• 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 CAA using CS-ETSO will be UK Technical Standard Order Authorisations (UKTSOAs).

    The UKTSOA is granted in accordance with Part 21 Subpart O when the manufacturer (Applicant) can demonstrate to CAA that the equipment meets a prescribed Minimum Operational Performance Specification (MOPS). The MOPS acceptable to CAA include those within or referenced from CS-ETSO (Certification Specifications for European Technical Standard Order).

    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 CAA.

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

    Note: 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. These approvals are listed here [link to Equipment Approvals].

    CAA also issued a small number of Equipment Approvals since 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.

    Guidance on equipment approvals.


    An Applicant for a UKTSOA must have a Production Organisation Approval (POA) in accordance with 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.

    For further information on DOA and ADOA see the guidance on how to apply for a Part 21 design organisation approval.

    For further information on POA see the guidance 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’d article
    x   Provide Declaration of Design and Performance (DDP)
      x Issue UKTSO Authorisation certificate