Robert sizes up the air currents

In the early 70’s, Robert Doornick began hang gliding and introduced the sport to the East Coast. He also helped make it safer and spread the word about it to tens of thousands of people. In this last part of his exciting story, Robert describes some insights into how a hang glider pilot thinks and sees and also how a hang glider flies.

An open field, road or other hard surfaces were like a frying pan that absorbed and reflected the heat of the sun, creating rising hot air thermals that could be used as makeshift elevators as you calculated their location and angular course then penetrated them to leverage their upward path. Trees on the other had represented the cooler areas, but when flying over the steep inclines of mountains, those trees provided a gliding path for the distant wind to make its way up the face of that mountain, supplying the pilot with yet another rising—lifting—current of air.

As you carefully evaluated the smoothness of the land below, or its occasional bumps and crevices, so would you be able to anticipate how these land masses would affect the behavior of the wind, its clean and beneficial rise up towards the top of the mountain, its possible turbulence or a mix of both. Be it smooth air or turbulence, these elements would be amplified by the speed of the wind with the usual mathematical equation (as the wind speed doubles, its impact on objects and surfaces it encounters —including your hang glider—quadruples. Understanding such principles would become a most humbling experience; helping the savvy hang glider pilot to know where, when and why to fly. Thus, standing atop a mountain on a beautiful sunny day with a pleasant breeze caressing your face could indeed be a misleading impression, unless one was able to properly “read” the terrain below and the meteorological conditions. As such; cloud formations, land forms, behavior of tree leaves and other important factors became your map to what was happening in the otherwise invisible space before you.

Most importantly, and with the simple study of aerodynamics; I learned how an aircraft wing functions and maintains flight in mid-air. Air is not going only under the wing. The leading edge is cambered, so that the air splits in two layers both over and under the wing, with the two layers eventually catching up to each other at the rear of the wing—the trailing edge. Because of the curvature of the upper wing surface, the upper half of flowing air has more distance to travel and—through simple compression forces—those air molecules go faster to catch up to the more slowly traveling air molecules passing on the less resistant and more direct path of the lower half of the wing. In this process, a curvature is created over the wing’s top, with a void underneath. Aerodynamically, a suction effect is created. So the air passing over the top is in truth “lifting” the wing, rather than air underneath pushing the wing up.

When the air molecules on top meet the air molecules at the bottom, they rejoin and continue their former speed. This is true whether an engine is pushing the wing or gravity is doing it, always with each wing having a lift over drag ratio, which is how many feet of descent for every forward foot to get the lift. This is why planes always take off and land into the wind.

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