Autokinesis illusion in fighter flying revisited

Introduction: Autokinesis refers to the perception of motion which is experienced by an aircrew when he fixates his gaze on a stationary point/source of light in an otherwise completely darkened environment. A study was conducted in the Department of Acceleration Physiology and Spatial Orientation, Institute of Aerospace Medicine to determine the time taken for onset of autokinesis in the disorientation simulator (Air Fox DISO) and the effectiveness of various intervention strategies to break the illusion. Material and Methods: A total of 103 randomly selected fighter pilots participated in the study. They were briefed about the illusion and the various interventions used to counteract it, such as: (a) Shrugging of shoulders without breaking gaze, (b) stretching of arms without breaking gaze, (c) breaking of gaze for 5 s and (d) breaking of gaze for 10 s (if the illusion is not broken after breaking of gaze for 5 s). Time taken for autokinesis to set in and the effectiveness of the interventions used were noted. Subjective feedback from the participating aircrew was also obtained on their experience on autokinesis illusion in active flying through a structured questionnaire. Results: The average time required for onset of the autokinesis illusion in the DISO was observed to be 20.3 ± 15.5 s (range 4.1–121.4 s). Of the 103 aircrew participants, 100 (97.1%) reported that the intervention of stretching of arms was effective, 94 aircrew (91.3%) reported that the intervention of shoulder shrug was effective in breaking the illusion and 99 aircrew (96.1%) were able to counter the illusion by breaking their gaze for duration of 5 s. Autokinesis was experienced in active flying by 17 aircrew, accounting for an incidence of 16.5%. This study reveals that autokinesis involves the interplay of vision, vestibular system, as well as the proprioceptive stimulus in counteracting this illusion. A combination of gaze break and shoulder shrug/arm stretch could be the most appropriate intervention strategy under such circumstances. The operational scenarios conducive for causing this illusion and the physiological basis for the various intervention strategies have been discussed. Conclusion: The autokinesis illusion though considered benign has got significant potential for distraction during operational flying. The intervention strategies discussed in the study are effective in breaking the illusion. The pilot community needs to be aware of the preconditions, mechanism, and effectiveness of the intervention strategies in countering this illusion.