A case of low G-tolerance: An approach to aeromedical evaluation and disposal

Conventionally, aircrew who is not able to withstand +7 Gz, 15 s with an anti-G suit (AGS) and anti-G straining maneuver (AGSM) is considered to have low G-tolerance. Aircrew suspected to have low G-tolerance needs to be comprehensively evaluated. This paper highlights our approach to aeromedical evaluation and disposal of a suspected case of low G-tolerance in an under-trainee (U/T) fighter aircrew. A 21-year-old U/T fighter aircrew presented with multiple episodes of gray out/blackout while flying syllabus sorties on exposure to 4.5 G and was not able to pull beyond 5 G. A detailed history did not reveal any likely predisposing factors for reducing G-tolerance. A detailed clinical evaluation did not reveal any organic pathology. During high-performance human centrifuge evaluation, his baseline relaxed (R) and straining (S) GOR and rapid onset rate (ROR) tolerance were found to be 3.2 G (R); 6.3 G (S) and 3 G (R); 4.5 G (S), respectively. He was unable to sustain beyond 6 Gz for the 30 s even with AGS and supervised AGSM. He underwent a 12-week supervised physical conditioning program. Reassessment following 12 weeks revealed a significant improvement in physical strength parameters. However, the aircrew could not withstand 6 G for 30 s even with AGS and supervised AGSM. The aircrew was diagnosed as a case of low G-tolerance and was recommended unfit for fighter flying. Any episode of visual symptoms of loss of consciousness due to G forces is potentially incapacitating in the air. Hence, aircrew suspected to have low G-tolerance needs to comprehensively evaluated. The evaluation should include a careful history to rule out any pre-disposing factors and a detailed clinical assessment to exclude organic disability. Aircrew needs to be indoctrinated on correct AGSM technique and proper fitment of AGS must be ensured during centrifuge evaluation. Before labeling an aircrew as a case of low G-tolerance, he should be assessed for his physical fitness and undergo a supervised physical conditioning program.