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Not Black Hawk Down! Helicopter Crash – Part 3

800px-HH-65C_DolphinCrashes into Water

Flying helicopters over water has an accident rate of 2.0 per 100,000h as compared to 0.4 per 100,000h in fixed wing aircraft, as reported by Civil Aviation Authority’s helicopter airworthiness panel report in 1986 [13]. High fatality rate in case of helicopter crash into water occurs due to sinking of helicopter and inversion under water due to its high center of gravity [13, 14, 15, 16]. Flooded cockpit traps and disorients the occupants who may fail to reach escape hatches in time [14], thus resulting in high fatality, as reported by several authors:-

  • Drowning or lost at sea as a cause of death in 55% helicopter accidents was reported by Glancy and Desjardins in 1971[17].
  • 60% deaths due to drowning were reported by Chen et al. in 1993 [18].
  • Clifford found that Drowning caused 83% and 57% deaths in military and civil helicopter accidents, respectively [15].

Brooks et al. analysed data of 46 civil helicopters accidents in water in Canada from 1979 to 2006. There was 78% survival rate, with 27 fatalities among 124 crew and passengers of which 63% were caused by drowning. They reported that 15 aircraft went down inverted in 33 accidents with helicopters sinking immediately. Interestingly, 63% accidents were due to human factors and 33% due to mechanical failure including loss of power [13].

Chances of survival during hover or flight at 60 ft are bleak with the helicopter sinking rapidly, while pilots could barely call out the emergency to alert the passengers. Brooks et al. further enumerated following factors for poor survival rate in such crashes, which delay escape in turn prolonging the breath hold underwater and increasing the chances of drowning of those marooned [13]:-

  • Poor preflight briefing,
  • Short warning time for preparation before the accident,
  • Poor crash positioning,
  • Inrushing water,
  • Inadequate breath-holding ability in water,
  • Darkness and disorientation,
  • Difficuly in locating and jettisoning emergency exits,
  • Exit hampered by debris or deformation of cockpit or cabin.

Continues…

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Reference

Acknowledgement  Image courtesy Wikipedia

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