Minimum equipment list compliance

When establishing an MEL, the starting point will be the Master Minimum Equipment List (MMEL) that was EASA approved on 31 December 2020. Any subsequent revisions of the MMEL will need to be verified, by the operator, as being CAA accepted/approved (validated) under the associated bilateral agreement with the State of Design (SoD).

The MMEL is a document established for a particular aircraft type/model by the organisation responsible for the type design (typically the TCH) with the approval of the SoD, which identifies items which individually may be unserviceable at the commencement of a flight. The MMEL is one of the Operational Suitability Data (OSD) constituents.

The operator should seek confirmation from the TCH that the MMEL (or revision) is either approved directly by the UK CAA or may be considered as UK CAA accepted/approved (validated) in accordance with an appropriate Bilateral Aviation Safety Agreement (BASA), Memorandum of Understanding (MoU) or Working Arrangement (WA), and their associated implementing procedures.

Whilst the TCH develops the MMEL, the MMEL will need to be read in conjunction with any applicable MMEL Supplements that may have been implemented by another DAH, via STC.

Changes to the MMEL and MMEL supplements are accepted/approved (validated) in the same way as other changes to a type certificate and are classified as Minor or Major in accordance with UK Reg (EU) No.748/2012 Annexe 1 Part 21.A.91 and associated Guidance Material.

For aircraft no longer in production, or where no UK accepted/approved (validated) MMEL has been established as part of the operational suitability data, then the MMEL to be used may be based on the current MMEL approved by the primary certificating authority. For example, non-UK TC holders whose SoD is the United States, then the latest FAA approved MMEL could be used. If a UK MMEL is subsequently established, it will replace the previous MMEL as the required source document.

The FAA maintains a full registry of its approved MMELs on its website.

When using a non-UK SoD MMEL as the source document, the operator may need to modify certain items in their MEL to ensure that they continue to comply with UK operating rules. This is permissible using the requirements published in CS-MMEL.

The operator’s MEL must use the most restrictive limitation as listed in either the non-UK SoD MMEL or CS-MMEL. For example, an FAA MMEL may state a repair interval of 10 days for a Flight Data Recorder, whereas CS-MMEL only permits 72 hours and/or 8 flights and is therefore more restrictive.

If a non-UK SoD MMEL has been used, the operator is required to demonstrate where the more restrictive CS-MMEL requirements have been implemented to support their MEL approval application.

Certain items may have slightly different ATA references in the non-UK SoD MMEL and CS-MMEL, in such cases the MEL should reflect the numbering used in the MMEL (to ensure correct cross referencing to any Operational or Maintenance procedures).

In the case of Airbus aeroplanes, the MMEL provided to operators is customised and is released to UK operators in accordance with Airbus procedures only when it has been confirmed that the MMEL content has been accepted or approved (validated) by the EU-UK Technical Implementation Procedures (TIP). Therefore, the operator does not need to seek additional confirmation from Airbus that the MMEL source document provided is UK accepted/approved (validated).

In addition to the above, a few MMEL items for specific aircraft types are associated with UK certification requirements and need to be retained. This would be where there are notified UK national requirements as published in the aircraft AFM. These generally refer to older models, but guidance and specific CAA Policy Items can be found on the CAA website at the following location: CAA MMEL Policy Items.

The CAA will approve MMELs (and revisions) from UK TCHs or UK DAHs as the SoD in accordance with CAA Design and Certification processes for Type Design. This includes amendments (supplements) to the MMEL via STC.

As a UK MMEL is not established as part of the operational suitability data for non-G registered aircraft and to ensure that all aircraft modifications have been included in the design of the aircraft’s MEL, then the source MMEL document should be the latest MMEL approved by the State of Register.

For aircraft registered in the IOM or Bermuda and declared to the UK CAA in accordance with ORO.DEC.100, Letters of Understanding (LoU) are in place between the UK CAA and the Civil Aviation Authorities of these territories. These LoU include provisions relating to approval of the MEL.

UK CAA will issue confirmation of the MEL approval on the applicable template, based on confirmation from the IOM/Bermudan Authority that the MEL has been approved.

In accordance with ORO.MLR.105(f) the operator may apply to the CAA for approval to use a procedure for the one-time extension of category B, C & D rectification intervals. This approval is in addition to gaining approval of their submitted MEL.

Before applying, the operator should ensure that the option to extend rectification intervals is within scope of the MMEL source document.

If an MMEL has not been established as part of the operational suitability data and the MMEL used is an FAA MMEL that allows RIEs to be applied, then RIEs may only be permitted for category B and C rectification intervals in accordance with the definition of ‘Continuing Authorization – Single Extension’ stated within the relevant FAA MMEL Policy Letter.

The operator is to submit their MEL application in accordance to ORO.MLR.105 and the guidance provide above. The following should be sent to apply@caa.co.uk:

• MMEL Source Documentation
• Operator’s proposed MEL
• Completed MEL Compliance Statement (SRG1447), confirming that they have obtained confirmation from the Type Certificate Holder that the MMEL on which this MEL is based has been accepted/approved by the UK CAA.

If applicable:

• Documentation demonstrating where the more restrictive CS-MMEL requirements have been implemented, if applicable (refer UK MMEL Source Documentation – Unavailable)
• SRG1762 Application for Approval of a Minimum Equipment List (MEL) for aircraft by an operator declaring in accordance with Part-NCC and/or Part SPO, with the appropriate fee.

• CS-GEN-MMEL - Issue 2 (Generic Master Minimum Equipment List issue)
• The Air Navigation Order 2016

• CS-MMEL- Issue 3

• MEL Compliance Document SRG1447
  Both PDF and Word versions available to download