The optokinetic cervical reflex in pilots of high-performance aircraft.

BACKGROUND For over 60 yr, researchers and engineers have based investigations and the design of cockpit displays and structures upon the presupposition that during flight the pilot maintains a head alignment coincident with the aircraft's vertical axis (z-axis). Recent simulator studies have verified the existence of a pilot neck reflex which refutes this long-standing assumption. This reflex, named the opto-kinetic cervical reflex (OKCR), occurs during visual flight and is theorized to be an attempt by the pilot to stabilize a retinal image of the horizon to maintain spatial orientation. As a result, during initial banking maneuvers, pilots view a fixed-horizon image and not a moving-horizon. The research objectives were to determine if the OKCR occurs during actual flight of high performance jet aircraft and to model the response. HYPOTHESIS Pilots of high performance aircraft will exhibit the OKCR. Additionally, the OKCR is dependent on the phase of banking (entering into or exiting from a banked position). METHODS This was an observational study in which the head positions of nine pilots were recorded during actual F-15 aircraft flight and subsequently analyzed. RESULTS Objective data indicate the OKCR caused pilots to tilt their heads during aircraft bank (p < 0.0001). Also, the reflex was found to be independent of the bank phase. CONCLUSION The OKCR was shown to be a strong, natural response and the flight results correlated closely with simulator results. The effect of these results on pilot training, spatial disorientation, physiological injury and safety, and the redesign of displays for aircraft attitude and virtual reality are discussed.