The SORA Methodology Explained for UK Operators

The SORA methodology can look intimidating from the outside, but it follows a clear logical flow. Each step feeds the next, and once you see the chain, the individual pieces make sense. This guide walks through the methodology as a UK operator would apply it for a Specific Category authorisation.

Step 1: The Concept of Operations (ConOps)

Everything begins with a precise description of what you intend to do. The ConOps covers the unmanned aircraft and its characteristics, the operational volume and ground risk buffer, the crew and their roles, the procedures (normal, contingency and emergency), and the operating environment. A vague ConOps produces a weak SORA, because every later step depends on accurate inputs here.

Step 2: Determine the intrinsic Ground Risk Class

The intrinsic GRC reflects how dangerous the aircraft would be to people on the ground if control were lost, before any mitigation. It is a function of the aircraft's characteristic dimension and the population density of the area being overflown — ranging from controlled ground areas through sparsely populated and populated areas up to assemblies of people. Larger, heavier aircraft over busier areas yield higher intrinsic GRC values.

Step 3: Apply ground-risk mitigations

You can reduce the intrinsic GRC using recognised mitigations:

• M1 — strategic mitigations that reduce the number of people at risk (for example, restricting the area or timing the flight to avoid crowds).
• M2 — reducing the effect of ground impact (parachutes, frangible design or other energy-reducing measures).

Each mitigation has a robustness level (low, medium, high) and contributes a defined reduction. The output is the final GRC.

Step 4: Determine the initial Air Risk Class

The ARC reflects the likelihood of meeting manned aircraft. It depends on the airspace environment — altitude band, proximity to aerodromes, and whether the airspace is controlled or uncontrolled. Operations in atypical or segregated airspace carry the lowest ARC; airspace near airports the highest.

Step 5: Apply air-risk mitigations

Air risk is reduced through two layers:

• Strategic mitigations — operational restrictions and airspace structures agreed in advance (for example, segregation, altitude limits, or a temporary danger area).
• Tactical mitigations — measures that work during the flight to avoid collision, such as detect-and-avoid or visual observers (depending on the operation type).

The result is a residual ARC.

Step 6: Derive the SAIL

The final GRC and the residual ARC are combined in a lookup that produces the SAIL — the Specific Assurance and Integrity Level, from I to VI. The SAIL is the single most important output of the methodology because it sets the bar for everything that follows.

Step 7: Meet the Operational Safety Objectives

The SAIL maps to a list of Operational Safety Objectives (OSOs). These cover technical reliability, crew competence, procedures, maintenance, and human factors. For each OSO, the SAIL tells you the robustness required — and robustness means both integrity (the measure actually works) and assurance (you can prove it works). A higher SAIL demands more evidence and more rigorous independent verification.

Putting it together

The methodology is deliberately iterative. If your first pass produces an unrealistically high SAIL, you revisit the ConOps and mitigations: perhaps a smaller operating volume, a parachute, or tighter airspace arrangements bring the SAIL into a manageable range. The goal is a coherent package where the operation, the risk assessment and the safety measures all reinforce one another.

Worked examples and the precise GRC/ARC tables evolve between methodology editions, so always build from the version the CAA currently references. The logical flow described here, however, is stable and gives you the mental model you need before tackling the detailed tables.