How Airplanes Fly (1968)
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- เผยแพร่เมื่อ 28 ส.ค. 2024
- Department of Transportation Federal Aviation Administration
How Airplanes Fly 1968
NTIS AVA08357VNB1
What makes an airplane get off the ground and stay in the air? Easy to understand film combines animation and live sequences to explain ... all » basic aerodynamics. Forces of lift, weight, thrust and drag are shown in relation to flight.
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I wish they showed us this in school instead of all the struggles we have to face to understand the POF. This summarizes everything I have been studying for more than a year now. Thank you!
Old classic videos are the best for explanations of everything instead today's high tech. confusing information..Great vid.
This helped me with my science fair And i got picked for rank 12 and got a B! thanks Uusually i get c- and c+ thanks
I thought the aeronautical engineer guy was the best actor of the film. I really felt his emotion.
offtopic: did anyone else feel the background music/ sound effects and narrators voice was reminiscent of those early Looney Tunes and other cartoons of the era gone by?
Yes. Brings back memories of when I was in school in the 1960's.
This video was the first video i ever watched at my local aeroclub where i started my Pilot License!
I love how the cesna has changed so very little over the years... a testament to a great design.
To put all this simply, a plane flys using the venturi effect. As air speeds up, it's pressure drops. Lower pressure on the top (higher pressure on the bottom) of a wing will cause it to lift.
I love these types of videos
Runway 31/13... you don't see that too often... Great post!!!! MUSIC IS CLASSIC IN THESE OLD VIDEOS!
i'm loving these old flicks, keep 'em coming!
This is one of the best videos I have seen on this subject. Thanks for posting it!
learning to fly was one of humans most noble and pure dreams throughout history. somehow we then decided to make this noble dream into weapons.... :(
When an aerofoil starts moving, air at the trailing edge would apparently need to double back round to join the rear stagnation point. The air is not a superfluid, and as a consequence the flow breaks away at the trailing edge and a starting vortex is left behind on the runway. This can actually be visualised.
In the air around the aerofoil there is vorticity of opposite rotation to the starting vortex, by the conservation of vorticity. This vorticity then generates lift by the Magnus effect.
Conservation of vorticity and the Kelvin circulation theorem are the same thing, and it is a topological requirement that vorticity can only exist in endless loops. The Magnus effect and the Kutta-Joukowski circulation theorem are also the same thing and we can switch between them by a linear transformation.
Explanations based upon Bernoulli's Principle or Newton's Laws are merely wisdom after the event of a starting vortex being formed. They would flop if our atmosphere were a superfluid like liquid helium.
It's a good views to learn and really appreciated!
It's me,
Sule Shangodoyin.
As a future aerospace engineer, I find the narrator's attitude towards equations around 2:10 hilarious. xD Math is awesome and fun, and it definitely makes stuff make more sense. :D That wasn't even a tough equation... They briefly introduce it in freshman physics for engineers. :P
the best video instruction I've ever seen
There is a logical reason. The molecule tend to stay at the same speed. In fact the airfoil just break the air in two part, the lower part tend to be compressed and the upper part tend to be stretch. (I usually speak french, thus I certainly made some fault)
@EFCthebest I agree with your idea. A flat wing with no camber has maybe a lift/drag ratio of maybe 3:1. Put some camber on, and the L/D goes to 6:1.The first conclusion is: increased lift. I believe it is simply decreased induced drag.Obviously there will be slight reduction in pressure on the top of the wing because the inertia of the airflow NOT following the shape of the wing. It is well proven the massive reduction in drag caused by airfoil shapes to struts etc. This is ignored completely .
@J1mmyWA Or is it. As one of my ground school teacher's put it, "If it is the law of equal and opposite reaction generating the lift, than put a pressure gauge or scale on the ground. Have an airplane or jet fly over it and see if it reads, at least near the same weight of the plane itself."
The movie emphasis the way the force is relayed to the wing too much, over where the force originates. in the end the lift originates in the displacement of air/mass, the resulting speeds/pressures are secondary effects.
>"change of direction". The lift is caused by objects (air molecules)hitting the wing and pushing it upward, (which results in the air moving downward). The air moving downward is the result of an event not the cause of an event. Just the same as a rocket moves forward because af very high energy molecules shoving the rocket forward, not the gasses which are exiting the back.
@EFCthebest the downward diversion of the airflow is the result of lift, not the cause. the cause is the difference in pressure between the upper and lower surfaces, generated by the difference in airspeed.
"air accelerating over the top of the wing (causing lower pressure) which is largely untrue"
No, it is not untrue, but it is no second separable effect. Of cause there must be lower pressure on top or else there would be no lift.
@jemhson no, that is not wrong. What the wind tunnel is showing is that air gets compressed when you have two airfoil shapes and that, even if you take one away, the same kind of effect happens. It is done to make more sense of how lift works because it shows how an airfoil acts like a funnel almost. Concerning biplanes, their wings are not like that. The airfoils are "upright" so to speak
Good video, refreshed my mind about airplanes.
Good point Ibrahim. I was scrolling all the posts on this video to see if anybody noticed the error! :)
Why don't you just reply to the comment?
Leo would be proud of how far his idea has come.
When you do the integral that come from solving the equations of motion from classical field theory you have to use complex analysis. You end up with a pole in the middle of the airfoil. This ends up giving a solution with nonEr
nonzero curl. This basically mean you get air rotating around the wing. The other independent solution is just air going over and under the wing. super position of these 2 solutions is air moving faster on top and lower on bottom.
Spend time listening to an instructor telling you about the air flow going the long way round the curved bit and the short way under the straight bit..... then ask how it works upside down...... drives 'em mad!
The way I explain is as follows: Assume a laminar flow in which there are two molecules of air right at the forward tip of the wing. They separate at this point as one follows the upper surface and the other the lower. For flow to be laminar, these need to meet at the aft end of the wing but since the upper surface is curved thus longer, the upper molecule has to move faster. Bernoulli has shown that a higher velocity creates a lower pressure. So pressure above is less than below. Hence, LIFT!
@J1mmyWA
I'm no engineer, but I think you're right on the money. I don't think airplanes are sucked into the sky. Look at how much downwash a helicopter makes. It couldn't fly w/ neutral blade pitch.
I don't think they explain stall right either. The condition called "stall" is the loss of laminar flow w/ a significant increase in drag. That doesn't mean it stops producing lift tho. It's just the drag increases way beyond the thrust of most airplanes' engines ability to keep it up.
the way lift is produced is not that particals pass over the wing and pressure's, that is only a little part of the equation. It is the direction of the after flow of the air leaving the wing, generally the air is force in a downwards motion off the wing and but newton 3rd law "for every action there is an equal and opposite reaction" therefore the downwards moving air pushes the wing up thus creating lift.
Awesome. Thank you for posting so many AWESOME videos!
i love it and better still can understand it...welldone for finding this :)
@adrianTNT
Look up Bernoulli's Law. For air moving on a streamline your dynamic pressure (speed), static pressure, and head (height difference) must add up to the same number. So if your dynamic pressure (speed) increase, your static pressure must decrease!
Timeless basics! Very informative.
12:55 hmmm, that seems a little unfortunate
I see that you really need to consult your physics textbook again.
Firstly, I think you feel for the same trick that the Greeks fell for. When Drag=Thrust, it does not necessarily mean that there is no motion. Newton's first law about inertia is clear. This means that when the drag is equal to thrust, an airplane ALREADY in uniform motion (in the case of straight flight) will remain in uniform motion.
the way lift is produced is not that particals pass over the wing and it's pressure's that is merely a little part of the equation. it is the direction of the after flow of the air leaving the wing, generally the air is force in a downwards motion off the wing and but newton 3rd law "for every action there is an equal and opposite reaction" therefore the downwards moving air pushes the wing up thus creating lift.
ok, now i know everything i need to fly a plane.
>works for u it works. As 4 me, I intend to explain it as a result of a event, not as the result of another result of th event.
As far as the aformentioned 0 AOA wing, lift is created because the change in direction of flow ultimately causes less energetic collisions of molecules (less pressure)on top the wing causing the greater pressure underneith to lift.
@Dithel yet i,ve seen the other ideas and videos and they seem to contradict each other. i,m sure if you know, it,s easy to understand.
THANKS
Thank you for acknowledging, Sir!
Good, I like that you share this video, I wish success always Department of Transportation Federal Aviation Administration
Great film!!
i usually wonder about 1 thing. Suppose, lets talk about airasia boeing accident in 2015. that boeing was stalling, and falling from 38000ft. the question is: why was it not possible to reposition the plane to its normal state? i think the pilot could make the nose of the plane lower than its body, maximized the jet power until the plane had enough speed, then simply pulled up that plane
heavy airliners have a limited angle in which the nose can be pointed down, beyond that point the airplane is doomed for it picks up speed really fast, as the pilot tries to pull up, wings stall, if he does it gradually, excessive speed begins to exceed the aerodynamic pressure for maintaining airframe integrity, the cycle repeats until the airplane hits the ground if the airplane doesn´t disintegrate in the air first. I am an A and P mechanic, but english isn´t my first language.
This accident was caused by a chain of bad events. The plane was flying in bad weather, so the plane was already hard to control. The pilot's mistakenly took an abnormally steep climb, which caused the aircraft to stall. Unfortunately the rudder travel limiter was malfunctioning, which cased the plane to go into a roll. Miscommunication between the pilot's and the bad chain of events, caused this crash to occur.
Secondly, you fell for the 'equal transit time fallacy'. This is much more understandable, as a lot of textbooks also preach this.
The problem is simply, there is absolutely no logical reason nor need for the air molecules to reach the the end at the same time.
why not say pushed up, it makes more sence then lift.?
Why the video stops loading after a few seconds? It only happens with this one.
the fact that we can generate enough lift with perfectly flat wings does not somehow deny that a wing curved on the top and flat on the bottom generates SOME lift. The test if this would be to put such a wing into a wind tunnel in a no-angle-of-attack condition an measure whether there is lift. This situation will cause less air pressure on top the wing thus the greater pressure underneath will push the wings up. You seem to be a little obsessed with the idea that lift is created by the airs>
When you see the ending music and font, don't you want you watch some Tom & Jerry ? :)
Think this is out of date
More recent articles I've read, suggest wings generate most lift by diverting air downwards
i.e Newtons law - equal and opposite forces - so volume of air diverted downwards equals force or lift upwards. The force generated by the reduced pressure above the wing due to increased airflow is apparently very small in comparison - interested to hear others thoughts on this ?
This theory is outdated, the major causee of lift is the reaction of the bottom of the wing surface forcing air downward. The low pressure on the top helps a bit, but the most lift is because of the theory "every action has an equal and opposite reaction"
So, if we increase speed the aircraft lift increases? due to the aircraft and airfoil angles and shape. Where the top surface is cambered negatively and the bottom surface is cambered not so much?
Great video thanx
thank you for this!
how will low pressure be caused on the top of the wing , what formula gives us that?
Nice video. Thanks for posting.
that was awesome!!
Awesome.
Can someone explain how is that LOWER pressure in the middle at 5:06 ? If they explained that margins have a larger volume of air then you would expect pressure to be higher when air is more compressed in the middle? What am I missing? Everything ?!
Wonderfully retro informative video! enjoyed it
hey at 03:48 seems wrong, why is the wing on top upright? is that what really biplane airfoil is? note that it cancels lift from below by the top airfoil
If a teardrop shape is at a moderate angle to the wind the air still flows smoothly around it but the air is deflected and generates a reaction force. Thats how wings work, exactly they way you think they work when you stick your hand out the window of a car. Forget about the crap you heard in science class.
@nakedleader Okay class, now we will learn about inverted flight in a Tiger Moth...... and how does a fully symmetrical section work? It is rubbish to ignore the fact that wings can work upside down despite the theory! Just add power and incidence, to get more pressure under than over......
So, how does it generates lift an acrobatic plane during invert flying? According to Bernoulli's Law it is suppose to lift it down or not?
I think it's an old video, but it was really amazing to give you a simple idea :) A+
this is great!
GearDownFS made it simplier to understand
Thats very imformative,thankyou....
To see this, simply make a paper airplane, whose wing does not have any curvature. And yet, they can fly.
Fantastic video, very informative.
There is also a downward Newtonian force caused by the air accelerating at a relative angle to the chord line of the wing that creates lift.
I believe that the pressure under the wing creates more of the lift than the accelerated air over the top. Hence a semi symmetrical wing that still works with the aircraft inverted albeit very inefficiently.
No, actually the redirected accelerated downward airflow is a majority of your lift.
+Brett Dull that's exactly what he said
IndustrialDonut Thank you
"I believe that the pressure under the wing creates more of the lift than the accelerated air over the top. "
above is the part of his post I was commenting on. The "pressure" on the bottom of the wing is a byproduct. The lift is created by the redirection of the air over the top of the wing as stated before.. The amount of air redirected is the most significant reason flight is possible.
@@fischermann5279 Both are the same thing. Pressure over the upper and lower surfaces explains all the lift, or equivalently change in momentum of air entering and leaving the airfoil explains all the lift
This is actually quite a good explanation, however most people summarise it and say it is the non-symmetrical aerofoil section that gives the lift. This is obviously not true as airplanes with this section can fly upside down. It is the angle of attack, adjusted by the elevator that is the main cause of the increase in pressure under the wing. I have seen a model aircraft with a plank of wood as a wing, (rather light weight!) and this flew quite well.
This aerofoil explanation is used in all TV summaries of the theory of flight I've seen. I think the producers just copy popular explanations, and thus the misinformation propogates...
The information here is not incorrect. They just don't go into detail about how a symmetric airfoil can be made to have a positive angle of attack that accelerates the airflow over the upper surface in the same way that camber does. Nothing incorrect is being propagated.
If I was to be kind I would say it is incomplete, but the missing bits are what causes all the confusion. NASA decided to put this to bed by having a section on their web site about how planes fly. There are two forces, the Newtonion force on the bottom surface of the wing, which changes the angle of the air and provides a reaction upwards. There is no reference to the upper surface of the wing in this. Then there is the Bernouilli force due to the speed of the air over the airfoil that is usually given as the reason for lift. In fact this second part only gives about 30% of the lift at near sea level. As NASA says in the upper atmosphere, the Newtonian force provides 100% of the lift. I tend to believe NASA.
Malcolm Connah "There are two forces, the Newtonion force on the bottom surface of the wing, which changes the angle of the air and provides a reaction upwards. There is no reference to the upper surface of the wing in this."
Strange!
Could you link me to that if you have the link handy?
Then NASA is wrong. An outrageous claim?!
Well, I have evidence!
If the upper surface of the wing did not create the lift airplanes would not crash simply from having a little bit of frost on the upper surface of the wing- and they do crash! There is a reason!
It looks like NASA can't make up their mind what their position is? www.nasa.gov/mov/178672main_020_ksnn_3-5_plane_cap.mov
StratMatt777
Yes, there are these two forces at work. But I think both sides contribute to both forces. Think about a sail. It also works because of both forces, but it doesn't have a lower side that's different from the upper side.
By the way, the law of bernoulli is just a law that gives you the pressure if you know the speed and vice versa. It doesn't explain why the speed on the top side is higher or why pressure is lower when the speed is higher.
Maybe the whole picture could be explained like this: The airfoil causes the stream of air to change it's direction. It accelerates the air, which directly means there has to be a force on the wing in the opposite direction.
But the "turning" of the air also causes changes in pressure and speed, which applies similar forces to the wing.
TheMasturCheef "By the way, the law of bernoulli... doesn't explain ...why the speed on the top side is higher"
Nope it sure it doesn't. I do know that Coanda effect explains why it stays attached.
"By the way, the law of bernoulli... doesn't explain ... why pressure is lower when the speed is higher."
Actually it does. That's exactly what Bernoulli explains.
@homies2531 If you cut off the pointed ends its actually like the bricks were layed on which the swastikas were mounted. 20 years ago there were plenty such structures but all I knew of disappeared. I am searching for pictures of such brick formations. The reason is: Some buildings in the BND area in Pullach south of Munich are oriented in this way. The BND is the renamed 3rd Reich GESTAPO.
Search for Pullach Germany in Google Earth and look at the the north east part of Pullach.
Very very good explanation
@nakedleader Okay class, now we will learn about inverted flight in a Tiger Moth......
you can experience stall by playing gta san andreas using the same plane shown here by pressing w+down arrow quickly from the keyboard during takeoff. Its a 0 airspeed 0 altitude scenario.
Damn awesome!!!
It can not all be BS or else you would be wrong as well. (but you are right) There are multiple ways to explain it correctly though. İbrahim Çağlayan is wrong though.
@shietalkr
Thanks for the reply. I have read about this but I don't claim to be an expert. I've read enough to know there are many opinions among aeronautical engineers about what creates lift and exactly what stall is. Perhaps you can reccomend a resource.
@5:10 the space gets smaller with an equal amount of air flowing in, shouldn't the pressure be higher? i don't get it
why do we say it's lower?
ngai1842 The air is accelerated. Refer to Bernoulli's Principle, when a gas is accelerated its pressure decreases. This is why it is not a higher pressure.
ngai1842 You are thinking of venturi effect and mixing up speed and pressure, speed increases and pressure drops proportionally, its same as aerofoil principle mentioned by Mr Gypsy
I'm confused by that too... I could understand it being the same pressure but I don't see how its lower when the volume of air is relatively larger to the area it's contained within
I agree. It's taking more pressure to make if flow faster, isn't it?
mitreswell
You can think of it as the molecules having less time to exert 'pressure' as they are whisked over the stationary (or other way round, as a wing) thing.
It is called the Bioshpere
does the bird get stall ?
Key Gen It could, yes
Yes, especially when it's walking on the ground.
sağol ciğerim
güzel video
@stewy1100 same here at first i thought it was gonna be hard
This may be a stupid question, but how is it that the flow separation above the wing causes it to stall? Theoretically, how come the air below the wing stops pushing the airplane up? Since the flow separated on he top, should there be even less pressure? Also, I heard a stall is simply an issue of a too high angle of attack and not speed. I mean, how come some airplanes can fly straight up and not fall out of the sky then? I am not fully sure about these things. Thanks.
well some airplanes like fighter jets can go straight up because of raw power or thrust like a rocket, prop planes that are powerful enough can do this too and sustain a vertical climb. I think that the stalled air after separation of airflow is either at the ambient air pressure or at a higher air pressure from that low pressure area on the center of the wing rather than being even lower in pressure. You are correct, a stall is simply when the plane reaches its critical angle of attack with the relative wing. If you go too slow you will stall if you try to maintain altitude because the slower you fly the greater your angle of attack needs to be to maintain lift. You can stall if you go too fast too, but thats for a whole other list of reasons...
Petr A, What your forgetting is that when an aircraft flies straight up the relative velocity of the airflow is directed straight downwards which gives you zero angle of attack while traveling straight upwards. As for separating the flow, this causes low velocities on the wing which creates higher pressure and equalizes the lower surfaces pressure and negates the total lift. hope this helps.
Petr A It doesn't matter what attitude you're flying at, it's all about relative wind. You can fly straight up with the same alpha as you do in level flight.
Sean Rita You can also exceed the critical alpha at high speeds with aggressive inputs on the elevator.
Petr A In a deep stall, look at the curvature of the still continuous streamlines on the top and bottom of the airfoil. They curve outward about the same, so their pressure is equal on both sides, so no lift and gravity pulls the plane down.
You could even state the high turbulence on the top surfaces makes the wing look somewhat symmetrical and really really fat to the upcoming wind. Even tho the space where the turbulence is not being an actual solid, the airflow doesn't know that, and just sees something pushing back on it making it feel just like a very draggy symmetrical object it has to curve around.
Some airfoils take advantage of this. A thin wing can have low drag and good lift in certain airspeed and angle of attack ranges, and a thicker airfoil might perform much better compared to the thin wing in other flight speeds and angles. If a thin wing's airflow is allowed to detach from the surface at a certain speed/angle, but is designed so that the flow reattaches a little bit further back on the wing, it is not actually a high drag stall, but the wing acts as if it is a thick one. That way a wing design can have the best performance of both thin and thick airfoils, so a broader flight speed range with low drag capabilities.
About when a stall occurs, it depends on airfoil. Generally if you slow the plane down very much, you need a bigger angle of attack to keep the same lift force on your wing. At a certain point you dont get any more lift out of the wing (reached CLmax,) and increasing the angle more even reduces lift a little. Increase more and it will reach the stall angle and you suddenly lose more lift.
About planes shooting straight up.... if trust > plane weight, you can just move vertically up. Rockets don't need wings.. In a slightly off vertical angle the wing is starting to help with the lift, but it needs not much lift to help so angle of attack is low. no stalls then unless you climb very slowly.
15:13 "you guess it?? STALL" Oh you dont say!!!!
how i wish i am pilot too.. ^_^
Thanks for uploading! certainly a really education one though it is in 20th century!
Btw, the video says. All forces must be imbalance ? or does it means, in- balance? can someone enlighten me please?
in balance.
hey ,,if u are a naruto fan then just please see the logo in first scene,,it looks like itachi mangekyou sharigan
why cant things be this easy nowadays! lol
alright im ready to make a plane
@lunamoth12 then be a pilot, cost about $30'000, a school in Houston, Hitech aviation will complete you in 8 months.
i like the old instuctional vids.people seem more interested in learning things like lift.drag.weight.and thrust sounds a little like my sex life , but im just a naughty boy and i like to fly
is this video meant for pilots are just anyone?
Sounds like a good traffic generater
um... No. If thrust is greater than drag, you are accelerating. In stable flight at constant speed, thrust and drag are equal. If they were not the plane' speed would not be constant.