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flyeslhost
158 Posts |
 Posted - 09/28/2004 : 9:14:54 PM
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By Anker Berg-Sonne
09/28/04 - Winch launching a sailplane has three stages, the throw, the tow, and the zoom. Of these, the tow is the easiest to master, and is easily learned with a little coaching. The zoom can be avoided entirely and learned gradually. |
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flyeslhost
158 Posts |
Posted - 09/28/2004 : 9:35:13 PM
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By Anker Berg-Sonne
09/28/04 - Winch launching a sailplane has three stages, the throw, the tow, and the zoom. Of these, the tow is the easiest to master, and is easily learned with a little coaching. The zoom can be avoided entirely and learned gradually. But the throw is mandatory, and bad throws destroy more planes than any other part of the launch. Personally, it took me quite a few years to throw the plane properly, and I found learning better techniques for throwing counter-intuitive and intimidating.
With captured video tape frames I’ll try to illustrate the most common throwing mistakes and also show the throwing technique that I have learned and now use.
If left to their own devices, right-handed pilots will pulse the winch with their right foot and hold the plane with their right hand, and lefties will use their left hand and foot. You can’t do this and execute a decent throw. Frames 1 through 5 show me throwing the plane with the technique I used my first 13 years as a pilot. On frame 1 I have my right foot on the winch pedal and my right hand around the tail boom of my Mantis. Notice how I need to lean back to balance the winch tension. Imagine what would happen if the line broke! Also, all I can do to throw is extend my elbow. That’s not going to give the plane a lot of speed. I am totally dependent on the winch line to pull the plane up to flying speed. Until the plane reaches flying speed I am at the mercy of any wind gusts. The last point I’ll make is that holding the tail boom does not give me much ability to resist wind gusts that try to lift a wing. On frame 2 I am half-way through the “throw”, and on frame 3 I have just released the plane. On frame 4 and 5 the plane is rotating into the tow. This was a windy day so the plane quickly reached flying airspeed. On a calm day the plane would not have started climbing before disappearing out of the picture.
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The next six frames show the throwing technique I use now. In frame 1 I have just started tensioning the winch line. Instead of pulsing the winch with my right foot, I have my left foot on the pedal. This allows me to rotate my body to the right and extend my right arm behind me, almost parallel to the winch line. I can hold a lot more tension this way than I can by bending my elbow. I have also put my right foot way behind my left foot which steadies me and eliminates the need to lean against the winch tension. I can almost stall the winch without losing control over the plane. Lastly, I have my hand around the fat part of the fuse, which gives me a much better grip than before.
On frame 2 I have started the throw. I am rotating my body and my arm is beginning to come straight over my head. It is important to keep the arm straight and have it come over you head. Otherwise you may hit yourself in the back of the head with the wing. I have seen this happen, and it gets pretty nasty - pretty quickly. On frame 3 my arm is getting close to the vertical. The plane is reaching flying speed, and I still have a pretty good grip on the fuse. On frame 4 I have just let go. The plane is at flying speed and is just beginning to rotate. On frame 5 the rotation is well under way and the tail is still behind my head. On frame 6 the rotation is almost complete and the plane is climbing rapidly.
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As I look at the video, I can see two improvements I could make. The major one is to point the nose a lot higher during the throw. The plane has plenty of speed to climb at release, and the time to rotate from the horizontal is a waste of energy and winch line. The other improvement is to extend further back and down as I tension. I feel like I am extending further, and am surprised to see how little it really is on the video.
The next few frames show an alternate technique, as executed by Fritz Bien. He is more comfortable throwing with his left hand and pulsing with his right foot, so he is turned the other way. Fritz doesn’t extend as far back as I do, and he doesn’t throw with a straight arm over his head. I believe he has a physical problem that prevents him from doing it, so he has to tilt the plane to avoid hitting himself in the neck with the wing.
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Next, a few frames that illustrate some of the issues I have covered. The first two show the plane just after release and next when it starts rotation. You can see that the plane hasn’t gained any altitude because it isn’t flying. It is simply being pulled along by the winch tension.
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The final frames are really interesting. On Fritz’ first launch with one plane, none of the servos in one wing were working. You can see that the plane rotates violently to the right. But because the plane rotates quickly and has high speed on release, he has enough altitude to deal with the problem and save his plane.
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If you are intimidated by a complete change in throwing technique, try changing one thing at a time. Start by pulsing the winch with the opposite foot, but without changing your grip and throw. You will be surprised at how easy it is. When you have become used to this, start gripping the fat part of the fuse and making the full turn. Just make sure you don’t make a half turn and whack yourself in the neck. Think straight arm, over the head!
Once you have mastered this technique you will be rewarded with higher launches and fewer “interesting and entertaining” incidents at the start of your launches.
Enjoy/Anker
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Winch Launching Sailplanes, The Throw
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