Head-up/head-down transition: measurement of transition times

A method was developed to measure transition times between a head-up signal and a response given to a head-down display. Various arrangements of motor response (vocal, hand) and HDD images were used. In the first experiment, vocal and manual response times were recorded in a current fighter aircraft mock-up situation. The shortest times were obtained for voice responses. The time elapsed between a HUD signal and the simple response to the HDD was approximately 1600 ms. The time for physical transition where accommodation changes occur was 700 ms. In the second experiment, two types of images were displayed on the HDD: a "positive" contrast (green symbol on black background), and a "negative" contrast (black symbol on green background) in order to compare accommodation to structured and unstructured backgrounds. Perception time was significantly shorter for the "positive" contrast, and transition times were similar to those measured in the first experiment. This method permits the evaluation in a dynamic aeronautical environment of the acquisition and processing of information. Changes in psychological conditions (heavier information processing) and/or physiological conditions (changing accommodation, gaze axis, convergence) can be evaluated in future research.