Master minimum equipment list

In aviation, a Master Minimum Equipment List, or MMEL, is a categorized list of systems, instruments and equipment on an aircraft which are not required to be operative for flight. Specific procedures or conditions may be associated with operation with the relevant item inoperative^[1]. Any equipment or system which is not included in the MMEL must be operative for the aircraft to be allowed to fly^[2]. Each aircraft model generally has a distinct MMEL.

Overview

The US Federal Aviation Regulations and European Joint Aviation Requirements forbid aircraft with inoperative equipment from flight, except in certain conditions. One of these conditions is that the aircraft have a minimum equipment list that indicates which items may be inoperative and the conditions under which each item may be inoperative for flight.

Even seemingly insignificant items such as light bulbs in the cabin may be on the MEL, as light bulbs are still part of the electrical system and thus part of the airplane's equipment (and potentially important for the safety of flight). Of course, a simple light bulb in the cabin may not be essential to safety, and so it may be noted as not necessary for flight if it appears on the MEL.

Implementation

Minimum equipment lists are issued to specific aircraft and specific operators. In order for an operator to use a minimum equipment list, the operator must receive a letter of authorization from the national aviation authorities of the countries where the aircraft will operate.

In the United States, a minimum equipment list is required by the Federal Aviation Administration^[3]:

• When operating any turbine-powered aircraft such as jets or turboprops.
• When operating under part 135 (Commuter and on-demand operations)
• When operating under part 125 (Non-airline large aircraft operations)

The same kind of regulation is enforced by aviation authorities in other nations, such as the European Aviation Safety Agency^[4].

References

1. ^ "Master Minimum Equipment List (MMEL)". Federal Aviation Administration. 2007-09-27. http://aero-defense.ihs.com/products/regulations/aviation-av-data/master-minimum-equipment-list.htm. Retrieved 2011-02-03. 
2. ^ "JAR-MMEL/MEL". European Aviation Safety Agency. http://www.dac.public.lu/documentation/procedures_ops/JAR-MMEL.pdf. Retrieved 2011-02-03. "The MMEL is a document that lists the equipment which may be temporarily inoperative, subject to certain conditions, while maintaining an acceptable level of safe, as intended in the applicable JAR or equivalent Requirement. Each MMEL is specific to an aircraft type. All items related to the airworthiness of the aircraft and not included in the list are automatically required to be operative." 
3. ^ "Publications - Master Minimum Equipment List (MMEL)". FAAA. http://fsims.faa.gov/PICResults.aspx?mode=Publication&doctype=MMEL. Retrieved 2011-02-03. 
4. ^ "MMELs". EASA. http://easa.europa.eu/certification/flight-standards/MMEL-list.php. Retrieved 2011-02-03.