G-tolerance standards for aircrew training and selection.

G tolerance widely among individuals. It stands to reason that aircrew with higher G tolerance are less likely to experience symptoms of G stress in flight than are those with lower G tolerance, and that they can fly highly maneuverable aircraft with greater safety and effectiveness. To assure that aircrew with abnormally low G tolerance are not assigned to aircraft that operate in the high-G environment, a G-tolerance standard and the means to implement that standard are necessary. Since 1977, for human centrifuge operations, the USAF School of Aerospace Medicine has used an informal G-tolerance standard for selecting experimental subjects, evaluating medically disqualified aircrew, and ensuring efficacy of high-G training for aircrew. That standard consists of the subject's being able to sustain a rapidly applied +7-Gz load for 15 s, without totally losing peripheral vision or losing consciousness, while wearing a functioning anti-G suit, performing an anti-G straining maneuver, and sitting in a conventionally configured fighter aircraft seal. Inability to tolerate a 7-G, 15-s, rapid-onset G profile in a centrifuge is also the basis of internationally recognized (NATO, ASCC) definitions of low G tolerance. The rationale for choosing the 7-G, 15-s standard is discussed. Experience with use of this standard, and the equivalent standard of 8 G for 15 s when the F-16-configured seat is used, reveals that fewer than 1% of actively flying aircrew are unable to meet the standard. Eventually a formal, more stringent, G-tolerance standard may become a valuable component of the means of selecting and training aircrew for high-performance fighter aircraft.