(2 of 3)
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."