The experiment was designed to compare three types of aircraft cockpit warning systems: (1) Visual: malfunctions simultaneously activated a master warning light and a specific malfunction indicator light. (2) Visual and tone: malfunctions simultaneously activated an intermittent sweeping tone (through earphones), a master warning light, and a specific malfunction indicator light. (3) Visual and voice: malfunctions simultaneously activated a master warning light, a specific malfunction indicator light, and a voice recording which informed the operator through his earphones of the specific malfunction needing attention. Three groups of 11 university students served as subjects. While responding to a visual, visual-tone, or visual-voice warning system, each subject was also required to find and position, under cross hairs, a series of strategic targets on a strip of rear-projected aerial photographic imagery. No statistically significant differences among the three warning systems were found in the speed of reaction to the master warning light, reaction to the specific-indicator panel, total reaction time, or number of strategic targets found or missed. The results of the study suggest that the addition of either a tone or a voice warning to a visual, master plus specific, malfunction warning system is of questionable value in a 'heads-in' cockpit situation where the visual system can be seen. The data from the experiment do not suggest that a voice warning system has any advantage over a simple aural signal for augmenting a visual system. (Author).