Training & Regulations
BVLOS drone ops in AAE's: Key updates in UK CAA’s CAP 3040
The CAA’s updated CAP 3040 provides clearer guidance for BVLOS drone operations in Atypical Air Environments. Learn what’s new and how it supports UK SORA.
UK CAA publishes version 3 of CAP 3040 — Unmanned Aircraft Operations in an Atypical Air Environment: Policy Concept;
Key updates include the addition of 4 annexes, offering important guidance, examples, and more clarity of how an AAE can be defined and presented;
These annexes cover 'smoothing' (normalising AAE base height in uneven terrain or discontinuous infrastructure); operations specifically tailored to railway and windfarms infrastructure in AAEs; and operational volume;
Leverage the support of heliguy™'s in-house regulatory specialists.
The UK Civil Aviation Authority has released the Third Edition of CAP 3040 - marking an important step in the evolution of BVLOS operations within Atypical Air Environments (AAEs).
While the main policy text received general refinements, the real substance of this update lies in the introduction of four new Annexes (A–D) — designed to offer guidance and examples of how an AAE can be defined, presented, and operated in.
These annexes — and the updated CAP 3040 generally — provide clarity where the industry has long needed it:
How to define AAEs in areas where varying infrastructure height/terrain creates inconsistent operational volumes.
How to interpret infrastructure such as railways or windfarms.
How to define operational and contingency volumes within an AAE.
How to justify air risk parameters in SORA submissions
This article unpacks all four annexes.
heliguy™ has a regulatory division, which has already achieved BVLOS permissions to operate the DJI Dock ecosystem in an AAE.
Leverage the support of our specialist team to help you prepare and submit a UK SORA application to the UK CAA, to accelerate your path to BVLOS adoption. We can conduct remote ops for you, help you obtain your own permissions, or offer a hybrid approach combining pathways 1 and 2 — as outlined in this article. For more details, contact us.
CAP 3040: Annexes A to D at a glance
Annex | Summary |
|---|---|
A — Smoothing | Defines how to normalise AAE base height in uneven terrain or discontinuous infrastructure. Useful for rail corridors, powerlines, and urban rooftop profiles. |
B — Railway infrastructure | Provides detailed rules for: • Using overhead line equipment height as a reference. • Handling cuttings using the highest boundary. • Proximity to urban structures beside railways. A substantial addition for rail-based BVLOS operators. |
C — Windfarm infrastructure | Defines AAE around wind turbines: • Blade tip height used as vertical boundary. • 100ft horizontal extent. • Continuous AAE if turbines ≤1000 ft apart. • Segmentation where wider spacing occurs. |
D — Operational volume | This now directly shapes SORA applications and emergency procedures. • OV and Contingency Volume must fit fully inside the AAE. • Small contingency volumes may force flight termination if breached. |
Expert insight
"CAP 3040 remains a Policy Concept, but it is encouraging to see some more meat on the bones. This increased clarity will benefit the operator and the regulator alike."
— Graham Hegarty, heliguy™ Regulatory Specialist
What is an AAE?
Operating in an Atypical Air Environment (AAE) reduces the chance of a drone encountering manned aircraft. This makes AAEs especially useful for BVLOS operations outside controlled airspace, where detect-and-avoid systems might not be available.
An AAE doesn’t have one fixed definition, but it generally refers to airspace where the presence of nearby infrastructure makes it unlikely that crewed aircraft will operate.
Typical examples include:
Within 100ft of a building or structure.
Within 50ft of a permanent linear feature such as a railway, road, or powerline.
Up to 50ft within private property, such as an industrial site carrying out perimeter inspections.
These examples act as guidance to help identify when an area may reasonably be treated as an AAE.
Why the new annexes matter
Until now, the industry lacked consistency in how AAEs should be defined, measured, modelled, and justified.
Now, Annexes A–D offer more clarity - offering clearer AAE design tools to give operators a more predictable framework to build compliant, defensible operational proposals.
The CAA says that applicants may propose an alternative example of an AAE; for example, an offshore installation or distances exceeding those recommended by the CAA.
CAP 3040: Annexes A to D in more detail
Here's a more detailed look at Annexes A to D, and why they matter.
CAP 3040 Annex A — Smoothing
Annex A introduces smoothing, a methodology allowing operators to create a consistent reference height when infrastructure or terrain varies enough to cause fragmented or inconsistent operational volumes.
The principle:
Identify the highest point within a defined segment (max 300m / 1000ft).
Use that height as the base reference across the entire segment.
Justify data using survey records or verified sources.
Why it matters: Without smoothing, an AAE could become a jagged, inconsistent “saw-tooth” vertical profile—impractical for BVLOS navigation and difficult to justify in a SORA.
All smoothing proposals will be assessed by the CAA on a case-by-case basis.
CAP 3040 Annex B — Railway infrastructure interpretation
Rail corridors are among the most promising AAE environments, but their geometry varies dramatically. Annex B clarifies how to set reference heights in three common scenarios.
1. Railways with Overhead Line Equipment (OLE):
If OLE or similar continuous linear structures are present, they may be used as the primary AAE reference structure.
Key rule: OLE must be continuous along the intended operating segment.
2. Railways in cuttings
Where the track sits below surrounding land, the uppermost point of any natural or man-made obstacle along the cutting margin may be used as the ground level reference for the AAE.
This is because the cutting face and surrounding topography provide vertical containmnemt, reducing the likelihood of other airspace users operating within this location.
Accurate survey data must be provided to define the elevation of the highest obstacle in the cutting boundary along the intended route.
3. Railways flanked by buildings / urban structures
Urban corridors often include buildings parallel to tracks. These buildings/other structures may be considered as the reference structure of the AAE above the linear infrastructure, provided they present a consistent and substantial linear obstacle within the proposed operational area.
Where building height or proximity varies, the operator must account for these variations and adjust the defined AAE base accordingly, ensuring that the operation remains within the bounds of reduced mid-air collision risk.
CAP 3040 Annex C — Windfarm infrastructure interpretation
Windfarms are ideal AAE environments due to their large, permanent structures. Annex C gives operators precise numerical rules for defining AAE boundaries.
Reference Height — Blade Tip Extremity: The AAE is based on maximum blade tip height, not hub height.
Horizontal Extent — 100ft Rule: The AAE extends 100ft horizontally from the outermost blade tip.
Continuous AAE — 1000ft Turbine Separation: If adjacent turbines are ≤1000ft apart (tip-to-tip), they form a continuous AAE. If turbines exceed 1000ft separation, separate AAEs must be defined, with a transition procedure.
CAP 3040 Annex D — Defining Operational Volume within an AAE
Annex D clarifies how operators must design operational volumes inside an AAE.
Key Requirements:
1: Both the Flight Volume (FV) and Contingency Volume (CV) must fit entirely within the AAE boundary.
2: A minimal CV is allowed—but the applicant must recognise the implications of such a decision.
3: With a defined CV which lacks the space to meaningfully react to the UA exiting the Flight Volume, the drone may enter the Ground Risk Buffer, but emergency produces must be followed, which may include activating the flight termination system.
Annex D removes ambiguity in how to build SORA-compliant operational volumes—previously one of the most inconsistent parts of AAE submissions.
CAP 3040 V3 vs V2: What else has changed?
Besides the introduction of Annex A to D, much of the rest of CAP 3040 remains the same from V2, although there are some differences.
Electronic Conspicuity
One key update relates to Electronic Conspicuity. CAP 3040 now references the March 2025 announcement between the UK CAA and Ofcom, which made the 978MHz frequency available for airborne transmission onboard UA.
For reference, a drone operating within an AAE should be equipped with a Universal Access Transceiver (UAT) device transmitting on 978MHz and receiving on dual frequencies 978 MHz and 1090 MHz
Remote Pilot Competency
Edition 3 of CAP 3040 formally embeds L2 RPC as an AAE baseline expectation, which did not exist previously.
The minimum requirements for a Remote Pilot (RP) to be granted an L2 RPC are:
Be registered as an RP on the CAA DMARES and hold a valid Flyer ID.
Hold a valid L1 RPC and have completed 50 hours of VLOS flight recorded in a personal RP logbook.
Have completed additional BLVOS operations theoretical knowledge training and passed an assessment.
Have completed at least 5 hours of BVLOS flight instruction in ARC-a including emergency procedures such as tactical deconfliction.
Have passed a practical flight assessment consisting of two flights lasting at least 30 minutes.
CAP 3040 Version 3: Summary
The latest edition of CAP 3040 marks a significant step forward for BVLOS operations in the UK, with the new annexes providing the practical clarity operators have long needed.
By defining how AAEs should be interpreted around real-world infrastructure—railways, windfarms, buildings, and complex terrain—the CAA has created a more consistent, predictable framework for safe low-level drone operations.
For organisations looking to scale BVLOS activity, these annexes turn the AAE concept into a usable, operational tool—helping operators design stronger applications, build safer missions, and accelerate the adoption of advanced drone operations across the UK.
