When blindfolded, you will find that the loss of visual reference to surrounding objects makes it difficult to
stand and nearly impossible to walk a straight line. The inner ear and postural senses are relatively
reliable when standing still. However, their reliability is different on a moving platform, such as an aircraft
in flight. Without the aid of sight, these senses are unable to distinguish gravity, centrifugal force, or small
The sense of sight, supported by the sense of motion and the postural sense, is present whether
orientation is maintained by reference to the horizon, flight instruments, or both.
For the proficient instrument pilot, orientation by reference to the flight instruments rarely produces false
sensations of any consequence. In becoming such a pilot, you will learn to overcome any false
sensations by relying on the sense of sight to the flight instruments. If these false supporting senses are
relied upon during such a conflict, you can easily experience spatial disorientation.
You can minimize spatial disorientation by learning to disregard the false information produced by the
supporting senses. Visual reference to the flight instruments is your only reliable solution for coping with
Optical illusions result from misleading visual references outside the aircraft. These illusions usually
occur at night or during marginal weather conditions when the pilot attempts to remain oriented by outside
references, rather than the flight instruments. Although the sense of sight is reliable, visual illusions may
cause severe spatial disorientation. You can avoid these illusions only by relying visually on the flight
Some examples of optical illusions are:
A sloping cloud bank can create the illusion of flying in a banked attitude even though the aircraft is
straight and level.
Light reflected on the canopy or windshield may give the false impression of a steep bank or inverted
Lights on the ground may be interpreted as stars during a turn at night.
When you are flying through clouds at night, the anti-collision and strobe lights may produce a false
sensation that the aircraft is turning.
MAINTAINING SPATIAL ORIENTATION
The false sensations of instrument flight are experienced by most individuals. You will become less
susceptible to those false sensations and their effects as you acquire additional instrument experience.
Although these sensations cannot be completely prevented, you can and must suppress them by self-
discipline, conscientious instrument practice, and experience. You must learn to control your aircraft by
visual reference to the flight instruments. You must also learn to ignore or control the urge to believe any
false inputs from the supporting senses. You must focus absolute concentration on the aircrafts
performance as depicted on the attitude indicator and confirmed by the supporting instruments.