What is SORA? Your Comprehensive Guide to Specific Operations Risk Assessment.

The Specific Operations Risk Assessment (SORA) is a methodical risk assessment framework used to evaluate the safety of drone operations in the ‘specific’ category. This guide provides a comprehensive overview of the SORA process, its components, and how to apply it effectively to your drone operations. 

UAS operator should verify before beginning the SORA process whether:

• The operation falls under the ‘open’ category;
• The operation is covered by a ‘standard scenario’ included in the appendix to the UAS Regulation or by a ‘predefined risk assessment’ published by EASA;
• The operation falls under the ‘certified’ category or
• The operation is subject to a specific NO-GO from the competent authority.

If none of the above cases applies, the SORA process should be applied.

What is SORA?

• A methodology to assess risks associated with UAS operations.
• An acceptable means to demonstrate compliance with Article 11 of the UAS Regulation EU 2019/947.
• A systematic process to evaluate risks and determine appropriate safety measures.
• Developed by JARUS (Joint Authorities for Rulemaking on Unmanned Systems) and incorporated by the European Aviation Safety Agency (EASA).
• A holistic, risk-based assessment model that considers all threats associated with UAS operations and provides guidance on how to mitigate them.

Purpose of SORA

• Guides both UAS operators and competent authorities (National Aviation Authorities) in determining if an operation can be conducted safely.
• Helps operators identify appropriate mitigations to reduce risk to an acceptable level.
• It is not intended as a checklist but as a tailoring guide for finding best-fit mitigation means.

The SORA Process: 10 Steps

Step #1 - ConOps Description

In step 1 of the SORA process, the UAS Operator shall:

• Collect and provide all relevant technical, operational, and system information.
• Describe the nature of the activities to be performed.
• Detail the operational environment and geographical area for the operation.
• Explain the complexity of the operation (planning, execution, personnel, technical means used).
• Document technical features of the UAS and its performance capabilities.
• Outline personnel competencies, composition, roles, and responsibilities.

Step #2 - Determination of Intrinsic Ground Risk Class (GRC)

In step 2 of the SORA process, the UAS Operator shall:

• Assess the risk of a person being struck by the UAS.
• Consider the maximum UA characteristic dimension.
• Define the operational scenario (VLOS/BVLOS, population density, etc.)
• Assign category for operations based on areas being overflown (controlled ground, sparsely populated, populated or assemblies of people).
• Determine intrinsic GRC using the appropriate matrix in the SORA document.

Step #3 - Final GRC Determination

In step 3 of the SORA process, the UAS Operator shall:

• Apply mitigations to modify the intrinsic GRC.
• Consider strategic mitigations for ground risk (M1).
• Evaluate means to reduce ground impact effects (M2).
• Assess emergency response plan effectiveness (M3).
• Calculate the final GRC by adding correction factors to the intrinsic GRC.

Note: if the final GRC exceeds 7, the SORA process does not support the operation.

Step #4 - Determination of Initial Air Risk Class (ARC)

In step 4 of the SORA process, the UAS Operator shall:

• Evaluate the risk of collision with manned aircraft.
• Use airspace characterisation and collision risk categories.
• Consider factors such as altitude, atypical vs. controlled vs. uncontrolled airspace, and airfield proximity.
• Apply the ARC decision tree to assign the appropriate initial ARC (a, b, c, or d).

Note that ARC-a represents the lowest risk, while ARC-d represents the highest risk.

Step #5 - Application of Strategic Mitigations

In step 5 of the SORA process, the UAS Operator shall:

• Apply strategic mitigations to reduce the initial ARC potentially.
• Consider operational restrictions, flight rules, or airspace structures.
• Evaluate the effectiveness of mitigations based on the process detailed in Annex C.
• Determine the residual ARC after mitigation application.

Note that this step is optional but can help reduce operational complexity.

Step #6 - TMPR and Robustness Levels

In step 6 of the SORA process, the UAS Operator shall:

• Determine Tactical Mitigation Performance Requirements (TMPR).
• For VLOS operations, visual detection is considered an acceptable tactical mitigation.
• For BVLOS operations, determine the required TMPR level based on residual ARC.
• Assign appropriate robustness levels to each tactical mitigation.
• Choose appropriate detect and avoid (DAA) systems based on requirements.

Step #7 - SAIL Determination

In step 7 of the SORA process, the UAS Operator shall:

• Consolidate ground and air risk analyses into a Specific Assurance and Integrity Level (SAIL).
• Use the SAIL determination matrix (combining final GRC and residual ARC).
• SAIL represents the level of confidence that the operation will remain under control.
• Ranges from SAIL I (lowest) to SAIL VI (highest).

Note: operations with a GRC >7 fall into the certified category.

Step #8 - Identification of Operational Safety Objectives (OSOs)

In step 8 of the SORA process, the UAS Operator shall:

• Identify appropriate Operational Safety Objectives based on the SAIL.
• Determine the required robustness level for each OSO (optional, low, medium, high).
• Address technical issues, external systems, human error, and adverse conditions.
• Consider UAS design, maintenance, procedures, and crew training.
• Ensure all OSOs are met with the appropriate level of Robustness.

Step #9 - Adjacent Area/Airspace Considerations

In step 9 of the SORA process, the UAS Operator shall:

• Address risks posed by loss of control resulting in infringement of adjacent areas.
• Ensure basic containment requirements are met.
• Enhanced containment is required for operations near assemblies of people or ARC-d airspace.
• Verify that the probability of leaving the operational volume is less than 10^-4/FH.
• Ensure software and hardware components are developed to appropriate industry standards.

Step #10 - Comprehensive Safety Portfolio

In step 2 of the SORA process, the UAS Operator shall:

• Compile all mitigations, safety objectives, and assessments into a comprehensive portfolio.
• Ensure consistency between the safety case and actual operational conditions.
• Address any additional requirements not identified by the SORA process.
• Consider security, environmental protection, or other needs.
• Identify relevant stakeholders for additional requirements.

Key Concepts in SORA

Semantic Model

• Operational volume is the 4D space where the operation takes place.
• Flight geography is the projected ground area where the UA will fly under normal conditions.
• Contingency volume is the area where contingency procedures are applied in abnormal situations.
• Ground risk buffer is the additional area to protect third parties on the ground after the emergency procedures are triggered.
• Adjacent areas are the areas outside the operational volume that could be affected. Distance is considered for the UA flying 2-3min at the maximum speed.

Robustness Levels

• Low integrity: minimal safety gain with a declaration of compliance.
• Medium integrity: reasonable safety gain with supporting evidence.
• High integrity: substantial safety gain verified by a competent third party.
• Achieved Robustness means the lowest level of either integrity or assurance met.

Ground Risk Assessment Details

• Intrinsic GRC is based on the operational scenario and UA dimensions.
• Controlled ground areas provide strategic mitigation.
• Ground risk buffer should use at least the “1:1 rule” (if flying at 150m, the buffer should be at least 150m). The ballistic approach could be acceptable depending on the UA type.
• M1 mitigation: measures to reduce the number of people at risk.
• M2 mitigation: measures to reduce the energy absorbed by people upon impact.
• M3 mitigation: emergency response plan implementation.

Air Risk Assessment Details

• ARC categories from 'a' (lowest) to 'd' (highest) risk.
• Strategic mitigations may include:
  • Restricting geographical volumes.
  • Restricting time of operations.
  • Common flight rules or airspace structures, unless SERA regulations are applicable and already in place.
• Tactical mitigations include:
  • VLOS operations (visual detection).
  • Detect and avoid systems.
  • U-space services.
  • Electronic conspicuity devices.

Prominent Roles and Responsibilities for SORA

• UAS operator: responsible for safe operation and risk analysis.
• Competent authority: assesses safety cases and issues operational authorisation.
• ANSP: when required, assesses whether the proposed flight can be safely conducted in their airspace
• UAS manufacturer: provides design evidence that may support the safety case.
• Remote pilot: charged with safely conducting the flight.

Contact Us Today

Understanding and implementing the SORA process can be challenging for UAS operators. Our company provides specialised training, comprehensive consultancy services, and expert assistance with operations manual preparation to help you navigate the complexities of SORA. Our experienced professionals can guide you through each assessment step, ensure all safety objectives are met, and help you prepare a robust safety case for your operations. Contact us today to learn how we can help you achieve regulatory compliance while maximising the operational capabilities of your UAS fleet.

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