Tuesday, December 30, 2008

Gliding Flight

Waiting for wind conditions to shape up for flying today...but nothing doing. So I've come to the Barrow public library to write a blog entry describing a paraglider launch; this should help explain the pictures posted here so far (scroll down). Cheers, Cameron

As Richard Harrison wrote in 1967, while powered aircraft perfectly describe the mechanics of flight, gliding aviation is its eloquence. Muscling through the sky with an engine is so very different from relying entirely on your reading of the movements of air, each stirring of which--however minute--is relayed down from the wing above to the control lines in your hands.

Even before you inflate the wing (“The paraglider is the only aircraft you have to assemble as you take off,” my instructor joked) you align it square to the breeze, indicated by a flag or, if you can feel the air on your skin, the unmistakable touches of air that moves like liquid.

With your back to the wind you draw on the leading-edge lines and wind flows into the open ports; now the wing pressurizes and spreads horizontally and then you step forward, not wanting it to rise just yet, and let the wing rest again. Final adjustment, a step this way, half a step that way, now you’re set. The wind is directly at your back, the wing is half inflated, resting on the ground; snow, in my case.

When the moment is absolutely right your heart pumps hard and you draw heavily on the leading edge lines, your body and mind are electrified as you focus on the move as you step backwards as the wing leaps up from the ground and then a moment later “BANG” it snaps into position above, it heaves at the sky, it’s trying to pick you up and you use your whole body weight to hold your ground and stabilize the airfoil that now hovers above you as if by sorcery.

Twist, shift, sidestep; you adjust minutely and constantly, with no conscious thought after a while, making sure the wing is stable and remains in the windflow; when the wind shifts around a bit, you match it, move for move.

And when everything is perfect you spin in position, now the wing is behind you as you run for takeoff. You’re doing so much at once; keeping the wing pointed into the windflow, shifting your weight under it as it leans, drawing on a brake to stop a surge and letting off the brake to prevent a stall; you’re watching the wind flag for unexpected whips and rotors, and you’re running hard on your toe-tips as the wing pulls up, trying to lift you into the air. Just a moment more now…down the takeoff slope, one stride then three then you’re airborne, your body swings forward under the wing. You’re flying.

If you can find rising air you can thermal up thousands of feet, following birds doing exactly the same thing. Birds sometimes accompany a wing, flying formation. One of my instructors once watched a spider fly by, at 3,000 feet, floating on a tangle of cobwebs.

Landing is a world in itself, a time of laser-like focus as you set up your approach and commit to landing. Without an engine, there are no second chances, it has to be right first time, every time.

But back to the takeoff run; all I’ve described is what happens when do it all right—but anywhere in the sequence you can make a mistake that collapses the wing. If your takeoff slope is a cliff, and your wing collapses after or on takeoff, you might or might not have the chance to throw your reserve parachute and come safely to the ground.

The best visual description I can recommend is a short clip of French pilot Sandie Cochepain, on YouTube at the link below:

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