by Had Robinson
Does getting really high on a tow sound like fun? Sometimes, you may want to have a 20-30 minute relaxing flight or you see a cloud street in the distance and there is nothing but sink between the tow area and the lift. You need to glide a long way – a high tow can be the only way to get there.
What is unique about a high tow
As your height above the ground increases, the angle of the towline changes. It starts out parallel to the ground and then slowly drops. At the top of tow (6,000' AGL or so), the towline is just a few degrees from being straight down. The towline force has a vertical and horizontal vector. As the height increases, the horizontal vector decreases and the vertical vector increases from near zero to a large percentage of the horizontal. The horizontal vector is what gets the pilot up. What is unique is that the slightest horizontal vector will cause the glider to climb even as the vertical vector increases dramatically. This is because the vertical vector is still a fraction of the overall weight of the glider and pilot. To the pilot, it looks like the towline is pulling him down but this is not what is happening. As the vertical vector increases, the horizontal is still there, though not as noticeable, so the glider continues to climb. Two miles of towline has appreciable drag which also increases the vertical vector. There is a theoretical limit but we do not get close to it.
Tips to make the high tow better
1. When you get really high (> 4,000' AGL), you may not be able to see the tow vehicle. No problem. The tow operator (TO) knows what to do. Just follow the towline that is hooked to you.
2. Make sure your two way-radio is working properly and that your battery is fully charged. The TO and others on the ground may lose sight of you. Do not assume they know where you are or where you are going. It is very difficult to see a glider a mile away in the sky.
3. Make sure you can obtain your GPS coordinates quickly. If you are miles away and need to land, you will have to quickly tell your ground crew or other pilots your coordinates so that they can help you or pick you up. Two-way radios work line of sight very well but have poor range when used at ground level.
4. Dress warmly. At the end of the tow it may be 25 degrees cooler than at the earth's surface.
5. While under tow, do not hesitate to contact the TO if you see something you are not sure about e.g. the towline going slack or straight down. You can be in strong lift, for example, and the TO will back off the tow force and this will cause the towline to appear to be straight down or slack. He can sense what is going on at the winch and will do what will get you as high as possible, safely.
6. If you get in strong thermal lift, pin off! You will get higher and faster that way. If the lift is weak, stay on tow.
7. If it is convenient, let the TO know when you are ABOUT to pin off. He can prepare the winch for the drogue retrieval. What is most important is for the pilot to say over the radio, "OFF TOW!" when he is no longer under tow. If you are off tow, the longer the TO waits to begin the drogue retrieval, the greater the chance it will hit the ground farther from the winch. Walking for hundreds of yards to find and bring the drogue back wastes time.
8. Any time you feel you want to stop for any reason, PIN OFF! It does not matter if your brain and what is fact are 180 degrees out of sync. It is never safe to be distracted by anything when flying a paraglider, regardless of the reason. The TO cannot see what is going on near you (weather events, equipment issues, etc.). While you are under tow, he is focused on the winch operation which is what keeps the pilot safe.
9. Always get as high as you can under tow unless you decide to pin off in a thermal. Being higher means you have more options.