The airplane in front of us begins to roll, the 60-metre yellow nylon rope connecting us to it tightens, and suddenly the glider I’m in comes to life, jouncing across the grass airstrip. In seconds we rise into the cloud-studded sky.
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All aircraft fly because their wings are shaped so that the air travelling over top of them has to go farther, and therefore move faster, than the air travelling underneath. Fast-moving air has a lower pressure than stationary or slow-moving air (Bernoulli’s Principle), so the higher-pressure slow-moving air underneath the wings pushes the aircraft up.
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About 600 metres above ground level (1280 metres above sea level), pilot Kevin Clifton of the Regina Gliding and Soaring Club, in the seat behind me, pulls a yellow knob. The tow rope falls away with a clunk, the tow plane banks left, and we’re soaring.
Wind noise instantly dies away, though there’s still more than I expected, and turbulence decreases. We’re no longer powering through updrafts and downdrafts in the wake of a prop-driven plane; now we’re riding the air like the hawk that rises periodically from its nest by the airfield, showing clumsy humans how it’s done.
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Four forces act on all aircraft: gravity, lift , drag (air resistance) and thrust. Lift counteracts gravity and thrust counteracts drag.
In a powered aircraft, thrust comes from the propeller or jet. In a glider, “thrust” is provided by gravity. The moment it’s released, a glider starts falling through the air, which rushes over the wings, producing lift — so much lift that some gliders can travel more than 40 kilometres in a straight line in still air for every kilometre of altitude they start with.
To travel even further, a glider pilot spends most of his time searching for “thermals,” updrafts of heated air. At low altitude, Clifton said, he looks for ground features such as bare or rocky fields, which heat up much faster than lakes or wheat-covered fields. At high altitudes, he looks for the visible indentations updrafts cause in the bottoms of clouds.
By riding thermals and other updrafts, gliders can remain aloft for hours, cover great distances, and soar to great heights. The world records are 1,461 kilometres for distance and an astonishing 14,102 metres for altitude. (Saskatchewan records are less than half that because of our lack of mountains, which generate strong updrafts.)
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A joystick pokes up between my knees, my feet rest on rudder pedals, and in front of me spin the dials of an airspeed indicator, altimeter, vertical speed indicator and variometer (which indicates a loss or gain of energy). The variometer reads negative, because we aren’t finding thermals: time to head in. Clifton lines up the landing strip and pulls a lever. A perpendicular spoiler rises out of each wing, and our rate of descent increases.
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Like powered aircraft, a glider is controlled by horizontal elevators and a vertical rudder in the tail and ailerons on the wings. Pulling back on the stick tilts the elevators up; the air striking them forces the nose up and increases the speed of the air flowing over the top of the wings, heightening lift. If the elevators are tilted down, the opposite happens. In turning, one aileron goes up and one goes down.
The rudder, controlled with pedals, helps the upright tail fin control yaw, the tendency to “fishtail” through the air. Yaw makes the airflow around the fin uneven, and the higher pressure on one side, enhanced by the rudder, forces the fin back to the centre. Despite the fibreglass glider’s sleek, high-tech appearance, the pilot detects yaw by watching a piece of yarn taped to the outside of the plexiglass canopy. The goal is to keep it straight.
The perpindicular spoilers Clifton deployed on landing disrupt the airflow over the top of the wing, increasing drag and decreasing lift. Ordinarily, the glider’s goals are just the opposite: to minimize drag and maximize lift. Its long, narrow wings are the closest designers can get to the idealized infinite wing of aerodynamic theory. A lot of drag is caused by wingtip turbulence, so the glider minimizes the tips. The wing is also much thinner from top to bottom than an ordinary aircraft wing.
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The ride gets bumpy as we run into eddies created by a stiff cross-breeze blowing the trees alongside the strip. But finally we’re bouncing along on almost hidden landing gear; and then we stop, and tilt gently to the left, our wingtip resting in the grass. We’re down.
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Science, technology and our age-old longing to fly have produced, in soaring, the most beautiful of aerial sports, an unforgettable combination of speed and grace.
I highly recommend it.
