Operational Categories Comparison

Comparison of Open Category, STS, PDRA, and SORA for Drone Operators in the United Kingdom

As a drone operator in the United Kingdom, it is vital to understand the various operational categories and assessment procedures that govern your activities. The UK Civil Aviation Authority (CAA) has established frameworks encompassing the Open Category, Standard Scenarios (STS), Predefined Risk Assessments (PDRA), and the Specific Operations Risk Assessment (SORA). This guide provides a thorough overview of these categories and processes, with emphasis on the UK regulatory context and how operators can comply effectively.

Open Category

The Open Category is designed for low-risk drone operations that do not require an operational authorisation or detailed permissions from the UK CAA. Drones must meet defined technical and operational requirements, including the need to carry a CE class identification label where applicable and operate within the visual line of sight (VLOS) of the remote pilot at all times. The Open Category suits recreational use and uncomplicated commercial operations that conform to these minimal risk criteria.

Operators must ensure compliance with all relevant technical standards and operational limitations, such as maximum weight and height restrictions, to remain within the Open Category. The CAA provides detailed guidance and resources for these requirements on their official webpages.

Low-risk operations without needing operational authorisation
Compliance with defined technical and operational standards, including CE class labelling
Flights must remain within the Visual Line of Sight (VLOS) of the remote pilot
Further information: https://www.caa.co.uk/consumers/drone-users/drone-safety-rules/open-category/

Standard Scenarios (STS)

Standard Scenarios are predefined, standardised operation types within the Specific Category that allow drone operators to conduct higher-risk drone flights under a streamlined approval process. Each STS is a risk-managed scenario with fixed operational conditions and mitigations that reduce complexity and regulatory burden.

In the UK, operators can carry out operations within an approved STS after submitting a mandatory Declaration to the CAA, without the need for a full operational authorisation. This practical approach facilitates compliance for common drone activities that don’t fit within the Open Category but remain controlled for safety.

It is important that operators carefully verify the applicability of the relevant STS to their intended operation and comply fully with its conditions.

Pre-approved operational scenarios by the UK CAA
Allows operations without full operational authorisation following a submitted Declaration
Simplifies compliance for more complex, but standard, operations
Further information: https://www.caa.co.uk/consumers/drone-users/drone-safety-rules/specific-category/standard-scenarios/

Predefined Risk Assessments (PDRA)

Predefined Risk Assessments (PDRAs) are standardised risk analysis templates for specific drone operations within the Specific Category. They help operators simplify the operational authorisation process when their operation matches a PDRA’s defined profile.

By applying the prescribed mitigations and risk controls from a PDRA, operators present a pre-assessed risk case to the CAA, enabling quicker and less complex approval compared to a fully bespoke risk assessment. However, not every operation has an available PDRA, and operators must verify with the CAA which PDRAs are applicable to their mission.

PDRAs offer an intermediate compliance pathway for common, well-understood drone activities requiring authorisation beyond the Open Category.

Standardised risk assessments tailored for certain Specific Category operations
Streamlines the operational authorisation application process
Appropriate for recurring, routine operations with known risk profiles
List of PDRAs: https://www.caa.co.uk/consumers/drone-users/drone-safety-rules/specific-category/predefined-risk-assessments/

Specific Operations Risk Assessment (SORA)

The Specific Operations Risk Assessment (SORA) is a comprehensive and flexible risk assessment methodology applied to drone operations that do not fit within the Open Category, STS or PDRA pathways. SORA is necessary for complex or unique operations presenting higher or more variable risks, requiring detailed hazard identification, risk analysis, and mitigations.

While more resource-intensive to develop and submit, a SORA enables operators and the UK CAA to systematically evaluate operational hazards and safety mitigations tailored to the specific scenario. It is an essential tool for achieving an operational authorisation for bespoke or high-risk flights, including those beyond Visual Line of Sight (BVLOS).

Operators should plan for establishing supporting documents such as Emergency Response Plans (ERP) and General Risk Controls (GRC) as part of the SORA submission to ensure comprehensive risk management.

Flexible risk assessment framework for non-standard operations
Critical for managing risks in complex, unique, or higher-risk drone flights
Facilitates detailed hazard identification, risk evaluation and mitigation
Further details: https://www.caa.co.uk/consumers/drone-users/drone-safety-rules/specific-category/specific-operations-risk-assessment/

Frequently asked questions

What is the difference between the Open Category and the Specific Category?

The Open Category covers low-risk drone operations that do not require an operational authorisation from the CAA. The Specific Category includes operations with higher risk levels that obligatorily require operational authorisation, obtainable through approved methods such as STS, PDRA, or SORA.

How can I apply for an operational authorisation in the Specific Category?

Depending on your operation’s complexity and risk profile, you may use a PDRA or undertake a bespoke SORA assessment. You must prepare and submit the relevant dossier to the UK CAA for scrutiny and granting of operational authorisation.

When is it suitable to use a Standard Scenario (STS)?

Use an STS when your operation aligns with a predefined and CAA-approved scenario, allowing you to operate legally without a full licensing process, by submitting a Declaration confirming compliance with STS conditions.

Can I use a PDRA for every Specific Category operation?

No. PDRAs apply only to certain common operational profiles. If no suitable PDRA exists for your intended operation, you will need to conduct a full SORA risk assessment.

What is an Emergency Response Plan (ERP) and why is it important in SORA?

An Emergency Response Plan (ERP) is a structured procedure designed to manage incidents or accidents during drone operations. Within SORA submissions, an ERP is a key component demonstrating preparedness and risk mitigation to the CAA.