Soaring on Silk
Dixon White teaches students how to use parachutes to go up as well as down.
- By Tom Harpole
- Air & Space magazine, January 2001
(Page 5 of 7)
White watches a more advanced pilot screw up a launch by mishandling his glider. He bites his tongue, turns to me, and says, “At some point I have to stand back and let them learn from blowing it.” Then he jogs over to help Matt Gerdes sort out his wing.
That night over ice cream with his apprentice instructors, White agonizes about a 300-pound student whom he reluctantly allowed to take lessons. That afternoon the big man belly-flopped a couple of times and began blaming his awkwardness on his glider’s performance. Swan and Zaenglein had watched incredulously as White ran downslope with the man on a launch and hung to the bottom of his harness as the guy got airborne for the first time. A gust carried them 12 feet into the air, whereupon White let go, tumbled, and popped up, still loping downhill and shouting directions to the big man trying in vain to fly.
“I don’t think I can let him come back,” he says, looking solemnly at the apprentices. “His weight isn’t the problem. If he told me he loves this and said some things about how fun it is, I’d stick with him. But he’s doing it for reasons that I can’t understand.”
The challenge of paragliding is that it takes place in an element that is invisible. Paraglider pilots have to deduce from easily missed cues how to find the rising currents that keep them airborne. They begin by looking and not seeing things in the air, and they progress, under White’s tutelage, to knowing where thermals are rising and flying boldly into their rough edges. He teaches advanced pilots how to ascend thermals to the highest altitude possible, how to glide and look for where the next one will be rising, and how to link up a series of these ascents and glides, a process that makes cross-country flights of more than 200 miles possible.
Of his students, DeVietti says: “They begin with the simplest little downhill flights, barely off the ground. Then we get them started on ‘sled rides,’ gliding down our 800-foot-tall hill into Spirit Canyon.” With the 7:1 glide ratio of the wings, those rides carry students nearly a mile in four or five minutes, with White or DeVietti up at the launch site talking to them by radio about how to handle the wing. “Soon the novice pilots want to start staying up longer and we take them to some higher places and get them soaring, staying up over the same place for a while, managing lifting air,” says DeVietti. “Then it gets to be time to try some cross-country flights. You start to consider what it would take to go over there. You start getting into more unstable conditions, more dramatically lifting air, which is what you need. Then you really begin navigating through some turbulence in the great river of air. At that point in a pilot’s progress, the decision to stay up depends largely on how the afternoon heating goes, and how much more turbulence the pilot wants to deal with. You also have to consider that as the afternoon heats up, landings get trickier.”
Students are told on day one to show up the next morning with weather information: the winds aloft, temperatures, and the location of the jet stream, all of which can be obtained by calling 800 WX BRIEF or tapping into White’s Web site at paraglide.com. He gives students succinct criteria for deciding whether to fly, based on information they gather in the morning. Beginners look at isobars—lines on weather maps that connect points of equal barometric pressure—and are told to forget about flying when there are more than two isobars within 300 miles. The closer together the isobars are, the higher the winds will be that day. And if the jet stream is within 100 miles of where you are flying, the base winds will be too high for safe flight. If the barometric pressure has dropped, unsettled weather is on the way.
If the initial weather predictions for the day are propitious, then paraglider pilots must observe the conditions at the launch site. They are instructed not to fly if cumulus clouds are taller than they are wide, if there is a multi-layered sky with clouds moving in different directions, and if wind gusts increase more than five miles per hour in five seconds—all signs that the air is too turbulent for safe flights. But if the signs are encouraging, students must start learning how to detect and use the thermals that create lifting air.
White uses an image to explain how thermals bloop up into the atmosphere. Slightly overfill a glass of water and surface tension allows it to bubble up over the top of the vessel. That tension is a fragile agreement between molecular attraction, barometric pressure, and gravity, and it breaks easily. Likewise, once the sun starts warming the ground, bubbles of warm air form along the surface, and eventually they exceed their ability to grow, whereupon they burst and rise. Their release may also be triggered mechanically, by something as small as a rabbit running through them.