It’s a Bird . . . It’s a Plane; It’s Weird--but It Can Fly
Hissed last month’s headline in one of the lesser grocery store tabloids: Horror of the Giant Flying Reptile.
Gasped the story: These are things from 60 million years ago, two or three flying reptiles hatched by recent lightning strikes on prehistoric eggs to terrorize both sides of the Texas-Mexico border. “Touching off a wave of panic . . . e yewitness reports indicate that the creatures most closely resemble a pterosaur, a winged, bat-like beast with a 50-foot wing span . . ..”
In truth, there’s only one creature. Further, it’s not just your common or Cretaceous pterosaur but a son (the feminine of the species being pterosauregina) of the sub order Quetzalcoatlus northropi , the largest and last of the pterodactyls.
He also wasn’t hatched by Texas lightning, but was stitched, zippered, painted and glued together in Simi Valley by scientists of AeroVironment Inc. as a stunning answer to an impossible assignment: to build an all-flying, full-flapping model pterodactyl for a movie about the history of flight.
And although radio-controlled QN (let’s face it, there’s nothing casual or cozy about Quetzalcoatlus northropi )
hasn’t shown any appetite for El Paso, it did manage to black out a community last year when a test flight ended among power lines feeding Moorpark.
It is arguable that this latex and carbon fiber model--whether by dint of hyperimaginative sightings or dearth of responsible journalism--was the basis of the National Examiner story.
But a clipping does hang in the workshop at AeroVironment. Team member Les King likes to think QN had something to do with it. “It would be a fun study to find out the genesis of that story,” agreed Paul MacCready, president of the company and creator of its creature.
MacCready is the physicist, aeronautical engineer, environmentalist, altruist and purposeful dreamer who has been the genesis of much aeronautical inspiration.
Gossamer Albatross, a package of aluminum and Mylar, a human-powered airplane that was pedaled across the English Channel in 1979, was his. So was Solar Challenger, the world’s first sun-powered aircraft that in 1981 flew 180 miles from Paris to England.
Then it was another gnatweight, the Bionic Bat, a hybrid powered by man and a battery pack recharged by the pilot’s pedaling.
Now it’s radio-controlled pterodactyls.
The idea of building a prehistoric flier was a logical and long-held extension of MacCready’s fascination with the “correlation between natural flight and mechanical flight and birds as role models for airplanes and aerodynamics.” In 1980, he had a design--extrapolations from the fossil remains of the genus Quetzalcoatlus northropi (after the Aztec feathered serpent god Quetzalcoatl and Northrop Corp., successful dabblers in the development of flying wing aircraft) found by paleontologists in 1972 in west Texas.
This dramatic victim of the Great Extinction about 64 million years ago was estimated to weigh 140 pounds with a wingspan of 36 feet. “The largest of the biological fliers and the size of a four-place airplane,” MacCready said.
In 1983, he found a sponsor and a vehicle for development--the Smithsonian Institution’s National Air and Space Museum and Johnson Wax, co-producers of an IMAX (large screen) public service movie called “On the Wing.”
Scheduled to premiere in June at the Smithsonian’s Samuel P. Langley Theater, the movie will explore aviation’s known and inexplicable, from condors over the Andes to 747s over Seattle. The QN replica will appear as star and stunt man throughout the movie and, MacCready said, “one goal of the project is to fly the QN replica on the Mall in Washington . . . in conjunction with the opening.”
In 1984, however, one minor detail remained unsettled. Building QN.
“But I realized that there had been recent advances in the aerodynamic theory of oscillating airfoils, in the theory and practice of stability and control, in robotics, mechanism, sensors and servos and in composite structural material and techniques,” wrote MacCready in a recent issue of Engineering & Science, an official publication of his alma mater, the California Institute of Technology. “Advances that mean that perhaps now a flying replica of Quetzalcoatlus northropi would be feasible. So we decided to try it.” Alec Brooks, who would become manager of the QN project, remembers his reaction. “Wow, that’s a wild idea,” he said. “Insane . . . but also a very serious project.”
With $50,000 in feasibility study money from the Smithsonian, MacCready and Brooks arranged a two-day workshop at Caltech with about three dozen scientists; robotic experts, electronic specialists, aerodynamicists, ornithologists, engineers and paleontologists.
QN was analyzed and dismembered. Why the long, strong legs? How did he fly without a horizontal tail to help with pitch (fore and aft) control and stability? How did it dampen yaw (movement around the vertical axis) without some vertical control surface?
Did the claws on the leading edge of its wings perform an aerodynamic function, such as airflow spoilers on a modern airplane? Or were they hands for shredding food and hanging from trees? Maybe this giant pterodactyl even walked on all fours.
“We sort of arrived at a consensus of how big it was, and how heavy and then whether or not it could actually fly,” Brooks said.
It was decided that QN in his original form was able to walk and make a running takeoff from flat ground. It could climb, but weakly. It could remain aloft for long periods, but only by harnessing up currents.
Described MacCready: “For Quetzalcoatlus northropi the takeoff and flight characteristics and behavior are envisioned as those that might appear if one combined various features of a frigate bird, an albatross, a pelican and a stork or crane, and then increased the size about sixfold, decreased the density somewhat, and cut the wing flapping rate down to one cycle every two seconds.”
MacCready, 60, formed a 15-man team (including sons Tyler and Parker MacCready) at AeroVironment facilities in Monrovia and Simi Valley. The group included a hard corps of real airplane, model airplane and hang glider pilots. QN became their intriguing break from toxic waste controls, wind farms, alternative energies, air quality sampling and other environmental products and sophisticated air services of AeroVironment.
“We wanted it to be as close to the original animal as we could make it,” Brooks said. “That meant no ailerons, no rudder, no propeller, no clear plastic tail. . . .”
Easier said than done.
A series of small gliders--with wingspans of three feet, six feet and then 12 feet--were winched aloft. They sacrificed themselves to science by spinning and nose-diving into the ground. Early tests with flapping wings separated QN’s centers of lift and gravity until, presto, a nodding and bobbing and tumbling pterodactyl.
“If the tail boom (jettisoned after takeoff) hit the ground before the bird it was considered a successful flight,” said AeroVironment facility manager and chief pterodactyl pilot Ray Morgan.
Then came QN’s fall into power lines. The flashes fell somewhere between summer lightning and a warm corner of the Tet offensive. The cost of restoring service to Moorpark, said Brooks, added $600 to the $670,000 cost of QN’s research, development and construction.
And that work, MacCready said, turned out to be longer, more expensive and “infinitely more complex than I in my naivete had imagined.
“Instead of jumping to the final solution, we had to go through the evolutionary cycle in our development just like nature did. But we were going about a million years a week.”
Said Brooks: “What we have is crude compared to what nature gave it. Mother Nature did it very elegantly.”
On the other hand, what MacCready and Brooks and the AeroVironment team now has, in the words of one Smithsonian official, is a test tube pterodactyl so realistic it could fly over a turkey farm and scare the feathers off everything below.
It is a half-scale replica, 18-feet across, propelled by wings with a flap factor ranging from a gentle quiver to the bald eagle breaststroke. The actuator system is a ball screw drive and gear box mated to two samarium-cobalt motors fed by nickel-cadmium battery packs. The rate of flap, in addition to wing positioning and other functions, is controlled by a ground-based, model airplane radio transmitter operated by Morgan.
This bird also has a brain, a custom-created autopilot incorporating stabilizing gyros and a vane that senses attitude changes. Example: If the bird begins to yaw, the delicate vane-sensor feeds that information to the autopilot. Corrective demands go to the pterodactyl’s head (which turns to counterbalance the yaw force) and one set of wing claws (acting as spoilers) extend to create drag and reduce the lift of the rising wing. And straight and level flight is maintained.
Pitch is controlled by sweeping the wings forward or backward in flight--the way a hang glider pilot transfers his body weight to maintain stability of a tail-less craft.
Roll and lift are controlled by twisting the wing and its latex membrane--just the way the Wright Brothers did it in 1903 in their passable impersonation of what nature has been doing for 150 million years.
Like a Pelican
Towed by a truck-mounted electric winch until it reaches an altitude of 500 feet, QN can neither gain nor maintain altitude by flapping. But it can propel itself forward, sustaining a glide ratio of 10 to 1 (10 feet forward for every foot of altitude) for a range of one mile. While bobbing and weaving and turning and clanking and wheezing with the rusty gasps of a geriatric pelican.
“But I’m delighted by it, it’s been a big success,” Brooks said. “We need to work harder on its flapping so that it doesn’t nod up and down so much. It’s thinking fast enough but only what we’ve programmed it to think. Right now, it only has very simple trains of thought. We need to make it think deeper.
“It’s not the greatest glider in the world . . . but I’m very pleased at how it looks. We’re very close to the rendering by (paleontologist artist) Gregory Paul.”
In a clumsy sort of way, QN is a cutie. His body fur is light and dark brown and almost Airedale. Curious, green eyes explore from beneath shaggy eyebrows. To some he’s an elegant condor. To others he’s from the Twilight Zone. To MacCready, whenever his bird is taken from its box for assembly: “I look at this and think of Thanksgiving.”
Last month, QN spent 10 days flying over Race Track Dry Lake at Death Valley and launching his Hollywood career in “On the Wing.” He performed, said his handlers, like a trouper. “We built an actor,” enthused MacCready, “who became a metaphor and a logo for the whole film.”
QN also became a superstar in the eyes of a group of schoolchildren who made a field trip to the filming. Questions by the dozen and in concert. Is it real? What’s that tail boom doing on there? What fur did you use? How fast does it fly? Can we ride it?
“That’s why you do it,” Brooks said. “To educate.”
MacCready agreed: “As a mind expander, as a symbol, as a catalyst, it (QN) is great. Building something like this is not like refining a motorcycle or a claw hammer. Here, we’ve duplicated nature . . . and, boy, has it been an education for me.
“Do you know that the Sooty Tern will take off and fly for four years, snapping up fish as it goes? Monarch butterflies start their lives in a grove in Mexico, travel tremendous distances and then their third generation, their great-grandchildren, will eventually fly back to the same grove in Mexico?”
Stirring thoughts. Posing questions. Presenting new knowledge. Teaching. Guiding the minds of 10-year-olds who, MacCready believes, are “the best life form on this earth . . . the kids out there who are going to determine if civilization survives.”
Partly because they’re there, partly because he sees a need for a more impressive promotion of “On the Wing” to extend its educational purpose, MacCready wants to build a second-generation pterodactyl with a 36-foot wing span.
This one will be able to flap and fly for at least five minutes. He wants it to be able to gain altitude and find thermals and soar like a sailplane. He wants QN II to be much closer to the original.
Then he would like to build a Bionic Bat, or a practical derivative, for an ultimate personal pleasure.
“I would like to have . . . an airplane that can slow to almost 20 miles per hour, and be able to soar with the birds, join them, not just charge through their element but be a part of their element.
“I’d like to be able to operate like a bird, land in a tiny space, drift along a river and go between houses. One horsepower to keep it aloft. Entirely silent . . . in the low speed, biological flight realm.
“That type of vehicle is do-able. I don’t think it makes any economic sense. But I’d like one. . . .”
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