Are SD accidents not so Common in Aviation?

Accidents due to Spatial Disorientation (SD), in military and general aviation, reportedly vary between 2.1 to 31% [1 – 11]. Despite of physiological limitations of the ‘human’ operator, accident statistics do not correctly reflect SD as a cause, as commonly as expected, especially in the military aviation. In fact, in a review of accidents due to SD, Gibb et. al. asserted “that SD contributes to at least 25-33% of all aircraft mishaps and it results in the highest number of fatalities [12].

There are five likely reasons, as Gibb et. al. stated, that has resulted in this inadequate or inaccurate consideration to SD both by accident investigators and those researching SD [12]. Those five reasons are enumerated here.

Operational Definition of SD – Its (Mis-)Interpretation by Investigators.  There is interplay of vision, vestibular and proprioceptive systems in defining a pilot’s perception for orientation in flight. In other words, a disoriented pilot, who in a state of compromised perception, in turn, lost situational awareness, may give incorrect or inadequate control inputs, with at times tragic outcome. Yet many a surveys report visual illusions as a cause independent of SD [10]. This in turn results in under or inaccurate reporting of fatalities due to SD. So also, mishaps due to SD are at times reported as “controlled flight into terrain, loss of control, inadvertent flight into weather, and loss of situational awareness” [12].

Investigating the Mishap – Fallacies in the Process.  Gibb et. al. summarised two accidents that occurred at night, with pilots using NVGs, with tragic loss of lives. In the first case, the F-16 pilot was using NVGs, which despite being a visual enhancing devices, is known to reduce contrast and acuity with limited field of view. This could have resulted in degraded visual cues for orientation and estimation of clearance from ground during the sortie at night. So also in the second case, the F-15E pilots, using NVGs, “overestimated their height above the featureless terrain” [12]. It aptly highlighted the fallacy that SD (due to degraded vision), though discussed, was neither stated as a causative nor a contributory factor in both accident reports [12].

Accident – SD as a Causative Factor.  Despite the intent of the accident investigation teams to determine the cause of accident, it is the experience and perspective of such teams that may affect the analysis and deductions drawn in the accident reports. Another limitations could be the use of established accident classification taxonomies [13], with accident reports being narrowed to “specific, predetermined classification options”, using the accepted nomenclature [12].

Unfolding Events including Cognitive Load on Pilot – “Perishable Data”.  During complex and dynamic environments of aviation, the rapidly changing situation may compromise a pilot’s situational awareness. This, in turn, compromises the decisions to be taken and actions required, especially with conflicting sensory inputs. Such perceptual conflicts could add a substantial amount of stress on the pilot. However, with a high fatality rate in SD related accidents, an understanding about the perceptual conflict, in turn affecting the decision making and the actions taken thereafter, as well as assessment of workload (to determine the cognitive resources) of the pilot during those crucial moments in flight, are lost. This is then left to the conjectural interpretation of the investigating teams, who may or may not choose to deliberate on those factors [12].

Reluctant Accident Investigation Board – Human Factors Taxonomy.  In the absence of an acceptable human factors and SD related accident taxonomies, accident investigation teams are reluctant to include “sensation-perception-cognition” into their reports [12]. This is despite of human factors investigators ability to analyse the prevailing or the likely psychological and physiological factors on the pilot in case of a SD related accident. But with the loss of “perishable data” (as discussed above), their failure to substantiate with the evidence, as is the wont of an accident report, leads to non-inclusion of human factors as a contributory factor(s) in an accident report [12].

Knowing that SD kills, it is time to sit up and take notice. There is a need for plugging the holes in accident investigations as well as accuracy in reporting of SD incidences. There may be need for defining SD taxonomy, on lines of HFACS [13] or similar classification systems, to enable accident investigators understand the dynamics of SD, its effect on human perception, which in turn may compromise cognition and lead to an accident, in a simplified ‘cause and effect’ concept [14]. So also, there is a need for clarity on SD, its illusions – named or not-yet labeled, while scientist study the incidence of SD, as well as those investigating accidents. It is only apt that Gibb et al surmise that “…it is time to stop SD” [12].


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12. Gibb R, Ercoline B, Scharff L. Spatial disorientation: decades of pilot fatalities. Aviat Space Environ Med 2011; 82:717-24

13. Human Factors Analysis and Classification System

14. Cause and Effect or Causality

Acknowledgement  Photo courtesy Wikemedia Commons


  1. Jenny Friedl

    It is astonishing that we, until now, even if we have the empirical evidence, do not consider perception and its role on our behaviour as being a decisive influence on our actions. Instead we continue to discuss the potential reasons and outcome of our decisions which are delivering us just an one-dimensional explanation – and one that shows – with all clarity in aviation – how dangerous it is to neglect perception – the process which organizes stimuli input and gives them a meaning.

    Thank you very much for an interesting, educating and thought-provoking article.

    1. Av Med

      Thank you Jenny.
      It all starts with “perception”, as far as Spatial Disorientation is concerned, but for the purpose of countermeasures we must indeed need to look beyond, epsecially to cognition and decision making, to plan future strategies.

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