Powered Flight

FOR centuries, men dreamed of flying. But a man does not have muscles powerful enough to lift his own weight into the air. In 1781, James Watt invented a steam engine that produced rotary power, and in 1876, Nikolaus Otto furthered the idea and built an internal-combustion engine. Now man had an engine that could power a flying machine. But who could build one?

The brothers Wilbur and Orville Wright had wanted to fly ever since they learned to fly kites as boys. Later, they learned engineering skills by building bicycles. They realized that the key challenge of flight was to design a craft that could be controlled. A plane that cannot be balanced in the air is as useless as a bicycle that cannot be steered. Wilbur watched pigeons in flight and noticed that they bank into a turn, as a cyclist does. He concluded that birds turn and keep balance by twisting their wing tips. He hit upon the idea of building a wing that would twist.

In 1900, Wilbur and Orville built an aircraft with twistable wings. They flew it first as a kite and then as a piloted glider. They discovered that it needed three basic controls to adjust pitch, roll, and side-to-side movement. However, they were disappointed that the wings did not produce enough lift, so they built a wind tunnel and experimented with hundreds of wing shapes until they found the ideal shape, size, and angle. In 1902, with a new aircraft, they mastered the art of balancing the craft on the wind. Could they mount an engine on it now?

First, they had to build their own engine. With knowledge gained from the wind tunnel, they solved the complex problem of designing a propeller. Finally, on December 17, 1903, they started the engine, the propellers whirred, and the craft lifted off into an icy wind. “We had accomplished the ambition that stirred us as boys,” said Orville. “We had learned to fly.” The brothers became international celebrities. But how did they manage to power themselves into the air? Yes, nature played a part.

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The Wright “Flyer,” North Carolina, U.S.A., 1903 (reenacted photo)

Nature Had It First

“Ask, please, . . . the winged creatures of the heavens, and they will tell you. . . . The hand of Jehovah itself has done this.”​—Job 12:7-9.

EVERYTHING about birds appears to be designed for flight. For example, the shafts of wing feathers must support a bird’s entire weight during flight. How can the wings be so light yet so strong? If you cut through the shaft of a feather, you may see why. It resembles what engineers call a foam-sandwich beam. It has a pithy interior and a rough exterior. Engineers have studied feather shafts, and foam-sandwich beams are used in aircraft.

The bones of birds are also amazingly designed. Most are hollow, and some may be strengthened by internal struts in a form engineers call the Warren girder. Interestingly, a similar design was used in the wings of the space shuttle.

Pilots balance modern aircraft by adjusting a few flaps on the wings and tail. But a bird uses some 48 muscles in its wing and shoulder to change the configuration and motion of its wings and individual feathers, doing so several times a second. No wonder that avian aerobatic ability is the envy of aircraft designers!

Flight, especially takeoff, consumes a lot of energy. So birds need a powerful, fast-burning “engine.” A bird’s heart beats faster than that of a similar-size mammal and is usually larger and more powerful. Also, a bird’s lungs have a different, one-way-flow design that is more efficient than a mammal’s.

Many birds are designed to carry enough fuel for amazingly long flights. A migrating thrush uses up half of its body weight for a ten-hour flight. When a bar-tailed godwit takes off from Alaska heading for New Zealand, over half of its body weight is fat. Astonishingly, this allows it to fly for about 190 hours (eight days) nonstop. No commercial aircraft can do that.