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UK Civil Aviation Regulations

These are published by the CAA on our UK Regulations pages. EU Regulations and EASA Access Guides published by EASA no longer apply in the UK. Our website and publications are being reviewed to update all references. Any references to EU law and EASA Access guides should be disregarded and where applicable the equivalent UK versions referred to instead.

Equipment used in aircraft may be eligible for a stand-alone approval or ‘authorisation’. These authorisations do not constitute an approval to install on an aircraft, but credit may be claimed from the equipment authorisation towards the showing of compliance with the aircraft Certification Specifications (CS) when certificating its installation.

The equipment approvals issued by the Civil Aviation Authority (CAA) using Certification Specifications for European Technical Standard Order (CS-ETSO) are UK Technical Standard Order Authorisations (UKTSOAs).

The UKTSOA is granted in accordance with UK Regulation (EU) No 748/2012, Part 21 Subpart O when the manufacturer (Applicant) can demonstrate to the CAA the equipment meets a prescribed Minimum Operational Performance Specification (MOPS). The MOPS acceptable to the CAA include those within or referenced from CS-ETSO.

Applicants may apply for Deviations to the MOPS. Deviations are based on a determination of an equivalent level of safety and are subject to industry consultation before acceptance. Deviations agreed by one Applicant may be used by any subsequent Applicant.

UKTSOA holders may classify and approve minor design changes (within an agreed scope) to approved equipment without further authorisation by the CAA. These minor changes are periodically notified to the CAA by the UKTSOA holder.

No application is required to the CAA for a minor change unless there is a need to amend the UKTSOA certificate. In these cases, an application for the approval of a Minor Change should be made using CAA Form SRG1726NR.

A major change to the article as defined under 21.A.611 would require the submission of an application for a new UKTSO Authorisation.

Equipment with a UKTSOA is eligible for release on a UK CAA Form 1.

Please note the CAA issued thousands of Equipment Approvals prior to the formation of EASA. Those approvals have been grandfathered and are considered equivalent to ETSOAs/UKTSOAs and remain valid. The process for minor and major changes to these equipment approvals is the same as the process for equipment with UKTSO authorisations.

Changes to equipment by applicants other than the equipment approval/UKTSOA holders must be approved at the product (in other words, aircraft or engine) level.

The CAA also issued a small number of Equipment Approvals after the formation of EASA and prior to the UK’s withdrawal from the European Union (EU). These approvals are valid only for use on aircraft registered in the UK.


An Applicant for a UKTSOA must have a Production Organisation Approval (POA) in accordance with UK Part 21 Subpart F or Subpart G and a design organisation approval (DOA or ADOA) that are acceptable to CAA.

The scope of the equipment approval project must be within the approved scope and Terms of Approval (TOA) of the POA and DOA/ADOA. Applications are also accepted in cases when the project is simultaneously being used to demonstrate applicant competence for the issue of or extension to the scope or ToA of the POA and/or DOA/DOA.

There is further information on DOA and ADOA on how to apply for a UK Part 21 design organisation approval.

There is also guidance available on POA on how to apply for a Part 21 Subpart G approval.

How to apply

An application is made using CAA Form SRG1726NR

Approval process (simplified)

x   Submit application on CAA Form SRG1726NR and provide the initial Certification Programme
  x Check eligibility of Applicant (to ensure that the Applicant holds a POA, DOA/ADOA as appropriate and that the project is within the POA/DOA/ADOA scope)
x   Provide Technical Familiarisation of the project (usually through the Certification Programme, but supplemented as necessary)
x x Review the Certification Programme
x x Agree the Means of Compliance (MOC) and Level of Involvement (LOI)
  x Consider any proposed Deviations and consult as necessary
x   Demonstrate compliance with the applicable MOPS
  x Determine compliance as per the agreed LOI and confirm with Applicant
x x Agree the scope of future minor changes to the UKTSOA article
x   Provide Declaration of Design and Performance (DDP)
  x Issue UKTSO Authorisation certificate