Visual Illusions
Describe the Crater Illusion
Landing at night, under NVG conditions, the IR searchlight is too far under the nose of the aircraft - it will cause the illusion of landing with up-sloping terrain in all directions (a crater).
Solution: proper use of landing and search light and scanning.
What are the 3 types of vision?
Photopic
Mesopic
Scotopic
At what rate does the moon change its angle?
15 degrees/hour (1 degree every 4 minutes)
What are some limitations of night vision?
Reduction in visual acuity
Color vision decreases / disappears
The night blind spot
What is the preferred color of light for use in the cockpit at night? Why?
Blue-Green
It does not disrupt dark adaptation. It falls naturally on the retinal wall and allows the eye to focus on the object without becoming fatigued. In addition, the intensity required for blue/green as opposed to red is less, resulting in a lower infrared signature and less glare.
Describe False Horizon.
Aviator confuses cloud formations with the horizon or the ground, thus they may fly the aircraft in a banked attitude.
Solution: Scan instruments and other visual cues
Describe Scotopic Vision
Used under low light
Rods are primarily used
Best Visual acuity 20/200
When is it considered to be "night" when flying?
Between the hours of official sunset and sunrise.
What are the 3 night vision techniques that can be used to overcome reduced visual acuity and color vision?
Scanning
Off Center Viewing
Shapes or Silhouettes
What is dark adaptation?
How long does dark adaptation usually take?
Dark adaptation is the process by which the eyes increase their sensitivity to low levels of illumination.
30-45 minutes - depending on the individual.
45 mins to readapt
Describe Autokinesis.
Primarily occurs at night when ambient visual cues are minimal and a small dim light is seen against a dark background. Aviator visually fixates on light for 6-12 seconds, the light appears to move up to 20 degrees in any direction and continues to "move".
Solution: avoid fixating on objects, develop a good scan.
Describe Photopic Vision
Used in daylight
Cons are primarily used
Best visual acuity 20/20
What is BMNT?
What is EENT?
Before Morning Nautical Twilight
Sun = 12 degrees below the horizon before sunrise
Roughly 48 minutes before sunrise.
End Evening Nautical Twilight
Sun = 12 degrees below the horizon after sunset
Roughly 48 minutes after sunset
What are the two types of cues we use for distance estimation?
Binocular Cues and Monocular Cues
Describe the night blind spot.
Occurs when the fovea becomes inactive under darkness or low level illumination - central vision becomes less effective and the night blind spot develops.
The night blind spot covers 5-10 degrees of central vision. This is due to the fact that there are no rods on the fovea centralis (the center of vision).
Describe the 3 types of Size/Distance Illusion.
1) Size Constancy Illusion – an example is landing at an unfamiliar runway. A narrower runway may lead a pilot to believe he/she is higher and further away.
2) Shape Constancy Illusion – Commonly encountered with sloping runways. An upsloping runway may give the pilot the illusion of being too high
3) Aerial Perspective Illusion – visual cues are of a different size or perspicuity (clarity and discrimination) than expected. An example is mistaking short immature trees for full grown ones. Also, objects within a hazy environment are often thought to be further away than they actual area.
What is the 5 major components of the eye?
Cornea
Iris
Pupil
Lens
Retina
What is equipment is required to fly at night?
(Name 5)
Where do I find this information?
Heading indicator
Airspeed indicator
Pressure Altimeter
Visual Speed Indicator
Magnetic Compass
Fuel quantity indicator
Clock or stop watch
Free air temp
Flight control computer/Inertial Navigation system/ Heading and Attitude reference System
Standby Flight instruments
Commo Equipment
Anticollision Light System
Position instrument lights
Landing/Search Light
Flashlight
AR95-1 Table 5-2, pg. 39
What are binocular cues?
Depend on the slightly different view each eye has of an object.
Binocular perception is of value only when the object is close enough to make a perceptible difference in the viewing angle of both eyes. Thus, binocular cues are of little value, as most of what we focus on is far beyond the scope of usefulness of binocular cues.
Describe the day blind spot.
The day (physiological) blind spot is present all the time (including at night). This blind spot results from the position of the optic disk on the retina. The optic disk has no light-sensitive receptors.
The physiological blind spot covers an area of approximately 5.5-7.5 degrees and is located about 15 degrees from the fovea.
What are the visual Illusions
(9)
Fascination/Fixation
False Horizon
Size/Distance Illusion
Height/Depth Perception Illusion
Autokinesis
Vection (Inducted Motion Illusion)
Structural Illusion
Confusion with Ground Lights
Crater Illusion
What are visual Deficiencies?
Myopia- nearsightedness
Astigmatism- unequal curvature of cornea
Night Myopia- visual difficulty at night with blue-green light causing blurred vision
Hyperopia- farsightedness
Presbyopia- lens becomes hardened
Retinal Rivalry- Eyes trying to focus on two things causing pain
What is the visual flight rule weather minimums for Night
G (Rotary Wing)- 1,200 ft or less (regardless of MSL)
G (Rotary Wing)- more than 1,200 ft above surface, but less than 10,000 MSL
G (Rotary Wing)- 1,200 ft above surface at or above than 10,000 MSL
G (Rotary Wing)- 1,200 ft or less (regardless of MSL)
1SM CC
G (Rotary Wing)-more than 1,200 ft above surface, but less than 10,000 MSL
3 SM 500ft below, 1,000 ft above, 2,000ft horizontal.
G (Rotary Wing)- 1,200 ft above surface at or above than 10,000 MSL
D/N 5SM 1,000 ft above and below, 1SM horizontally
What is a monocular cue?
What are the monocular cues?
Factors that aid in distance estimation and depth perception.
Geometric Perspective
Retinal Image Size
Aerial Perspective
Motion Parallax
Where is the Anti-Collision Lights located?
upper left console. Second Row from the windshield. 3-4th pin.
3rd is "Both upper/lower" 4th is "Off day/night"