The McDonnell Douglas MD-80 turbofan jet had just lifted off from New York's LaGuardia Airport and was streaking toward the Manhattan skyline when its left engine burst into flames. Pilot Bob Harry kept his cool. Banking sharply, he cut a swath over the city, put the Statue of Liberty behind his right wing and headed back to LaGuardia. In a matter of minutes, he had lined up his plane over an empty runway, pulled out the flaps and felt the familiar jolt of a successful touchdown.
But this was one emergency landing that was not greeted with relieved applause from the passengers. No rescue crews or fire engines scrambled on the tarmac. No fire engines rushed to the runway. In fact, there was no fire, no passengers and no plane. The MD-80 that Harry "flew" was really a van-size contraption perched on six spindly legs, one of 20 advanced flight simulators at American Airlines' Fort Worth training facility. Operating 20 hours a day, seven days a week, the earthbound machines prepare thousands of would-be pilots every year for one-engine landings, sudden wind shears and impenetrable fog. The experience is judged to be so realistic that when most trainees finally get to fly a real MD-80, the airplane is on a scheduled flight carrying paying passengers.
The art of simulation has come a long way in the 60 years since Edwin Link, the father of the technology, first used organ bellows and a suspended box to approximate the motion of an airplane in flight. The box has evolved into an instrument-crammed capsule equipped with color video and stereo sound. The bellows has been replaced by electronically controlled hydraulic actuators. And the illusion of motion has become so powerful that it is indistinguishable from the real thing. Moreover, with a few minor changes, the same technology has been used to simulate everything from spaceships to submarines, from armored tanks to oil tankers, re-creating every possible combination of bad luck, foul weather and faulty equipment. Says William James, American Airlines' director of flight training: "There's nothing we can't simulate."
Now the same experience is becoming available to the general public. Following the lead of Disneyland, which used four full-scale flight simulators in 1987 to create its wildly popular Star Tours ride, the biggest amusement parks are adapting state-of-the-art technology to do with computers what used to be done with Ferris wheels and roller coasters. Says David Fink, director of research and development for Disney's Imagineering division: "It's the wave of the future for theme parks."
All simulators, whether designed for work or for play, rely on a bag of electronic magic tricks to fool body and mind into believing they are somewhere they are not. At the heart of the illusion are two basic technologies, one sensed through the eyes, the other felt in the belly.
No earthbound machine can fully duplicate the dives or turns of a plane in flight. But it turns out that a person does not need to be flying through space to feel as if he were. The human body responds not so much to motion as to acceleration, what the experts call "onset cues." By rapidly extending or retracting its hydraulic legs, a simulator can effectively create the sensation of a sudden pitch or yaw.