SORA vs PDRA: Which Authorisation Route Should You Take?

One of the first decisions in any Specific Category drone application is which route to take: a Pre-Defined Risk Assessment (PDRA) or a full Specific Operations Risk Assessment (SORA). Choosing correctly saves time and avoids unnecessary work. This guide explains the difference and how to decide.

What is a PDRA?

A PDRA is a ready-made risk assessment published by the authority for a common, well-understood operational scenario. The hard analytical work — identifying the hazards, setting the mitigations, defining the safety objectives — has already been done. If your operation fits the scope of a PDRA, you adopt its conditions rather than building your own risk assessment from scratch. It is the simplified, faster route.

What is a full SORA?

A full SORA is the complete methodology: you define your Concept of Operations, assess Ground Risk Class and Air Risk Class, apply mitigations, derive the SAIL, and demonstrate the Operational Safety Objectives. It is flexible enough to cover almost any operation, but it is substantially more work. You build it when no PDRA covers what you want to do.

The key question: does a PDRA fit?

The decision hinges on whether an existing PDRA matches your operation closely enough. PDRAs come with defined boundaries — aircraft characteristics, operating environment, altitude, distances from people, and so on. If your operation sits comfortably within those boundaries, the PDRA is almost always the better choice.

If your operation differs in a material way — a heavier aircraft, a different airspace, BVLOS beyond what the PDRA permits, or flight over areas the PDRA excludes — then the PDRA does not apply and you need a full SORA.

Trade-offs at a glance

Advantages of the PDRA route

• Faster to prepare — the risk analysis is pre-packaged.
• More predictable — the conditions are known in advance.
• Lower assessment burden — you demonstrate compliance with set conditions rather than justifying a bespoke safety case.

Advantages of the full SORA route

• Flexibility — it can cover operations no PDRA addresses.
• Optimisation — you can tailor mitigations to your specific situation, potentially achieving a lower SAIL than a generic scenario would.
• Future-proofing — a well-built SORA can support expanding your operation over time.

A decision sequence

1. Describe your intended operation precisely.
2. Check the available PDRAs against that description.
3. If one fits within its stated boundaries, adopt it.
4. If none fits, build a full SORA.
5. If a PDRA almost fits, consider whether you can safely adjust the operation to bring it within scope — sometimes a minor restriction is far cheaper than a full SORA.

Common misunderstandings

• A PDRA is not a loophole — you must genuinely meet all its conditions, not just most of them.
• A SORA is not always "harder to get" — for a well-mitigated low-risk operation it can land at a low SAIL, though it still takes more effort to prepare.
• You cannot mix and match freely — you commit to one route; you do not borrow conditions from a PDRA into a SORA without justification.

The bottom line

If a PDRA fits your operation, use it — it is the faster, more predictable route. Reserve the full SORA for operations that are genuinely novel, complex, or higher-risk, where the flexibility of the full methodology is worth the extra effort. The available PDRAs and their boundaries are revised over time, so always check the current set the CAA publishes before deciding, and treat any older list as illustrative.

Making this choice early — before you invest in building a safety case — is one of the simplest ways to keep a Specific Category application efficient.