Physiologic effects of seatback angles 45degrees (from the vertical) relative to G

Eight experimental subjects from the USAF Sschool of Aerospace Medicine (SAM) and four YF-16/17 test pilots were exposed to a simulated aerial combat maneuver (SACM) which included a maximum G exposure of 6 s at 8 G. The following physiologic parameters were examined relative to seatback angles of 23degrees, 28degrees, and 40degrees; heart rate and rhythm; arterial oxygen saturation; performance; intrathoracic (esophageal) pressure; arterial pressure; and subject comfort, effort, and fatigue. Relaxed and straining high sustained G (HSG) tolerances (6 G for 60 s) were also determined using only SAM subjects. The advantages of the 40 degree setback angle during the SACM included increased subject comfort, less fatigue and effort, greater pilot acceptance and a statisically significant reduction in the increased mean heart rate associated with G exposure. On the other hand, a statistically significant reduction in arterial oxygen saturation was obtained during the SACM at 40 degrees compared with the 23 degree back angle. An increase in relaxed G tolerance was found with the 40degree seatback angle--statistically significant only compared with the 28 degree seatback angle.