Spatial Disorientation Flashcards
What is spatial disorientation?
Pilot’s erroneous perception of position,
attitude, or motion in relation to the
gravitational vertical and the Earth’s surface.
What are the three types of SD?
(URI)
Unrecogonized, Recognized and incapacitating
What is unrecognized SD?
Most Dangerous
Pilot does not perceive any indication of
SD. Fails to recognize and correct disorient
leading to crash. (Height/Depth Perception)
What is recognized SD?
Pilot perceives a
problem but may fail to recognize it as SD.
(believes instrument fail / control failure)
What is incapacitating SD?
Pilot experiences
overwhelming sensation of movement.
Transfer controls or focus.
What is incapacitating SD?
Pilot experiences
overwhelming sensation of movement.
Transfer controls or focus.
What are the three systems of SD?
(VVP)
Visual, vestibular, Proprioceptive
Explain the visual system in SD
the most important in maintaining
the ability to orient and move in three-
dimensional space.
Explain the vestibular system in SD
Inner ear contains
Semicircular Canals (angular acceleration using
endolymph fluid sense rotation of head) and
Otolith Organs (linear acceleration and gravity,
hairs and crystals located in vestibule proper
sense head position changes).
Explain the somatosensory system in SD
pressure on joints,
muscles, skin, and internal organ movement
What are the visual illusions?
Vection (Induced Motion Illusion)
• False Horizon
• Confusion with ground lights
• Height/Depth Perception Illusion
• Crater Illusion
• Structural Illusion
• Fascination (Fixation)
• Autokinesis
• Size – Distance Illusion
• Aerial Perspective
• Size Constancy
• Shape Constancy
What is a vection illusion?
(Induced Motion). Falsely perceived motion of oneself when no physical motion is actually occurring.
When stationary and things move around you.
What is confusion regarding visual illusions?
A common occurrence is to confuse ground lights with stars. A good cross check will prevent this illusion.
What is a crater illusion?
Occurs when aircrew members land at night, under NVG conditions, and the IR searchlight is directed too far under the nose of the aircraft. This will cause the illusion of landing with up-sloping terrain in any directions. Depressing lulls the pilot into continuing to lower the collective. Could result in the aircraft prematurely impacting the ground, causing damage.
What is Height/depth perception illusion?
When flying over terrain lacking good contrast (water, desert, snow), crew members may think the aircraft is higher or lower than it actually is. This is due to a lack of visual references. It can be overcome by dropping an object of known size or intensity from the aircraft or by using shadows cast by surrounding objects or the aircraft. At night drop a chem.-stick or flare before landing. Flight in DVE conditions can produce the same illusion.
What is autokinesis?
When a static light is stared at in the dark for 6 to 12 seconds, the light appears to move up to 20 degrees in any direction. Reduce or eliminate by visual scanning, increasing the number of lights, or by varying light intensity.
What is Fascination/fixation?
This occurs when aviators ignore orientation cues & fix their attention on a single goal or object without seeing the whole environment. May occur during times of task saturation or target fixation.
What is false horizon in SD?
Confusing cloud formations, mountain ridges or “cultural” lighting (coastline or highway) w/ the horizon. This is usually occurs when the aviator looks up after a prolonged period in the cockpit or from poor scanning technique.
What is structural illusion?
The distortion of objects caused by heat waves, rain, snow or other factors that obscure vision. Curvature of the wiindscreen can also cause this. This illusion can be linked to mirages.
What is a size distance illusion?
(SSA: Size Constancy, Shape Constancy, Aerial Perspective)
What is size constancy?
occurs when shooting an approach to a large runway vs. a small stage field lane. On larger runways an aviator may perceive he is too low when landing.
What is shape constancy?
can occur on approach to a down-sloping runway giving the illusion that the aircraft is lower than it is; or to a up-sloping runway giving the illusion that the aircraft is higher than it is causing the pilot to fly lower in an attempt to achieve that normal sight picture.
What is aerial perspective?
occurs when visual cues such as a runway or trees are different size than expected. Washington’s vs. Alabama’s vegetation differences.
What is a SOMATOGRAVIC ILLUSION?
caused by
linear acceleration / gravity – causes the otolith
organ to sense a nose-high (or nose low)
attitude.
• G-Excess Illusion - results from a change in
the direction of the net gravitoinertial force, a
G-excess illusion results from a change in the
direction of the net gravitoinertial force.
• Elevator – occurs during upward
acceleration pilots eyes track down, nose
seems to rise and pilot push fwd on cyclic
What is ocular fixation ?
The illusions
occur due to the misperception of movement
of a fixed object (such as, instrument panel)
relative to the pilot during change of direction
of gravitoinertial force. This is likely due to
reflexive desire to maintain visual fixation.
Occurs during downward motion
(autorotation), causes eyes to track up, feeling
nose low pilot pulls aft cyclic and slows to
unsafe speeds.
What is a somatogyral illusion?
caused by
angular acceleration / decel – semicircular. Moves fluid in your inner ear bending tiny hairs inside the canal which send signal to your brain letting it know your spinning.
What are some Somatogyral illusion examples?
LGCP
• Leans – Most Common, pilot perceives the
aircraft is in a turn and leans to correct the
illusion
• Graveyard Spiral – occurs when in a long
turn semicircular canals reach equilibrium and
when you roll out it feels like you rolled into a
turn in the opposite direction. If instruments
aren’t used pilot rolls right back into the
original bank.
• Coriolis Illusion – Most Dangerous,
overwhelming disorientation. Prolonged turn
allows fluid in semicircular canal to come to
equilibrium. If head is moved out of plane other
canals are stimulated causing a head over heels
tumbling sensation.
• Post-Roll (Gillingham) Illusion - Pilot may
initiate a roll rate into a coordinated turn,
complete the maneuver, but then incorrectly
provide control input to add additional bank in
the same direction with the misperception of a
decrease in bank or roll-reversal. This also
sometimes called a “roll-after effect.”
How to prevent SD?
Training,
Instrument proficiency, Good health, Aircraft
design.
(Never, Never, Avoid, Trust)
• Never fly VMC and IMC at the same time
• Never fly without visual reference points
• Avoid fatigue, smoking, hypoglycemia,
hypoxia, and anxiety
• Trust the instruments, develop good scan
How to treat SD?
-DR.T-
• Delay intuitive actions
• Refer to instruments
• Transfer controls to other pilot.
What should you do if feeling middle ear discomfort?
• Avoid flying when sick (cold, sinuses)
• Avoid Valsalva during ascent
• Perform slow descent if able or climb back to
altitude
• During climb, yawn, swallow, or rock their jaw
to help equalize pressure
What are the exogenous factors that restrict you from flight duties for 12hrs after exposure?
• Anesthesia (+ Dental)
• Alcohol
• Immunizations
• Chemical exposure (Gas chamber)
• Simulator sickness (symptoms)
What are the Exogenous factors that restrict from flying duties for 24hrs after exposure?
⌲ 24 Hours
• Plasma donation
• Hypobaric Chamber
• Decompression sickness (Scuba)
• After Dunker training if flight is above 10,000msl
•Eye dilation
What are the Exogenous factors that restrict from flying duties for 72 hrs after exposure?
Blood donation ≥200cc
• Hypobaric exposure > FL180
What is orientation illusion?
False perception of position or motion
True or false
Orientation illusion is the main cause of SD
True
How much percentage is used individually in vision, vestibular and propioceptive?
Vision 80%, vestibular 15% and propioceptive 5%
What does orientation of vision require?
Perception, recognition and identification
What are the two modes of the visual system?
Focal and ambient vision
How many degrees of field of view can be achieved with focal vision?
30-40 degrees
How many degrees of field of view can be achieved with ambient (peripheral) vision?
120/200 both eyes
What is nystagmus?
(Shaky eyes)
Results from jerky undulating eye movements
What are the functions of the vestibular system?
Visual tracking
Reflex information
Orientation without vision
What is the function of the semicircular canal?
Change in both speed and direction
Angular
What are the functions of the otolith organs?
Change in speed without a change in direction
Linear
What is the cúpula?
Fluid around the hair cells in the semicircular canal
What is visual dominance?
Where one uses visual cues to overcome other sensory cues
What is vestibular suppression?
An active process of visually overriding undesirable vestibular sensations.
What is vestibular opportunism?
The ability of the vestibular system to fill any orientation void swiftly
