MONROVIA, CA--THE TINY, ROCKY OUTCROP was an unlikely easy chair, but it did provide the lonely and scared climber a place to rest and wait for rescue. He had been stranded there on the down-sloping ledge for hours, inches away from a 70-ft vertical drop to eternity. Night was falling, the temperature was dropping, and there was no sign that anyone had heard his cries for help. Legs and arms aching, heart pounding with fright and fatigue, his mind raced with the usual thoughts of someone in danger: How did he get into this spot? How would he get out? If he didn't, would his family be okay without him? What would be the best design strategy for low-speed flight?

Design strategy? Low-speed flight?

Yes, in one of the most perilous situations of his life--stranded overnight while climbing in California's San Gabriel Mountains on Thanksgiving Day 1993--Paul MacCready was still thinking of pioneering design ideas. By the time of his early-morning helicopter rescue, he had actually come up with a draft concept. Not a good design, mind you, but, typically, it would prove a valuable catalyst that would unleash a process that would eventually produce a concept worth pursuing.

No one who knew him was surprised--either at his perch on the ledge, or at the owlish-looking engineer's calm persistence, despite the odds, in roughing out a new design idea.

In a career that dates back to his boyhood in Connecticut when he began building model airplanes, Paul MacCready, B.S. and M.A. in physics and PhD in aeronautics, has followed many technology paths that others said would lead nowhere. He persisted. They eventually applauded.

Today, he is known as the father of human-powered flight for his design of the Gossamer Condor. Tomorrow, he could be known as the godfather of solar-powered stratospheric flight for his influence on the Pathfinder, Centurion, and Helios solar planes his company is developing. They are spinoffs of his Solar Challenger, a plane that in 1981 made the first long-distance piloted flight powered solely by sunbeams.

Or, they might say he brought silent flight to the masses, if his ideas about the "Owl," a two-person plane that makes almost no sound, get off the ground. He envisions the 100-mph plane, which will take off at 20 mph, as an inexpensive and socially desirable substitute for helicopters. Will it fly? His own history puts the odds in his favor. Consider these accomplishments:

- Winning the long-standing Kremer Prize for the first sustained, controlled flight by a heavier-than-air craft--the famed 70-lb Gossamer Condor--powered solely by its pilot's muscles. The 1977 feat showed how much could be done with very little in the way of resources. The Condor is now housed in the Smithsonian National Air and Space Museum, adjacent to Lindbergh's Spirit of St. Louis and the Wright Brothers' 1903 Flyer.

- Human-powered flight across the English Channel. In 1979, his Gossamer Albatross, with the same 70-lb weight and 96-ft wing span as the Condor, crossed the Channel in turbulent winds in three hours. Cyclist Bryan Allen, who pedaled the Gossamer Condor, also provided the human power for the Albatross.

- The first unofficial manned aircraft to demonstrate climbing flight powered by the sun. That was in 1980, and the craft was called the Gossamer Penguin.

- The Solar Challenger, a solar-powered craft that carried its pilot 163 miles from Paris to an airfield in England in 1981.

- The 70-lb Bionic Bat, a human-powered aircraft with on-board battery energy storage, which won speed prizes in 1984 by flying a one-mile course in less than three minutes.

- A radio-controlled replica of a giant pterodactyl, which flew with its wings flapping.

- The Pointer, a 9-lb, 9-ft, video-equipped surveillance drone. This silent, battery-powered airplane requires no prepared launch/landing area because it is hand-launched and rugged enough to land in a full-stall vertical descent.

And there's more. The remotely controlled, 120-ft-span, solar-powered Pathfinder Plus reached 80,000 ft, far higher than any previous propeller aircraft. It's one of a series of vehicles developed with NASA support by engineers at AeroVironment, the company MacCready founded in 1971. Another, the 206-ft Centurion, started test flights in late 1998. Though he had little day-to-day involvement with these latter two designs, his vision and persistence, all agree, played a big part in their success. Now, the team is developing Helios, a regenerative-fuel-cell-powered aircraft that would stay up for months at a time. The vehicles could perform stratospheric communications relay functions, and monitoring for assessing and describing the mechanics of global climate change.

Back on terra firma, he has made his mark as well. He guided the team that developed the GM Sunraycer, a solar-powered car that won a 1,867-mile race across Australia. MacCready's team, with GM support and help, then developed the Impact demonstrator electric vehicle, which in 1991 stimulated California's zero-emissions mandate. The Impact became the currently available EV1.

Each achievement, from the model airplanes of his boyhood to the latest solar-powered craft, laid the groundwork for the next as he and AeroVironment engineers applied what they learned.

The vision thing. "Paul MacCready does things unconventionally," says Howard Wilson, former vice president at Hughes Aerospace who worked with the AeroVironment team on development of the Sunraycer and Impact. "He is a free thinker who follows his own paths, and that characteristic attracts very bright people to work for him."

MacCready insists that it's those AeroVironment engineers who deserve the credit for breakthroughs often associated with his name. Indeed, they do the heavy lifting on development of products that spring from his and their own imaginations. But the AeroVironment teams credit him for his vision, and for planting the seeds and nurturing the growth of company-wide capabilities.

Says Tim Conver, president of AeroVironment, "He is the chief visionary officer, almost child-like in his optimism, and he is open to ideas and possibilities many of us aren't open to. Once he has an idea, he's tenacious."

"It's a running joke around the company that any seemingly wacky idea he has will eventually get funding from somewhere," says Matthew Keennon, AeroVironment's program manager for MAVs. "He breaks down problems to the smallest nugget, then lashes something together fast and drives down the street with it hanging out the car window to see how it works."

MacCready's penchant for hands-on research and quick-and-dirty prototypes is legendary--and, in fact, he preaches the value of both to students and colleagues alike. "If you want to do something, just go out and do it," he says. "When you're pioneering something, quick-and-dirty can be elegant." The one caveat he offers: Don't disobey the laws of Newton, Carnot, and other scientific thinkers.

He crystallizes his own thinking about engineering problems in many ways, including exaggerating the physics involved. Case in point: While trying to solve stability and control problems on the Gossamer Condor, he supplemented computer simulations on apparent mass with personal observations. Apparent mass is the effective mass of air to which a vehicle's accelerations are coupled, and it's connected to vehicle size and shape. For the Condor, it seemed to MacCready to be the culprit for making the vehicle dynamically unmanageable.

Extensive computer simulations merely verified the problem's existence, but gave him no insights on how to fix it. So, he concocted a simple 3-ft balsa model and pushed it through the water in his swimming pool. The forces resulting from using a fluid almost 1,000 times as dense as air exaggerated the effects, and he could feel them in his hand, which substituted for a wind-tunnel balance. He banked the model without yawing and yawed it without banking and quickly got the breakthrough insight for a successful Condor configuration. He made the wing tips smaller to decrease mass effects during yaw and roll, and modified the control systems to accept rather than fight apparent mass.

The swimming pool isn't the only makeshift lab MacCready has used. Alec Brooks, vice president and chief technical officer of AeroVironment, recalls a more mobile one he employed during design of the Solar Challenger.

On his orders, the design team mounted the Challenger's wings on a van. "Paul strapped himself on the wings and used a control stick while the van was traveling to 50 mph to find where the aileron reversal of the flexible wing would make flight dangerous," Brooks remembers.

Of course, MacCready is perfectly capable of using more traditional testing venues, but even there he adds his own twist. "While working on the Sunraycer, Paul stood in the GM wind tunnel with the wind blowing and put a stethoscope with a pitot tube on the car to see if the point where the boundary layer tripped from turbulent to laminar was consistent with theoretical predictions," Brooks says.

The model youth. That kind of first-hand observation and investigation is a habit MacCready developed as a 13-year-old building model airplanes. Too small to be a star athlete, too shy to be a student leader, he found fulfillment designing and building the models and winning contests with them. "Doing the models, I had to take total responsibility," he says.

He also eventually got involved in flying sail planes, and continued his pioneering efforts. In 1947, he invented the MacCready Speed Ring, a concept used by glider pilots worldwide to select the optimum flight speed between thermals. In 1948, 1949, and 1953 he won the U.S. National Soaring Championship, and in 1956 was the first American to win the International Championship. For those accomplishments, the French, with their keen sense for the nuance of language, dubbed him "Le Machine."

Four years earlier, he earned his PhD in aeronautics from the California Institute of Technology. He met and had many discussions with Irving Langmuir, a Nobel Prize-winning chemist who was one of the pioneers in weather modification, and was inspired by the latter's disregard for barriers and conventional wisdom. "He would plunge into a new subject, ask a lot of questions, make mistakes, distill the essence, and create advances," MacCready recalls.

It was an approach that felt natural to MacCready, and he wanted to take it to a large company after college. "But none were doing the kind of pioneering work I wanted to be involved in," he says. "The exciting thing about pioneering is that there is no program or record to help you get the right answers. You don't even know the right questions."

The best way to pioneer in America is to start your own company, and MacCready did. His Meteorology Research Inc. became a leading firm in weather modification and atmospheric science research. He was the first to use small instrumented aircraft to study storm interiors, and performed many of the piloting duties. In 1971, he sold the company and, after a short stint consulting, started AeroVironment Inc., which today provides services and products in the fields of environment, alternative energy, and energy-efficient vehicles.

The project that solidified MacCready's reputation and that of his company--and which laid the groundwork for so much of what he and AeroVironment engineers have accomplished--was the Gossamer Condor. But, it was no great strategic plan that got him into the project. He had co-signed a loan for a relative who defaulted. While pondering how he would make the loan payments, he remembered the offer that British industrialist Henry Kremer had made several years before. Kremer promised $95,000 to the first person to use human power to fly a plane along a prescribed course. The plane would have to trace a figure eight around two markers four-fifths of a kilometer apart. Seeing the prize as his way out of debt, he went to work.

The effort took him into uncharted territory, and there were plenty of problems to solve. Power, steering, and extremely light-weight materials were just a few of the challenges. Other groups had been successful in getting a human-powered craft off the ground, but no one had been able to build such a plane that would turn. When they turned at those low altitudes (about 15 feet), they always crashed.

A different path. Most Kremer contestants stressed drag reduction through aerodynamic efficiency and streamlined airframes. MacCready took a different path. The combination of large size and low weight would more than compensate for an inelegant and simple--thus, quick and cheap--construction, he reasoned. So, he designed 96-ft wings made of aluminum tubing, corrugated cardboard, and balsa wood, and made the wings rigid with exterior bracing of piano wire. The covering was Mylar, from DuPont, which became a sponsor of some of his later projects.

The design technology he used would be of no help to engineers using CAD and finite element analysis for airliners, he admits. But, the focus on efficiency trickled down to other projects. "We got a lot of people at AeroVironment to think about doing more with less, both as a design approach and as a category of devices that would operate with the low power of muscles, batteries, and photovoltaic cells" he says. One consequence was long-term funding, now by NASA, of solar planes such as the Solar Challenger, Pathfinder, Centurion, and Helios.

No fear of failing. To be a pioneer requires a certain amount of fearlessness. His associates say MacCready fears neither criticism nor failure. "He gets plenty of resistance," says AeroVironment's MAV Program Manager Keennon, "because his ideas at first seem so way out." But, adds Ray Morgan, director of AeroVironment's design development center, "he is very reluctant to give up on an idea. He is famous for saying, 'I bet one could just...'"

His fearlessness and zest for pioneering extend to his personal life as well. Last summer he and his wife Judy vacationed in Africa visiting nature parks that most tourists don't see, and where you have to be accompanied by armed guards as you walk to the next tent. A couple of years before that, he rafted on the Upper Yangtze River in Tibet, where few westerners had ever been. "He had more fun than anyone on the trip," recalls Judy. "He enjoyed the mix of nature and mingling with Tibetans who have little contact with the outside world."

'Ambivalent Ludite.' In fact, he frets that humans in general are having little contact with nature, or with their own selves. Ironically for a person who has made so many engineering breakthroughs in his life, he considers technology a mixed blessing.

Calling himself an ambivalent Ludite, this philosopher-engineer says,"Technology can disconnect us from life. E-mail lets us work faster, but somehow we have less time to sit, digest, and enjoy. Cars give us wonderful mobility while they erode our motivation to walk, exercise, and meet our neighbors."

MacCready says that the human mind is at present "the most powerful force on earth," but acknowledges that the number of things humans can do that computers can't do is dwindling. "Technology in perspective and under control is great, but as a master it's worrisome," he laments. So, he spends some of his free time encouraging students to develop thinking skills and what he calls their unique human ability to deal with big themes. "They don't have the limiting factor of expertise," he says. "I encourage them to unleash their minds."

That's something he says the country's public education system doesn't encourage. "Students are rewarded for the right answer, not for learning from mistakes, nor for seeing multiple sides to an issue and comprehending the big picture, and definitely not for asking a new question," he asserts. "We need people able to perceive reality and contemplate our future options as civilization changes faster and faster. We need a nation of wolves and revolutionaries, but the schools are giving us sheep."

Asking questions is a lifestyle for Paul MacCready. And in finding his own answers, he has changed the fields he works in. He recalls that while perched all night on that rocky ledge in the San Gabriels he kept thinking about what Dorothy asked the Scarecrow in The Wizard of Oz: "If you had a brain, what would you do with it?" MacCready's career shows the possibilities.

Mechanical Insects

AeroVironment is a leader in the emerging field of micro air vehicles (MAVs). These tiny craft, about the size of insects on steroids, have several potential military uses, hence the interest of the U.S. Defense Advanced Research Projects Agency (DARPA) in their development. DARPA is funding several MAV projects, with an eye to using the best designs for reconnaissance operations.

In general, MAVs have maximum dimensions of six inches and weigh no more than 65 grams. Flapping wings propel some. All will contain small video cameras, motors, and actuators.

Minimum power requirements for MAV flight, assuming 50% prop efficiency and 50% motor efficiency, might be five watts from the battery. Hovering flight with a 15-cm-dia. prop takes three or four times as much power as the minimum for level cruising. Controls, servos, video, and telemetry consume less than a watt for a typical short-range system. High-resolution video, with wider frequency band requirements and ranges of several kilometers, increases the power needs. Matthew Keennon, the company's MAV program manager, has come up with servos of less than 0.3 gms. Such mechanical miniaturization, combined with microchips, lets vehicles edge toward bird capabilities.

While Paul MacCready has little day-to-day involvement in AeroVironment's MAV activities, they borrow heavily from his early work with model airplanes. During talks on innovation, he sometimes flies a 1.4-gm shimmering ornithopter given him by a modeler friend, Warren Williams. The flight seems like an art happening with no practical purpose, but MacCready points out that if he hadn't been creating equivalent models as a youngster in 1939, there would be no Gossamer Condor, Solar Pathfinder, or EV1, though he admits that equivalents would have eventually emerged from another source.

Says Keennon, "He pours out many ideas. Many of them are just improvements, very few are cosmetic. He is always thinking of how to make something better."

Follow the sun

In late November 1998, AeroVironment's Centurion solar-powered aircraft took its maiden flight. The remotely piloted aircraft is designed to fly to 100,000 ft on sun power alone. It consists mostly of an eight-ft wide wing spanning 206 ft. Four landing-gear pods support the wing. The vehicle's lift-to-drag ratio is about 32 at sea level and 23 at 100,000 ft. It is designed to stay aloft for 24 hours or more, even without energy storage except for potential energy of height times weight.

Next up for the company will be the Helios, an evolution of the Centurion platform that will incorporate a regenerative fuel-cell energy storage system to provide power for flying through the night. The Helios, say AeroVironment engineers, will be capable of continuous flight for months at a time at altitudes of 50,000 to 70,000 ft, and could be used for communications, imaging, reconnaissance, and positioning.

Both craft are offsprings of earlier work Paul MacCready and Ray Morgan did on solar-powered flight, starting with the Gossamer Penguin in 1980 and the Solar Challenger in 1981. The Challenger, in particular, posed engineering problems that would present themselves in future solar craft. It had to fly high above the ground in turbulence, which meant it had to be very strong while still light. With the support of DuPont, MacCready and his team developed new structural techniques. Airplanes use the strength of the wing skin to handle torsion. For the solar planes with only a wing span of thin plastic, MacCready decided the spar would have to do the work.

The Pathfinder Plus set the world propeller altitude record in 1998, soaring to 80,200 ft on solar power.