old-sparky

am having problem with "take it easy" powered glider. sometimes when starting a turn from a glide condition the wing tip drops quickly and it is a struggle to recover control. poor trim, lack of speed, cg, etc.?

Ollie

It sounds like the tip of the wing is stalling first. this can be caused by a wing warp, a design aspect, a trim setting, a piloting mistake or a combination of these causes. The problem is to diagnose the cause(s).

First, check the wings to see that the tips are not twisted so that the incidence is greater at the tips (wash in). Also, make sure that any wash out (incidence less at the tips) is symmetrical from side to side all along the span. About two degrees of washout may be helpful in avoiding tip stall. Fly the model to see if this cures the condition.

Second, trim the model so that there is a little more stall margin by adding a click or two of down elevator trim. Fly the model to see if this cures the condition.

Third, before starting a turn, give the model slightly more air speed by finessing a little down elevator. The extra air speed will provide more stall margin. The steeper the angle of bank in a turn, the more airspeed is required to prevent a stall. Enter turns gradually rather than abruptly and gradually increase the angle of bank to the desired size turn. It takes skill and judgement to match the airspeed to the angle of bank for a low sinking speed yet with adequate stall margin. This takes a lot of practise. It is easy to judge the ground speed but it takes quite some mental effort to judge the air speed. Air speed is the vector sum of the ground speed minus the wind speed. Air speed is your friend. Keep sufficient airspeed all the way to touch down and you won't stall and loose control.

Move the CG aft in small increments until the plane is slightly difficult to fly smoothly. A plane that is nose heavy (too much stability) has a strong tendency to return to the trimmed flight speed. Paradoxically, this makes it harder to control the airspeed.

old-sparky

thanks for the imput. i am anxious to try all of these .the last one about cg was the most susprise. the planes i fly at much higher speed (.40 trainor and zagi) i assume are not so sensiive to this. thanks again

Ollie

The airspeed of a powered model is controled mainly by the throttle. The glider, lacking a throttle, has its airspeed controlled by the exchange between potential energy (mass times altitude) and kinetic energy (half the mass times the velocity squared). In other words the glider converts altitude loss into speed and speed into altitude gain while always paying a tax to drag. A stall suddenly shifts the plane into a much higher tax bracket. Rising air currents (lift) increases the potential energy without increasing the drag (tax rate) which is analogous to a tax free inheritance.