17

Indeed, when an aileron moves upward, it locally generates less lift and less drag. Assume we are talking about the aileron on the right wing. The reduced lift drops that wing, rolling the aircraft right. But the reduced drag accelerates that wing, yawing the aircraft left. On the left side the opposite happens, but it has the same effect. The aileron ...


8

You can't from the planform alone. First, winglets are no magical device. Calling the wing with bell-shaped lift distribution one with horizontal winglets tries to free-ride on the mystique that NASA marketing has created around the winglet. But the physics behind it are rather mundane and the thrust which is created by the outer wing is a bit of payback ...


6

The aileron going up does produce drag as well - once it is producing a sizeable amount of downforce. At rest, it is aligned with the back end of the wing, and in a wing with no camber at zero Angle of Attack the aileron produces symmetrical drag. But wings usually do have camber and/or AoA ≄ 0, so at rest the aileron points trailing edge downwards and ...


5

Yes. For deliberate cross control situations, adverse yaw helps. This means during side slip or forward slip maneuvers, where adverse yaw means less rudder is required to keep the nose pointed in the opposite direction to the lowered wing. If you are in a glider or an old classic aircraft with lots of natural adverse yaw, if you lower a wing without any ...


4

The principal drag in question is induced drag, that is the drag necessarily induced by creating lift. The aileron that goes down increases lift on that wing, and thus also induces more induced drag; conversely, the aileron that goes up reduces lift on that wing and thus induces less induced drag. Hence, the aircraft will tend to yaw towards the aileron ...


3

I have several posts and snarky comments on here that describe the function of winglets precisely as outlined in this video; that is, they exploit the circulation around the tip to generate thrust (like sails on a boat, which is why they were originally called "tip sails"). Almost all descriptions talk vaguely about how they give a reduction in induced drag....


2

Maybe they have tried winglets as part of their design iteration and then decided to leave them off, or rather bend them downward thus obtaining a bigger wingspan. "Horizontal winglet" seems to be a term used in windtunnel studies to indicate "the winglets are bent down" as opposed to 60 degree, etc. winglets. The difficulty with these "horizontal ...


2

Great work from the NASA team and an interesting way of thinking in 3 dimensions. A look at bird wing anatomy shows how they decrease lift and increase drag on the same side: by using their "wrist" to pivot their wing tip leading edge down. You can do this by sticking your arm out and rolling your wrist. Conventional aircraft need rudders to counteract "...


2

Looking at the picture of the glider, the orientation of the hinges indicates that the winglets should provide directional control, replacing the rudder as well as the ailerons. The original Horten aircraft had spoilers to perform the same role as the rudder in a conventional design.


2

I would add that it depends on what you mean by "proverse yaw", and that vertical fin size is key. Proverse implies "too much" yaw in excess of the appropriate yaw rate for the angle of bank, which would be a skidding turn. That's bad. If proverse just means an into-turn yaw rate that is appropriate for the bank, that's good. Airplanes with spoilers-...


1

A two part answer here. Yawing in the direction of the roll in a turn is known as a "coordinated turn". How to do it depends a lot on the design of your plane. In a high wing dihedral (trainer), with slight aileron deflection for a left roll, the dihedral and pendulum will neutralize the roll and the downward right aileron may actually start to skid the ...


1

Is it even possible to have no yawing tendency at all during rolls in a plane? No. Once the aircraft is in a steady roll, the roll damping will fully compensate for the differential lift caused by aileron deflection. Now the rolling motion will increase the local angle of attack on the downward moving wing the farther you are away from the center, and ...


1

Turns with balanced flight at less than 90 degrees angle of bank (but more than zero) are actually rotations about two axes at once in steady state. It is a continuous combination of pitch and yaw. For it to be a level turn, the yaw has to be in the same direction as the angle of bank. With proverse yaw, on rolling into a turn the yaw is in the right ...


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