In-flight loss of consciousness in a fighter aircrew – G-LOC or No G-LOC conundrum

The differential diagnosis for inflight loss of consciousness in a fighter pilot is G-induced Loss of Consciousness (G-LOC) as it is physiological and 10–20% of fighter pilots may experience it during their career. However, it is very difficult to establish the diagnosis in many cases. Three cases of in-flight episodes of loss of consciousness (LOC) have been discussed in the paper highlighting how to investigate such cases to establish the diagnosis of G-LOC. Three cases have been discussed in the paper where two cases were considered as a case of G-LOC based on the circumstantial evidence and data from the flight data recorder. However, one case was diagnosed to be of LOC (Inv). One case did not benefit from the high-G training as he repeatedly experienced “GLOC” at very low G levels while wearing Anti-G Suit and performing an Anti-G Straining Maneuver (AGSM). He was recommended unfit for fighter flying. Another aircrew was experiencing G-LOC due to incorrect technique of AGSM as he had not undergone “high-G training.” After correction of technique, he could successfully meet the qualifying requirements of 9G for high G training. The third case was considered as a case of inflight LOC, not due to G exposure. Subsequently, he was diagnosed to have Focal Cortical Dysplasia. The paper describes the approach and aeromedical disposition of in-flight LOC among fighter aircrew. The paper also discusses the need for “G tolerance standard” at entry and high G training for fighter aircrew. The first case highlights that not all case of in-flight LOC among aircrew is G-LOC, even if it occurs in conjunction with high-G exposure. Ruling out the presence of any potential cause for inflight LOC is extremely important before labeling a recurrent case of inflight LOC as G-LOC. The second case re-iterates the fact that there are a set of people who will not be able to endure high G exposures due to inherent individual characteristics. These people need to be identified and screened at initial entry into fighter flying itself. The cause for the recurrent episodes of inflight G-LOC in the third case was identified as improper AGSM. The problem could be identified and corrected in the Dynamic Flight Simulator. This highlights the significance of high-G training using High Performance Human Centrifuge before the commencement of operational flying and high-G sorties and also establishes it as a diagnostic tool for such cases. In-flight LOC in a fighter pilot poses a challenge in diagnosis and differentiation from G-LOC. The paper discusses an approach to such a case in detail.