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As drone operations grow more complex with BVLOS flights, automation, and integration into controlled airspace, human-machine interaction (HMI) and human error prevention have become central to safety and regulatory compliance.

To support this, EASA released Certification Memorandum CM-HF-001 (Issue 01), which provides detailed guidance on two critical safety objectives from the SORA framework:

• OSO #19: Systems must detect and help recover from human error

• OSO #20: Human-machine interfaces must be designed to minimize mistakes and support effective decision-making

This edition of the AirHub Knowledge Series explores what these objectives mean for operators and how these principles can be applied in real-world drone operations.

Why Human Factors Matter in Drone Operations

Whether operating a drone-in-a-box setup from a remote location or coordinating complex multi-pilot missions, humans remain at the center of the operational decision loop. Errors can stem from:

• Misinterpreting system status

• Poor interface design (e.g., ambiguous button labels)

• Stressful or unclear operational procedures

The goal of both OSO #19 and #20 is to minimize human error and improve decision reliability, especially during high-stakes or complex missions.

OSO #19 – Detecting and Recovering from Human Errors

According to EASA, systems should be designed to help operators:

• Avoid making mistakes (e.g., by locking out unsafe commands)

• Recognize errors early (e.g., clear visual or auditory alerts)

• Recover from errors before they escalate (e.g., safe-mode activation)

For operations in SAIL III, this requires at least a low level of assurance, meaning you must declare and justify the design choices that reduce the chance of human error.

Examples include:

• Confirmation prompts for critical actions like arming the FTS or switching flight modes

• Automatic status monitoring (e.g., battery health or GPS quality)

• Physical barriers or interlocks to avoid accidental activation of key systems

OSO #20 – Human-Machine Interface (HMI) Design

A well-designed interface helps the operator:

• Understand system status at a glance

• Receive and interpret warnings or alerts clearly

• Perform tasks confidently and without ambiguity

EASA highlights that HMI design must be intuitive, especially for remote pilot stations, tablets, or multi-control setups.

At a minimum, your interface should:

• Use standard color codes (green = safe, amber = caution, red = warning)

• Display key system information clearly (e.g., mode, position, health, telemetry)

• Provide quick, unambiguous feedback after every operator input

• Avoid information overload or confusing visual layouts

Depending on the complexity of your setup, EASA expects some level of human factors validation, from usability walkthroughs to full scenario-based testing with representative users.

The Feedback Loop: How Operators Interact with Systems

EASA identifies five essential elements of HMI feedback loops in UAS operations:

1. Detect – The system or operator identifies an issue or change

2. Decide – The operator interprets the data and determines a course of action

3. Command – A control input is made (e.g., return-to-home triggered)

4. Execute – The system carries out the command

5. Feedback – The system confirms the action and provides updated status

If any link in this loop is weak (e.g., poor feedback, unclear options), error risk increases. A good HMI design supports all five stages clearly and reliably.

How AirHub Supports Better HMI and Error Management

At AirHub, we integrate human factors thinking directly into our software and services:

• Clear workflows in our Drone Operations Center (DOC), including visual status indicators and confirmations for critical steps

• Pre- and post-flight checklists aligned with your operations manual and user manual

• Scenario testing support as part of our consultancy services for SORA authorizations

• Customizable training support to ensure your pilots know how to use systems under both normal and abnormal conditions

We also support clients in documenting compliance with OSO #19 and #20, including declarations, evidence collection, and usability validations.

Final Thoughts

HMI design and human error prevention are no longer just best practices, they are regulatory requirements for advanced drone operations. By prioritizing clear interfaces, predictable workflows, and scenario-based testing, operators can reduce risk, improve safety, and meet SORA expectations for SAIL III and beyond.

Whether you are working on your SORA documentation, evaluating a CMU, or training your team, these principles will keep your operation safe, efficient, and future-ready.

If you would like help evaluating your interface or ensuring OSO compliance, our team is ready to support you.

Following our previous discussion on Step 4 of SORA: Initial Air Risk Class (ARC) Determination, we now focus on Step 5, which involves the application of strategic mitigations to reduce the risk of mid-air collisions.

This step is essential for reducing the initial Air Risk Class (ARC), making drone operations safer and ensuring regulatory compliance. Strategic mitigations are applied before the flight to proactively limit the exposure to risk, either by operational restrictions or by utilizing airspace structures and rules.

What Are Strategic Mitigations?

Strategic mitigations are pre-flight risk reduction measures aimed at lowering the probability of a UAS encountering a manned aircraft in the operational airspace. These mitigations modify the Initial ARC and result in a Residual ARC, which determines the necessary level of tactical mitigations in subsequent steps.

Strategic mitigations can be classified into two main categories:

1. Operational Restrictions – Measures that the UAS operator directly controls.

2. Common Airspace Structures and Rules – Measures that are controlled by the Competent Authority or ANSP (Air Navigation Service Provider) and must be followed by all airspace users.

Strategic Mitigation by Operational Restrictions

Operational restrictions are mitigation strategies that limit the operational exposure of the UAS, thereby reducing the likelihood of encounters with manned aircraft. These mitigations include:

1. Geographical boundaries

• Limiting the operational volume to specific areas where manned aircraft operations are rare.

• Operating away from high-density airspace, such as airport control zones or busy flight corridors.

• Flying in segregated or restricted airspace to reduce collision risk.

Example: A UAS operation within Class C airspace near an airport may be limited to a defined sector where no regular manned aircraft traffic is expected.

2. Time-based restrictions

• Restricting operations to specific time periods when manned air traffic density is lower.

• Conducting night-time operations in airspaces where manned aircraft predominantly operate during the day.

Example: A drone operator intending to fly over a port area may restrict operations to late-night hours when helicopter traffic is minimal.

3. Limiting time of exposure

• Reducing the total operational duration within airspace where manned aircraft operate.

• Minimizing transition time in high-risk areas, such as flying a shorter route through controlled airspace.

Example: A drone performing a powerline inspection near a busy flight corridor might be required to quickly transit through risk areas, rather than operating there for extended periods.

Strategic Mitigation by Common Airspace Structures and Rules

Unlike operational restrictions, common structures and rules apply to all aircraft within a given airspace and are enforced by authorities like ANSPs or U-Space providers.

1. Common Flight Rules

• Right-of-way rules that establish priority between manned and unmanned aircraft.

• Requirements for electronic conspicuity, such as ADS-B transponders.

• Mandatory flight planning and submission to a central ANSP system.

Example: Some controlled airspaces require all manned aircraft to use electronic conspicuity to improve detectability.

2. Common Airspace Structures

• Designated UAS corridors to separate drone traffic from manned aircraft.

• Predefined airways or procedural routes for safer integration.

• Mandatory participation in UTM/U-Space services, ensuring dynamic air traffic awareness.

Example: A country might implement dedicated drone transit corridors near urban areas to safely integrate drone operations without affecting general aviation.

Lowering the Initial ARC Using Strategic Mitigations

The Initial ARC is assigned based on Airspace Encounter Categories (AECs), which define operational environments and their respective air traffic densities. The ARC can be lowered through strategic mitigations by demonstrating that the local air traffic density is lower than the generalized risk assumptions.

Understanding the AEC and Density Rating

• The AEC classification assigns a density rating to airspace based on the probability of encountering manned aircraft.

• Density ratings range from 1 (low) to 5 (very high).

• The Initial ARC is based on these ratings and can be found in standardized tables.

Steps to Lower the Initial ARC

1. Identify the AEC applicable to the operation (e.g., operating near an airport, in uncontrolled rural airspace, in segregated airspace, etc.).

2. Determine the initial ARC based on the AEC and generalized air traffic density rating.

3. Apply strategic mitigations to justify a lower local air density rating, such as:

   • Operating in a restricted time window when fewer manned aircraft are present.

   • Using airspace segregation or pre-coordination with ATC/ANSP.

   • Providing traffic studies, radar data, or operational assessments to validate reduced encounter rates.

4. Submit evidence to the Competent Authority for approval of the adjusted ARC level.

What If Strategic Mitigations Are Not Sufficient?

If strategic mitigations alone do not sufficiently reduce the ARC, operators will need to apply tactical mitigations (Step 6), such as:

• Detect and Avoid (DAA) systems.

• UTM-based conflict resolution tools.

• Real-time pilot intervention measures.

  
  

Conclusion

Step 5 of the SORA process helps operators implement strategic mitigations to proactively manage air risks before flight. By applying operational restrictions and common airspace structures, operators can potentially lower the required safety measures in subsequent steps.

At AirHub Consultancy, we specialize in risk assessments, airspace integration, and strategic planning for enterprise drone operations. Our AirHub Drone Operations Platform provides tools to analyze operational airspaces, manage air risk, and ensure compliance with SORA.

Stay tuned for our next blog, where we explore Step 6 of SORA: Tactical Mitigations and Detect & Avoid Requirements!

Need help with your SORA application? Contact AirHub Consultancy for expert guidance on navigating the SORA process and ensuring compliance with UAS regulations.

As drone operations expand into more complex environments, ensuring safety becomes paramount—especially for Beyond Visual Line of Sight (BVLOS) and urban operations. Two technical measures stand out in enhancing operational safety and enabling regulatory compliance: parachute systems and Flight Termination Systems (FTS).

These systems play a key role in risk mitigation strategies under the Specific Operations Risk Assessment (SORA) methodology. In particular, their design and performance are assessed against EASA’s Means of Compliance (MoC) 2511 and MoC 2512, making them critical for obtaining operational authorizations.

Why Parachutes and FTS Matter

When operating over people, in populated areas, or at higher altitudes, the consequences of a system failure or flyaway are significantly higher. Parachutes and FTS are designed to reduce the severity of ground impact or prevent uncontrolled flight by:

• Reducing the kinetic energy at impact (parachutes)

• Halting flight before exiting the operational volume (FTS)

• Enhancing compliance with SORA Operational Safety Objectives (OSOs), particularly those related to containment, impact reduction, and emergency handling

These systems are often used in combination to address the overall risk profile of the mission.

MoC 2511: Parachute Systems

MoC 2511 outlines the compliance criteria for parachute systems used as a mitigation measure under SORA. Key aspects include:

• Deployment reliability: The system must be capable of autonomous deployment in case of emergency or be activated manually/remotely with low latency.

• Kinetic energy limitation: The parachute must limit the impact energy below thresholds established for operations over people or critical infrastructure.

• System testing: MoC 2511 requires documented testing under various scenarios to demonstrate reliability, including multiple deployments.

• Maintenance: Clear guidelines must be in place to check the repack cycle, battery health, and sensor calibration.

Examples of compliant systems include the MOC2511-tested parachutes from companies like Drone Rescue and Parazero, often deployed on DJI platforms and custom drones.

MoC 2512: Flight Termination Systems

MoC 2512 specifies the requirements for FTS used to contain the operation within the defined volume and reduce risk in case of loss of control. Key principles include:

• Fail-safe architecture: The system must have an independent triggering mechanism that can terminate the flight reliably even when the main flight controller fails.

• Secure communication: Commands to terminate flight must be encrypted and tested against interference.

• Termination zone planning: The operation must define areas where the FTS will land the drone in case of activation, and ensure that the impact zone aligns with acceptable ground risk.

FTS is particularly important for operations close to airspace boundaries or critical ground infrastructure, where flyaways can introduce serious risk.

Regulatory Implications in SORA

In the context of SORA:

• Parachutes are considered strategic mitigations under Step 3 (Final Ground Risk Class)

• FTS are considered containment mitigations, helping to fulfill OSOs like:
  
  

  • OSO #12 (Limitation of the effects of the UAS impact)

  • OSO #13 (Ability to terminate the flight)

  • OSO #15 (Design for containment)

Proper documentation, testing evidence, and integration with the operational concept are needed to satisfy the competent authority.

Support Through AirHub

At AirHub, we support drone operators in two ways:

1. Consultancy:

   • Advising on selection and integration of MoC-compliant parachute and FTS systems

   • Supporting the risk assessment and documentation for SORA-based authorizations

   • Assisting in operational testing and validation

2. Software:

   • Mapping operational volumes and termination zones

   • Logging maintenance cycles and system readiness

   • Embedding checklists and SOPs for launch, activation, and emergency use

Conclusion

As the drone ecosystem moves toward routine, scalable BVLOS and urban operations, safety-critical subsystems like parachutes and FTS will be indispensable. Understanding and applying the regulatory framework through MoC 2511 and 2512 not only increases safety but also unlocks operational approvals that would otherwise be out of reach.

By combining technical preparedness with smart tools and regulatory support, operators can ensure their missions are both innovative and compliant.