ORIGINAL: Jim Thomerson

Now you see why in Control Line Precision Aerobatics, we fly the square loops (and other maneuvers) on the down wind side of the circle.

ORIGINAL: BMatthews

Yep, the figure you gave are nonsense because you're mixing air, wind and ground speeds up in a salad of confusion. None of your numbers add up to anything that makes sense.

You said-"There is a 20kt wind from left to right and I start from the left at 20kts "

That implies that you are approching the square loop with a tailwind of 20 kts plus a forward airspeed of 20 knots because you're flying downwind for a total ground speed of 40 kts.

You then said- "(I) pull straight up directly iin front of me. I maintain a straight line and slow to 20 kts at the top where I turn into the wind"

Well, since you were already doing 20 kts AIRSPEED when you were flying downwind to enter into the square loop you can't very well slow down in the vetical line to 20 kts. <span style="color: rgb(255,0,0)">I was going 40 kts ground speed, did I somehow lose all of this speed when I pulled up?</span> <span style="color: rgb(255,0,0)">The air (wind) is staionary in respect to the plane now. </span> This is the start of the confusion. But forget that for the moment. So the airplane flew along at 20kt airspeed and pulled vertical and maintained a 20kt airspeed up the line (perhaps thanks to adding power?). <span style="color: rgb(255,0,0)">Throttle management is to understood but not defined.</span> That's fine. As it did so the wind hitting the top of the model along with it's momentum from the 40kt ground speed kept it drifting belly first downwind at 20 kts all while the model was heading up at 20kts. <span style="color: rgb(255,0,0)">I do not understand why you would think that this is happening. By definition a vertical line has no ground speed. </span>

Now you turn the next corner to inverted to fly back into the wind where you said- "...at the top where I turn into the wind, lose 5 kts and continue at 15 kts plus the added wind speed of 20kt for an air speed of 35kts."

So why is this corner costing you 5 kts where the other one didn't? <span style="color: rgb(255,0,0)">The speed loss was not specified but you can see by my previous statement that the plane is slowing down. </span>Let's skip any drag related speed losses in the corners for now even though they certainly occur. So the model flips inverted from the 20kt upline to flying at 20 kts of AIRSPEED into the 20kt headwind that is still coming from the left as per your original statement where both the model AND the wind are coming from the left at 20kts each. <span style="color: rgb(255,0,0)">The plane is traveling up at 20kts when it turned inverted and lost 5kts. This speed is in relation to the ground now and is flying into a 20kt wind. The speed of the air over the plane is now 35kts.</span> So you see where our and your confusion is coming from?<span style="color: rgb(255,0,0)"> I am not confused by my scenario. </span>So anyway, our model has just rotated to inverted and heading back the way it entered and facing the 20 kt wind from that direction. So it sits in the air upside down at zero ground speed apparently defying gravity but is actually very happy because it is still plowing through the passing air at its happy speed of 20 knts. <span style="color: rgb(255,0,0)">You are saying that the upward speed has somehow disappered? Underlying this discussion you seem to be saying that the momentum of a plane continues to move a plane in it's original direction after turning in a new direction. If you dive to the ground and level out do you continue to descend toward the ground at the original diving speed?</span>

So from here you pull the last corner for the downline where you said- "I proceed to the down ward turn and dive straight down while chopping the throttle to a speed of 20kts. At the bottom of the leg I pull level, lose 0kts because gravity helped in keeping the speed up in the turn and proceed at 20kts minus the wind speed of 20kts coming from behind for a net air speed of 0kts and hope I can accelerate to a flying air speed before I hit the ground."

Nope, not the case at all. The model does come down at 20 kts like you say but it also is now being pushed by the drift so by the time you get to the bottom line where you pull back to level the model is being pushed canopy first "upwards" at 20 kts. <span style="color: rgb(255,0,0)">Again, Ican't understand why you think this. You are saying that a plane can't fly in a vertical line in a wind. Ithink it can because Ido it when Ifly. </span>Also it maintains it's speed through the corners because we're ignoring the drag losses in the turns so it pulls out with both 20 kts of airspeed PLUS the 20kts of wind speed from the tail and is immediately flying at 40 kts with out any sign of sag towards the ground.