Once we get clearance from the tower, Jones-Bowman comes up on the throttle and Flapper beats its wings down the runway. Taking their cues from the rhythm of the wings, the fuselage pulsates up and down, the tail takes little dips, the main gear does mini-squats, and the wing supports flex. The cadence picks up as Jones-Bowman accelerates to 35 mph, turns around, and does it again. We're in formation at her two o'clock, sitting in the back of a rusty VW pickup, when Flapper's engine sputters and dies.
The crew pushes Flapper off the active runway. After 20 minutes, the problem is declared to be a blockage in the fuel filter. An engine failure in flight has been thought of, and DeLaurier calculates that wing loading—essentially, the difference between the pressure of the air above the wing and that below it—would overcome the engine compression and drive the wings to their full-up position. "Lateral control would be pretty sensitive with all that dihedral," he says. "But with small and tender inputs, it would be flyable."
By now the wind is picking up. Since sideslipping into a crosswind without both aileron and rudder is dicey, testing the aileron-less Flapper is best done in calm, limp-windsock mornings, so testing is called off for the day.
I ask Jones-Bowman how it feels to be inside the Big Flapper. "I'm steering, controlling, bouncing, watching instruments and everything," she says. "Once I rev up, it's up and forward, down and backward, and the stick goes with me. I tell myself not to try and stop it but it's difficult. If I do, PIOs are gonna be a problem." ("PIOs" are pilot-induced oscillations—the pilot's attempts to correct pitching motions actually increase their amplitude, rather than diminish them.)
A few months following my interview, Jones-Bowman resigned as project test pilot, citing safety concerns related to the liftoff incident. Jack Sanderson, a longtime ultralight and homebuilt enthusiast, jumped at the chance to replace her. "I had to go on a crash diet," he says. "But once I got in the cockpit it felt natural."
Near the start of his project, DeLaurier had heard that other attempts were under way to make the first flapping-wing flight. But he never met the other Jim until one of his students attended a Flapping Forum at the 1999 Oshkosh fly-in and heard Jim Theis talk about his project. The following May, the two Jims got together at Zumbrota, Minnesota, where Theis' ornithopter project, Nighthawk, lay in parts. After that meeting, Theis and project manager Brian Said, perhaps inspired by Big Flapper (or by the thought of Flapper beating Nighthawk), accelerated their efforts to make the first ornithopter flight. BY late October they had finalized a plan to fly within a year. Things were well under way when Theis died last January. "Jim Theis was one of the most innovative researchers I've ever met," DeLaurier says today. "If our respective design approaches hadn't been so far along, I'm sure that we would have collaborated." The Nighthawk project is now in the hands of Brian Said.
For hundreds of miles along all Ocean Boulevards of Florida's Atlantic coast, pelicans enjoy catching ocean breezes, using the occasional flap of a wing to correct for gusts or to gain a little altitude. Brian Said lives here with his wife Winnie, in a palm-shaded house near the Jupiter Inlet, and he envisions human beings delighting in the same sort of flying. The deep-thinking engineer is surrounded by waist-high stacks of logbooks and the da Vinci-esque sketches of Jim Theis, whom he met in 1976 at Florida Atlantic University.
Said's ornithopter design philosophy differs from DeLaurier's. He wants to fly more like birds: control flapping angles and rates, no vertical tail, soar when the currents are right, turn with wing warping rather than yaw-roll coupling to a vertical rudder.
Without Theis, Said has more to do than DeLaurier and Harris. The original Nighthawk, built more than 20 years ago, was not an ornithopter—it had no flapping-wing drive—but rather a smaller-than-average ultralight with a pusher drop. It was designed to prove the team's system for lateral control. Said explains that in the wing warping that the Wright brothers used for lateral control, the warping was coupled—when on wing warped, the other warped in the opposite direction. That produces adverse yaw, he says, and that's why the Wrights had to add a vertical stabilizer. Then Said pulls out a case of video tapes to demonstrate his and Theis' alternative—"independent reverse wing warp."
We watch scenes reminiscent of early black-and-white movies of flight. In them, Theis lays prone in Nighthawk I's cocoon-like cockpit, gets airborne to roughly 10 or 12 feet at about the speed of a man running, and flies back and forth across a field, turning at each end like a bird. There's no vertical stabilizer or rudder, just a separately controlled pigeon-like tail that moves up-down, left-right, and twists around its long axis, plus wings that "reverse warp" independently. "With independent reverse wing warp," Said explains, "when you want to make a right turn, the right wing is twisted to a more positive angle." That increases the angle of attack, and therefore the lift and drag, on the right wing, which, when coordinated with tail inputs, turns the aircraft to the right. The movement is similar to the way a bird turns while soaring, deflecting airflow to one side of the other by adopting asymmetrical wing positions and twisting its tail. Said says there's no adverse yaw.
Testing progressed nicely until 1979, when, on a final test run over a polo field late in the day with low visibility, Theis pulled up over a scoreboard. On the other side was a speaker post; on wing struck it, and Nighthawk rolled over, slamming Theis into the ground. His back broken, he spent the rest of his life in a wheelchair. "Jim was undaunted, but [the accident] set back our program," says Said.
For the next 20 years, Theis and Said dabbled with designs for a flapping-wing version of Nighthawk, but earning a living took priority (Theis had his own engineering design firm, and Said is an engineer at Lockheed) and the project languished. That is, until the visit by DeLaurier. "After that we sat down and got our heads together seriously for a solid month—the longest sustained effort yet," says Said. Using Nighthawk's wing, Theis worked into the night completing all stress and performance analyses and computer-simulated lift and thrust curves. He and Said perfected a design for a flapping drive mechanism powered by hydraulic actuators. "It was a real light bulb for me," says Said, who like hydraulics because they enable the pilot to exert control over flapping angles and rates, with micro-computers used to regulate response to control inputs. "The actuator is designed for a high repetition rate and high fatigue tolerance," he says.
But research needs to be funded. "We hadn't actively sought external funding," says Said. For now, funding is split between Said and the Theis family, supplemented by donations of parts and materials from corporations.