By Brandon Guillot, RPC, MAS

Completing a risk assessment prior to a flight is a critical Flight Planning step for remote pilots. Risk assessment involves identifying potential hazards, assessing the risk of that hazard, and creating a strategy to reduce the risk. Remote Pilots in Command (RPICs) need a systematic process to gather all data together and make the final “Go” or “No Go” decision before the flight mission. A Hazard Vulnerability Analysis (HVA) in the aviation safety world is a process to identify hazards the pilot may encounter during the mission based on likelihood and severity.

This graphical display of an HVA (shown below) is an example of how the tool is used to take identified hazards and rank them according to how likely the hazard would occur and how severe it would be if it did occur. It is critical to examine all factors that could affect your flight as part of your Flight Planning process, because those factors will help determine which areas require mitigation. Based on the information gathered, the RPIC can determine methods used to mitigate each risk.

Graph used for hazard vulnerability analysis (HVA)

Hazard Vulnerability Analysis Graph


Identify Potential Hazards

Imagine the following scenario: You have been hired by an engineering firm to fly a photo map of an Interstate bridge. You have followed the Flight Planning items that we have discussed in previous articles — the Airspace is Class G, so no issues there. Weather will be sunny, so your Control Station visibility will be at least 3 miles and no clouds. But the winds are at 13 miles per hour and could increase.

Furthermore, when you assess the Environment, you have a series of concerns. You will be launching immediately next to the Interstate in the wake turbulence zone of vehicles, and then you will be flying over trees on each side of the bridge to avoid flying over people in their vehicles.

Aerial view above interstate highway bridge taken by drone.You run the risk of going Beyond Visual Line of Sight (BVLOS) because of the trees, and even worse, you may have video signal breakup or even loss as a result. Also, it is a hot, sunny day which may have additional impacts on your fatigue levels leading to issues with decision making and mission effectiveness through hazardous attitudes.

For the purposes of this discussion, we will focus on four potential hazards identified in our scenario: 1) High winds on the leeward side of the tree line; 2) Wake turbulence from passing vehicles; 3) Tree line causing a BVLOS situation and video degradation; and 4) Heat effects on flight crew members.

Assess the Potential Hazards using the HVA Graph

Next, we will examine each potential hazard identified in terms of how likely and severe it could be. The most severe types of sUAS accidents result in injury to people or property damage, so we can use that as our “Very High” or Category 5 Hazard Severity limit on the HVA scale. We might assess each potential hazard as follows:

1) High winds in the leeward side of the tree line are Likely (Category D). The severity of a loss of control at altitude is probably High (Category 4). This combination would place this threat at a High level (D4), and it would require mitigating actions.

2) Wake turbulence from passing vehicles are Very Likely (Category E). Because of the proximity to those vehicles, the severity would be a Very High level (Category 5). This combination makes this a High level (E5) threat, and it would be our most serious issue to consider for mitigation.

3) A BVLOS situation above the tree line is both legally and technically dangerous, and it may be quite Likely (Category D). However, the severity would be lower since it probably would not result in a loss of control making it Moderate (Category 3). This combination is a threat of a Moderate level (3D), and it would still need to be mitigated.

4) Heat issues affecting crew members is Very Likely (Category E) if the mission will go over a series of hours. It could result in High severity levels (Category 4) due to heat exhaustion, or even heat stroke. This combination is a High level threat (E4), so it will need to be mitigated as well.

Determine How to Reduce the Risk of Potential Hazards

Now that each potential hazard has been assessed using our HVA graph, it is crucial for the RPIC to determine the appropriate methods to mitigate the hazards. For mitigation, our efforts will focus on either reducing the Likelihood that an incident will occur or diminishing the Severity in the event the hazard occurs. We might mitigate each potential hazard as follows:

1) For the issue of high winds, we can probably reduce both Likelihood and Severity as the result of our actions. For instance, I would recommend taking off away from traffic and slowly climbing in order to “feel out” the wind currents as they pass the tree line. It is important to climb over a safe area that would limit the potential of striking a vehicle in the event of a sudden loss of control. By slowly climbing and accounting for the wind, and by staying away from the vehicular traffic over a safe area, we can reduce the hazard to a Possible yet Slight risk (or a 2C).

2) For the issue of wake turbulence from vehicles, we could use Visual Observers to help call out gaps in traffic for our departure or arrival and reduce the Likelihood of getting into that wake turbulence. Having the option of launching from a safe point off the side of the road, away from traffic, would put our operations outside the envelope of that turbulence entirely. These elements could also reduce our hazard to safe levels (such as a 2C or below).

3) For our BVLOS situation, we really cannot mitigate the Severity—a BVLOS is illegal and dangerous, no matter where it occurs. However, we can reduce the Likelihood by choosing an appropriate Takeoff and Landing area that will allow us to maintain VLOS throughout the flight. We may even use multiple Takeoff and Landing sites throughout the project to avoid a BVLOS. While we cannot reduce the Severity, we can reduce the hazard Likelihood to a Low level (or a B3).

4) We know that heat will cause numerous problems for our crew, and it will be extremely Likely, simply because we will be outside on a hot day. However, we can diminish Severity by providing cover, sunscreen, hats, sunglasses, and plenty of hydration. We can mitigate the severe portions of the hazard by reducing the impact upon our crewmembers, reducing the hazard down to a Low level (or an E1).

Determine if the Mission can Safely Continue

In some situations, you may not be able to sufficiently reduce Likelihood or diminish Severity to acceptable levels. If Likelihood or Severity levels are not acceptable, the responsibility is on the RPIC to determine that the mission cannot safely continue in its current form. The RPIC should communicate results of the HVA with your client while also making suggestions about how to proceed with changes to the flight plan.

It is vital for remote pilots to gather the appropriate level of information for their flight operations before considering the feasibility of the mission. The RPIC who does not gather the necessary information will go into the final Hazard Vulnerability Analysis without specific information and will draw conclusions that could be in error. A series of poor decisions based on faulty information will increase the possibility of an accident or incident that could have been avoidable.

By gathering the critical information and honestly examining each potential hazard before we even unpack the batteries to fly, we all help ensure the safety and progress of sUAS in the professional setting.

Brandon Guillot, RPC, MAS
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