Aviation spatial orientation in relationship to head position, altitude interpretation, and control

Recently, a visually driven neck reflex was identified as causing head tilt toward the horizon during VMC flight. If this is the case, then pilots orient about a fixed rather than moving horizon, implying current attitude instruments inaccurately present spatial information. The purpose of this study was to determine if the opto-kinetic cervical neck reflex has an effect dependent on passive (autopilot) or active control of the aircraft. Further, findings could help determine if the opto-kinetic cervical reflex is characteristic of other flight crewmembers.

There were 16 military pilots who flew two 13-min VMC low-level routes in a large dome flight simulator. Head position in relation to aircraft bank angle was recorded by a head tracker device. During one low-level route, the pilot had a supervisory role as the autopilot flew the aircraft (passive). The other route was flow manually by the pilot (active).

Pilots consistently tilted the head to maintain alignment with the horizon. Similar head tilt angles were found in both the active and passive flight phases. However, head tilt had a faster onset rate in the passive condition.

Results indicate the opto-kinetic cervical reflex affects pilots while actively flying or in a supervisory role as the autopilot flies. The consistent head tilt angles in both conditions should be considered in attitude indicator, HUD, and HMD designs. Further, results seem to indicate that non-pilot flight crewmembers are affected by the opto-kinetic cervical reflex which should be considered in spatial disorientation and airsickness discussions.