Optokinetic Cervical Reflex (OKCR) in Pilots of High-Performance Aircraft

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Optokinetic Cervical Reflex (OKCR) in Pilots of High-Performance Aircraft

R. F. Merryman

For over sixty years, 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 flight simulator studies have verified the existence of a pilot neck reflex which refutes this long-standing assumption. This reflex, named the optokinetic 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, pilots view a fixer-horizon image and not a moving-horizon. The objectives of the research were to determine if the optokinetic cervical reflex occurs during actual flight of high performance jet aircraft and to model the response. This was an observational study in which the head positions of nine pilots were recorded during actual F-15 aircraft flight and analyzed. Results indicate that the OKCR caused pilots to tilt their heads during aircraft bank. Also, the reflex was found to be independent of the bank phase: entering versus exiting the turn. The OKCR was shown to be a strong, natural response and the flight results correlated extremely well with the simulator results. The impact of these results on pilot training, spatial disorientation, physiological injury and safety, and the re-design of displays for aircraft attitude and virtual reality are discussed.