Aileron position

[IFLYHI]

Here's my thinking (yes I know this spells danger )

My ailerons are to high in relation to my top wing surface. This has the effect that I am always dragging my butt in the air. If I apply flaps the attitude of the wings change to nose down.
Excuse the drawing


I'm talking 15-20mm down each side.
Am I correct in my assumption that when I move the ailerons down the wing attitude will change more horizontal during flight, resulting in me achieving "on step" easier/faster

[Cloud Warrior]

What's an aileron?

[Arnulf]

Hi IFLYHI,

If you select flaps, you increase the curvature of your wing, making it fatter. Depending on the design of the wing selecting flaps may also increase the angle of attack of the wing. This gives the wing more lift at a given speed. So if your lift is increased at a given speed, and you do not want to climb, you will have to lower the nose attitude. Remember that by applying flaps, not only does your lift increase, but also your drag. If you now tweak your ailerons down, they start acting like flaps, increasing not only the lift but also the drag. I doubt you would want that. The best you can do is to rig the aerrie according to the manufacturers specs.

The "step" is also a bit of a myth. Only boats and amphibious aircraft really get on the step. Thats when they start planing on the water. Aircraft don't fly on the air, but through the air. The closest you get to a step is if you fly just a bit faster than your best lift/drag speed. The best lift drag speed is influenced by proper rigging, correct C of G and weight.

Regards,
Arnulf

[Morph]

If I understand you correctly you want to drop the whole aileron down by 15 to 20 mm so the ailerons are in effect mounted lower that the bottom surface of the wing.

If that is the case look at a Bush Baby, they have exactly that design. Give Boet Laubsher or Monty at the factory a call and find out from him what the implications are. Boet is as 0276-621245 He builds a lot of BB's and specialises in their wings

[kb]

Cloud warrior,

[IFLYHI]

If I understand you correctly you want to drop the whole aileron down by 15 to 20 mm so the ailerons are in effect mounted lower that the bottom surface of the wing.

If that is the case look at a Bush Baby, they have exactly that design. Give Boet Laubsher or Monty at the factory a call and find out from him what the implications are. Boet is as 0276-621245 He builds a lot of BB's and specialises in their wings

No
and i thought my drawing was obvious just the trailing edge in a straight line with the top of the wing surface

[Morph]

OK,

Now I understand, not sure about the on-step thing.

My plane has Flaperons, infinittely adjustable ailerons that act as flaps when fully deployed or for trimming the plane when not. I have the ability to adjust from -10deg to +30, i.e. I can adjust them up or down.

When I adjust the ailerons down the nose of the aircraft drops and the airspeed increases. Obviously by doing this I need to increase rpm to maintain straight and level flight. Otherwise you would have to fly with a significant amount back pressure on the stick just to maintain straight and level at a lower rpm and speed. I guess that the plane reaches it's fastest speed when the aileron is producing minimum drag which I suppose is somewhere between your two options. The second option of your drawing would be incurring drag from the airflow over the bottom of the wing.

Aditionally, lowering the aileron increases lift and decreases the stall speed, pretty much like flaps would do.

I would be careful in permanently adjusting this on the plane, you don't want to end up in a situation where you have insufficient rpm to maintain level flight or even climb capabilities and you do not have the ability to be able to adjust the trim significantly to reduce back pressure on the stick.

I do notice on mine, the more down adjustment you have the heavier the stick gets, to a point that it is downright uncomfortable and a pain on takeoff.

[justin.schoeman]

Hee hee... That could be really fun - especially if the plane does not have full length ailerons. When you lower the aileron, you increase the angle of attack. Now, if you don't have full length ailerons, then by lowering both ailerons, you end up increading the angle of attack of the wing tips relative to the root.

Now pull up, close to the stall, and your wing tip will stall before the root, giving you an almighty wing drop on the stall.

If you have full-length ailerons, things are different. Most airfoils produce optimum lift at a 15deg angle of attack. This is why you are always flying nose-up at low airspeed. The lower your airspeed, the closer you have to be to optimum lift to stay airborne, so at low airspeed, you end up with about 12deg nose-up. (Most A/C have a built-in 3deg incidence.) To get the nose down, simply increase your airspeed. With a higher airspeed, more lift is available, and to stay level, you have to decrease the angle of attack - therefore take up a lower nose attitude.

Now, if you drop both trailing edges (by lowering the ailerons), you increase the wing incidence (lets say by 2deg). Now, since the airfoil still produces max lift at 15deg, you will now have a 10deg nose-up attitude to get max lift, so yes, you will have a lower nose position. Only difference is that, with the higher camber, you now have more lift for a given speed (good), but correspondingly more drag (bad). Also notice that a significant change in aileron position only made a small change to the attitude. However, since lift is proportional to the square of speed, it only takes a relatively small increase in airspeed to produce the same lower nose attitude.

And all this really means is: 'Listen to Arnulf and rig the plane according to specs.' Everything is carefully balanced to give you the best flying experience.

Oh yes - another drawback of lowering the ailerons is the effective increase in decalage, which will have a serious negative impact on pitch stability.

-justin