Stephan van Vuren

Stephan van Vuren

AirHub Knowledge Series: SORA Step 2: Determination of the Intrinsic Ground Risk Class (iGRC)

An image visualising the ground risk buffer and contigency zone

AirHub Knowledge SeriesBuilding on our previous blog about Step 1 of SORA, where we explored the Concept of Operations (ConOps) and how it forms the foundation of UAS operational planning, we now move forward to the next critical step. The Specific Operations Risk Assessment (SORA) methodology provides a structured approach to evaluating risks in Unmanned Aircraft Systems (UAS) operations. Step 2 of the SORA process, determining the Intrinsic Ground Risk Class (iGRC), is essential for assessing the potential risk a UAS operation poses to people and property on the ground. This step lays the groundwork for identifying necessary mitigations and shaping safe, compliant operations.


What is the Intrinsic Ground Risk Class (iGRC)?

The Intrinsic Ground Risk Class (iGRC) is a numerical value (ranging from 1 to 10) that reflects the baseline risk level posed by a UAS operation to people and infrastructure on the ground before any mitigations are applied. The iGRC is determined based on:

  • UAS Physical Characteristics:

    • Maximum characteristic dimension (e.g., wingspan for fixed-wing aircraft, blade diameter for rotorcraft, or maximum distance between blade tips for multi-copters).

    • Maximum speed at impact (the highest possible commanded airspeed as defined by the manufacturer).

  • Operational Environment:

    • Population density within the operational volume and the surrounding ground risk buffer.

    • Whether the flight occurs over sparsely populated, populated, or densely populated areas.

Understanding the iGRC is crucial, as it establishes the baseline risk before applying any mitigations. This classification is a key input in subsequent SORA steps.


Visualizing Ground Risk

The iGRC is also represented graphically to help visualize the risk footprint of a UAS operation.

This figure highlights how different operational environments influence risk classification and the potential impact zones of an uncontrolled UAS.


Determining the iGRC

The iGRC is determined through a structured process that assesses both the operational footprint and environmental factors:

1. Identifying the iGRC Footprint
  • Flight geography: Define the area where the UAS is expected to operate under normal conditions.

  • Contingency volume: Calculate the additional volume of airspace that accounts for potential deviations from planned flight paths.

  • Initial ground risk buffer: Establish an initial safety buffer (the final ground risk buffer will be determined in Step #8 of SORA).

  • Population density analysis: Identify the highest population density within the iGRC footprint. If multiple segments of the flight pass through areas with varying population densities, the segment with the highest density should be used.

2. Evaluating UAS Physical Characteristics
  • Maximum Characteristic Dimension:

    • Fixed-Wing UAS: Measure wingspan.

    • Rotorcraft: Measure blade diameter.

    • Multi-Copters: Measure the maximum distance between blade tips.

  • Maximum Speed Considerations:

    • Defined as the highest possible commanded airspeed of the UA, as specified by the manufacturer.

    • Not limited to mission-specific maximum airspeed since operational reductions may not necessarily reduce the impact area.

    • Speed-reduction mitigations, which limit impact velocity, can be accounted for in Step #3 of the SORA process (SORA Annex B).

3. Population Density and Risk Assessment
  • Official mapping tools: Population density should be determined using officially designated maps with an appropriate grid size for the operation.

  • Alternative methods: If no suitable population density maps exist, qualitative descriptors (see the table below) may be used to estimate the population density in the operational volume and ground risk buffer.

  • Submission of custom maps: In certain cases, authorities may allow applicants to submit their own population density maps if official sources are inadequate.

4. Adjustments to Population Density Estimates
  • If an applicant identifies inaccuracies in a static population density map, they may provide alternative data sources such as:

    • Other mapping products.

    • Satellite imagery.

    • On-site inspections.

    • Local expertise and historical data.

  • If approved by the competent authority, these alternative sources may be used to refine iGRC calculations.

  • Time-based adjustments: Considerations such as time-based restrictions (e.g., flying at night to reduce ground risk) are addressed in Step #3 of the SORA process.

5. Alternative Methods for iGRC Calculation
  • Operators may find that the default iGRC values are too conservative for their specific UAS operation.

  • In such cases, an applicant may apply a mathematical model, as defined in Annex F of SORA, to determine a more precise iGRC.

  • Operations beyond the scope of SORA: If an operation does not correspond to an existing iGRC category (i.e., grey cells on the reference table), it falls outside the scope of SORA and should be considered under the certified category.

Since exact population density data is not always available, qualitative descriptors can help estimate the density of people in the operational area. These estimations are crucial in assigning the correct iGRC.

For example:

  • Sparse areas include remote locations, forests, and industrial zones with minimal human presence.

  • Populated areas include suburban neighborhoods and parks with occasional crowds.

  • Densely populated areas cover city centers, stadiums, and mass gatherings.

By overlaying UAS operational volumes onto population density maps, operators can make informed decisions about risk levels and necessary mitigations.


Conclusion

Step 2 of the SORA process, determining the Intrinsic Ground Risk Class (iGRC), provides the foundation for evaluating the potential impact of a UAS operation on people and property. Understanding iGRC classification allows operators to:

  • Identify the baseline risk level of their operation.

  • Establish necessary mitigation measures.

  • After determining the iGRC, strategic mitigations are applied to reduce the ground risk, ultimately leading to the final ground risk class (GRC).


At AirHub Consultancy, we help professional drone operators navigate the complexities of risk assessment and regulatory compliance. The AirHub Drone Operations Platform provides tools for determining the density of people on the ground and identifying other potential hazards, such as critical infrastructure and No-Fly Zones, to enhance situational awareness and safety planning.

Stay tuned for the next blog in our SORA series, where we explore how to apply mitigations to reduce ground risk effectively.

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What to Expect During an Audit of the CAA

Since the introduction of the EASA legislation and regulations, your Civil Aviation Authority (CAA) has decided to audit drone operators on a regular basis. A date is agreed upon for this visit, during which CAA will come by to carry out the audit. Various topics are discussed during this audit. This includes checking documents, viewing flight logs, asking function-specific questions, et cetera. In this blog, we'll discuss this in more detail so that you're always ready for an audit.


Why are the audits done?

Audits are common in the world of (manned) aviation, without them aviation would be a lot less safe. It's important to understand what happens in practice, what works and what doesn't. They're always looking for how the legislation and regulations can be further improved. This has been done for manned aviation for decades, but is still fairly new for unmanned aviation. The CAA also comes by to learn for itself. This is to see how, for example, the approved procedures in the manual are carried out in practice.


What happens during an audit?

During an audit, inspectors from the CAA visit the site. During this visit, they check if the processes and procedures in the manual are carried out as described. They'll check the documents (such as training and insurance certificates), view the flight logs and ask substantive questions to the responsible persons. For this reason, the people with the following positions must be present:

  • Accountable Manager

  • Flight Operations Manager

  • Safety Manager

The CAA will try to do an audit when a flight is planned. This way they can see how it's implemented and if everything is going according to procedure. If it's not possible to plan this during a flight, they'll check the most recently operated flight or ask you to plan a (potential) flight.


What questions can you expect?

The questions asked by the CAA will concern various subjects. The most important questions will be about the content of the manual. They'll check if you know how to apply the manual in practice, and if you know the appropriate protocols and procedures. The questions may also concern EASA legislation and the conversion from national to European legislation.

Each position within the organization also comes with a different set of questions, as each position also has a different set of tasks. The questions will thus be tailored to the tasks the person handles. For the Safety Manager this can, for example, concern how incidents and accidents are dealt with, when and how this is reported and whether this is done in accordance with the guidelines of European legislation.


Which documents are checked?

During the audit, the CAA will check for the operational obligations. This includes the following documents:

  • Emergency Response Plan

  • Operational Plan(s)

  • Checklists, Operational Manuals (e.g. A and B)

  • Flight Logs

It's also important to have the management of (internal) incidents in order during an audit. This includes noting which incidents and accidents have occurred, and how these were dealt with (implementation of improvements).

Finally, they'll check if the maintenance of your drones is up-to-date. For example, what maintenance has been carried out in the past, whether the drones that will fly are current, and what maintenance is scheduled for the future.


How do you ensure that you are always ready for an audit?

Make sure you always have all the necessary documents in order, keeping them up-to-date will save you a lot of work. The workflow within the AirHub software ensures that many of the necessary documents are ready for you. Everything comes together in one organised and structured place. From the automatic logging of flight to having all your checklists and documents in order.

As soon as the documents have to be transferred to the CAA, you can export everything to a PDF document with the click of a button.

If you have any additional questions after reading this blog, make sure to reach out to us! Fill in the contact form or schedule a demo if you're curious about what our software can mean for your drone operations.

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Safety is one of the top priorities in aviation, including drone operations. Risk-based operational assessments (such as SORA in the drone industry) with corresponding mitigations in the Operations Manual, training, checklists, etc. contribute to the high level of safety that has been achieved in manned aviation. To start operating Unmanned Aircraft Systems (UAS), you are also required to comply with regulations set by international, such as EASA and the FAA, and national authorities. However, being, and more specifically staying, compliant might be an underestimated part of drone operations.

In the (manned) aviation industry, it has been proven that efficient and effective data collection and processing are critical to enable safe operations. Data collection is one of the key elements that is part of a compliant organisation. The Federal Aviation Authority (FAA) has defined a compliancy philosophy, which emphasises the need for collaboration within the aviation community, and organisations in it, to share data about safety issues. One of the goals of this philosophy is to identify safety issues that underlie deviations from standards. The next step is to correct these issues efficiently and effectively in the shortest time span.


Why do we want to achieve a ‘logging culture’ in drone operations?

To stay compliant, you are required by law to log your flights. The European authority EASA requires that all flight operations should be (electronically) logged for a period of two years by the UAS operator. The required data includes all flight characteristics, incident or accident reports and maintenance logs. But there are more arguments to consistently log your drone operations.


Operational logging

In manned aviation, almost every pilot keeps a logbook. A logbook is the indispensable diary of a pilot’s training, career, and flight journeys. It not only records where a pilot has flown, but also who he or she has flown with, the number of hours, how many landings were undertaken, the kinds of instrument approaches and what kind of airplane he or she was flying in. Due to the short flight times in drone operations, logging all your flights can be a struggle for operators. However, remember that you do not only log your flights because it is required by law, but also because it is your own ‘proof of experience’!

We know that ‘it is better to be safe than sorry’, so regularly maintaining your fleet of drones and all other equipment will increase safety across your organisation. Insights in the history of your drone can be very useful to look ahead for any component replacements. It will save you time and costs by being prepared for your drone’s maintenance activities. So, it is also essential from an operational and technical point of view to log your drone operations within your organisation.


Incident or Accident logging

Lastly, Civil Aviation Authorities require you to report any incidents or accidents related to your drone operations. Types of reports can be, but are not limited to, incidents such as unsafe or special situations in the air (e.g. a near collision with other aircraft). Therefore, the ‘Just Culture’ principle is essential in your organisation. In the manned aviation industry, it has also taken some years to accept this as normal working practice in day to day operations. The principle of ‘Just Culture’ supports learning from hazards (including incident or accidents) through structural sharing of safety information - instead of blaming the person(s) who caused it - to prevent future accidents. So, besides meeting legal requirements, logging and reporting also enhances your company’s safety culture.


How AirHub can help

At AirHub we have guided many organisations across various industries with setting up a safe, efficient and compliant drone operation. We can deliver a combination of consultancy and online tools to get your operation approved by the CAA, but also to stay compliant. AirHub's Ground Control Apps enable you to instantly log all flight times, schedule maintenance actions and report incidents in the field. But the mobile applications for iOS and Android are not limited to the required logging of personal flight hours, also management of teams, maintenance reporting and incident management are features that are used a lot. You can download the free AirHub application or log in to the online Dashboard to encourage a ‘logging culture’ in your organisation. By downloading the app you will not only have an easy to use and comprehensive drone logbook, but also a complete compliance system for your drone operations. Our enterprise customers will furthermore profit from advanced features such as live streaming, AI recognition and even remote operations.

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Online and Practical Drone Training for the Enterprise

Why having a properly trained and qualified crew is essential to setting up a safe and SORA compliant drone operation at your company.

Building a safe and efficient drone operation is not only about having the right equipment and procedures. Probably the most important thing is to have your crews gain the necessary experience and expertise in what they are doing. Providing them with high quality theoretical and operation specific practical drone training is crucial when it comes to this.

Together with our training partners AirHub can ensure that your flight crews receive the right standardized #training for operations in the European Open and Specific categories. Our team of experienced ground school and flight training instructors will develop a custom training program specific to your company's needs.


Custom Made Online Training

European legislation dictates that when flying a drone within the airspace of the member states, you - the operator - must have sufficient knowledge on the applicable regulations and other subjects such as navigation and meteorology. Depending on if you are operating in the Open or Specific category various requirements will be applicable to your drone operation.

Setting up a comprehensive training syllabus for your flight crew is essential for a successful drone operation.

When operating your drone in the Open category you will need to know in which geographical #zones you are allowed to fly, what the applicable rules are for the different subcategories (A1 - A3) you can fly in and where to #register your drone. You will also want to know what the requirements are for electronic #identification and geo awareness for the class of drone (C0 - C4) you are operating. To get you ready for the legally required tests, our online training for the Open category will guide you through subjects like:

  • Air safety and Aviation regulations

  • Airspace structure concepts

  • Human performance limitations

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  • UAS flight performance

  • UAS general knowledge

  • Privacy and data protection

  • Insurance and Security

When operating within the Specific category the level of theoretical knowledge and practical skills required strongly depends on the type of operation you want to conduct. Depending on the SAIL level that results from the #SORA analyse you have completed, different requirements will be set for your ground school training. That is why we have developed a modular online training course that can be adjusted to your specific needs. The basis of this online training covers subjects - above those in the Open category - that are required by all operations within the Specific category:

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  • Situational awareness and workload management

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Depending on the type of operation you will be conducting you can then add extra modules to your training course. So if you want to operate within a #CTR with #UTM service for example or fly Beyond Visual Line Of Sight (BVLOS) you can add these modules to your training course. All the modules are presented in an easy to access online video by experts in their field, so you can take full advantage of their experience and expertise.

At AirHub we will create a custom online training specific to your flight crew's needs.


Operation Centric Practical Training

Just like every company is different, every #drone operation is different as well. Our flight training instructors will help you develop an internal training syllabus suited for your flight crew and maintenance personnel and will provide them with the initial training needed to get certified. We have developed many programs for various sectors including:

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Management Training

Setting up a drone operation does not only affect the personnel directly involved with flying the drones but also the management of the company. Our consultants can guide the directors and managers at your organization in the implementation and management of your drone program. Trough our coaching and training you will be able to get the highest return on investment from your drone operation as quickly as possible.


How AirHub can help

At AirHub we have guided many organizations across various industries with setting up a safe, efficient and compliant drone operation. Contact us to take advantage of the experience and expertise of our consultants and trainers. They can help you develop and validate your training syllabus and verify the competencies of your flight crew. And with our AirHub Drone Operations Management platform you will be able to gain a comprehensive insight into your training needs.