagnate mid 50's. Its up for debate why, possibly because the people in power were all too old and resistant to change, I personally believe its because the rest of the world was at war and improvement was a necessity. This is all too evident when Russia is concerned who completely revolutionised the ground war in response to German attacks, and quite frankly a large part of what they learnt is still in use today, at least in the broad strokes.
TMI
To
Much
Information
@@cisko6175 You couldn't even spell too correctly. Let alone understanding what he said.
Hi! Great Channel can I ask what software you use for the animation of your videos?
^
Sad no answer after 5 years. I rlly wanted to know that :(
@@pixelbogpixxelbog2090 its actually really sad :(
@@RahulSingh-ec1nm I am gonna continue waiting till i get the answer :)
:
I would have liked to see you also go into forward swept wings.
ua-cam.com/video/RN6vGxyMcVU/v-deo.html
It's been five years, but Brian has a video about that if you haven't caught it. It's from 2019, and it's called "Why Do Backwards Wings Exist?".
I saw this about three years ago when this vid was posted. I randomly watched it again and I’m so happy to have seen it.
Frank Daws dude same!
The Су-47 Беркут says: "fuck that i'm gonna have forward swept wings."
Also your videos are great. Are you going to be focused mainly on aerospace engineering in your videos? Because i like that.
I'm an aviation nerd, but no, I plan to cover a lot of topics.
That's cool, thanks. Subscribed.
I learned a lot of interesting stuff about aviation through flight simulators like IL sturmovik 1946 and the DCS modules. The P-38 control surface lock during transonic speeds was one of them.
Keep it up.
That's fascinating, I've never used them.
That does make me wonder. Obviously there are both real-world and fictional examples of planes with forward swept wings, but they are rare. (even more so than pusher prop aircraft)
The question arises though, what are the upsides and downsides of a forward swept wing, and why are they not used much? (Is there an obvious downside, or is it just not fashionable?)
The tips of a forward-swept wing can twist upwards, increasing the angle at which the tips hit the air and twisting it even more up to the point of structural failure.
I'd recommend you do your own research and take my words with a grain of salt, as i'm not exactly an aerospace engineer.
again, thank the Germans.
Nazis invented the jet fighter.
A gay guy invented the Turing machine.
And slavery built the pyramids. :(
@@perfectsplit5515 Slavery did not built pyramids, it's a myth.
@@melo3814 So I should believe an anonymous UA-cam poster and disregard what the history books say?
@@perfectsplit5515 Wait what? No, I'm not talking about any youtuber. Just read about it, they were free men, simple workers hired by Pharaoh.
The Gemans' were the first to use swept back wing. When a Scientist noticed the angle that the water came off the stern of a ferry . He used everyday to go to school when he was a child . He used this angle to help to solve the problem of highspeed flight . Messerschmitt Me 163 being one of the first to it.
I like this channel and watched your videos with great interest.
Unfortunatly this design wasn't developed by Americans but by Germans who reached +1000 km/h in 1944 with the Me 163.
The engineer of this plane was Alexander Lippisch who was brought to the States and helped the USAF to develope its inmature technical unnderstanding of avionics close to the sound barriere.
The german engineers where aware of these effects since at least 1934, this is why the Ju 87 already had a dive break to reduce speed and avoid the effect of shockwaves.
you forgot the me262,
how could you forget the me 262
Me 262 did not have swept wings. They were not angled enough to provide an advantage over straight wings.
+Smartuy +Smartuy I am praying to every deity conceived by humanity that you are a troll... "the Me-262 did not have swept wings"? You have to be joking... Also, do consider a name change.
The 262s wings were only angled to change the centre of lift to compensate for the change in centre of gravity due to the installation of heavier engines. The DC-3 was similarly modified--in 1935.
The X5 was modelled after the Me. P.1101 FYI
Nice informative video. Although not related to swept wings, one key invention that made the Bell X-1 controllable was the all moving stabilizer. These are now standard on every aircraft that flies near or above Mach speeds.
You're saving my life. Aviation Technology is interesting but difficult.
I fucking love your videos. I need more.
+Eoin Dineen Again I really appreciate the support Eoin! You are consistently the first person to comment. Thank you
+Real Engineering Would be awesome if you also made a video about the pros and cons of swept forward wing designs as well (SU 47 Berkut, Grumman X 29, etc.)
+Real Engineering Please make more videos. Your research and information is so informative and intersting. Thank you for making such a channel and putting time into it for us :D
I fucking love them TOO
So... If you want the history of the swept wing, start with Germany 1935 and onwards.
No it goes slightly further back than that. One of the first documented inventors of the swept wing was a fellow Irish man called William Dunne, but he invented it for different reasons. He invented it for longitudinal stability
+Real Engineering That's true! The swept wing has the advantage of raising the Mcrit but it also has a stabilizing effect.
Well, the first platform that took advantage of it properly was most-likely the Me-262
there were even biplanes with essentially swept wings
Try Jack Northrop in 1929... and many others earlier.
Wow. This is an actual contribution to UA-cam. Really great video.
This video has answered my question. Thank you Real Engineering.
Yes, but the video does not explain why the passenger planes, which fly at normal subsonic speed, need those wings
Today the planes are needed these wings to be efficient, but it is interesting as it has developed historically
Passenger planes still fly pretty close to 400 knots (about 800kph) which is way faster than the p38 lightning. Also they reduce drag and are generally more efficient.
He is talking about the airflow speed over the wing, not the airspeed
All modern passenger jets fly at transonic speeds, in other words, above their critical mach number. Part of the airflow over the wing is supersonic and therefore a shockwave does exist. Sometimes you can even see the wave as a weird refraction of light just above the wing if you are lucky and sitting in a window seat near the wing. I've seen it on Airbus A330.
Swept wing not only delays the onset of the shock wave (= increases critical mach number) but also makes the shockwave less severe, allowing the aircraft to be accelerated further into the transonic speed range without suffering too much drag or other undesirable effects of the shockwave.
You might want to do some research... Look up "transonic" in Wikipedia.
The oversimplified explanations of the challenges of high speed flight have led a lot of people (including many professional pilots) to believe that the critical Mach is something so "critical" that you must not ever reach it... without realising that we fly above it all the time. Actually we almost never cruise below it! The whole foundation of the design of modern jets is flying safely and effectively in the transonic speed range.
What? Who? How? What do you mean? Now I'm confused. :D But I'm not confusing the speed concepts. IAS has nothing to do with this, what matters is the Mach number.
So how did the German engineers figure out about the swept wing?
The same way.
00PiggyCosmonaut I'm pretty sure the video was clear on how the American engineers learned the swept wing from the captured German planes. So what do you mean by "same way?"
teitake
Well first the Germans studied in wind tunnel tests, and that's how they figured it out. Then the Americans found out about it. They used wind tunnel tests to figure out WHY it helped. He kind of explains that in the video, but not to much.
00PiggyCosmonaut It's typical of Discovery Channel but it's too America-centric to me. The important research had been done in German with regard to the topic of the video but they just skimmed over. Very disappointing.
Very observant. What happens in Vegas, stays in Vegas. That apparently applies to Wars, too. Like the Second World War...
In the mid 80s I had a field trip to a nearby Air Force base where I asked one of the airmen why some planes have straighter wings and some have very angled wings.
Airman: _"You know how when you're running down the hall with your arms out straight, then you put your arms back and you go faster?"_
Me: _"No 🤨"_ . I'm starting to suspect he didn't actually know...
FANTASTIC description of span wise flow!
What about the Me-163 and Me-262? Didn't they have angled wings during WWII already?
yes.Also Horten H IX.
+methanbreather Makes you wonder why the Americans took so many German engineers and all the German research into swept wings? Why would the US need it if they knew everything already?
+methanbreather Makes you wonder why the Americans took so many German engineers and all the German research into swept wings? Why would the US need it if they knew everything already?
They did - but not because of any transonic or supersonic requirements. With the 262 it was in order to maintain the centre of lift and gravity of the aircraft within tolerable bounds. The 163 was tailless, so needed sweepback to retain longtitudinal stability.
Just because an aeroplane has swept back wings does not imply that the sweepback has been put there to enable it to go faster than sound. The De Havilland Tiger Moth also has swept back wings.
Where the hell is the me 262 from Germany on this list? They had used the swept wing design because it allowed the plane to go faster and solved the issues you stated just a lot sooner than you spoke of in the video.
They did not. The wing was swept on the 262 for the same reason it was swept on the piston engined DC-3 a decade earlier... to move the centre of lift closer to the centre of gravity because of design changes (developing the DC-3 from the DC-2... and installing heavier engines on the 262).
Only recently discovered this channel. I. AM. LEARNING!!
the captured german design is Me. p1101 prototype, 80% complete while captured; it was to be fitted with Hes011 turbojet engine; the Bell X-5 was based on this design.
"If God had meant for seagulls to dive He'd have given them the short stubby wings of a falcon...!!!"
- [Jonathan Livingston Seagull]
A good video explaining the mechanics of the swept wing design, but you got your history wrong. During WWII the German engineers were aware of the need and were designing swept wind aircraft during the 40's up to the end of the war. The most famous being the Messerschmitt Me 262, the first practical jet that, while very deadly to Allied bombers, were manufactured in too few a number and too late to affect the outcome of the war.
Just discovered your channel (you are shared by a french new technologies website), and I couldn't stop before watching all your videos, incredible quality here, looking forward to your next contents! Thanks man.
General stability of Dunne's plane design was so good it flew as a pair of swept back wings, only.... no tail at all. It would also allow for totally hands-off flying, which was considered amazing at the time (1912)
en.wikipedia.org/wiki/Dunne_D.8
JW Dunne was more famous for his book "An Experiment with Time" which was first published in 1927. It has remained popular, and has never been out of print.
German prototype? As far as I know Me 262 was no prototype, it was the first in the world jet that have seen military service.
Timur Pirkhal the gloster meteor was the first jet fighter . But the 262 was the first to go into frontline service. So they are both very important.
He's actually referring the Messerschmitt P.1101. it also had Variable wing angles, but it had to be adjusted on the ground.
good to know ww2 ended in 1951?
What?
It’s 5 years late but he didn’t say anything about WW2 ending in 1951. He said they started to develop it after WW2 and came out with a model in 1951.
Outstanding video. I hope your channel continues to grow so we can keep getting awesome content. Thanks again!
for those of you that dont have time.
normal straight wings gives higher lift but more drag (slower)
angled wings gives less drag but has lower lift (worse when going slow)
When you make it sound like Americans came up with swept wings when Germans found out this guys findings During the Development of the me 262
He literally said the airplane used for testing the swept wing design was based on a captured German plane, pay attention.
@@dakotataylor2712 And then glossed over it.
@@dakotataylor2712 Except it wasn't the case
Americans! This is what an Irish accent sounds like.
That he is. ;)
tanks for watching
There are so many Irish accents and his 'troo-la-loo-la-le' accent is just silly, I bet probably pronounces Donegal as (Don-A-Gul) instead of the Irish way.
My fart has a better accent.
LisztyLiszt i like his accent
The engineer who worked at the development of the swept-back wing and other features of high subsonic as well as supersonic wings was Adolf Busemann. It was on his calculations that the wings of the Me 262 were based. Imho he would have deserved some mention.
The AN-225s tail is interesting since it’s a swept back but not tapered at all. The non tapered swept back tail is compensated by large rudders/vertical stabilizers that function kinda like huge winglets.
well, actually the wing doesnt just develop lift due to the faster flowing air on the upper side. There is also a waaaay more important thing called circular stream around the wing. The direcion of flow matches on the upper side, wich accelerate the air and goes counterways on the bottom side. This circular stream produces a whirl kinda thing behind the wing, wich actually develops the lift of an airplane. Can u pls correct this? the theory was found out watching planes start in the rain, u could see the whirls behind the wing with bare eyes. This theory is totally approved by now and the basic thing for developing new profiles
That turbulence produced behind the wing is called wake turbulence in a normal plane.
For planes like concorde or other planes with delta wing, this vortex is captured and used for lift, but for the average commercial planes, this vortex only adds to the drag, and not lift, which is why devices like winglets and raked wingtips are developed to avoid this vortex.
Newton's third law is also very important.
All he said was air accelerates on top of the wing--which is what circulation describes as well. Nothing to correct.
Circulation is a modeling tool, not a theory of flight. Bernoulli's theorem still explains the physics of flying; circulation reduces a 3D flow calculation to a 2D approximation, so models can be developed & compared MUCH more quickly than CFD or FEA methods.
Howie Au, he is describing the Kutta Jukowski lift theorem, not turbulance.
Thank you for producing this informative video! I'm slightly confused however, about modern jet airlines, which don't fly at supersonic speeds-- are their wings swept back because they still add efficiencies add enough stability even in subsonic flight?
+Victor Chen That is what I explained at 0:50. The plane can develop areas of supersonic flow while travelling at subsonic speeds because the air accelerates over parts of the plane.
learnt this in the first week of aerospace engineering school.. if only things were this simple for everything!
You can go supersonic with straight wings. Witness the first plane to break the sound barrier - the Bell X-1. The Lockheed Starfighter famously had pretty straight wings - and was capable of Mach 2. The first rule of making a supersonic wing is make it thin.
Sweepback does, of course, help - a lot.
Sorry about the delay, I managed to corrupt my animation file and my most recent back-up was a week old. Let me know what you think!
Great video with nice animations and clear and consise explanation
+Brian McManus You should keep things in the cloud. It will save every single version for you.
Very good! One thing though, you misspelled "separation" at 1:19.
+Push Back ah Jesus, yeah I wouldn't notice that if I looked at it a hundred times. Dyslexia is great
Real Engineering Dude, don't worry about it. Just keep pushing ahead. Little shit like that doesn't diminish your intelligence or ability to grasp larger concepts that a lot of people grapple with. Keep on kicking ass! Subbed.
You should have consulted an aerodynamicist first.
Planes haven't flown transonic speeds in decades. THE REAL reason they still sweep the wings back is so they can be much lighter.
In a sudden gust or pulling out of a dive, a straight wing, any wing, bends up about the line which is along the centers of lift. This is 1/4 the way back from the leading edge. No matter how much stronger the spar is than the skin, there's always the tendency to twist the wing while it is bending up. On a straight wing, the twist is such as to make the tips twist with increasing alpha; that is more lift than the root. If the plane is above the maneuvering speed, more twist comes with more lift which comes with more twist and so on until one or the other wing breaks off. Below the maneuvering speed, it won't rip the wing off, but one tip will stall before the other and the plane will go out of control.
But when the wing is swept back as the wing bends up, the twist is such as to unload the wing. A swept back wing doesn't have to be as strong so it can be allowed to bend 20 feet or more. A straight wing must be made very rigid so it won't even think about twisting. This was discovered way after the transonic advantage the video was about.
+Walter Clark Before you get too pleased with yourself in calling out how "wrong" this video is, let me remind you that *all* jet airliners today cruise at around Mach 0.8-0.9, which is well within the transonic regime. In fact, for classical aerofoil profiles designed with classical incompressible flow theory in mind, the critical Mach number can be as low as 0.6-0.7. Modern wing design manages compressibility effects and its associated drag with a combination of wing sweep and supercritical aerofoil design.
*Drag reduction is the primary driver of wing sweep.*
The effect that you've written about certainly is true, referring to what is known in the aeronautical engineering field as "static aeroelastic stability". Sweep-back does entail an inherent increase in this form of stability, but this is largely serendipitous. In practice, modern wings are designed far more elegantly by taking advantage of the anisotropic material properties of fibre reinforced plastic composites. This allows the aerodynamicist to concentrate on his work of minimizing drag, while leaving it to the structural and aeroelastics engineers to ensure that the wing is structurally sound.
+throbbingweener
Good points, well said. Thanks for leaving it.
All airliners? I believe .6 to .7 is the average speed of airliners.
+Walter Clark hint: economical cruising speed vs maximum speed vs designed maximum speed
for the smaller airliners it's usually .70-.80 and all large airliners at .80-.85
How did they originally investigate swept wings? Because by 1951 Sabres and MiGs were flying and supersonic fighters were only a few years away.
If you have not already done so, please consider explaning why the canard wing set up (the first to fly under power) has never been adopted for large commercial aircraft in great numbers. Also perhaps comparing it's advantages n disadvantages.
what about the planes shaped as Y?
What the fuck is a 'Y' shaped plane, please share light. Give me a make and model.
Tasman McMillan you are right, it wasn't the best way to describle. I meant models like X-29
It's essentially the same thing, but there are different positives, negatives and limitations.
You lost me at "The air over the top of the airfoil accelerates; this is how the wing generates lift"... which is NOT how a wing generates lift. If it was, then you would be able to stand underneath a rotary wing aircraft (ie. helicopter) and there would be almost no air movement. Clearly the lift is generated by pushing the air mass downwards (ie. Newton's Third Law of Motion) and not from any Bernoulli Effect.
Air accelerating over the top of the wing is one way the wing generates lift. It isn't the only way. The way you mentioned is the primary source of lift.
It would be more correct to say it generates a 'trivial amount of lift' - it may as well be zero. But you didn't say that. You said, "This is how the wing generates lift" further extending this daft notion that Bernoulli's Principle is why wings work. :-/
Depending on the airfoil, the Bernoulli effect can generate 5 degrees of angle of attack worth of lift. That is not trivial or daft in any sense. I simplify these videos down to allow them to flow and teach the specific point I am trying to make. Teaching the principles of lift entirely will be saved for another video.
The debate about which of the "effects" "creates" the lift misses the point completely and shows a lack of understanding of physics. Lift is a complicated process and all of the laws of physics apply to all parts of it all the time. You can't cherrypick one of the laws and claim that this law alone is the "explanation".
Because lift is so complicated, the best you can do if trying to explain it in simple terms is describe some aspects of it to give at least a rudimentary intuitive understanding of what is going on. In this sense focusing on Newton's 3rd is a lot more meaningful exercise than the ridiculous Bernoulli effect "explanation" which is complete nonsense. Wing pushes the air down, air pushes the wing up. Of course this doesn't explain the how and why it pushes the air down but going into such detail is not possible without having a rather advanced level understanding of physics.
There absolute is NOT several "effects" or "ways" in which the wing generates lift. There is only ONE process that cannot be cut into pieces. Newton's 3rd, pressure distribution, speed of the airflow, circulation... these are all aspects of the one and only lift-creating process.
It is true that pressure differentials must be present for lift to happen. However, saying that pressure differentials "cause" lift is just as incorrect (or correct) as saying that the wing pushing air downwards causes lift. It is not meaningful to say that any single aspect of this process "causes" lift. All aspects are integral parts of the process.
Actually, it would probably be more meaningful to say that lift causes the pressure differentials! ;-)
Imagine two guys fighting over what makes a car move. One claiming that it is the engine, other insisting that it is the tires. Who is right?
I recommend you read "The Simple Science of Flight" by Hendrik Tennekes. You'll find that the Bernoulli effect accounts for only a small percentage of a plane's lift! The vast majority is simply conservation of linear momentum from the wings pushing air downwards while not stalling the airflow (a principle which leads to Bernoulli's effect with some assumptions)
No, it does not make any sense to break down lift into Bernoulli and linear momentum. Both must be satisfied and both are completely true.
Wing sweep isn't the only factor, aerofoil thickness also plays its part. Those the F-105 was able to fly supersonic with unswept, but tapering wings. Sweep is usually measured not on the leading edge, but on the quarter chord line.
Does anyone still believe that business about the lift being generated by the air travelling faster over the top of the wing?
You don't have to believe it, you can study it and you will KNOW how it works...
Šimon Hubatka
That's what I mean - the traditional explanation doesn't stand up to analysis. A wing can only generate lift by directing part of the airflow downwards = reaction force. Thus it's the angle of attack that generates lift.
Šimon Hubatka Actually I once saw a video of aerodynamicist who explained that the pressure difference is caused by deflection of air. The pressure difference then causes the speed difference in airstream above and below the wing. So the speed difference doesn't actually cause pressure differences, it's the other way around.
Pressure difference and deflection of air are just two ways of describing the same thing. Both are accurate, they're just two different descriptions of the same stuff.
@@S0umin When I was in engineering school studying fluid mechanics we were explicitly told that Bernoulli's principle is an outdated explanation for the cause of lift, and that a reaction force caused from the deflection of air on the lift surface is a more complete explanation. OP seems to understand more than you do......
This is so detailed and accurate I wonder why I am paying so much for an aerospace engineering degree, may as well just watch youtube all day long.
+Sean Sun Well I hope it helps with the understanding! I have a master's degree in aeronautical engineering. Stability and control subjects are so interesting and a lot more understandable when explained visually.
I thought that was a bit too detailed for an average youtuber, I am on my way in getting a master's in aerospace engineering, finals coming up
+TinnInches What I meant was, this video is too detailed and technical for an average UA-cam content creator to create without any background info.
if you read chuck yeagers book they certainly didn't solve the problems by moving the elevators higher on the tail he almost died due to pitch control failure and was only saved by his training and quick wit when he compensated with manual pitch trim control.
the bell xs-1 later corrected those problems.
You forgot like the biggest advantage with the swept wing. They created more stability, making it posible to reduce the size if the rudder, or decrese the minimum landing speed.
Funny, you just don't say that this kind of wings are German inventions during the war..
Swept wings predate WWI.
2:28
Funny how many of these retarded comments there are from people who apparently couldn't be bothered to actually watch the video.
They also stole the nukes from British researchers and threatened to leave Britain to Germany if they didn't comply with the theft.
Let's not forget Microsoft and the US government. Japan had a vastly superior OS under works, US government went in and threatened the developers via the Japanese government. Development was stopped. Now Americans are going around saying "we invented everything".
3:42 there are no passenger airplanes flying at speed of sound...
There used to be one called the concorde. Technically i guess that you're right because the concorde is no longer in use but there was at one point a passenger jet flying at mach 1+. He has a video on it.
Transonic means close to the speed of sound, which is difficult as explained in the video.
then , though it isn't a civilian machine, the Avro Vulcan was interesting because its wing had varying degrees of sweep depending on the thickness of the wing at any given point...
AFAIK, transistors were invented in America and they're arguably the most important thing in our modern world.
Why are these important things? Motor cars have devastated the World. There must be more peaceable inventions that are important, like electricity, penicillin, television, fertilisers, vaccination, the pill, computers, the Internet etc.
I was watching the right stuff movie and was wondering why the wing wasn't swept. I could remember the exact reason, thanks.
Amazing content. Just found your channel today and i already watched all your videos, keep up the great work man, and thanks for getting me excited about going into engineering this upcoming year
Do you proofread your videos? It's Lockheed, not Lockhead; separate, not seperate.
Bell X-5's wings were modeled after the Mig-15, they won't admit it because the Mig was Russian.
whos they?
It was actually Messerschmitt p.1101. It also had variable wings. The X-5 looks almost exactly like it too, much more than to the Mig-15.
It is fascinating to read all the different explanations of 'lift'. So it is not clear-cut, by any means.
This may be apocryphal, but I thought the ME 262 had a swept wing because the engines were so big that they needed to move them back to give the pilot a better field of view, unintentionally improving the aircraft's aerodynamic performance in the process.
well done, ignoring planes like the Me262 who had swept wings during the war.
Another american-centric fail video.
yeah I was annoyed too
fucking americano. cyka blyat
exactly! so stupid, put them self in the center
He's irish
To be fair, the Me 262 wing sweep had nothing to do with critical Mach or shock waves, but simply with re-positioning the center of lift to accommodate heavier than anticipated engines.
Escape is pronounced Eh-Scape. Not Ex-Scape.
sorry, but you are not pronouncing that right. It is a hard C not a soft C.
You're right. Pronounced Eh-Skape, not Eks-Skape.
Eh-Scap-ee
Patrick Coston it doesn't matter you knew what he said
Everyone pronounces things differently depending on accent. I think that yanks mispronounce tons of words
It's interesting that some aeroplanes have swept wings that are very much not super-sonic eg Tiger Moths! (the wings for my 1/6th scale one are propped beside my desk as I type)
I don't understand the aerodynamics very well (but I try!) but I understand swept wings simulate dihedral and so add stability to slower aircraft. It seems that is applied to biplanes because the modern Pitts aerobatic biplane has the upper wing slightly swept so that its root can be in front of the cockpit (for pilot upward visibility) whilst the bottom wing has a degree or two of dihedral.
So perhaps swept wings weren't discovered after all only when supersonic flight problems were being solved.
Thanks for your excellent series of videos
Not a bad video on engineering and aerodynamics trivia. I think it would work even better as an educational video if you addressed, however briefly, the following questions:
Why does the air above the wing accelerate?
Why does that produce lower pressure and therefore creating lift?
What are shockwaves and why do they form at the locations of supersonic flow?
Why do shockwaves reduce lift and increase the drag of the wing?
Why does airflow separate from the wing at supersonic rather than transsonic speed and why does the shockwave move towards the rear as the speed increases?
Why does air in straight wing design only flow parallel to the chord?
Why does the span-wise component of the airflow not accelerate?
Alas, if your videos are aimed at aviation engineers and physicists who already do understand these concepts, then I guess it's fine. :)
amazing videos and chanel, you made freaking easy to understand very complex things in a such way that even one person wiht no idea about aerodynamics can understand, not anybody can do that you had a unique talent for this, keep going
so well researched. so well done.
The F-14 Tomcat has wings that can retract in flight, thus reducing the drag and increasing speed. I used to work on these jets when I was in the Navy.
Thanks to Real engineering ,you certainly contribute to the development of knowledge.
Hi Jerry , of course you can get angry but those are the facts. Maybe you did not know that the Mustang P-51, among other aero engineers, constructed also a German who was not a Nazi, because in the United States came as a little child ... you can use google if you want.
Could you please do a video on forward swept wings?
There is another reason for swept wing: Stall recovery. With the AOA highest near the body, that part of hte wing will stall first, which leaves the remaining lift further back at the tips of the wings. This causes the nose to drop and the plane to recover from the stall.
Except for all of the swept wings which experienced tip stall. Look up the Sabre Dance.
This is also why birds, will actually make their wings smaller when diving through the air. You'll notice this if you observe a seagull, or some sort of bird of prey diving through the air at high speed. Their wings are never fully out, they are slightly tucked in, so they have greater flight control at higher speeds.
The Boeing 747 takes advantage of this wing design and the newest version of the 747, the 747-8i flew 12 km/h below the sound barrier on it's test flight. Of course, it used extra powerful engines, but the wing design helped the plane not to be ripped apart at that speed.
That must have been quite a feet of Airmanship. Although lacking the good judgement usually associated.
you've won. i can no longer bear a second longer of this unimaginative drivvle.......................................
Great video, small note: a .50 caliber bullet (not round) can be of many different weights (grains) 655 grain - 800grain. which are identical in diameter but different in length. I wonder exactly which bullet the Bell X-1 was modelled after.
Because it looks awesome. Enough said.
This is a fantastic channel. Keep up the awesome work!
The reason why the Bell X=1 could maintain stable supersonic speed was its variable position horizontal stabilizer originally developed by Miles aircraft M52
There is also a pretty interesting story behind the US development of supersonic control surfaces. If I am remembering correctly, US engineers approached British engineers to have an information swap on supersonic technology. After the British gave their info to the US engineers, the US engineers pulled out of the deal. Pretty messed up.
I believe those flaps in the P-38 you were referring to are called dive flaps or air breaks. I am familiar with glider air breaks which is where I got the name. Not sure if it is the same.
*IT’S THE LAW!*
Russia: are you going to place the wings angled to the front or to the rear?
SU-47 designer: Yes
Good video. Should cover how a swept wing impacts CG.
Would be interesting to do a video on the advantages/disadvantages of a forward swept wing.
+alan connelly I will be covering CG and stability concepts in a later video. Quite excited about that one actually!
I try to base my videos around a story, rather than just the raw engineering. You have an suggestions there? Why did the forward swept wing come into existence?
Better maneuverability was the reason for a forward swept wing, but it has engineering challenges, under high loads the wing tips bend up causing greater and great lift, carbon fiber fixed greatly alleviated this issue. A Blanik glider uses a forward swept wing, the engineering reason was to help with CG balance issue with a two place glider with one pilot, the forward swept wing moves the CG forward which helps.
Actually wings have different angles at different parts, the wing is twisted and gets straighter towards the plane. This increases speed, efficiency and safety.
1:53 The german Messerschmitt Me 163 B (or C-model) was the first manned plane, which flew with supersonic, not the X-1.
Nope.
that angled flow over the swept wing looks like it should produce a lot of drag
LOVE THIS CHANNEL.
interesting video! after watching this video i realised even birds sweep their wings backward while diving :)
Would that not have more to do with decreasing frontal area (and thereby drag) as they don't need much (if any) lift when diving?
dude2106 i have no clue man! i was just commenting. i'm not some physics expert.
Birds sweep their wings backwards when they are facing strong relative windspeed (in wind gusts and/or when diving) or when plunging into the sea. In all cases this is to reduce frontal wing area to minimize drag.
Simple and easy. Nice video.
You got a new subscriber
So, if the air traveling over the top going faster is what generates lift, explain symmetric wings. It's the downward flow of air that provides lift, not the flow going over the top of it, in line with Newton's Third Law. If you ever look at the wings of a plane they are angled so that the trailing edge is lower than the leading edge.
Germans...When will they cease to amaze me...they had the tanks, the planes and the brains during the war up to today.
Great Work man!!
I love your way of laying out the secrets of the craft in such a plain and smooth way, ( I am a fellow Aerospace Engineer), and currently I do teach in an Aviation Academy. I really want you to make a video about the Variable Camber concept, which is achieved in the B-787 through a VCTU (Variable Camber Trim Unit)
Thank you.
Actually there is another reason for swept wings. The airplane is more direction-stable, because when it is flying sideways, there is more drag on the wing which is turned to the front, which turns the airplane back in straight flight. It's a bit hard for me to explain because I'm not a native speaker.