2:56 No. That is not lift. The shape of your drawn wing is horrible, BTW. The air at the back of the wing has nothing to do with the lift effect of a wing. It is the vacuum pressure created on top of the wing, that creates lift. Lift also comes from pressure hitting the wing, when it's at an angle to the air flow, increasing pressure on bottom, decreasing pressure on top. That creates lift.
you statements are not correct, or at the very least so general and contradictory as to be confusing for any aeronautical student. A pressure gradient is indeed responsible for a proportion of the lift generated by any aerofoil, to state otherwise, as you do here, is nonsense. There are much better and clearer videos on U Tube that I suggest students find and take on board.
Point 1: a symmetrical aerofoil still generates lift. Yes, but from what i saw the lift is zero if the angle of attack is zero on a symmetrical aerofoil. If the angle of attack is greater than zero it is no longer symmetrical relative to the airflow.
How does deflection works on a paper plane again? I though that lift was a combo Bernoulli/newton third law , so paper planes kinda going for creating lift mostly with newton third law
You can't separate Bernoulli and Newton. You can describe lift as the pressure distribution over the upper and lower surfaces (if you sum that pressure distribution over the entire wing area, you will get the lift). But also if you measure the change in momentum of air from before it hits the wing to after it hits the wing, you'll also get a number for lift. Those physically both have to be satisfied, not one or the other.
Currently doing my ATPL, and I must say, you are doing a super job at explaining. Keep it up! I would love to see you do examples in fx Fuel Planning with CAP697 with the MRJ, and also how to do the fuel/time to climb calculations.
those kind of calculations are relatively straight forward, you just need to find the right table in your airplanes manual and follow the lines inputing the correct data until you get to the result! thanks for watching
I can't help but point out two amazing takes from Babinsky's video: 1. It DOES NOT show air accelerating over the top of the wing and 2. It DOES NOT show the deflection you claim. A wing requires a positive AoA to generate lift, so the underside of the wing is moving into the air, the topside is moving away from the air. The wing pushes the air causing it to compress which creates the high pressure below. The wing moving forward generates a void of low pressure above the wing. That's what causes the low pressure above and the high pressure below. It's absolutely nothing to do with the new-existent deflection!
Hi Ed, good video overall. Good job identifying 2 problems with the Equal Transit Time fallacy 1. Not always a longer path on the top 2. Particles don't need to meet up with each other. Good explanation concerning Newton's 3rd Law. I think you dismiss the pressure gradient too much though. The pressure gradient made by faster flowing fluid on the top of an airfoil contributes to lift more than a little bit, and both theories are very important to lift.
If this is the case then the reaction force based on the Newton's third law suppose to push at the trailing edge of the wing from the bottom since the deflection action (force) is taking place at the trailing edge rather than lifting the whole wing.
The "deflection" occurs over the entire wing. In potential flow you model the airfoil as a sheet of vortices over the upper and lower surface; each of those vortices is contributing to the deflection a little bit.
Very interesting. It makes more sense that disturbing airflow would reduce lift when you think of lift as a mechanism of fluid dynamics and not just pressure zones.
Great video, PilotEd. I think it was really important to knock out the misconceptions at the beginning of the video to prevent any confusion. I did notice that you mentioned that the lift is generated through deflection at the trailing edge of the airfoil, but I also think it is important to mention that the deflection of the streamlines over the whole airfoil contribute to the lift with Newton's third law of motion through a pressure force. You also mentioned towards the end of the video that the low and high pressure regions of the airfoil add a "little bit" of lift and the main source of lift is the deflection in the airflow. This is true, except for the part where pressure differences contribute little to lift. The streamline curvature creates a pressure gradient and is exerted through a net pressure force upwards (lift) and this is sustained through lower velocity fluid particles along streamlines on the bottom surface and higher velocity fluid particles along streamlines on the top surface.
Thanks for your videos again, PilotEd, really enjoy to watch them! I'm also doing my ATPL, so that really helps me to understand the topic more comprehensively. :) However another thought about it has emerged while watching, it'd be interesting to discuss. So, what we see here is that due to the airflow deflection downwards from the wing, according to the 3rd Newton Law, an equal opposite force is generated which is an actual lift for us, wright? Ok, now let's consider this in scope of ground effect. Air is not so much deflected downwards, still aircraft is perfectly able to fly even more, it flies better than higher in the sky due to the reduction of induced Angle of Attack and its consequences. Similarly, we can think about high speed flight where downwash decreases. Anyway, thanks again, cheers :)
from what i understand, the majority of lift is produced as a result of the differential in pressure above and below the wing. This can be explained by Bernoulli's theorem WITH the venturi effect. The venturi effect relates to the pressure and velocity of a fluid flowing through a constriction. As the fluid travels through the constriction, the pressure will decrease while the velocity of the fluid increases. The other end of the constriction this will revert with the pressure increasing again and the velocity decreasing. An aerofoil is like that constriction, and as a result the air traveling over the wing has an increase in velocity and a decrease in pressure. The downwash from the training edge does contribute to the lift vector however it alone is not enough to get an aircraft off the ground. I am coming to the end of three years of studying aerospace engineering and this is what all of my lecturers have stated. There is not one soul cause of lift but instead multiple laws acting together to create enough lift for something to fly, be that an actual plane or a paper one.
And again, PilotEd saves the day of yet another confused ATPL-student! Thank you so much for this mate, I think i speak for all of us when I say these videos are inspiring, motivating and last but not least full of knowledge! Cheers
This is a good, simple explanation of lift! I really liked that you took the time to disprove some common misconceptions that many people are taught. I think it would be a great point to add that the low pressure, high velocity at the top and high pressure, low velocity at the bottom isn't only at the surface. Instead, the airfoil affects the velocity and pressure fields in a very large swath around it, which also works to generate lift. Overall though, great video!
Yes, I agree! Also it is stated that there is a difference in pressure, but why there is a difference in pressure is not explained. There is not only a difference in pressure between the upper and lower surfaces but between the leading edge and the trailing edge of the airfoil. As shown in the smoke particles experiment that Dr. Babinsky performed streamlines close to the airfoil become increasingly curved. This is proof that a pressure gradient is present and the pressure drops as we move downwards. This explains why the pressure is lower at the upper surface and higher at the lower surface.
I would have thought a paper airplane would be generating lift only when it has a positive angle of attack, like how you put your hand out of the window in the car. If the paper plane had an AOA of 45 degrees then it would be producing lift and drag in more or less equal amounts. If this theory of deflection were true, then wouldn't the centre of pressure of an aircraft wing be right at the back (where your arrows are located)?
Hi PilotEd! Thank you for your great videos ! I have a question regarding to your videos: are the theory parts and principles explained in your videos really simplified with respect to the atpl theoretical exam or is it quite close to what you can find in the questions/books of atpl theory? Looking forward to your answer ! Fly safe :)
good question XD! they are a little simplified some videos! it depends, the altimetry one for example is very detailed. also the polar navigation. it depends on the video. and the subject. thanks for watching
Sir, In my air regulation subject there is a topic on RUNWAY CODE. BUT IT IS NOT EXPLAINED IN THE BOOKS. CAN U HELP ME OUT AS I AM GIVING CPL AND bsc. (aviation). LIKE THERE ARE RUMWAY CODE 1 TO 4 . CAPT. PLS HELP ME PLS
@@jaybabcock9123 well paper aircraft dont have any propulsion, remember lift is a formula with speed as a big factor, so the more speed you have, ie a fighter jet, the less angle of attack you need :)
Angle of attack, i believe. Think of an aerobatic plane flying inverted. The wing is symetrical, so a change in the angle of attack allows it to fly regular, or inverted (maybe not substantially, but pretty well.)
The science is that the top-bottom pressure difference provides *ALL* the lift force and these same pressures also cause all the air accelerations of air around the wing including behind, ahead, around the curves and around the tips. If it is viewed as the downward deflection leaving the trailing edge causing a reaction force, it would all be at the trailing edge, not forward as we measure it. So, that is not correct. .. There must obviously be the 'action-reaction' pair. However, that is not a cause, but a result of the pressures. Pressure pushes the wing up and it pushes against some air which then moves down. . If we're on skate boards and I push you, we both respond by moving away, but your movement away from me is not pushing me away. My push between us pushes us both. It is your mass, your inertia that gives me something to push against. The pressures around the wing also have the mass/inertia of the air to push against; and that air moves down - while the wing is held up. . The wing's motion changes the pressures around it How and why that occurs requires more detailed explanations.
If air hits a flat(plane) at an angle the air compresses because it cant follow its path that compression is pressure which pushes the wing up and the air down this would not cause lift at the trailing edge but as a splope throughout the wing if the wing is uniformly curved the 2nd derivative is constant and thus the acelleration of air is constant which spreads lift somewhat equally along the wing
@@hund4440 Correct. I was not clear and edited it. My comment points to the flaw in the common 'reaction' explanation. __if__ the upward lift came from the 'reaction' of the air leaving the trailing edge, that would mean that the center of lift is at the trailing edge. We know the center of lift is towards the leading edge and, therefore, that explanation is faulty. The underside pressure, as you say, is distributed throughout the wing..
That's Fxxking one awesome video, I am studying toward my CPL seven subjects as well as preparing for my upcoming Airline cadetship interview. God, I already learnt more by watching your video. wondering if you are an instructor somewhere else or flying for airline only?
Okay let me know if I have this right. The deflection forces the air over the wing downward and an equal and opposite reaction occurs pushing us up. And the reason the deflection happens in the first place is because of Coanda Effect? And then Bernoulli's Principle is kinda just tacked on there as a contributing factor, but not the sole cause of lift. Is that sounding accurate? I'm preparing for my Commercial check ride.
yes, not so much emphasis on the coanda effect, but yes as the wing deflects air down, pushes us up. also little negative pressure on the top part of the wing.
@@RealRadiantBeing Coanda is not important (only applies to fluid jets, which can be the case for gaps between slotted flaps or slats but not for main airfoils). Air doesn't want to separate from the upper surface of the airfoil because doing so would create a low pressure zone underneath which would just suck it back in.
Hey Ed, thanks for the different perspective … but I’m confused about this theory creating equal/opposites force at the trailing edge. If the lift force is taking place at the trailing edge…that would create a nose down moment, no?
