SORA (Specific Operations Risk Assessment): A UK Overview

SORA — the Specific Operations Risk Assessment — is the analytical backbone of Specific Category drone operations in the United Kingdom. When your intended operation does not fit within the Open Category limits, and no pre-defined risk assessment (PDRA) covers your scenario, you build a SORA to demonstrate to the Civil Aviation Authority (CAA) that the operation can be conducted at an acceptable level of safety.

What SORA actually does

SORA is a methodology, not a form. It guides you through a logical chain: describe the operation in detail (the Concept of Operations, or ConOps), assess the risk to people on the ground, assess the risk of a mid-air collision, and then combine those into a single integrity-and-assurance figure. That figure tells you how robustly you must build and prove your safety case.

The methodology was developed by JARUS (the Joint Authorities for Rulemaking on Unmanned Systems) and is adopted by the CAA as part of its guidance in CAP 722. It is the same conceptual framework used across Europe under EASA, which is why operators familiar with EU rules find the UK approach broadly recognisable.

The three building blocks: GRC, ARC and SAIL

Three terms appear constantly in SORA work, and understanding how they connect is the key to the whole process:

• GRC (Ground Risk Class) — the level of risk the operation poses to people on the ground. It is driven by drone size, kinetic energy and the type of area you fly over (controlled, sparsely populated, populated, or a gathering of people).
• ARC (Air Risk Class) — the likelihood of encountering manned aircraft in the airspace you intend to use. Low-level rural airspace carries a lower ARC than airspace near an aerodrome.
• SAIL (Specific Assurance and Integrity Level) — derived from the combination of the final GRC and ARC. SAIL runs from I (lowest) to VI (highest) and dictates how rigorous your operational, technical and organisational safety measures must be.

How mitigations change the picture

SORA is not a fixed score. You can apply mitigations to lower your GRC and ARC, which in turn lowers the SAIL and the burden of proof. Reducing the number of people overflown, adding a parachute or geofencing, or operating in segregated airspace are examples of measures that can pull the risk down. The art of a good SORA lies in identifying credible, demonstrable mitigations rather than optimistic claims.

When do you need a SORA?

You need a SORA when:

• Your operation falls outside the Open Category limits (for example, beyond visual line of sight, over assemblies of people, or with heavier aircraft); and
• No existing PDRA matches your operation closely enough to be used instead.

If a PDRA does fit, you generally use that simpler route. The full SORA is reserved for operations that are novel, complex, or higher-risk.

The SORA process in outline

1. Define the ConOps — describe the drone, the operating area, procedures and crew.
2. Determine the intrinsic GRC from the operation and aircraft characteristics.
3. Apply ground-risk mitigations to obtain the final GRC.
4. Determine the initial ARC from the airspace.
5. Apply strategic and tactical air-risk mitigations to obtain the residual ARC.
6. Read off the SAIL from the GRC/ARC combination.
7. Identify the Operational Safety Objectives (OSOs) and demonstrate them to the robustness required by the SAIL.

SORA 2.5 and what it means in the UK

The JARUS methodology has been revised to version 2.5, refining terminology, the semantic model and parts of the quantitative approach. UK operators should always work from the edition the CAA currently references in its guidance, because the detail of GRC tables and OSO expectations can shift between editions. Treat any older worked example as illustrative only.

A SORA is a substantial piece of work, but it is also the gateway to operations that the Open Category simply cannot accommodate. Building one carefully — with honest risk assessment and evidence you can actually produce — is the single best investment you can make in a successful Specific Category application.