Dr. James DeLaurier, an aeronautical engineer and professor emeritus at Canada’s University of Toronto Institute for Aerospace Studies, fulfilled a lifelong dream July 9 when his full-scale ornithopter took flight with a pilot on board.
DeLaurier’s ornithopter, dubbed “Flapper,” was airborne for 14 seconds, during which it flew about 1,000 feet down the runway at Downsview Park, near Toronto, reaching an altitude of about 6 feet, the professor said.
It was the culmination of a quest that DeLaurier had pursued for more than 30 years but that has been going on since Leonardo da Vinci proposed a flapping-wing, man-powered artificial bird some 500 years ago. DeLaurier and his team of volunteers and students built the only successful manned – but not man-powered – ornithopter in half a millennium.
The flight ended when the ornithopter rolled to port. The left wing touched the runway and the “bird” spun around, collapsing its nose gear. At first the team blamed the roll on a crosswind, but video analysis showed that the wing had buckled, DeLaurier said.
“Photographs from the chase vehicle clearly showed a bulge occurring during the downstroke, on a portion of the left wing’s upper trailing edge about 2/3 of the way out from the flapping hinge,” he told General Aviation News. “The flight loads, in conjunction with the flapping loads, caused the buckling strength of that portion of trailing-edge strip to be exceeded. The consequence is that the shear-flexing action was jammed, reducing the aeroelastic twist. This would have caused flow separation with resulting loss of lift and thrust. The aircraft’s behavior bears this out.”
Pilot Jack Sanderson said that the banking felt like it was due to some sort of direct roll moment and not due to cross-wind effects.
The world’s first successful ornithopter was jet powered. “The important thing to remember is that the aircraft needed the jet boost to stay aloft,” DeLaurier said. “It wasn’t a pure flapping-wing flight. The wing was marginal because it was trying to fly a 770-pound aircraft, whereas it was designed for a 600-pound aircraft.”
The original plan was that Sanderson would throttle back the jet to assess the wing’s capability to sustain flight, DeLaurier said, but the flight’s brief duration forestalled that experiment.
“The videos and photographs provided a great deal of additional information,” DeLaurier said. “Once off the ground, the cockpit environment is very tolerable, with smooth motion in response to the flapping. This is largely a consequence of the three-panel wing design. The longitudinal trim conditions were near perfect, showing that the standard airplane criteria apply to this type of ornithopter. There was no tendency for pilot-induced oscillations in response to the flapping forces. The stabilator was rock steady.
“The stored energy from the small flywheel attached to the engine, in conjunction with the 60:1 drive reduction, allowed smooth sinusoidal flapping motion even under flight loads,” he continued. “That is, the upstroke and downstroke were of the same duration; the wing wasn’t slowed during the downstroke.
“The ability of an ornithopter to take off from a ground roll, without bouncing, has been demonstrated,” DeLaurier concluded, adding, “This is largely due to using a boost from the jet engine, and this would be a valuable feature for any future ornithopter.”
Until July 9, the notion of human-carrying ornithopters seemed to be in the realm of fantasy, or of the hapless inventors whose failures are seen in so much film of early flight experiments – usually collapsing in a heap of flailing parts.
“Even though I have envisioned this flight for decades and have seen it in numerous simulations, seeing it for real was an experience almost beyond my words to express. Until the trailing-edge buckling happened, it was smooth, steady, and looked almost…well…normal,” DeLaurier sighed. “Perhaps that is the greatest contribution of this project.”
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