title: G-Induced Visual Symptoms in a Military Helicopter Pilot.
abstract: Military helicopters are increasingly agile and capable of producing significant G forces experienced in the longitudinal (z) axis of the body in a head-to-foot direction (+Gz). Dehydration and fatigue can adversely affect a pilot's +Gz tolerance, leading to +Gz-induced symptomatology occurring at lower +Gz levels than expected. The potential for adverse consequences of +Gz exposure to affect flight safety in military helicopter operations needs to be recognized. This case report describes a helicopter pilot who experienced +Gz-induced visual impairment during low-level flight.
  
  
  
  The incident occurred during a tropical training exercise, with an ambient temperature of around 35°C (95°F). As a result of the operational tempo and the environmental conditions, aircrew were generally fatigued and dehydrated. During a low-level steep turn, a Blackhawk pilot experienced significant visual deterioration. The +Gz level was estimated at +2.5 Gz. After completing the turn, the pilot's vision returned to normal, and the flight concluded without further incident.
  
  
  
  This case highlights the potential dangers of +Gz exposure in tactical helicopters. Although the +Gz level was moderate, the pilot's +Gz tolerance was reduced by the combined effects of dehydration and fatigue. The dangers of such +Gz-induced visual impairment during low-level flight are clear. More awareness of +Gz physiology and +Gz tolerance-reducing factors in helicopter operations is needed.
authors.affiliation: Department of Aviation, Faculty of Science, Engineering and Technology, Swinburne University, P. O. Box 218 Hawthorn, Victoria, 3122 Australia.
authors.forename: Terry W
authors.initials: TW
authors.lastname: McMahon
authors.affiliation: Griffith Aviation, School of Natural Sciences, Griffith University, Nathan Campus, 170 Kessels Road, Nathan, Queensland, 4111 Australia.
authors.forename: David G
authors.initials: DG
authors.lastname: Newman
mesh_terms: D000328:Adult; D000337:Aerospace Medicine / Q000379:methods; D000401:Aircraft; D001315:Australia; D003681:Dehydration / Q000150:complications; D005221:Fatigue / Q000150:complications; D006112:Gravitation; D006801:Humans; D008297:Male; D008889:Military Personnel; D000070356:Pilots / Q000639:trends*; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology*