Originally Posted by
learn2turn
The reversal thing is not aileron reversal in the aerodynamic sense. What I was trying to convey altering of flight path do to non-level wings and how that reverses when inverted.
Scenario--
- Plane is flying straight and level left to right.
- Pilot applies up elevator at center of box to begin loop.
- The wind is toward the pilot so pilot uses ailerons to roll plane left, left wing down, right wing (nearest pilot) up.in an attempt to keep the plane on a straight path.
- At top of loop, since the right wing was toward the inside of the loop during the beginning of the loop it is still toward the inside and therefore now down.
- If the plane slows at the top of the loop, the wing will begin to lift while inverted (negative Gs).
- With the wing lifting inverted and the wing toward the pilot now down, instead of preventing the plane for altering course toward the pilot, the wing has the opposite effect, adds to the displacement do to the wing and actually alters the path further toward the pilot.
- Since the plane is slow and now out of a line, the loop is not completely on time. That lengthen's the top segment even more extending the time inverted and exacerbating the problem until the plane is out of path to the point of heading almost toward the pilot.
I think that sums up the issue.
I think the cure is --
- Go into the loop slower.
- Apply throttle from the 4 to 1 o'clock phase (flying the loop counter clockwise, to avoid neg Gs at the top).
- Make the loop big but not so big that there is an extended neg G segment at the top. (If you want to do the math, I don't care how fast the plane is flying or how much power it is, there is a loop radius at which it will pull negative Gs at the top.0
- Be more subtle about adjusting course in the loop.
I know someone said to avoid rudder correction but I would think that rudder correction would be what's needed here to compensate for wind. If the winds blowing straight at the pilot and the pilot applies a tad of left rudder through the entire loop (loop entered left-to-right), wouldn't that compensate for the wing and help keep the plane on a straight heading?
-l2t aka Ken
PS
Please drop aerodynamic control reversal from this thread. There is no need to debate how wing twisting or supersonic compressibility might or might not cause it as it is 100%
not germane to this thread.
4. If the right wing is up at the bottom to maintain heading, then the right wing MUST to be down at the top otherwise the model will come in.
5. For the wing to provide lift, it has to have angle of attack, that's why there is positive incidence on the wing. When the plane is inverted there is still positive incidence on the wing which will naturally try to make the plane drop. That's the positive incidence providing lift on the model which is now inverted. If you release the elevator to neutral just before the top of the loop, the plane will continue on the arc of the loop, which is positive G. Slow speed will not change positive G's to negative G's. You would need to push down elevator to get a negative G condition in an inside loop.
6. In level upright flight the lift of the wing is acting upward. When the plane is inverted, the lift is still acting the same way on the model, which is now trying to pull the plane down. The right wing needs to be down at the top of the loop to prevent the plane from coming in. If the right wing is lifted so it is up at the top, then the plane will come in towards the pilot.
7. Flying slow does not make the top segment longer. It will take longer to travel that segment, but the distance is still the same. Inverted flight isn't the cause of the lost heading. Incorrect plane attitude and control inputs are.
1. All models behave different at the same speed. You need to work out what speed best suits your model. As a rule of thumb, trim for level flight at 1/2 throttle and adjust until it suits your plane.
2. You need to start gradually increasing throttle at or before center to maintain the momentum. Adding alot of power at the 4 o clock position will most likely cause the plane to veer off (Really??).
3.The size of the maneuver will depend on the size and power of your particular plane. Negative g's at the top? That's a negative.
4. Yep, small gentle corrections is what's needed.
I did say it's best to avoid using rudder and I still say that. Rudder is used for wind correction, but the less you use it the better, especially while performing loops. A slight aileron roll to keep the model on track will be easier to manage and less noticeable.
On most models, applying rudder will affect elevator and aileron control. Holding a constant amount of rudder while adjusting throttle, elevator and aileron is not as easy as it sounds.
The main things that will help are; 1. Trim the model as best you can, 2. Ensure the wings are level, 3. Good throttle control, 4. Fly at a speed that suits your model.