Sofema Aviation Services www.sassofia.com looks at the document behind the Aircraft Minimum Equipment List (MEL) the “MASTER” MEL – MMEL
The MMEL is essentially a list established for a particular aircraft type by the organization responsible for the type design with the approval of the State of Design containing items, one or more of which is permitted to be unserviceable at the commencement of a flight. The MMEL may be associated with special operating conditions, limitations or procedures.
The MMEL Regulates dispatch of an aircraft with inoperative equipment. It should be noted that it the use of the MMEL should not encourage operation with inoperative equipment. The MMEL may be approved or modified by the appropriate authority.
The MMEL shall ensure the required level of safety (FAR25 or CS25) must be maintained
The MMEL should focus on the continued operation with minimal use of MMEL procedures. Repair Intervals are established to identify the allowable time period for each allowable item.
MMEL Introduction
Aircraft are designed with installations which exceed airworthiness requirements, moreover some equipment is not required for all operations (eg. lights for day). There are some equipment’s (for example “Passenger convenience items” which are not included within the scope of the MMEL.
Development of the MMEL shall consider
The potential Consequences of further failure, Changes in crew workload, Degradation in crew efficiency as well as adverse weather conditions.
MMEL Substantiation to be achieved to include
Adjustment of operating limitations
Transfer of the function
Reference to other components
Change in operating procedure
Change in maintenance procedure
Equipment considered optional
Equipment considered redundant
Qualitative safety analysis
Quantitative analysis
Approval by the relevant FOEB/JOEB (FOEB Flight Operations Evaluation Board – JOEB Joint Operations Evaluation Board) performing an Item by item review with Justification by the TCH (manufacturer) together with a review of Operations and maintenance procedures reviewed.
MMEL Prohibited Items
No item shall be included in the MMEL which conflicts with the limitations or invalidates the emergency procedures of the AFM or of an airworthiness directive unless the AFM or directive provide otherwise.
Some Procedures are not approved with the MMEL for example the Boeing – Dispatch Deviation Guide
The MMEL is not to include any item of equipment which, if inoperative, is likely to significantly affect performance of the aircraft unless noted in the AFM and MEL.
The MMEL shall not include any part or structural component of the aircraft which is the subject of the Configuration Deviation List (CDL).
CDL – Configuration Deviation Lists are considered as amendment to type certificate which are not included in MEL. CDL Information will be included in the Limitations Section to Flight Manual and typically concerns Operation with Missing Secondary Airframe Engine Parts
Sofema Aviation Services provides regulatory training including the use and development of the MEL for details please see www.sassofia.com or email office@sassofia.com
