Induced Drag | Pilot Tutorial

[@russellhawkins6811]

Terrific video-very clear

[@ridewyoming]

Good description, makes sense

[@massimilianoc2436]

best video on drag on youtube

[@jimziemer474]

Fail. You started out fine. However, the wing doesn’t need to produce wing-tip vortices to produce downwash.

[@PilotEffect]

uuuuummmmmmmmmmmmmmmmmm

[@jeffreyleftovers]

Correct. PHAK 5-7 “This induced downwash has nothing in common with the downwash that is necessary to produce lift. It is, in fact, the source of induced drag.” Two downwashes. One is a result of unequal velocity’s and pressures of two air bodies as they meet on the trailing edge of the wing. The other is vortices as the air flips and mixes at the tip. An annular wing (circle) would not have vortices, but would still produce downwash. Induced drag is any drag as a result of increase in AOA. Vorticies, shifting lift vector, and separated air forming a pocket on the trailing edge of the wing are all part of induced drag.

[@calebatha7133]

I went straight to the comments when he said a wing with no tips would have no induced drag. thank you

[@calebatha7133]

@@jeffreyleftovers BIG thumbs up!

[@mw6272]

I'm just watching this for some review for my CFI checkride, there's one thing I disagree with. Wingtip vortices are NOT responsible for downwash. The wingtip vortices serve to exacerbate the downwash that already exists. Downwash is a factor of the coanda effect in which the air "sticks" to the top of the airfoil because of the laminar and fluid properties of air and will continue to conform to that shape as it exits through the trailing edge. Because a force is applied in a downward direction, that means relative wind is shifted in the opposite direction which allows for the lift vector to be tilted backwards, which explains induced drag even in straight and level flight with a theoretical AoA of 0 degrees. In an end of course check at my flight school, if I were to say that wingtip vortices are indeed induced drag itself, I'd get failed right on the spot.

[@j.a8678]

Yes, but if you read the PHAK, you will see that wing tip vortices create and additional downwash as well. “ Bearing in mind the direction of rotation of these vortices, it can be seen that they induce an upward flow of air beyond the tip and a downwash flow behind the wing’s trailing edge.” You are correct about the vortices exacerbating the existing downwash needed to create lift. But there are actually two different downwashes, the one created by wingtip vortices is the source of induced drag.

[@camilosarmiento4929]

@@j.a8678 also with agree with Max. Also to mention the type of operation and being specific to straight and level flight. High airspeed low angle of attack (unless you accept a climb), low airspeed high angle of attack up the critical angle at which the aerofoil will stall. So in essence high coefficient of lift in straight and level equals high angle low airspeed and as a consequence high induced drag (using the drag curve would also help in the explanation) the rest of your explanation is partly right. Would also explain span wise flow and how the airflow in the lower part of the wing will naturally want to move outwards towards the wingtip in contrast to the airflow in the upper side moving inwards. When both streams meet at the trailing edge, they also creat a sheet of vortices.

[@ShonMardani]

I discovered that Parasite drag is produced by VERTICAL surfaces and Induced drag is created by HORIZONTAL surfaces, for example when the Flaps are at 0 degrees they produce Max Induced drag and Min Parasite drag, at 90 degrees Min Induced and Max Parasite drag and at 45 degrees in the middle of both. Please let me know if you think it is a valid observation. Thanks

[@wbeaty]

There is no net downwash without vortices. In an airfoil-section diagram (a wing of infinite span,) first the air is forced upwards, then forced downwards, then forced upwards again. Each of these accelerations requires a force. All these forces are produced by the wing-ground system. Summing them up, the total average downwash is exactly zero. If instead we ignore the forces in the total flow-pattern, and just concentrate on the wing surface alone, with its down-deflection of the gas parcels, well, that's simply wrong. It pretends that the wing didn't cause the parcels to rise as they approached, and later to halt after the airfoil has passed by. And, this error has confused students for an entire century. (To avoid the error we must examine net downwash experienced by each parcel, summing it all up, and not just micro-level downwash at isolated locations.) When a short wing is flinging vortices downwards, only then does a net downwash appear, because after the wing has passed by, the air parcels do not halt again. They keep moving downwards. (Without viscosity to stop them, they'd keep moving downwards forever.) This is completely different than the closed circulation seen with an airfoil-section in two dimensions.

[@wbeaty]

@@ShonMardani parasite drag is produced both by unwanted turbulence and by laminar flows. Imagine the air to be like thick syrup. The parasite drag isn't only caused by viscosity. Also, if the moving object stirs the "syrup," that's another origin of drag. Even if the fluid flows horizontal, parallel to the surfaces, it still produces these two types of parasitic drag. (This force might be far smaller than the drag produced by vortices shed by vertical surfaces.) Here's one insight: the core of the wingtip-vortices represents unwanted turbulence! If the down-flung vortices could rotate like solid disks, rather than like tornadoes, then the lift would be the same in both cases, but the induced drag would be much larger for the "tornado." And, that's why we add winglets to the tips. The wingtip winglets are trying to eliminate the fast spin in the center of the tip-vortices. That fast spin is unwanted turbulence, and uses up fuel in needless drag. (Heh, so instead make our wings in the form of a giant arch, with no wingtips, like the "Channel-wing" topology. It flies like one of those tube-shaped paper airplanes. Winglets on modern aircraft are just very short segments of a complete arch or tube.)

[@snsdb42]

Love this video and the graphics really helped! Thank you!

[@andregf]

Thanks for the video. Well done!

[@TurboDirectSA]

Excellent presentation - well done.

[@kru7780]

Great explaination...☺️

[@vojtechslavik8262]

I am a bit confused how Is induced drag connected with downwash? I see it everywhere And don't understand it. Because when He showed picture of An airfoil where He shows parallel Force with airfoil the drag Is caused by the angle of airfoil not by the downwash in my eyes i dont understand

[@torawestrum2508]

Correct me if i’m wrong someone, but I would explain it like this: the spanwise flow over the wing get trapped at the wingtips due to the plane’s speed through the air. This forms the vortices. Then, these vortices will curve around the tips and push the air down on the backside of the wing. This will move the lift vector backwards and make a new angle between the lift vector and the new lift vector (effektive airflow) - and this new angle is the induced drag.

[@wbeaty]

@@torawestrum2508 Somewhat true, but don't forget that the vortex-shedding takes place at the wing's entire trailing edge, and not at the tips. Aerodynamics people call this the "Vortex Sheet." The name "tip vortices" can be misleading. After the vortex-sheet gradually scrolls itself up, it may appear that the tips created the vortex-pair. But look at the wing itself, not at the vortex-structure trailing 100ft back. Induced drag results from the down angled shedding of the entire vortex-sheet. (A 3D diagram is absolutely required for understanding this. We can't just view the wing as a sort of long rod with losses concentrated at the two tips. That's oversimplified. It's 2D thinking.)

[@davidwallace5738]

Thank you sir. Great video lesson!

[@sheikhshafayat6984]

Very helpful video. Thanks

[@alexdoherty5589]

Why does induced drag act parallel to the ground and not parallel to the direction of flight? Drag is meant to be opposite to the direction of velocity, but you showed that if the angle of attack increases, the induced drag still remains horizontal. I'm just a little confused and I have an engineering exam in two days. Sorry for the long question.

[@xvdarkshadowvx]

The airfoil itself causes the induced drag so it is parallel to the wing in my understanding

[@jimziemer474]

@@xvdarkshadowvx No, the person that asked the question is correct. Induced drag is the component of lift acting opposite to the aircraft velocity (flight path).

[@youtubeyerr]

The induced drag acts perpendicular to the relative wind. The downwash effectively increases the "relative wind" angle, so the "induced drag vector" tilts back, because it must remain perpendicular. Because it is tilted back, it is opposing thrust, which means it is creating drag. It is not fully horizontal because it is lift! If it was fully horizontal, there would be no component of lift to it.

[@WAVEGURU]

What force moves a glider forward through the air?

[@qzboanynj]

I don't understand the argument that if no vortices, then no induced drag. Let assume that we put a model airplane in a wind tunnel, the the wing of the airplane is as wide as the width of the wind tunnel. This way air will not be possible to be pushed out from the side of the wing, so no vortices. In this case if the airplane needs to fly, it has to have angle of attack and this will create induced drag in order for airplane to float. So the angle of attack creates both lift and induced drag, vortices cause down wash airflow which reduces the lift of the wing. So the wing has to increase the angle of attack which in turn creates more induced drag.

[@ShonMardani]

I discovered that Parasite drag is produced by VERTICAL surfaces and Induced drag is created by HORIZONTAL surfaces, for example when the Flaps are at 0 degrees they produce Max Induced drag and Min Parasite drag, at 90 degrees Min Induced and Max Parasite drag and at 45 degrees in the middle of both. Please let me know if you think it is a valid observation. Thanks

[@alloy299]

>3:12 You sure about that? I would understand the wing itself would produce downwash even without the vortex.

[@rossodonnell5933]

Happy to be educated if I’m mistaken but… Is it correct to state that “without vortices, a wing won’t produce downwash” and therefore no induced drag, as you described with the infinite wing example? I’m under the impression that even without wingtip vortices, the act of redirecting air downward (Induced Flow) generates an equal and opposite force upward (Lift). Because there’s an Induced Flow the Resultant Relative Wind is modified downward. The Lift vector is perpendicular to this modified Resultant Relative Wind, which inclines the Lift vector backwards, and the aft’ing of the Lift Vector is called Induced Drag. Truly hoping for a deeper understanding, I would love to know if my understanding holds water.

[@wbeaty]

Without wingtip vortices, no air is redirected downwards. (Or in other words, the "circulation" pattern has closed loops.) Instead, the wing causes oncoming air to **rise** to meet it. Then the air curves downward. Then its forced to curved upwards again, to be left at the same altitude as it started. Zero net momentum is transferred to any gas parcel. Zero work is done on average. No drag is produced, and the airfoil glides forever without needing fuel. This is idealized ground-effect flight. During ground-effect, the ground pushes upwards on the wing, and the wing pushes equally downwards on the ground. Essentially it's a type of venturi. The forces of course are transferred back and forth via the gas, as an instantaneous exchange-force (it's same as with any venturi, where the solid surfaces always create zero average force, even though two surfaces can create equal and opposite forces.) When the wing is short, or at least many wingspans above the ground, then the wing is flinging vortices down, and the ground is no longer pushing upwards on the wing. The venturi and ground-effect, has vanished. (Think of vortices as being weighty baseballs made of gas. In conventional flight, the wing is like a hovering rocket-engine, with the down-flung vortices being the exhaust-plume of the rocket.) If airfoil classroom started out with the infamous Wham-O Air Blaster(tm) gun, things might become clearer. Such a gun has a kick. If fired continuously and repeatedly, it could propel a vehicle. The Air Blaster gun is a reaction motor. So is an aircraft wing. Both of these take in air from all directions, which produces no momentum-transfer and requires zero work. Then they fling air out in a single direction, which produces an equal reaction-force, and the required work is seen as Induced Drag. As with helo rotors, a fixed wing is an example of fluid propulsion. (And, when a jellyfish swims by pulsing, then the energy in its long emitted chain of ring-vortices is exactly the same as the Induced Drag losses in an aircraft wing. But the aircraft flings one long, long vortex ring, rather than a pancake-stack of multiple vortices.)

[@siddharthpg2919]

Ok im gonna watch this video now .

[@hmabboud]

What are you do not understand and I have seen in many videos is that why and how do the vortexes cause wind or air deflection?

[@innooshiqoutes2947]

Thankyou...it was easily understood

[@mafarachisi]

Great video... thanks white version of Anthony Anderson

[@حيدرالساعدي-خ4م]

❤🌹Thanks❤🌹

[@atauygur8104]

Couldn't understand something. Okey if there is no wingtip there is no wingtip vortices but why there is not any downwash? Not just wingtips produce lift right? All wing is effected with the lift force caused by pressure difference between both sides of the wing , even if there isn't any wingtip wing still effected by upward force so also applies a downward force to air molecules and creates downwash. Which point of my logic is wrong? To summarize, I couldn't understand necessity of wingtips for downwash.

[@masterdaddychris5986]

You are correct. Induced drag exists even without wingtips, this guy has his explanation sort of wrong. Induced drag can exist without wingtips/wingtip vortices. Induced drag effects ALL areas of the wing, because as you mentioned the entire wing is creating lift, not just the wing tips. Induced drag is just more pronounced at the wingtips due to wingtip vortices.

[@atauygur8104]

@@masterdaddychris5986 Thanks for making it clear:)

[@giovannigiorgio0]

Can we say induced drag comes out because of downwash (which is tip vortex)?

[@doralu2770]

Thank you for your video! it’s clear and helpful 😀

[@killeroftanks]

Why does lift move perpendicular to air flow?

[@mariano4859]

Because the shape of an aircraft wing is an airfoil.