+Gz Exposure and Flight Duty Limitations

BACKGROUND: High +G_z exposure is known to cause spinal problems in fighter pilots, but the amount of tolerable cumulative +G_z exposure or its intensity is not known. The aims of this study were to assess possible breaking points during a flight career and to evaluate possible determinants affecting pilots' spines.METHODS: Survival analysis was performed on the population who started their jet training in 1995-2015. The endpoint was permanent flight duty restriction due to spinal disorder. Then the quantified G_z exposure and possible confounding factors were compared between those pilots with permanent flying restriction and their matched controls. Cumulative G_z exposure was measured sortie by sortie with fatigue index (FI) recordings. FI is determined by the number of times certain levels of G_z are exceeded during the sorties.RESULTS: The linear trend of the survival curve indicates an annual 0.86% drop out rate due to spinal problems among the fighter pilot population. A conditional logistic regression did not find any difference in the FI between cases and controls (OR 0.96, 95%CI 0.87-1.06). No statistical difference was found for flight hours, a sum of intensive flying periods, fitness tests, or with nicotine product use. Additionally, a maximum +G_z limitation without airframe restriction was assessed and is presented as a useful tool to manage loading and developed symptoms.DISCUSSION: No particular breaking point during follow-up or individual factor was found for G_z induced spinal disorders. The results of the study outline the multifactorial nature of the problem. Thus, multifactorial countermeasures are also needed to protect pilots' health.Sovelius R, Honkanen T, Janhunen M, Mäntylä M, Huhtala H, Leino T.