 This involves the simultaneous stimulation of two semicircular canals and is associated with a sudden tilting (forward or backwards) of the pilot's head while the aircraft is turning.This can occur when tilting the head down (to look at an approach chart or to write on the knee pad), up (to look at an overhead instrument or switch), or sideways.This can produce an overpowering sensation that the aircraft is rolling, pitching, and yawing all at the same time, which can be compared with the sensation of rolling down a hillside.