FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-23/6

Title and Subtitle: Cerebral Blood Flow Based Computer Modeling of Gz-Induced Effects

Report Date: January 24, 2023

Authors: K. Copeland; J. E. Whinnery (Ret.)

Abstract: Introduction: There is continued interest in acceleration (G) effects in civil aviation, as G-induced loss of consciousness (G-LOC), impaired consciousness, and visual effects play a role in aerobatic, agricultural, and military aviation accidents. Methods: A software model (the Civil Aerospace Medical Institute G-Effects Model [CGEM]) based on physical and physiological variables related to inflight tissue resupply, using oxygen flow as a proxy for supply availability, was developed to evaluate risk of G-LOC and related phenomena in aeronauts. Aeronauts were modeled using several parameters, including sex, cardiovascular fitness, and other common modifiers such as G-suits, positive pressure breathing gear, anti-G straining and other muscle-tensing. The software was validated by comparison with experimental data from the peer-reviewed literature. Results: CGEM predicted physiological effects of Gz exposure accurately, particularly for rapid onset rates. Predicted times to G-LOC and absolute incapacitation periods were consistently within one standard deviation of pooled results obtained during centrifuge experiments using USN and USAF pilots. Predictions of G tolerance based on visual effects onset also compared well with published data, as did evaluation of symptoms expected during a difficult aerobatic maneuver. Discussion: CGEM is a new tool for civil and military aviation. Rather than providing a simple G tolerance number, through proper selection of parameters flight surgeons, pilots, and accident investigators can gain insight into changes in risk from factors such fatigue, medications, dehydration, and anti-G countermeasures used.

Key Words: acceleration, aerobatics, G-LOC, G-tolerance, modeling

No. of Pages: 18