Into The Wild Blue (Digital) Yonder

By Philip Elmer-DeWitt

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 The bellows has been replaced by electronically controlled hydraulic actuators.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.

Meanwhile, a different kind of magic is playing in front of the trainee's eyes, as the horizon dips and turns in sync with the false motion of the capsule. Two decades ago, flight simulators used movie projectors to give pilots a sense of visual reality. Later they used 2,000-to-1-scale model boards and tiny mobile cameras.

Now it is all done with computers. By making mathematical transformations on a digital landscape, today's simulators can display on a screen exactly what a pilot would see through a windshield. In military models, much of the information comes from the Defense Mapping Agency's library of the world's hills, valleys, rivers and towns. The processing power required to sort out that mass of data is staggering. Says Ronald Hendricks, technical director at Singer's Link Flight Simulation Division, a descendant of Edwin Link's original company: "When you look out the window, you see 18 billion bits of information. To make that scene unfold in real time, you have to compute a new image 60 times a second."

To cut down on that computational burden, future simulators will use a trick borrowed from the eye itself. Rather than create the entire 360 degrees horizon, they will concentrate their imaging resources on the narrow cone where the pilot is looking at a given moment. Link's new ESPRIT (eye-slaved projected raster inset) system uses an infrared scanner mounted in the pilot's helmet to track his eye movements. Then it projects a detailed, high- resolution picture in the pilot's direct line of sight and a fuzzier, less detailed peripheral image.

The most advanced simulators use tactile cues to take the illusion one step further. In Honeywell's F-18 fighter simulator, the strap-in harness pulls back on the trainee's chest when the jet slows down. Similar controls regulate the pilot's G suit, rushing air into pockets in the legs and abdomen to mimic the circulatory effects that accompany supersonic flight. Even the cockpit seat contributes to the illusion; the cushion contains seven air bladders that are pressurized or depressurized according to the flight maneuver.

The combined effect can be gut wrenching. In the catapult launch of a Honeywell T-45 Goshawk trainer from the deck of an aircraft carrier, for example, the body is crushed against the back of the seat and the wind roars in the ears. "You forget the whole thing's bolted to the concrete floor," says David Figgins, a program manager at Honeywell. "I've seen top guns climb out wringing wet. I've seen seasoned pilots throw up."

Link's AH-64 Apache helicopter simulator, perhaps the world's most sophisticated, combines mock flight with battle effects so realistic that a visitor needs security clearance to ride it. When a trainee is struck by enemy fire, he actually feels the hit. Indeed, the simulation can be dangerously % realistic. "We had to turn this one down," says Ray McCabe, flight- simulation supervisor at the Army's Fort Bragg. "We had a lot of guys lose teeth or have their nose broken from the impact."

The world's most popular simulator, Disneyland's Star Tours, poses no such hazards. As many as 27,000 people a day wait between 45 minutes and two hours for a chance to take a 4 1/2-minute imaginary excursion to the Moon of Endor. They are rewarded with a nonstop thrill ride in which a mock spaceship climbs, banks and even reaches the speed of light -- all with white-knuckle realism. "This is easily the most popular ride," says Bob Roth, manager of publicity for the park. "On a roller coaster, you have the lingering feeling that the car can go off the tracks. Star Tours gives you all the thrills without the insecurity."

Earlier this year, Los Angeles-based Showscan opened a 36-seat space-flight simulator at Futuroscope, a high-tech theme park in Poitiers, France. Universal Studios Tour in Universal City, Calif., is working on a time-travel simulation, based on the movie Back to the Future, that is scheduled to open next summer. By 1990 Texas-based Six Flags plans to install a Dynamic Motion Theater at its Great Adventure theme park in New Jersey. It will feature a series of changing attractions that may include airplane dogfights and car chases. Meanwhile, the folks at Disney are putting the finishing touches on an anatomical extravaganza called Body Wars that will take visitors on a microscopic race against time through the human immune system.

None of this comes without a price. Star Tours took six years to make and cost $32 million. Link's Apaches, at $20 million apiece, cost at least $5 million more than the helicopters themselves. Even so, simulators are a bargain compared with the expense of training on the real thing, not to mention the expense in equipment and human lives when a real-world training mission goes awry. "One of the greatest things about simulators," says Honeywell's Figgins, "is that after the worst possible accident, everybody goes off and has a drink."

With reporting by Elaine Dutka/Los Angeles and Linda Williams/Binghamton