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Spatial Disorientation: An Introduction

Spatial Disorientation is ‘an erroneous sense of the magnitude or direction of any of the control or performance flight instruments’.

Stated in the words of Benson, “Spatial disorientation is a state characterized by an erroneous sense of position, attitude, or motion of oneself or one’s aircraft in relation to a fixed, three dimensional co-ordinate system defined by the surface of the earth and the gravitational vertical. In addition, this also includes errors of perception by the aviator of his position, attitude or motion with respect to his aircraft or of his own aircraft relative to other aircraft”. 

The most important consequence of SD is the orientation error accident, which may have tragic consequences.

There are three types of spatial disorientation described.

  • Type-I.  or, Unrecognized SD. Here pilot gets disoriented, but does not recognize it, in turn leading to incorrect or inadequate decisions, tragically resulting in an accident.
  • Type-II.   or, Recognized SD. Here pilot knows that he is disoriented and takes corrective action.
  • Type-III.  or, Incapacitating SD. Here the pilot knows that he is disoriented but is incapacitated and thus failing to take any corrective action. Incapacitation may be psychological, physiological or physical in nature.

Various conditions conducive to give rise to SD are:

  • Lack of visual cues, cloud flying etc.
  • Night flying.
  • Inattention.
  • Lack of experience.
  • Environmental factors like hypoxia, cold, etc.
  • Under influence of alcohol or drugs.
  • Violent manoeuvres.
  • Unnecessary head movements.
  • Fatigue.
  • Psychological stressors like anxiety, preoccupation and emotional stresses.
  • Glare or Dazzle.
  • Inadequate cues from vestibular and other mechanoreceptors.
  • Errors of expectancy.
  • Gz forces.
  • Diseases of vestibular system.

There are various illusions as per the limitations of the sensory organs viz. visual or vestibular.

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Reference

1. Ernsting’s Aviation Medicine. Rainford DJ, Gradwell DP (Editors). 4th Edition. Hodder Arnold, London 2006.

2. Fundamentals of Aerospace Medicine. DeHart RL, Davis JR (Editors). 3rd Edition. Lippincott, Williams & Wilkins, Philadelphia 2002.

3. Human Performance & Limitations – JAA ATPL Theoretical Knowledge Manual. 2nd Edition. Jeppesen GmbH, Frankfurt 2001.

Acknowledgement Image courtesy www.freedigitalphotos.net

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