The simplest form of airplane flight is found in the glider. It uses only pockets of rising air, and the movement of air past its wings, to fly above the surface.
The extreme opposite of the super-light glider is the modern fighter plane. This plane is heavy and relies on the enormous thrust from its jet engines to remain aloft.
“It glides like a rock,” said retired Air Force Col. Art Evans, who now teaches mathematics at Brenau University. “That means very little, or not at all.”
Evans flew F-4 Phantom fighter-bombers on many missions over Vietnam, Cambodia, Korea and other combat zones. Because of its power and speed, the fighter plane isn’t as vulnerable to sudden downdrafts as lightweight planes are in violent thunderstorms.
“You avoid the core of the storm cell, of course,” Evans says. “The anvil of the cloud produces hail, which can get you in trouble when chunks of ice form at the engine intakes. One time, a severe updraft lifted us suddenly to 50,000 feet and the engine flamed out. That’s like a car quitting on the highway, except we can’t coast into a side lane and stop. The only choice was to drop unpowered, almost vertically, back to 30,000 feet where there’s enough oxygen to restart the jets. Luckily they cranked right up again.”
Even with high-powered jet engines, the weight of onboard equipment and ordinance poses a problem. This is why many fighter-bombers take off with little gasoline in the tanks, then refuel in the air at 20,000 feet altitude, traveling at flight speed.
“Turbulence isn’t as much a problem as it is with passenger planes, because we’re so fast and heavy,” says Evans. “But even a strong shaking shouldn’t worry passengers on a commercial flight. You’re passing through air of different temperatures, and that makes for some bumps. Passenger flights certainly don’t do the risky stuff we had to do on missions, like flying just 150 feet above the ocean to avoid radar.”
Evans’ treasury of stories includes St. Elmo’s Fire, a static electricity phenomenon dancing around the cockpit, or even hanging there in a blue ball.
“Our technology is so good now that it’s nothing to worry about.” It is reassuring to know that McDonnell-Douglas, now merged with Boeing, is the same company that produces many of the passenger planes you see every day at Hartsfield-Jackson airport.
Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.