Falling with the Falcon
Peregrines think simple thoughts: See food. Fly down. Go fast. Very fast.
- By Tom Harpole
- Air & Space magazine, March 2005
(Page 3 of 4)
An important effect of Frightful’s imprinting is that she regards Ken, in effect, as her mate. “Training techniques are all about feeding and breeding,” Franklin says. Frightful flies along with him on training jumps because she is following her instinct to fly with a mate, especially in pursuit of food.
Her trust in the Franklins is obvious in the easy, comfortable way they are able to handle her. When I warily offer my gloved fist as a perch, she becomes agitated. “Tilt your wrist a few degrees, until you feel her settle,” Suzanne instructs. “Feel her.”
A “haggard,” or mature falcon, Frightful has stiff, unyielding feathers. She is roughly the size of a loaf of bread, and with her wings tucked away and her feathers lying flat against her body, she feels as firm as a football. “Every feather on her body has a saw-toothed, jagged edge that tapers into nothingness,” Franklin points out. She can flex her feathers individually or in groups, an ability that lets her make tiny corrections at high velocity. Frightful flies with agility at almost any attitude. Occasionally she flips over in the middle of a 150 mph vertical dive and awaits her prey in midair as it helplessly falls into her talons, unable to pull out of its own dive so quickly or adeptly.
When Franklin and Frightful began freefalling together, they dropped at roughly 1,000 feet every six seconds, equivalent to about 120 mph. For a human in a skintight jumpsuit, spread-eagled with a parachute strapped on, that is terminal velocity—a natural speed limit that a falling object reaches when aerodynamic drag balances the acceleration due to gravity. During their first few dozen freefalls, Frightful learned to stoop at exactly Franklin’s terminal velocity. “She was [regulating] her speed to match mine,” Franklin recalls. Then Franklin began releasing lures that could fall faster, at about 195 mph. Frightful tucked into increasingly more streamlined shapes and caught up with the lures, no problem. So Franklin tried increasing his own speed, pulling in his arms and legs as experienced skydivers do. The falcon kept pace with her “mate,” and soon they were falling together at more than 240 mph. At that speed they can cover 100 yards faster than you can say “football field.”
Franklin describes Frightful’s configuration when going into “hyper drive” as asymmetric; she deforms her shoulders the way a person would when trying to squeeze through a very small opening. “She’s slipping through molecules,” he says; “the asymmetry seems to be part of that.” He holds no hope that airplanes could imitate the malleability and asymmetry of a diving falcon. But his years of study and observation of falcons all over the world lead him to suggest that copying certain aspects of peregrine flight could improve aircraft efficiency.
John Szabo, an articulate and agreeable theoretical mathematician in Cheney, Washington, is a master falconer who collaborates closely with the Franklins. Szabo has calculated that when the two-pound Frightful pulls out of a high-speed dive clutching her nearly two-pound lure, she undergoes 27 Gs of deceleration: At that moment, she and her prize weigh slightly more than 100 pounds. Based on Szabo’s mathematical modeling and Franklin’s measurements of Frightful in mid-dive, the two men think the secret to a falcon’s speed may be in the jagged edges of its feathers, which mitigate the effects of air turbulence and make the bird more streamlined. The jagged edges disrupt the airflow less than squared-off edges would. “Look at the wake turbulence behind a canoe compared to a rowboat with a square transom,” Szabo says.
Szabo, who has done research for NASA in computational fluid dynamics, says that nature is full of these kinds of adaptations for moving through air and water efficiently. In the case of shark skin, for instance, the ribbed texture of the scales helps to reduce drag, a finding that in recent years caught the interest of swimsuit manufacturers. “It wasn’t until the 2000 Olympics that the obvious advantage of minuscule dimples in swimsuits could radically improve efficiency over smooth suits by more effectively diffusing turbulence,” says Szabo. “Altering the design of swimsuits took a cross-disciplinary approach.”
Likewise, a stamped or incised surface that replicates the jaggedness of falcon feather tips, could, he and Franklin suspect, significantly improve an aircraft’s efficiency. “Look at how vortex generators have revolutionized aviation,” Franklin says. “There’s still room for improvement in drag reduction.”