Loss of acuity for visual details in aircraft during unusual maneuvers has been documented. Recent investigations of this problem have served to define the magnitude of semicircular canal stimulation necessary to produce nystagmus of sufficient strength to degrade visual acuity. Present work extends former observations by investigating the effects of levels of illumination during semicircular canal stimulation on the performance of a task requiring vision. The illumination levels were selected to encompass the range used in aircraft cockpits. A compensatory tracking task with an aircraft instrument as the display provided an indirect measure of this loss of visual acuity and a direct practical measure of performance. (Author).

A practical procedure was developed for obtaining reliable measures of sensation associated with semicircular canal stimulation. Theoretically these measures can be used along with measures of nystagmus to estimate several vestibular response system parameters relevant in the clinical assessment of pilot vertigo. In this experiment, responses produced by stimulation of the horizontal semicircular canals are compared with those produced by stimulation of the vertical canals. Group mean estimates of subjective angular displacement obtained from 40 naval flight students were approximately accurate for stimulation of both horizontal and vertical canals. Significant individual differences were found within the group. From the responses obtained, mean estimates of vestibular system parameters were calculated. (Author).

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