Deferred Defect Management - Correct Use of the Minimum Equipment List (MEL)

Sofema Online (SOL) www.sofemaonline.com considers the best practice related to the use of the Aircraft Minimum Equipment List (MEL).

Introduction

The MEL is a commonly used tool allowing for the safe and continuous operation of the aircraft until rectification of certain inoperative equipment or unavailable system functions that are not adversely affecting the airworthiness of the aircraft. Understanding the principles and rules for correctly applying MEL items is crucial for both maintenance personnel and flight crews

» Incorrectly using the MEL could lead to dispatching an aircraft in a configuration that is not airworthy and with potential consequences that could impair the safety of the flight.
» When dispatching under a MEL item, the conditions of dispatch and the rectification interval must be taken into account and the associated maintenance and operational procedures must be accurately applied.

Important Note - It is ultimately the Captain’s responsibility to decide to dispatch the aircraft for flight under the MEL conditions.

Correct Use of the MEL

Dispatch under a Minimum Equipment List (MEL) allows to dispatch an aircraft in a safe and airworthy condition when certain system functions or equipment are temporarily unavailable or inoperative, enabling the aircraft to continue earning revenue without compromising the safety of the flight.

» Assessment of the MEL item to identify any operational impact or impact on other system functions, and check if there is any influence on the safety level of the aircraft.
» Identification and assessment of the operational and safety impact of the next critical aircraft system failure which may occur during subsequent flights.
» Performance of any maintenance actions or operational procedures that may be necessary as a means of mitigation for the assessed impacts of the MMEL item.

Dispatch Status is defined for each MEL item as either:

» “GO” when the dispatch is permitted for a limited period of time without specific dispatch conditions, or
» “GO IF” when the dispatch is permitted for a limited period of time with specific dispatch conditions, or
» “NO GO” when the dispatch is not permitted and corrective maintenance action must be undertaken before the aircraft can continue operations.

Introduction

The Operator’s MEL is a dispatch document which should be tailored according to the Operator’s routes, procedures, and applicable local regulations, and within the constraints defined by the aircraft manufacturer’s MMEL.

» As per regulations, when there are failures or defects that cannot be rectified, and which are covered by a MEL item, the MEL must be applied prior to departure and accepted by the Captain.
» “The commencement of the flight” is defined as the moment when the aircraft starts to move under its own power for the purpose of takeoff (i.e. the taxi phase). EASA and FAA require Operators to define procedures in their MEL for the management of any failure that occurs during the taxi-out phase.

Decision for Dispatch

Maintenance personnel may propose to dispatch the aircraft under the MEL item provided that all of the associated dispatch conditions are fulfilled.

» It is the Captain’s responsibility to accept the aircraft dispatch under the MEL item for the flight; taking into account not only the MEL dispatch condition but also the applicable operator’s policy and the operational constraints.
» Initial dispatch after applying the MEL item, all dispatch conditions and associated limitations must be accounted for and any relevant maintenance (m) and operational (o) procedures must be applied to maintain an acceptable level of safety for the operation of the aircraft, even with the inoperative equipment or unavailable system function.
» For the subsequent flights, the flight crew must check that any open MEL item in the logbook is within the window of the repair interval and that this time limit won’t be exceeded during the next flight mission.
» When the dispatch conditions are accepted by the captain, all necessary operational procedures must also be applied.
» In the case when a new MEL item is recorded in the technical logbook, the maintenance personnel must also review all of the pre-existing MEL items to ensure that all of the dispatch conditions for each item are fulfilled.
» In the case of multiple MEL items logged, flight crew and maintenance personnel must check before each flight that dispatch conditions of all MEL items are fulfilled.

Sofema Aviation Services (www.sassofia.com) and Sofema Online (www.sofemaonline.com) offer EASA Regulatory Compliant and Vocational Training across a range of Aviation Areas including the following course in support of the understanding regarding development of an effective Defect Control Process within a Maintenance Control Centre. For additional details, please see our Websites or email Team@sassofia.com