What scientists haven't solved and hot-shot pilots won't talk about.
- By William Gregory
- Air & Space magazine, May 2002
(Page 2 of 4)
William Ercoline is a former instructor pilot who has taught in heavy, motion-based simulators and now works on spatial disorientation countermeasures at Brooks Air Force Base in Texas. He says that once a pilot becomes stressed, “he is more likely to experience what we call Type One disorientation, which is unrecognized. That means he or she will start focusing on one thing and let another go, and it could be the attitude of the airplane. I’ve seen that. I have some friends that do aerobatics and they get this thing called the wobblies, which causes long-term effects. They start driving their cars, start shaking, and have to stop.”
Kay Stanney, an industrial engineer at the University of Central Florida, tells of a helicopter pilot who, driving home after a long hop in the simulator, suddenly “saw” his car roll upside down. Though he got the car off the road and his head right side up, the experience has become a legend in the small world of simulator sickness research. Robert S. Kennedy, a Navy flight surgeon and expert on motion sickness, tells a similar story about an operator of a Navy Landing Craft Air-Cushion vehicle (LCAC): After getting out of a simulator, he began weaving so much on his drive home that cops pulled him over for drunk driving. The man was having a post-simulator disorientation flashback.
Disorientation can happen in flight because of the same man-versus-machine disconnect. A high-time Navy pilot, who asked not to be identified, remembers a night bombing drill in an A-7 in which he could see the lights of the target ship through the windscreen, paired with its FLIR (forward-looking infrared) head-up display image. Abruptly the FLIR ran out of gimbal travel and the two scenes diverged. “I had an overpowering wave of nausea,” he recalls, “but I had enough instinct to pull back hard on the stick.”
The Federal Aviation Administration and the military have established limits on the amount of jitter and latency that can take place in a simulator, but no standards exist for helmets. In one study Stanney and Kennedy found that about 10 percent of simulator users reported vision-related symptoms, like a headache, another 7.5 percent reported nausea, and five percent suffered from disorientation. While using a virtual reality helmet, a remarkable 25 percent experienced nausea, and another 30 percent reported disorientation.
A full-motion simulator can cost $10 million to $15 million, while a helmet costs maybe $50,000, which helps explain why the military still uses them, even though they are more likely to cause motion sickness. Indeed, military instructors are incorporating more helmet displays into flight simulators; well engineered, these can work just fine, says Kruk.
Helmet displays are important for reconfigurable helicopter simulators, like the one in an Army program that can be changed from a UH-64 Apache to a UH-60 Black Hawk by switching moveable cockpit modules around and exchanging virtual reality software. Engineers still have to make sure the tracker beacon in the headset stays in sync with the scene that rolls by on the screen.
Researchers like Kennedy are looking into the causes of all of these reactions and hoping to find a way to counteract some of the more dangerous side effects. In his office, Kennedy has a seven-foot-wide, six-feet-high drum made from aluminum stringers, which he uses to conduct tests on motion and peripheral vision. He’s wrapped a corrugated-cardboard skin around it and pasted some cheap wallpaper with a nauseating horizontal ocean wave pattern on the inside. The test subject sits in a chair two feet off the floor with nothing much visible except the wallpaper.
“Close your eyes,” a Kennedy aide says to a young man in a demonstration run, whereupon the drum gradually spins. When the speed tops 130 degrees a second, the aide gives an “eyes open” command. All the subject sees is a fast-moving ocean scene turning right. But as the drum accelerates toward its maximum, 160 degrees a second, the ocean scene seems to stop and the chair appears to spin left.
No question, it’s quick and queasy, a classic case of the inner ear saying “You’re not moving” and the eyeball saying “Oh yes you are.”
David Graeber is writing a doctoral dissertation on the reactions of volunteers spinning in Kennedy’s drum. His findings reiterate what pilots and sailors learn on the job: Adaptation is the key. When you’re in a simulator, don’t try to bull your way through motion sickness, something hot-rock pilots, disdainful of electronic flying, are prone to do. Back off, get acclimated in short bursts.