Nights Check Ride Study Guide

Question 1

Types of vision

Answer 1

• Photopic - Day - Cones(fovea centralis) - rhodopsin is bleached
• Mesopic - Dawn, Dusk, Full moon - cones and rods - acuity/color decreases
• Scotopic - Rods - rhodopsin - Visual acuity < 20/200 - night blind spot

Question 2

Self-Imposed Stressors

Answer 2

• Drugs
• Exhaustion
o Illness
o Poor physical conditioning
o Inadequate rest
• Alcohol - likely to stare & neglect scanning techniques
• Tobacco - increases CO in red blood cells - equals a phys altitude of 5,000 feet
• Hypoglycemia and Nutritional Deficiency
o Hypoglycemia - impairs night flight performance
o Vitamin A deficiency. Insufficient vitamin A may impair night vision.

Question 3

Distance estimation and depth perception

Answer 3

Binocular Cues - distances outside the cockpit are so great they are of little, if any, value

Monocular Cues- •Geometric perspective, •Retinal image size, • Aerial perspective, • Motion parallax

Question 4

Monocular Cues

Answer 4

• Geometric perspective - An object may appear to have a different shape when viewed at varying distances and from different angles.
o Linear perspective - Parallel lines converge
o Apparent foreshortening - object or a terrain appears elliptical
o Vertical position in the field - Objects farther away appear higher on the horizon
• Retinal image size
o Known size of objects - estimate the distance of familiar objects
o Increasing or decreasing size of objects
o Terrestrial associations - Comparing to an object of known size
o Overlapping contours or interposition of objects
• Aerial perspective - The clarity of an object
o Variations in color or shade - clearer the closer you are to an object
o Loss of detail or texture - farther from an object, details become less apparent.
o Position of light source and direction of shadow - Shadow towards you = object closer than light
• Motion parallax - apparent motion of stationary objects as viewed by an observer moving across the landscape

Question 5

Visual illusions

Answer 5

• Flicker Vertigo - 4 and 20 cycles per second (rotor blades, anticollision light)
• Fascination (Fixation) - ignore cues and fix attention on a goal or object
• False Horizons - Clouds confused with the horizon
• Confsion of Ground Lights - confuse ground lights with stars
• Relative Motion - mistake the motion of another aircraft for that of your own
• Autokinesis - static light in the dark, the light appears to move
• Structural Illusions - (heat waves, rain, snow, sleet) factors that obscure vision.
• Height Perception - (desert, snow, water) illusion of being higher than you are
• Size-Distance - light that is increasing or decreasing in brightness
• Altered Reference Planes - Mountains or clouds, feel that you need to climb
• Reversible Perspective - Red on Right Return

Question 6

Dark Adaptation

Answer 6

• First 30 minutes, eye sensitivity increases roughly ten-thousand fold
• The lower the starting level, the faster dark adaptation is achieved
• Optimum night visual acuity in about 30 to 45 minutes (recovered in 5-45)
• NVD - does not fully bleach out rhodopsin – can 30 min dark adapt in 2 min

Question 7

Blind spots

Answer 7

• Physiological Blind Spot – caused by optic disk – 5.5 – 7.5°
• Central Night Blind Spot - occurs when cone-cell sensitivity is lost - 5-10° - caused by fovea centralis – to overcome use off center viewing and scanning

Question 8

Protection of night vision

Answer 8

Equipment
• Sunglasses (neutral density N-15) - intense sunlight for 2-5 hours decreases scotopic visual sensitivity for as long as 5 hours
• Oxygen supply - Aided night vision is not significantly affected by a lack of oxygen. Should use 02 unaided above 4,000 ft PA
Precautions
• Airfield lighting - should be reduced to the lowest intensity. Select departure routes that avoid highways and residential areas
• High-intensity lighting - turn the aircraft away, shut one eye
o Avoid built-up areas
o Flares - maneuver to a position along the edge of the illuminated area
o Weapon flashes - limit time, short bursts, look away

Question 9

Infrared theory/characteristics of FLIR and interpretation

Answer 9

• Infrared Radiation
o Reflectance–the ratio of radiant energy reflected by a body to the radiant energy incident upon it.
o Absorptance–the ratio of radiant energy absorbed by a body to the radiant energy incident upon it.
o Transmittance–the ratio of radiant energy that, having entered a body, reaches its farther boundary.
o Emissivity–the relative power of a surface to emit heat by radiation. Black absorbs & emits 100% of its IR energy

• Minimum Resolvable Temperature
• Atmospheric Effects
• Atmospheric transmission
• FLIR performance
• IR Crossover