Simulator sickness

Simulator sickness is a subset of motion sickness that is typically experienced by pilots who undergo training for extended periods of time in flight simulators. Due to the spatial limitations imposed on these simulators, perceived discrepancies between the motion of the simulator and that of the vehicle can occur and lead to simulator sickness. It is similar to motion sickness in many ways, but occurs in simulated environments and can be induced without actual motion. Symptoms of simulator sickness include discomfort, apathy, drowsiness, disorientation, fatigue, vomiting, and many more. These symptoms can reduce the effectiveness of simulators in flight training and result in systematic consequences such as decreased simulator use, compromised training, ground safety, and flight safety. Pilots are less likely to want to repeat the experience in a simulator if they have suffered from simulator sickness and hence can reduce the number of potential users. It can also compromise training in two safety-critical ways:

Simulator sickness can also have post-training effects that can compromise safety after the simulator session, such as when the pilots drive away from the facility or fly while experiencing symptoms of simulator sickness.

Though human-piloted aviation has existed since the early 20th century, simulator sickness did not arise as an issue for pilots until much later when the first fixed-base simulators were created.Bell Aircraft Corporation created a helicopter simulator for the Navy during the 1950s, and it was found "that a large number of observers (mostly helicopter pilots) experienced some degree of vertigo during these demonstrations". Navy psychologists performed further study on the pilots who participated in these simulator exercises, and found that 28 out of 36 respondents to their evaluations experienced sickness. Additionally, psychologists found that experienced flight instructors seemed to be most susceptible. In fact, 60% of the instructors reported simulator sickness symptoms compared to only 12% of the students. "The SS usually occurred in the first ten minutes of a training session and frequently lasted for several hours afterward."

Two main theories exist about the causes of simulator sickness. The first is sensory conflict theory. Optical flow patterns generated in virtual environments typically induces perception of self-motion (i.e., vection). Sensory conflict theory holds that, when this perception of self-motion is not corroborated by inertial forces transmitted through the vestibular system, simulator sickness is likely to occur. Thus, sensory conflict theory predicts that keeping the visual and vestibular inputs in agreement can reduce the likelihood of simulator sickness experienced by users. Additionally, according to this theory, people who do not have a functioning vestibular component of their nervous system should not show either simulator sickness or motion sickness.

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