MEL Preparation Guidance

Where are the IOM standards published?

To prepare an MEL which is compliant with the IOM standards, please read Registry Publication (RP) 4 Chapter 5.2.

Which MMEL should be used?

The MEL must be based on the MMEL issued by the State of TCDS compliance, e.g. if the aircraft is accepted onto the IOM Register as an FAA TCDS compliant aircraft, the MEL must be based on the FAA MMEL.

Please check with the operator BEFORE you start working on the MEL.

Which National Regulations should be used?

The MMEL is intended to be used by aircraft on the issuing State(s) Register; therefore it will refer to their own national rules (14 CFR, Air Ops, CAR etc).

All references must be changed to reflect the actual IOM National Regulations.

Where can I find the IOM National Regulations?

M- Registered aircraft must be equipped with the mandatory equipment required by our legislation.  Whilst the definitive list is contained in our legislation, to assist our operators, the Registry has produced a set of Operational and Emergency Equipment Tables.

Make sure the MEL is FULLY CUSTOMISED to the aircraft: 

  • Front page must identify the aircraft (Serial Number / Registration Mark) and Operator (not MEL author);
  • Ensure MEL identifies all the equipment installed (“If installed" comments are NOT acceptable).

Ensure MEL identifies serviceable equipment required for operational approvals held, e.g. RVSM, NAT HLA, AWOPS, RNP operations (if applicable), alternatively the MEL can identify another document held on board that does identify the required equipment (ie AFM). Conversely references to operational approvals NOT held must not be included in the MEL.

Remember who the end user is…

The end users are the pilots who have to be able to easily determine whether the aircraft can dispatch.  The MEL should be a stand-alone document or refer to other documents (e.g. the AFM/RFM) which will be readily available onboard the aircraft (with the exception of Maintenance manuals such as the AMM).

If you require any further assistance or have a question relating to the production of an MEL, please contact the Flight Ops team [email protected] or ring +44 1624 682358.


The MEL Preamble does not reflect the intent of the example in Appendix 1 or 2

Operators are encouraged to use the Preamble provided in RP 4. Deviation from the format is acceptable provided the spirit of the intent is met.

The MEL still contains phrases such as “As required by regulations” or “Any in excess of those required” etc. 

Where the MMEL refers to other NAA regulations, or similar statements, these must be changed in the MEL to reflect the Isle of Man requirements contained in Isle of Man legislation which is published on our website

Where the MMEL states, “As per National Regulations” etc, or “Any in excess of those required”, this wording must not appear in the MEL; instead, the text should be adjusted to reflect the equipment requirements mandated by our legislation, please refer to

The MEL uses references to other documents which may not be available on board

The MEL should be a single source document to provide personnel with clear, concise direction. It would not be acceptable to make reference to other documents as these may not be carried on board or could be subject to misinterpretation.

It is acceptable to make reference in the MEL to O&M Procedures which are already contained in another document that is routinely available; e.g. elsewhere in the Operators Manuals for ‘O’ procedures or the Maintenance Manual for ‘M’ procedures.

It is acceptable to make reference in the MEL to information contained in the AFM or RFM as applicable.

The MEL has not been customised to the aircraft

The MEL must reflect the particular aircraft equipment and configuration.  For example:

  • The ‘number installed’ and/or ‘number required for dispatch’ should be listed.
  • Where optional items i.e. SBs/Mods are referenced in the MMEL, only the appropriate entries which reflect the actual aircraft mod status should be included in the MEL.
  • Where the MMEL and/or TC holders source O&M procedures require the operator to establish ‘Alternate Procedures’ these must be developed and included in the operators MEL or O&M procedure.
  • Where the MMEL and/or TC holders’ source O&M procedures state “Required Distribution is maintained”, the operator must clearly indicate in the MEL the required distribution to meet our legislation, refer to Operational and Emergency Equipment Tables.

The MEL is not in the name of the Operator

The MEL is an Operator controlled document which is managed by the nominated Flight Operations Representative (FOR).  Where the Operator contracts a third party to produce the MEL, the MEL must clearly identify the operator.

The MEL does not list the equipment required for Specific Approvals

The MEL should identify the equipment, where applicable, that is required for specific approval(s) held, e.g. PBN, RVSM, NAT HLA (MNPS), & AWOPS etc or alternatively identify where it can be found. i.e. Aircraft Flight Manual.

For example purposes only, an MEL could identify the equipment as per the following:

Specific Approval Minimum Navigational Equipment Required
• 1 ATC
• 1 Altitude Alerting System
• 1 Air Data System
• 2 GPS
• 2 IRS
RNAV 10 (RNP-10) • 2 FMS
• 1 GPS
• 1 DME
• 1 VOR
• 1 IRS
RNP 2 Continental en-route ONLY • 1FMS
• 1 GPS
• 1 DME
RNP 2 Oceanic & Remote •2 FMS
•2 GPS
• 1 Autopilot or Flight Director
• 1 Primary Flight Display
• 1 SATCOM with ICAO Safety Services Certification. VHF Datalink radio may be used in regions of VHF coverage.

What is the registry's Definition of day of discovery?

The Registry's policy is that this should be defined as 'the calendar-day an equipment/instrument malfunction was discovered'.

This day is excluded from the calendar days or flight days specified in the MMEL for the repair interval of an inoperative instrument and/or equipment items. This provision is applicable to all MMEL items; ie. categories A, B, C & D.