Hot answers tagged

40

Yes. The wing doesn't care what is causing air to flow past it. Headwind, propwash, 747 wake, gopher sneezes. If the airplane is restrained from forward motion, and the propwash over most of the wing is fast enough, let's say more than the airplane's stall speed, then the wing must generate enough lift to support the airplane, causing it to take off. It's ...


12

In principle yes, but why would you do it? For vertical take-off this would be grossly inefficient. Lift is produced by deflecting air downwards. This becomes easier as more air is available for deflection since the amount of deflection needed for a given lift can be reduced. However, when all air movement is provided by the propeller, why reduce efficiency ...


9

Restricting the question to approximately horizontal airflow ... it's been tried. The Custer Channel Wing was one that tried ... it didn't quite make it, but was claimed to be able to fly at 8 to 11 mph. That may have been optimistic but the CCW5 (pictured : image from linked Wiki) apparently flew as slow as 35mph. And it keeps being tried... this time in ...


5

There are multiple ways to decompose lift and drag forces, and they are unfortunately not compatible with each other. If you know the flow field (for example because you ran a CFD simulation), then to compute lift and drag, you need to integrate: pressure forces (i.e. local pressure times surface normal, over area) viscous forces (local viscous stress times ...


4

Absolutely. Here's what it looks like: It's a turbojet here (this is an F-35 engine) but from a physics standpoint there's no reason you couldn't do it with a propeller. So long as you have some means of directing a sufficient portion of the thrust downward, you can lift off. An airfoil would also redirect the thrust slightly downward, but far less ...


4

Presumably you are referring to using wings fixed to the airframe with props driving air over them. If instead you move the wing through the air to create airflow over it you "cut out the middleman" and end up with a helicopter or typical multirotor craft. Similarly an ornithopter moves the wing through the air to attain lift.


4

Draw a line from the leading edge to the trailing edge. This is the chord, and it has a positive angle of attack as the shape is oriented. Therefore your premise that this has zero angle of attack is incorrect. Since you can produce lift with a positive angle of attack using a flat plate, it is reasonable to assume that this shape, as drawn, should produce ...


3

A wing has geometric twist when, from root to tip, its chord line changes angle, typically without changing the airfoil shape. This is colloquially known as washout when the root stalls before the tip (or, much more rarely, its opposite, wash-in). A wing has aerodynamic twist when, from root to tip, its airfoil changes in camber and thus in shape, typically ...


2

In my opinion the vertical position of the center of gravity (CG) is negligible. First of all the variation will be very small. Between an airplane with lead on the bottom of the cargo and an airplane with all passengers on the upper deck the CG will not move that much. And statistically the CG will probably be somewhat around the centerline of the fuselage. ...


2

Would definitely create some lift if flying supersonic ;) Otherwise, sharp edges force the flow to detach and thus destroy any lift capabilities of the shape.


1

Yes, it will produce lift, just like any body that is asymmetrical w.r.t. the flow field will produce lift. A program like XFOIL can estimate its lift and drag at various angles of attack and at various Reynolds numbers. If you wanted to convince a professional to build such an airfoil, they'd want such numbers first.


1

This is good one. Doug Mclean: Let’s first put induced drag in perspective by looking at drag in general. Drag is just the flight-direction component of the total aerodynamic force, excluding engine thrust. (For purposes of this discussion, we’ll assume drag and thrust can be cleanly separated, ignoring some serious theoretical difficulties.) The air acting ...


1

I think it's based mostly on perception of altitude above ground level. If you're hovering over trees, or over a rough sea, what you care about first and foremost is your clearance from the tops of the trees and waves. And if the surface of the vegetation is dense, like tall crops, trees or bushes, that's what your eyes will focus on, so you perceive that as ...


Only top voted, non community-wiki answers of a minimum length are eligible