Thresholds for detection of constant rotary acceleration during vibratory rotary acceleration

The effects of vibratory angular acceleration (aR) on detection thresholds for constant aR in a dynamic flight simulator are reported in three experiments. Detection thresholds were determined for 10 pilots and four nonpilots using a random, double-staircase procedure while the subjects sat erect in a device which rotated about an earth-vertical axis. Constant aRs were presented for 0.5 and 1.0 s with concurrent, vibratory aR at 1 and 5 Hz, and thresholds with no vibratory aR were established. The thresholds were obtained while the subjects observed a visual reference in the enclosed cockpit in two experiments and in total darkness in a third. The results confirmed earlier experiments showing an inverse relationship between the duration of constant aR and detection threshold and showed that the detection thresholds in darkness were higher than with a visual reference present. Two analyses of variance revealed no significant differences in thresholds across the three vibration conditions. These results indicate that vibratory aRs of fairly high levels can be present in a dynamic flight stimulator without masking the pilot's ability to detect either maneuver or disturbance motions.