The Autokinetic Illusion gives you the impression that a stationary object is moving in front of the airplane's path; it is caused by staring at a fixed single point of light (ground light or a star) in a totally dark and featureless background. This illusion can cause a misperception that such a light is on a collision course with your aircraft (Figure 12, below; click on image for larger view).

False Visual Reference Illusions may cause you to orient your aircraft in relation to a false horizon; these illusions are caused by flying over a banked cloud, night flying over featureless terrain with ground lights that are indistinguishable from a dark sky with stars, or night flying over a featureless terrain with a clearly defined pattern of ground lights and a dark, starless sky (Figure 13, below).

Vection Illusion: A common example is when you are stopped at a traffic light in your car and the car next to you edges forward. Your brain interprets this peripheral visual information as though you are moving backwards and makes you apply additional pressure to the brakes. A similar illusion can happen while taxiing an aircraft.

Take the opportunity to personally experience sensory illusions in a Barany chair, a Vertigon, a GYRO, or a Virtual Reality Spatial Disorientation Demonstrator (VRSDD). By experiencing sensory illusions first hand (on the ground), pilots are better prepared to recognize a sensory illusion when it happens during flight and to take immediate action. The Aeromedical Education Division of the FAA Civil Aerospace Medical Institute offers spatial disorientation demonstrations with the GYRO and the VRSDD in Oklahoma City and at all of the major airshows in the continental U.S.

• Obtain training and maintain your proficiency in aircraft control by reference to instruments.
  
• When flying at night or in reduced visibility, use and rely on your flight instruments.
  
• Study and become familiar with unique geographical conditions where flight is intended.
  
• Do not attempt visual flight when there is a possibility of being trapped in deteriorating weather.
  
• If you experience a visual illusion during flight (most pilots do at one time or another), have confidence in your instruments and ignore all conflicting signals your body gives you. Accidents usually happen as a result of a pilot's indecision to rely on the instruments.
  
• If you are one of two pilots in an aircraft and you begin to experience a visual illusion, transfer control of the aircraft to the other pilot, since pilots seldom experience visual illusions at the same time.
  
• By being knowledgeable, relying on experience, and trusting your instruments, you will help keep the skies safe for everyone.