Visual Illusions/vestibular Flashcards
VECTION (INDUCED MOTION ILLUSION)
Induced motion is falsely perceived motion of oneself when no physical motion is actually occurring.
FALSE HORIZON ILLUSION
False horizon illusions occur when a pilot confuses a wide sloping plane of reference such as sloping cloud tops, mountain ridges, or so-called ‘cultural’ lighting at night (such as a coastline or highway) with the true horizontal
CONFUSION WITH GROUND LIGHTS
confusion with ground lights, occurs when a pilot mistakes ground lights for stars
The illusion prompts the pilot to place the aircraft in an unusual attitude to keep the misperceived ground lights above the aircraft.
HEIGHT-DEPTH PERCEPTION ILLUSION
Height-depth perception illusions are due to absent or insufficient visual cues and cause crewmembers to misjudge depth perception. Flying over areas devoid of visual references such as desert terrain, snow, or water may deprive crewmembers of their perception of height
CRATER ILLUSION
Crater illusions occur when crewmembers land at night under night vision device conditions and the infrared searchlight is directed too far under the aircraft’s nose. This combination creates the illusion of landing with up sloping terrain in all directions or landing in a crater.
Structural illusions
Structural illusions are caused by the effects of rain, snow, sleet, heat waves, or other visual obscurants. A straight line can appear curved when viewed through heat waves in the desert.
SIZE-DISTANCE ILLUSION
Size and shape constancy are important when a familiar object’s known size and shape is used to judge its distance from the observer. Size-distance misperceptions give rise to a number of related illusions whereby a crewmember misinterprets an object of unfamiliar size and shape by comparing it with what they are accustomed or familiar to seeing based on experience.
Size Constancy
A common example of a size constancy illusion is that of landing at an unfamiliar runway. A runway that is narrower than expected may cause the pilot to think he or she is higher and further away resulting in the flying of the approach too low and land short. Likewise a wider runway than expected may cause the pilot erroneously to think he or she is closer resulting in flying the approach too high and land long.
Shape Constancy
commonly encountered with sloping runways (figure 9-14). A typical glideslope to landing of 3 to 4 degrees is such that only a one degree change in runway slope can affect the landing sight picture. With the shape constancy illusion, the foreshortened picture of an up sloping runway may give the pilot the illusion of being too high
FASCINATION (FIXATION) IN FLYING
Task saturation: occurs when crewmembers become so engrossed with a problem or task within the cockpit that they fail to properly scan outside the aircraft.
Target fixation: commonly referred to as target hypnosis, occurs when crewmembers ignore orientation cues and focus their attention on an object or goal
AUTOKINESIS
Autokinesis occurs primarily at night when ambient visual cues are minimal and a small, dim light is seen against a dark background.
After about 6 to 12 seconds of visually fixating on the light, an individual may perceive movement at up to 20 degrees in any particular direction or in several directions in succession, although there is no actual object displacement.
This illusion can cause a pilot to mistake the fixated object for an object in motion (such as, another aircraft)
Illusions Acronym
Induced motion
Confusion with ground lights
Crater
Height depth
Autokinesis
Fascination
False horizon
Structural
Size distance (size constancy, shape constancy, aerial perspective)
Aerial Perspective
These illusions can occur if visual cues are of a different size or perspicuity (clarity and discrimination) than expected.
A classic example would be for a pilot to mistake immature, short or stunted trees for large, tall ones causing him or her to misjudge altitude above the ground
