Not Black Hawk Down! Helicopter Crash – Part 2

800px-Sikorsky-S92-cougar-helicopters-ilulissat-airportOffshore Oil and Gas Operations

Baker et al. reported that there were 178 helicopter crashes from 1983 to 2009 related to offshore oil and gas operations in the Gulf of Mexico. This was based on the database of the National Transportation Safety Board [2, 11]. 30% of those crashes were fatal, with 139 lives lost including 41 pilots. The annual accident rate was 6.6 during the period of this study.

Most of these crashes occurred away from airport, and resulted in fatality especially those that crashed into water (68%). Majority of crashes (89%) occurred on the seas, with mechanical failure, being the predominant cause in 38% accidents. The cause of mechanical failure in descending order was engine failure (31% in fatal accidents), tail rotor or tail rotor driveshaft related (23% in fatal accidents), control system failure and undetermined cause (due to inability to recover aircraft). It is noteworthy that the component failure was due to metal fatigue and not corrosion!

Second on the list of precipitating factors was weather (16%) which was responsible for the largest percentage of fatality – 40%. 11% crashes occurred due to “helicopter or one of its rotor striking something on the landing platform”, commonest culprit being: “tail rotor striking a safety fence on approach or take-off”. Loss of control of aircraft by the pilot accounted for 9% of total accidents, due to inattention, distraction, or decision making [2].

Human Error.     A major contributing factor to 47% crashes, as reported by NTSB, was pilot error. 39% of those occurred due to poor decision making including:-

  • Continuing visual flight in IMC,
  • Neglecting to check the weather,
  • Starting up in wind gusts exceeding helicopter capabilities,
  • Making a downwind or crosswind approach in high winds, and
  • Gusting conditions.

Controlled flight into terrain (CFIT) (12) or into an obstructing object occurred in 22% of crashes due to misjudged altitude or clearance from an obstructing structure. 17% of pilots involved in crashes applied incorrect control input, particularly failing to maintain appropriate rotor speed or giving abrupt inputs with cyclic or collective. An interesting cause of few crashes was failure by pilot to release all tie-downs before take-off, aggravated by absence of any ground crew during pre-flight, start up or take-off. A few cases of pilot inattention resulted in three mid-air collisions, while an equal number ditched into sea during low-level manoeuvring.


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Acknowledgement  Image courtesy Wikipedia

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