airspacemag.com

• Flight Today

Falling with the Falcon

Peregrines think simple thoughts: See food. Fly down. Go fast. Very fast.

• By Tom Harpole
• Air & Space Magazine, March 01, 2005

SHE PERCHES ON A BALD CESSNA TIRE in Ken and Suzanne Franklin’s country kitchen. Frightful, a six-year-old peregrine falcon, is just being herself, loudly cacking and occasionally opening her wings to their full 41-inch span. She flaps her wings and stretches a little, then preens herself with her hooked beak.

Sixteen inches long and weighing 2.2 pounds, she catches other birds, up to the size of ducks, in midair for a living. She ignores a savory piece of barbecued chicken, even though it’s within easy reach.

Frightful is a world-class athlete whose directly recorded speed beats that of any other animal ever measured. Cheetahs, sailfish, and black cutworm moths all top out at about 70 mph. When Frightful is stooping—diving after prey—from nearly three miles up, she has been clocked at 242 mph, and it’s possible she can go faster.

Until recently, estimates of peregrines’ velocity varied wildly, from 70 to 300 mph. No one had ever measured exactly how fast the birds can fly until Ken Franklin started stooping with Frightful, or, more to the point, Frightful learned to skydive with Ken.

“Studying falcons from the ground is like studying sharks from a boat,” Franklin says. Yet entering any predator’s realm, even just to observe, entails certain risks—Frightful’s sharp talons and bill are, of course, designed to hold and tear flesh. That didn’t discourage Franklin, his wife Suzanne, his father Roy Franklin (a World War II Navy Corsair pilot), several other falconers, two film crews, and Norman Kent, a world-renowned skydiving videographer, from their plan to study a speeding falcon at arm’s length—literally. To understand how a two-pound bird can achieve higher speeds than most small airplanes, Franklin has done more than 200 skydives, sometimes as many as five a day, with Frightful.

“Birds are the blueprint for aeronautical engineering,” says Franklin, a 46-year-old pilot and master falconer from Friday Harbor, Washington. Orville Wright would have agreed. In 1941 he wrote, “Learning the secret of flight from a bird was a good deal like learning the secret of magic from a magician. After you know what to look for, you see things that you did not notice when you did not know exactly what to look for.”

Franklin first took the controls of an airplane at age nine, and now, as a pilot for Federal Express, he would like to see the knowledge he has gained skydiving with Frightful and other fast-flying birds applied to mechanized flight. “Can human flight benefit from these observations?” he asks. “What remains to be learned?”

To capture their unique data, Franklin and a few mathematicians and engineers devised an elaborate method of clocking falcons in mid-dive. They stripped down a skydiver’s Pro-Track recording altimeter/computer, usually worn like a wristwatch, to a computer chip weighing just 0.4 ounce, then fastened it to the underside of Frightful’s tail feathers in a way that wouldn’t interfere with her flying. During dozens of skydives in 1999, made while the National Geographic film Terminal Velocity was being shot, the device recorded Frightful’s stooping speeds by measuring how far she fell in a certain time interval.

It’s an improbable and wonderful sight to witness Franklin release Frightful into the slipstream of a Cessna 172 at 17,000 feet above sea level. She stabilizes immediately into level flight and matches the speed of the airplane. She flies just off the wingtip, keeping her sharp eye on Franklin, inside the airplane, as he prepares to dive out the door. Then he leaps, and they fall together for more than two miles, along with a lure that Franklin drops during the descent to simulate prey.

Franklin’s team verified Frightful’s dive velocities with measurements from altimeters worn by videographer Kent and Franklin himself as they plummeted alongside the bird. A fourth altimeter was packed into the lure, and all four altimeters were compared after each jump. The team spent a couple of months working out these techniques and training Frightful, then another seven weeks shooting the film, which aired on the National Geographic Explorer program in 2002 and was nominated for an Emmy award. Frightful also stars in Birds of Prey, a yet-to-be-released IMAX film produced by Roy Disney.

But while Franklin and his raptor have caught the attention of the entertainment world, aeronautical engineers and other technical types have largely ignored them. Jim Crowder, a Boeing engineer and leading authority on airflow dynamics who died last year, was one of the few aerospace professionals who paid attention. Crowder lamented the aviation industry’s lack of interest in bird flight, particularly peregrine flight. In June 2000, I asked him whether falcons had anything to teach aeronautical engineers. “The easy answer, if talking about Boeing-type aviation, is ‘no,’ ” he replied by e-mail. “Our [Boeing’s] position is that aviation is a mature business, and that the discoveries waiting to be identified are probably not worth looking for. Someone would have found them by now.”

Crowder thought this corporate indifference, or perhaps arrogance, was misguided. “Personally, I am convinced that birds do all kinds of things that are unknown and potentially worth finding out about,” he said. “I have spent my entire career inventing and innovating equipment and testing methods. All too frequently I am asked, ‘What good is it?’ My usual answer is ‘Nothing at all unless you think about it.’ ”

Franklin has been watching and thinking about falcons for most of his life. At age 12 he captured and began training a red-tail hawk. He’d take the bird to his father’s 66-acre airport adjacent to Friday Harbor (see “The People and Planes of Friday Harbor,” Apr./May 2004), where it caught rabbits and small rodents. Falconry became a lifelong avocation, and eventually Franklin sought a way to combine it with his career in aviation. Then he got Frightful from a falcon breeder in Spokane, and knew he had the bird he’d been dreaming about.

On the ground, Franklin looks like Sam Shepard on a bad hair day, as though all those skydives have permanently startled him. He roams his 14-acre farm like a raptor. Shoulders still and head thrust forward, he looks like he’s hunting up a meal. In the sky, he is nearly as comfortable as Frightful. At 21, he was the youngest pilot then working for a U.S. commercial airline. He has logged more than 17,000 hours in the cockpits of just about every type of civilian aircraft currently flying, including 747s and MD-11s for Flying Tiger Airlines and FedEx. Arrayed around his farmhouse and sheds are two Cessnas, a Robinson R22 helicopter, and two ultralights, along with the parachutes he uses when diving alongside Frightful.

“Frightful got her name because she is the closest thing to a wild falcon that I’ve ever trained,” Franklin says, yet within two days of hatching she was swept in to the center of the family, to the point where she sometimes acts as if Ken and Suzanne’s king-size bed is her nest, preferring to sleep there instead of in her aviary. She often spends hours perched on a ledge above the kitchen counter. She also can be raucous, cacking and flapping her wings when stimulated or displeased, as when a visitor steps out suddenly from behind her.

Frightful became “imprinted,” or bonded, to Franklin through an incremental training regime, which he devised with Suzanne. The training eventually led to side-by-side skydives. Suzanne, who retains the physique and pluck of a collegiate swimmer, is also a master falconer and ornithologist. She would hold the hooded bird while Ken started flying low and slow in an ultralight over the grass landing strip on his property. When Ken, carrying a lure with fresh quail meat, passed by in the ultralight, Suzanne would pull off the hood and release the falcon. Frightful unhesitatingly chased the ultralight in pursuit of the lure. From there it was a natural progression for Ken to take Frightful up in his Cessna, with his father Roy at the controls.

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.”

Although they arrived at this conclusion independently from aeronautical engineers, the falconers are hardly alone in suggesting it. Nearly 20 years ago, scientists at 3M developed an adhesive film with a micro-structured texture that, when applied to the surfaces of an aircraft wing, will reduce drag, resulting in greater fuel efficiency. Even a one percent reduction in fuel use for a wide-body jet saves about $100,000 in fuel for each aircraft annually, according to 3M’s Web site.

Not everyone agrees that Franklin’s research tells us much about the behavior of wild peregrines. Some falcon experts have called his studies artificial, because freefalling from 17,000 feet is unnatural behavior for falcons, who normally stay below 14,000 feet. Franklin says the only reason he goes so high is to get more time for his observations, and that doing so doesn’t make much difference to the bird. “Falcons can accelerate from 100 mph to 200-plus mph in eight seconds in pursuit of prey,” he says. “They don’t need that vertical space to accelerate. But they often ride thermals up to cloud base, getting a free ride up the column of air, checking out everything in the airspace for a meal. They soar at altitude, practically invisible, waiting for prey—then they stoop. To say that stooping from 14,000-plus feet is not normal for a falcon is like observing a Ferrari on a crowded freeway doing 55 mph and assuming that’s all they can do.”

Ken and Suzanne Franklin would love to see their falcon studies contribute to even modest improvements in aircraft efficiency. And even though aerospace companies are hardly beating their door down, Franklin takes every opportunity to deliver his message. Last September, he addressed a meeting for Boeing engineers and the British Royal Society of Aeronautical Engineers at the Museum of Flight in Seattle, and he regularly talks to groups of pilots and birders.

In the meantime, he and Frightful continue their high-dive act. Looking each other in the eye while falling at 242 mph, they share a knowledge and a bond that few people, let alone people and animals, could ever know.