Drone safety: Risk assessment and common hazards

What is a hazard?

The definition of “hazard” is undergoing review. The currently accepted terminology refers to “an object or condition that has the potential to induce an accident or incident.”

The strategic risk assessment process, relevant to Remote Piloted Aircraft (RPA) operations, includes:

Hazard identification

Common hazards for RPAs

The most common hazard when operating an RPAs is the likelihood of your drone crashing into someone or something. Drones will crash. For this reason it is essential that your flight planning process includes an identification of objects and people you could potentially crash into.

These will vary according to the mission you are planning to fly, however, even flying in clear weather in accordance with the SoCs, as a minimum you need to identify:

• Buildings
• Trees and other plants
• Bodies of water
• Geographical attributes (cliffs, hills, embankments)
• Traffic that could move through your flight plan
• Animals
• People presently in or near your flight plan and people who could potentially enter into your flight space during the flight.
• Powerlines and power infrastructure
• Weather and wind

Of course, the existence of hazards does not automatically mean you should cancel your flight. It is extremely important however that you identify the hazards and have in place measures to detect and avoid the hazards.

Avoiding hazards

The first part of avoiding hazards is to make sure your drone is not itself a hazard. Your pre-flight checklist must include a thorough inspection of the drone to ensure it is functioning and airworthy. This includes checks on the airframe, batteries and drive train. You also need to check your controller is functioning correctly.

Once you have pre-flight checked your drone and the airspace requirements (NOTAM, weather, airspace class etc.), you should thoroughly observe the flight path to identify potential hazards and ways of mitigating them.

Your flight plan must then be updated to include the hazards and how you intend to avoid them. This may often be done implicitly through the flight path and navigation system, however, you need to continuously monitor the environment for changes that present new hazards during the mission.

Air traffic incidents

The Global Air Traffic Management Operational Concept (Doc 9854) identifies the need to limit the risk of collision to an acceptable level between an aircraft and the following hazards: “other aircraft, terrain, weather, wake turbulence, incompatible airspace activity and, when the aircraft is on the ground, surface vehicles and other obstructions on the apron and manoeuvring area”. Doc 9854 also notes “for any hazard (i.e. any condition, event or circumstance that could induce an accident), a risk can be identified as the combination of the overall probability or frequency of occurrence of a harmful effect induced by the hazard, and the severity of that effect.”

Most air traffic “incidents” featuring RPA occur when operating illegally outside standard operating areas, particularly at higher altitudes. Operating below 400ft is relatively free of air traffic, but will the traffic come to you?

Civil Aviation Regulation (CAR 157) states a manned aircraft must not fly at a height lower than 500ft above ground level (AGL). However, there are a number of occasions manned aircraft will be lower than this height. Situational awareness is key to avoiding conflict with manned aircraft.