SORA Containment Requirements: A 2026 Guide for Drone Operators & UAS Manufacturers
- Anne-Lise Scaillierez
- 2 days ago
- 6 min read
UNDERSTANDING THE PURPOSE OF CONTAINMENT
The UK’s Specific Operations Risk Assessment (SORA) framework, now the standard pathway for higher-risk drone operations, introduces the concept of Containment. This refers to the measures and systems in place to ensure that a drone remains within its designated operational area, even in the event of a system failure or flyaway.
“Containment consists of technical and operational mitigations that are intended to contain the flight of the UA within the defined operational volume and ground risk buffer to reduce the likelihood of a loss of control resulting in an operational volume excursion.”
Let’s first step back and review the layers of safety volumes under the SORA methodology, surrounding the flight volume where the operator carries out drone operations under normal conditions using standard operating procedures.
Diagram of the Flight Volume, Contingency Volume and Ground Risk Buffer
Side View  | Top View  |
Flight Volume
The Flight Volume is the volume where the operator is carrying out the aircraft operation under normal conditions, using standard operating procedures.
The entire operation must be contained within the Flight Volume.
Contingency Volume
The contingency volume surrounds the flight volume. The outer limit of the contingency volume is equivalent to the outer limit of the operational volume.
Entry into the contingency volume is always considered an abnormal situation and requires the execution of appropriate contingency procedures to return the UA to the flight volume, and the operation to normal conditions.
Note that the Contingency Volume is also vertical.
Contingency procedures must be activated as soon as the UA deviates from its intended flight path, or behaves abnormally, even when it is well within the Flight Volume, to prevent it leaving the Operational Volume.
Operational Volume
The Operational Volume is made up of the Flight Volume and the Contingency Volume.
Ground Risk Buffer
The ground risk buffer is an area on the ground that surrounds the footprint of the contingency volume.
If the UA exits the contingency volume during a loss of control of the operation, it should end its flight within the ground risk buffer.
Size of the contingency volume and ground risk buffer
SORA details formulas to calculate the minimum horizontal vertical size of the Contingency Volume and Ground Risk Buffer.
The key driver to the contingency volume minimum size is the Remote Pilot’s response time to implement the procedures, if not automated, and the UAS operational speed
The key driver to the ground risk buffer minimum size is the ballistic crash trajectory once the flight termination is implemented, with the 1:1 rule as a proxy option.
Containment Emergency String of Events
If the UA behaves abnormally, even within the Flight Volume, the Remote Pilot monitors behaviour and takes immediate measures as necessary to recover control within the Flight Volume
If the UA exits the Flight Volume, the contingency procedures must be implemented. Typically: Return to Home, or Geocaging stop and hover.
If those functionalities fail and/or the Remote Pilot fail to secure regained control of the UA so that the UA exits the contingency/operational volume and enters the ground risk buffer:
the Emergency Flight Termination procedures must be immediately activated so that the UA does not leave / crash outside of the Ground Risk Buffer.
UNDERSTAND CONTAINMENT ROBUSTNESS LEVELS: LOW, MEDIUM AND HIGH
Containment requirements must be met at low, medium or high robustness level, depending on the operation’s risk.
The level of robustness depends on the following criteria:
The size and maximum Design speed of the UA
The average population density in the adjacent area – the area that is exposed in case of fly-away or excursion outside of the ground risk buffer. The adjacent area is minimum 5km
The existence of assemblies of people within 1km of the Operational Volume
The Operations SAIL level.
For higher size and/or speed: additional tables are provided in SORA.
THE CHALLENGE OF SORA CONTAINMENT AT MEDIUM ROBUSTNESS LEVEL
In the UK, and in most countries applying SORA, containment at Low level of robustness is declarative. The Operator declares that they are meeting the requirements.
At Medium level of robustness however, the Operator must provide compliance evidence. That body of evidence for criterion 1,2 and 4 is reviewed by one of the RAE-F, recognised assessment entity – Flightworthiness. The RAE-F provides its report to the CAA that forms its final decision on compliance.
Meeting SORA containment at medium robustness is challenging.
Reference is made to table 7: in many locations, operations under SAIL 1 and 2 with a UA of max 1 m and max 25 m/s design speed will fall under the Low level of robustness, i.e. declarative.
Reference is made to table 8: however, if the UA is more than 1M in size, and/or its design speed is higher than 25m/s, operations under SAIL 1 or 2 may fall into the Medium level of robustness due to the average population density in the adjacent area.
HOW TO ACHIEVE SORA CONTAINMENT COMPLIANCE?
The SORA Safety Methodology describes the 4 criteria that an operator must meet in order to comply with the Containment requirements.
Please bear in mind that:
an Operator, or a UAS Designer, can offer an alternative means of compliance as long as they demonstrate equivalent safety outcomes
the demonstration of compliance, in the UK, kicks in at the Medium Robustness level.
Criterion 1: Operational volume containment
“(a) No probable single failure of the UAS or any external system supporting the operation must lead to operation outside of the operational volume (qualitative approach), or,
(b) The probability of the failure condition “UA leaving the operational volume” must be less than 10-3/FH (quantitative approach).”
Criterion 1 can be met, for example, with a Return to Home or Geocaging function.
Criterion 2 – End of flight upon exit of the operational volume
“When the UA leaves the operational volume, an immediate end of the flight must be initiated through a combination of procedures and/or technical means.”
Criterion 2 can be met, for example by a set of procedures to manually activate Flight Termination when the UA leaves the Operational Volume - or by an automatic flight termination upon breach of geocaging.
Criterion 3 – Definition of the final ground risk buffer
“A ground risk buffer must be defined which adheres at least to the 1:1 principle, unless the Applicant is able to demonstrate the applicability of a smaller buffer.”
Criterion 3 can be met by applying the calculations provided by SORA.
Criterion 4 – Ground risk buffer containment KICKS IN AT MEDIUM ROBUSTNESS
“(a) No single failure of the UAS or any external system supporting the operation must lead to operation outside of the ground risk buffer.”
Criterion 4 can be met, for example, with an independent flight termination system.
SORA CONTAINMENT COMPLIANCE: EXPERT SUPPORT
The notion of Containment is introduced by SORA. Its purpose is to mitigate the risk of an excursion outside of the operational volume and a crash outside of the ground risk buffer.
At medium level of robustness, demonstrating containment is challenging. It requires a robust body of evidence, including a Design and Installation Appraisal of the containment functionalities and the UA system. In the UK, that body of evidence is first reviewed by a RAE-F before final acceptance by the CAA.
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We make drone regulations and compliance faster and simpler. Understanding drone regulations, applying for SORA Operational Authorisations, can be challenging - lack of time, lack of resources, lack of internal expertise. We make drone regulations and compliance accessible, we guide you through your approval journey, we alleviate your documentation and administrative burden, so you can focus on growth. The Drone Office empowers end-users, drone operators and technology providers in both commercial and military markets to quickly understand the landscape, streamline their compliance and accelerate their success. We make your regulatory compliance simpler and faster —so you can focus on your growth. 🌐 Visit: www.thedroneoffice.com
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