It is commonly believed that flight simulators capable of supporting tactical combat tasks should possess full field-of-view visual displays with high levels of brightness and resolution. The problem of designing such a visual system is that the three factors (field-of-view, brightness, resolution) are not independent. For instance, as field-of-view is increased brightness and resolution decrease. An attempt to overcome this dilemma uses head-driven visual displays with limited instantaneous field-of-view. Head-driven systems overcome the full field-of-view problem by providing a full field-of-regard for the head-driven instantaneous field-of-view. Important considerations for head-driven systems are the horizontal and vertical dimensions of the instantaneous field-of-view. This study examines the effect of the instantaneous field-of-view size on pilots' ability to perform pop-up weapons deliveries using both stationary and head-driven visual displays. The field-of-view sizes used were 127° H by 36° V, 150° H by 80° V, 160°H by 88° V, and 180° H by 88° V. A 300° H by 150° V size provided a full FOV control condition. An A-10 dodecahedron simulator configured with a seven window color light valve display, computer generated imagery, and a Polhemus magnetic head tracker provided the cockpit and display apparatus. Aircraft performance measures (altitude, airspeed, etc.) and head position data were the dependent measures. Ten F-5 instructor pilots from Williams AFB Arizona served as subjects for the study. The results did not confirm initial hypothesis that performance would be better for head-driven conditions and larger fields-of-view. This may be due to an increased use of instruments in the smaller field-of-view conditions to maintain performance levels. This conclusion is difficult to verify, because no eye position data is available. However, it is clear that the smallest condition (127° H × 36° V) is inadequate to support training.