BVLOS Risk Assessment UK 2026

What Is SORA?

SORA stands for Specific Operations Risk Assessment. It is a structured methodology developed by JARUS (Joint Authorities for Rulemaking on Unmanned Systems) and adopted by the UK CAA as the standard approach for assessing risk in Specific Category UAS operations.

The purpose of SORA is to provide a consistent, repeatable framework for evaluating the safety of a proposed operation. Rather than relying on subjective judgement, SORA uses defined criteria and classifications to determine the level of risk and the mitigations required to bring that risk to an acceptable level.

For BVLOS operations, SORA is not optional. The CAA requires a completed SORA as part of every Operational Authorisation application for beyond visual line of sight flights.

Step 1: Define the Concept of Operations

The SORA process begins with a clear description of the operation. This Concept of Operations (ConOps) defines the parameters that feed into the risk assessment. Key elements include:

• The type of UAS — its maximum take-off mass, dimensions, kinetic energy, and performance characteristics.
• The operational environment — whether the flight is over controlled ground areas, sparsely populated areas, populated areas, or assemblies of people.
• The airspace — whether the operation takes place in controlled or uncontrolled airspace, and the typical traffic density.
• The operational procedures — how the flight is conducted, including crew roles, communication protocols, and contingency plans.

The accuracy and completeness of the ConOps directly affects the quality of the SORA. A vague or incomplete ConOps leads to an unreliable risk assessment.

Step 2: Ground Risk Class (GRC)

The Ground Risk Class evaluates the risk of the drone causing harm to people on the ground. The intrinsic GRC is determined by two factors: the maximum characteristic dimension of the UAS (which correlates with its kinetic energy) and the type of area overflown.

The SORA framework provides a matrix that maps these factors to a GRC value ranging from 1 to 10. A small drone flying over a controlled ground area receives a low GRC; a large drone flying over an assembly of people receives a high GRC.

The intrinsic GRC can be reduced by applying ground risk mitigations. These include strategic mitigations — such as restricting the operation to areas with low population density — and design mitigations, such as parachute recovery systems or frangible construction. Each mitigation must be supported by evidence, and the CAA assesses whether the claimed reduction is justified.

Step 3: Air Risk Class (ARC)

The Air Risk Class evaluates the risk of a mid-air collision between the drone and another aircraft. The initial ARC is determined by the airspace in which the operation takes place.

SORA defines four Air Risk Classes: ARC-a (atypical airspace, very low encounter rate), ARC-b (low encounter rate), ARC-c (moderate encounter rate), and ARC-d (high encounter rate, such as near aerodromes or in controlled airspace).

The initial ARC can be reduced through strategic mitigations — for example, by using airspace segregation (such as a Temporary Danger Area) or by operating at times and in areas where traffic is known to be minimal. Tactical mitigations, such as detect-and-avoid systems, also contribute to managing air risk but are assessed separately as part of the Operational Safety Objectives.

Step 4: SAIL Determination and Operational Safety Objectives

The final Ground Risk Class and Air Risk Class are combined in a SORA matrix to produce the Specific Assurance and Integrity Level (SAIL). SAIL values range from I (lowest risk, least demanding requirements) to VI (highest risk, most demanding requirements).

Each SAIL level maps to a set of Operational Safety Objectives (OSOs). There are 24 OSOs covering areas such as operator competency, UAS technical performance, operational procedures, and external systems support. For each OSO, the SAIL determines whether the requirement is optional, at a low level of robustness, a medium level, or a high level.

The operator must demonstrate how each applicable OSO is met, providing evidence proportionate to the required robustness level. For higher SAIL levels, the evidence burden is substantially greater — the CAA may require independent testing, third-party audits, or formal design assurance.

Common Pitfalls in SORA Assessments

Several recurring errors weaken SORA submissions:

• Underestimating the overflown area classification: Classifying an area as sparsely populated when it is actually populated, or failing to account for seasonal variations in population density.
• Claiming mitigations without evidence: Stating that a mitigation is in place but not providing the data, procedures, or technical documentation to support the claim.
• Incorrect SAIL determination: Errors in the GRC or ARC calculation that cascade into an incorrect SAIL, leading to insufficient safety measures.
• Treating SORA as a formality: Completing the assessment as a paperwork exercise rather than as a genuine tool for identifying and managing risk. The CAA can distinguish between a thoughtful SORA and one that has been completed mechanically.

The strongest applications treat the SORA as a living document — one that genuinely informs the design of the operation, rather than being completed after all decisions have already been made.