M05 Human Factors

Three sensory systems for orientation

Visual, vestibular, and kinesthetic

Most important sensory system for flight

Visual system

Cones

Cells primarily located in the center of the eye that are used for color and day vision

Rods

Cells that provide grayscale vision and are very sensitive to light

Rods and bright light

Bright light can temporarily wash out vision until rods readapt

Factors affecting night vision

Smoking, alcohol, oxygen deprivation, and age

Day blind spot

The location where the optic nerve and retina bundle exist

Night blind spot

The central area of vision where rods are less concentrated

Off-center viewing

Used at night to take advantage of rods located toward the outer edges of the eye

Night vision adaptation time

Approximately 30 minutes after entering a dark environment

Bright lights and night vision

Bright lights can destroy night vision instantly

Night vision and altitude

Altitude can greatly affect night vision

Night vision and fatigue

Fatigue can greatly affect night vision

Night flying altitude recommendation

Try to stay below 5,000 feet at night or use oxygen

Night vision oxygen requirement

Rods require more oxygen to operate at night

Vestibular system

Inner-ear system used to sense motion and orientation

Semicircular canals

Three inner-ear canals arranged at right angles to one another

Semicircular canal axes

Roll, pitch, and yaw

Semicircular canal function

Detect angular acceleration of the body

Semicircular canal fluid

Each canal is filled with fluid

Cupola

A gelatinous structure in the center of each semicircular canal that rests on sensory hairs

Semicircular canal motion sensation

Movement of the sensory hairs through fluid creates sensations of motion

Semicircular canal fluid lag

Due to friction, fluid can take approximately 15 to 20 seconds to reach the same speed as the canal

Starting a turn vestibular sensation

Fluid initially moves slowly and correctly signals turning

Sustained turn vestibular sensation

After several seconds, fluid reaches the canal's speed and the body senses that turning has stopped even though it continues

Stopping a turn vestibular sensation

The body may feel a turn in the opposite direction

Vestibular turning danger

A pilot may incorrectly reenter a turn after stopping one

Otolith organs

Detect linear acceleration and gravity

Otolith structure

Gelatinous membrane containing chalk-like crystals

Otolith response to head tilt

Weight of the crystals shifts the membrane and sensory hairs detect the shift

Otolith response to acceleration

Acceleration and deceleration can shift the membrane similarly to head movement

Kinesthetic sense

Signals from skin, muscles, and joints that tell the brain about body position relative to gravity

Acceleration kinesthetic sensation

Acceleration is felt as a push into the seat

False gravity sensation

Acceleration forces can create a false sense of gravity and confuse the pilot about which way is up

Uncoordinated turns and kinesthetic sense

Uncoordinated turns can make the brain sense banking or tilting

Turbulence and sensory illusions

Turbulence can create similar misleading sensations

Fatigue and illness

Fatigue or illness can make misleading sensations worse

Vestibular illusions

Leans, Coriolis, graveyard spiral, graveyard spin, somatographic, inversion, and elevator

Visual illusions

False horizon and autokinesis

Spatial disorientation

An incorrect perception of aircraft attitude or motion caused by conflicting sensory information

Leans

An illusion occurring when a gradual turn is not sensed properly and abruptly leveling causes the body to feel a turn in the opposite direction

Leans example

Entering a right turn too slowly may not move the semicircular canal fluid enough; abruptly leveling can make the pilot feel a roll to the left and cause reentry into the right turn

Coriolis illusion

During a sustained turn, abrupt head movement into another plane causes fluid movement that creates an illusion of movement or acceleration in a different plane

Coriolis danger

The disoriented pilot may maneuver into a dangerous attitude while trying to correct a perceived motion

Graveyard spin

Recovery from a spin that has stopped stimulating the motion-sensing system can create an illusion of spinning in the opposite direction

Graveyard spin danger

The pilot may try to correct the perceived opposite spin and return the aircraft to its original spin

Graveyard spiral

An illusion in which an aircraft loses altitude during a turn and the pilot perceives the aircraft as being in a level descent

Graveyard spiral response

The pilot pulls back to stop the descent, tightening the turn and increasing altitude loss

Graveyard spiral sustained-turn illusion

A prolonged coordinated constant-rate turn can create an illusion of not turning; leveling out then produces a sensation of turning in the opposite direction

Graveyard spiral correction illusion

The pilot may try to return to the original turn

Somatographic illusion

Rapid acceleration stimulates the otolith organs similarly to tilting the head backward

Somatographic acceleration illusion

Rapid acceleration creates a sensation of nose-up pitch and can cause the pilot to pitch down and begin a dive

Somatographic deceleration illusion

Rapid deceleration has the opposite effect and can result in a nose-up attitude

Inversion illusion

An abrupt change from a climb to straight-and-level flight causes the otolith organs to create a tumbling-backward illusion

Inversion illusion response

The pilot may push the nose down, intensifying the illusion and potentially creating a nose-low attitude

Elevator illusion

An abrupt upward acceleration, such as an updraft, stimulates the otolith organs and creates an illusion of a climb

Elevator illusion response

The pilot may pitch nose-low in response to the false climb sensation

Elevator illusion downdraft effect

An abrupt downdraft has the opposite effect and normally results in a nose-up attitude

False horizon

An illusion in which sloping clouds, obscured horizons, or patterns of ground lights are mistaken for the true horizon

False horizon danger

The pilot may align the aircraft with the false horizon and place the airplane in a dangerous attitude

Autokinesis

In darkness, a stationary light appears to move when stared at for a period of time

Autokinesis danger

The pilot may attempt to align the aircraft with the apparent movement and lose control

Seat-of-the-pants flying

Relying primarily on sensations from the skin, joints, and muscles interpreted relative to Earth's gravitational pull

Seat-of-the-pants flying danger

Acceleration forces can overpower gravity and create false sensations

Instrument reliance during disorientation

Become proficient with flight instruments, trust the instruments, and disregard misleading sensory perceptions

Optical illusions factors

Runway width, runway and terrain slopes, featureless terrain, water refraction, haze, fog, and ground lighting

Narrow runway illusion

A narrow-than-normal runway creates the illusion of being high and can cause a pilot to fly a lower approach

Wide runway illusion

A wider-than-normal runway creates the illusion of being low and can cause a pilot to fly a higher approach

Upsloping runway illusion

Upsloping creates the illusion of being higher and can cause a lower approach

Downsloping runway illusion

Downsloping creates the illusion of being low and can cause a higher approach

Featureless terrain illusion

Absence of surrounding ground features can make the airplane seem higher than it is and cause a lower-than-normal approach

Black hole approach

An approach over featureless terrain such as water, darkened areas, or snow-covered terrain that can make the airplane appear higher than it is

Water refraction illusion

Rain on the windshield can make the pilot think the aircraft is higher because the apparent horizon seems lower, resulting in a lower approach

Haze illusion

Haze diffuses light, affects depth perception, and creates the illusion of being farther from the runway

Haze approach response

Haze can cause a tendency to fly a low approach

Fog illusion

Flying into fog can create an illusion of a pitch-up attitude

Fog approach response

The pitch-up illusion can cause pilots to steepen the approach

Ground lighting illusion

Lights in a straight path, such as roads, can be mistaken for runway or approach lights

Bright approach lights illusion

Bright approach lights in a dark featureless area can create the illusion of being closer to the runway

Bright approach lights approach response

The illusion of being closer can cause the pilot to fly a higher approach

Preventing optical illusion landing errors

Anticipate visual illusions, use PAPIs and VASIs, use visual descent points, and maintain proficiency in landing procedures

PAPI

Precision Approach Path Indicator

VASI

Visual Approach Slope Indicator

Hypoxia

Reduced oxygen or insufficient oxygen

Primary concern with hypoxia

Reduced oxygen to the brain can reduce mental function and cause life-threatening errors

Four types of hypoxia

Hypoxic, hypemic, histotoxic, and stagnant

Hypoxic hypoxia

Insufficient oxygen to the body as a whole

Hypoxic hypoxia examples

Drowning and blocked airway

High-altitude hypoxic hypoxia

At high altitude there is the same amount of oxygen, but less pressure to push oxygen into the body

Most deadly type of aviation hypoxia

Hypoxic hypoxia

Hypemic hypoxia

Blood cannot transport enough oxygen to body cells

Hypemic hypoxia causes

Reduced blood volume from severe bleeding, anemia, and carbon monoxide poisoning

Histotoxic hypoxia

Cells cannot effectively use oxygen even though oxygen is being transported to them

Histotoxic hypoxia causes

Alcohol or drugs

Alcohol physiological altitude effect

One ounce of alcohol can equate to approximately 2,000 feet of additional physiological altitude

Stagnant hypoxia

Oxygen is not moving throughout the body

Stagnant hypoxia example

A foot falling asleep from sitting on it

Stagnant hypoxia flight cause

Pulling G-forces in flight

Hypoxia symptoms

Cyanosis, headache, decreased response to stimuli, increased reaction time, impaired judgment, euphoria, visual impairment, drowsiness, lightheadedness or dizziness, tingling in fingers and toes, and numbness

Cyanosis

Bluish discoloration of fingernails and lips