G-Tolerance in Acute Repetitive Acceleration Conditions Relevant to Air Combat Maneuvering

Air combat maneuvering produces frequent, repetitive excursions to headward acceleration (+Gz) but little is known about physiologic tolerance to successive Gz exposures. Human responses to simulated air combat maneuvering (SACM) were measured with SACM comprised of 10 repetitive cycles of moderate +Gz loads in two investigations, on a human centrifuge (N=13), and an electronic tilt-table (N=15), respectively. Physiologic responses (blood pressure, visual field, head-level blood content) were significantly improved in cycles 2-10 compared to cycle 1 indicating +Gz tolerance increased approximately 0.4 Gz (range 0.3 - 0.6 Gz depending on SACM type and test facility). The gains are attributed to enhanced vascular resistance. Therefore, a pilot's physiologic tolerance is not expected to decrease due to repetitive +Gz during aerial combat engagement. Anti-G straining maneuvers were not studied and could produce secondary effects in such environments.