Spatial Disorientation

Question 1

Explain how various sensory systems contribute to spatial orientation

Answer 1

Visual 80% + vestibular 10% + proprioception 10%&raquo_space;> CNS (cortex, brain stem, cerebellum)&raquo_space;> ocular reflexes + postural control

Question 2

Describe vestibular system and proprioception re anatomy, function and limitations

Answer 2

Anatomy: made up of the semicircular canals and otoliths
Used to establish body position by sensing angular and linear accelerations.
Message taken to brain via CN8
- in urticle there are otoliths and hair cells that detect linear acceleration when the capsule moves thus moving the endolph and hair cells. During prolong rolls and turns, the endolymoh movement reaches a steady state with acceleration of < 2 deg/s/s is not sensed as movement.
Subsequent change in angular acc is sensed as new movement
Basis for somatogyral, Coriolanus and leans.

Otoliths organs&raquo_space; somato-gravic illusions

Propriorecptors contribute to 10% of info

Question 3

Describe the vestibule ocular reflex

Answer 3

EO muscles are linked to the vestibular system via the medial longitudinal fasciculus with conjugate eye movements coordinated with head movements.

Movement of fluid in SCC sends input to brain to register angular acc which also stim signal from brain to EO muscles to start eye tracking in flicking motion

Question 4

What terminology is used to describe vestibular illusions?

Answer 4

Gyral - angular acceleration, affects the semicircular canals
Gravic- refers to linear acc or G, affects the otoliths
Somato - refers to the body
Oculi - refers to vision

Question 5

What is the role of propioreceptors?

Answer 5

To sense position of body parts and gravity. They are located in the joints, muscles and tendons. They are stimulated by touch, joint position, muscle stretch and vibration

Question 6

Give a summary of the orientation system

Answer 6

1. Vision: dominant sense, uses peripheral retina (ambient system), streaming views
2. Otoliths organs: senses linear accelaration, tilt sensation and gravity
3. Proprioception: senses position of body part and gravity, in joints/tendon/muscle- stim by touch/pressure/muscle stretch/ vibration/ gravity
4. Semicircular canals: senses angular accelaration, linked up with vision via VOR, senses turn/rotation

Question 7

Define spatial disorientation

Answer 7

Failure to correctly sense position/motion/altitude of yourself, or the aircraft, in relation to gravity and the Earth’s surface

Question 8

List risk factors that contribute to SD

Answer 8

1. Degraded visuals: night, high altitudes, featureless terrains, NVGS
2. Accelaration s: subthreshold change, sustained, long turns
3. Human fx: fatigue, distraction, high workload, Illness

Question 9

How do you classify disorientation?

Answer 9

Type 1 = unrecognised:
Incorrect perception + pilot unaware > control based on incorrect perception&raquo_space; loss of control + inappropriate control = accident

Type 2 = recognised:
Correct perception + aware on conflicting inputs > conflict > conflict resolved = correct control

Type 3 = incapacitating:
Aware of conflict but conflict not resolved&raquo_space; SD stress&raquo_space; inappropriate control

Question 10

Define somatogravic illusion

Answer 10

Illusion caused by otoliths and perception, where there is a confusion of accelerations and tilt, giving the false sensation of pitch up or down

False climb illusion
With sustained linear acc the otoliths can interpret this as pitch up

Question 11

Explain Coriolus illusions

Answer 11

Tumbling sensation created when cross coupling of the SCC and by the conflicting signals sent to the brain.

3 SCC are stimulated in 3 different ways&raquo_space; confusion

Question 12

Explain the Leans visual illusion

Answer 12

Involves both SCC and otoliths has both somtogyral and somatogravic components
Is caused by a false sensation of roll attitude

Aircraft has slow roll below detection threshold 2deg

Question 13

Explain somatogyral illusions and the graveyard spiral

Answer 13

In a constant spin, the fluid in SCC stabilises and acceleration is t/f not detected. When the pilot then recognises that he is in a spin, he will stop abruptly. The inertia of fluid in SCC will cause a relative motion and sensed as mvm in the opposite direction. The pilot may then incorrectly recover by putting the aircraft back into a spin in the original direction.

Occurs with poor visual cues and with prolonged turning in spin recovery

Prevented by preparedness and avoiding plrolonged spins and use of instruments

Question 14

Explain somatogravic illusions.

Answer 14

With increasing linear accelerations, movement of otoliths mimic the same as if there was movement up against gravity, this signal can be interpreted as pitch up movement

False climb illusion

Question 15

Recommend strategies for overcoming disorientation during flight

Answer 15

Use of visual and instrument aides/cues

Be prepared for the flight: know the mission and flight conditions - transition early into instruments- stay on instruments until good visual cues- ASOR

proficiency: maintain proficiency in instrument flying

Physiology: maintain good physical, mental health, manage fatigue, avoid l alcohol and self medications
IMSAFE checklist

Question 16

Explain G excess illusions

Answer 16

+Gz and otoliths
False sensation of rolling off bank&raquo_space; compensate with over banking

When bankingG force is applied, the pilot then looks down and when looks back up, he may have sensation if not flying straight and over correct

Prevent by don’t look into a turn

Question 17

Explain the SD experienced in a Barany chair

Answer 17

Oculogyral illusion

Involves visual and angular acc (SCC)
Sensation of apparent rotation

When spin in chair, in the SCC the endolymph moves in a direction and stimulates the cupula to send signal to brain about rotational directions. Once the fluid stabilises, acceleration is not detected. When chai is stopped, the inertia of the fluid slows down and is interpreted by brain as movement in opposite direction.
When eyes open, as the head turns the eyes want to fix on an object until the limit of the VF is reached and then the eyes flick ahead to fixate onto another object (saccadic vision)