This article considers the safety risks specific to Helicopter Emergency Medical Services (HEMS) operations and the measures that can be taken to reduce those safety risks.
There are several unique hazards faced by HEMS operators. The time pressures, planning challenges and environmental factors associated with air ambulance operations makes them inherently high risk opertions.
Contributory factors identified in an AMPA (Air Medical Physician Association) investigation of HEMS accidents include:
Time Pressure: The condition of a patient, and the time critical requirement to get that patient to an appropriate medical facility, is the major reason for an air ambulance to be tasked to support a medical emergency. That time pressure means that pre-flight planning and mission preparation are necessarily compressed and can lead to incomplete planning or inappropriate decisions.
Environmental Factors: A significant proportion of HEMS operations take place at night and often in poor weather. The crew is under considerable pressure to carry out the mission regardless of the environmental and geographic conditions. Approximately a quarter of all HEMS accidents were weather related, with most occurring because of reduced visibility and IMC while the helicopter was conducting the en route phase of the mission. Inaccurate or out of date weather forecasts contribute to the risk.
CFIT: Controlled flight into terrain (CFIT)is a significant challenge. That is the case particularly in the takeoff or landing phases of flight, as well as collision with objects (for example wires and towers).
Communications: Communications problems with air traffic control (ATC) or a lack of communications due to remote locations and terrain can increase the risk.
The AMPA report also stated that HEMS accidents occurred more often when flight crews were en route to pick up a patient than at any other time during flight.
Regulation: Specific regulations for HEMS operators specifying minimum safe operating standards and risk reduction techniques for HEMS operations can assist in reducing the risk.
Technical: Accurate navigation systems, terrain awareness and warning systems, Night Vision Imaging Systems (NVIS), suitable means of illumination to identify landing area to enable safe approach, landing and take-off are all helpful in reducing risk.
Meteorology: Risk can be reduced by providing a means of observing, recording, and reporting accurate and timely local weather conditions, including cloud base and visibility, at HEMS operating bases.
Risk Management: Risk assessment must include, but not be limited to, terrain and obstacle awareness, inadvertent entry into Instrument Meteorological Conditions (IMC) at low level, pilot disorientation/loss of situational awareness, accurate and timely operating base and en-route weather information, ground risks to personnel at the operating site, pilot NVIS-related fatigue, and illumination of final approach and take-off area.
Accidents and Incidents
A selection of events on the SKYbrary database that involved helicopters engaged in HEMS operations:
EC35, Sollihøgda Norway, 2014: On 14 January 2014, the experienced pilot of an EC 135 HEMS aircraft lost control as a result of a collision with unseen and difficult to visually detect power lines as it neared the site of a road accident at Sollihøgda to which it was responding which damaged the main rotor and led to it falling rapidly from about 80 feet agl. The helicopter was destroyed by the impact which killed two of the three occupants and seriously injured the third. The Investigation identified opportunities to improve both obstacle documentation / pilot proactive obstacle awareness and on site emergency communications.
S76, vicinity Moosonee ON Canada, 2013: On 31 May 2013 the crew of an S76A helicopter positioning for a HEMS detail took off VFR into a dark night environment and lost control as a low level turn was initiated and did not recover. The helicopter was destroyed and the four occupants killed. The Investigation found that the crew had little relevant experience and were not "operationally ready" to conduct a night VFR take off into an area of total darkness. Significant deficiencies at the Operator and in respect of the effectiveness of its Regulatory oversight were identified as having been a significant context for the accident.