The Minimum Equipment List is a document used by air operators consisting of a list of inoperative equipment that an aircraft can have before making a flight. It is a way to ensure that the remaining pieces of equipment are operational.
The aim of this list is to postpone the aircraft maintenance and continue with the operations, avoiding delays and cancellations, whenever possible and when the associated risk of the inoperative equipment is under control.
There are two types of Minimum Equipment Lists or MELs. One of them, the Master Minimum Equipment List or MMEL, is a handbook developed by the aircraft manufacturer that shows with which inoperative pieces of equipment that aircraft can fly. In these MMELs, there are parts that are left to the discretion of the operator or the authorities that regulate airworthiness in the country in which they operate.
The European Aviation Safety Agency, EASA, regulates the formats and the structure of the MMEL, specifically with the parts CS-GEN-MMEL and CS-MMEL of the Certifications Specifications in the 748/2012 regulation.
Usually, the modifications in the MMEL of an aircraft are notified to the operators through a subscription obtained with the acquisition of the aircraft.
The MEL is a more restrictive document than MMEL, as it has been completed with the operator’s criteria and with the approval from the competent authority, and it must be included in the organisation’s operation manuals.
MELs are usually developed in a collaboration between the operations and maintenance departments, the latter normally having more weight in the development. The ORO.MLR.105 requirement of the 965/2018 EASA regulation establishes the way in which the operators’ MELs should be managed and used, and at an international level, the MELs are regulated by the Annex 6: Operations of Aircraft from the International Civil Aviation Organisation, ICAO.
The modifications performed in the MMEL of a specific aircraft must be included in the MELs of the operators within a maximum period of 90 days since the modification. Operators may only operate an aircraft that does not comply with an approved MEL with the explicit permission of the National Aviation Authority (NAA) or of a competent authority.
For more details on how to be updated with the EASA regulation, as well as on quality control of the Minimum Equipment List, subscribe to the EASA Quality Compliance Newsletter, where you will find information on new technologies, tools for the aeronautics industry and quality and compliance monitoring management for air operators.
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