Pilots can routinely encounter up to 9 g's during maneuvers. They need a way to practice this without risking their life or their plane.
The centrifuge simulates a high-G environment by spinning around rapidly.
The pilot steps inside of the centrifuge and is strapped into an aircraft
seat. The centrifuge then starts spinning, slowly at first, and then very
rapidly.
When the centrifuge is up to speed, the pilot practices a straining
maneuver that can help keep him from passing out while he pulls up to nine
Gs. The pilot is monitored by a video camera in the centrifuge and his
performance is critiqued. This controlled environment is a very good place
to practice the anti-G straining maneuver, since should the pilot pass
out, the centrifuge is automatically stopped and a physiological officer
can help the pilot improve his strain during the next centrifuge run. Should
the blackout occur in an aircraft, the results would be a bit more severe
than the minor embarassment felt by the pilot after he regains consciousness.