Just Simply Beautiful

images/aeros_phantom1 This is a brand new rigid-wing hang-glider designed and manufactured by Aeros, of, of all places, the Ukraine. Apparently, after the fall of the USSR, some ex-aeronautical engineers became entrepreneurs. In both the flex and rigid wing categories, it is quite well known the world over that Aeros delivers the best in performance for the money. Their wings are always near the top of the stack in all national and international X-C competitions, and they significantly under price the other 3 top manufacturers of the world (Wills Wing of the US; Moyes of Australia; Icaro of Italy).

To see a small side show of this beauty, christened the Phantom, go here.

Now, what’s different about this rigid wing from the one I fly, and the other brands is that it has ailerons instead of spoilerons. Ailerons, basically, modify the twist of each wing in roughly opposite quantities (remember how the Wright Brothers controlled roll–through physically twisting the wings). This makes the wing roll one direction or another and is how a turn is typically initiated. With spoilerons, you simply have a panel on the top surface of each wing, and you cause the panel to be raised on the wing in the direction you wish to roll. This spoils the lift over that section, the wing drops, and you have initiated a roll.

But, here’s the problem. Adverse yaw. This is a condition where your airplane wants to yaw away from the direction of your roll/turn. The reason is because when you modify the twist of your wing with the ailerons, you are decreasing lift on the inboard wing and increasing it on the outboard wing. More lift, more drag. Less lift, less drag. So, by using your ailerons, you set up disequilibrium in drag on the wings, and it happens to be exactly the opposite disequilibrium that you want. Now, when you have 3-axis control, like most airplanes have, you lead with a little rudder in the direction of your roll/turn, and this counters the adverse yaw. Of course, hang gliders are flying wings. They have no rudder, so adverse yaw is a major concern.

And so back to spoilerons. The reason all the other rigid-wing hang-gliders use them is because they create drag only on the inboard wing, so you get a beneficial yawing of the wing into the direction of your roll/turn.

If you look closely at the slide show of the Phantom, above, you’ll notice three separate sections of controllable surface on the wings. Most inboard are the flaps. Then you have the ailerons, and then a small section Aeros has dubbed the “spad.” This little gizmo actuates on the inboard wing a bit ahead of and more severely than the aileron in order to minimize the effect of adverse yaw. From what I hear, they have not eliminated it completely, but have reduced it a lot.

We now return you to your regularly scheduled programming.

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