Minimum Equipment Lists (MEL) Part 2

By Jack Hessburg February 2001 Continuing on from the last column regarding what an MEL is and why it’s important, let’s examine the details of the list and how it is developed and used. There is usually a separate Master Minimum Equipment List (MMEL) for each large airplane type design. For example, the list for the 747 addresses all model variants and all installed standard and optional equipment/systems for the type. An FAA Flight Operations Evaluation Board (FOEB) controls the MMEL. It is predicated upon the following criteria: An acceptable level of safety is assured considering subsequent failure of the next critical component within a system, and, any interrelationships between allowed inoperative items do not compromise safety. The usefulness of the document is inversely proportional to its physical size. Thus, items that are obviously either required or not required for flight are not listed. If an item is not listed in the MMEL, then it is required and may not be deferred. If a system is allowed to be inoperative, then any individual components of the system may be inoperative. The list includes: • Items of equipment or systems related to airworthiness • Equipment required by the operating regulations. • Other items the Administrator finds may be inoperative and yet will permit an acceptable level of safety to be maintained by appropriate operating conditions and limitation. The list will not include: • Obviously required items such as wings, flaps, and rudders. • Obviously not required items such as coffee makers. • Any deviation from Airplane Flight Manual limitations, emergency procedures or Airworthiness Directives.

Developing the MMEL
MMEL development begins during the initial design of an airplane. For new designs, the manufacturer submits a preliminary list of items to be considered by the FOEB. Airplane operators, interested public (safety organizations, foreign regulatory agencies, union representatives, and the like), use this list to develop the master. The final MMEL is released, after review by the Chief of Air Carrier Division in Washington, DC, by the FOEB.
Once adopted, an MMEL is periodically revised. These revisions arise from individual operators petitioning the FOEB through their Principle Operations Inspector (POI) for additions, deletions, or clarification of items. The FOEB continues its activities throughout the useful life of the airplane type. There is no set schedule for the Board to meet. Rather, they meet on an as needed basis. Early in an airplane model’s life, meetings might be held yearly, whereas later in its life, the meetings can be several years apart.

MMELs are for airplanes, not airlines
The MMEL is not directly useable by the airline. It is a generic list for a given airplane type. Thus, items are included in the master that may not be installed in a given airline’s fleet. There is no system for tracking recording, crew notification and clearing of a deferred item contained in the list. The list also contains time limits on how long a given item may be deferred. It identifies requirements for placarding the cockpit. It requires which items must have maintenance and flight operations procedures or limits.
Each airline must prepare its own MEL using the master as the source. Operators are responsible for exercising the necessary control to insure that an acceptable level of safety is maintained. This includes a repair program embracing the parts, personnel, facilities, procedures, and schedules to insure timely clearance of deferred items.
An individual airline’s MEL may be more restrictive but not less than the Master Minimum Equipment List. They may include, with appropriate conditions and limitations, items not contained in the master list such as equipment not required for a given flight operation; that which is more than required by the FAR; and equipment that, for internal administrative control reasons to the operator, is best placed within the context of his MEL .
However, the Administrator, through the POI, must also approve these non-essential items.

Process for deferring items
The specific process for deferring at any given airline will differ. However, the following is representative of existing procedures.
Once it has been determined that an item is deferrable, a decision is made to defer or fix. This normally involves, at the minimum, station maintenance personnel and the pilot-in-command. However, in many instances, flight dispatch, maintenance engineering and a quality control organization will be party to the decision. Some airlines designate in the body of their MEL, specific individuals or organizations with deferral authority for each item listed.
Station maintenance personnel have several responsibilities that include properly securing the deferred item, logging item correctly in required documents, notifying specific individuals and organizations to ensure that the necessary bookkeeping will take place, thus insuring that the item is properly tracked and scheduled for later repair within allowable time limits.
Dispatch and/or the pilot-in command shall, as appropriate observe any special limitations or modified operating procedures attendant to the deferred item and notify other operations organizations and down line stations that are affected by the deferral.
Maintenance control or other appropriate organization charged with tracking deferred items and scheduling will take appropriate action to clear the item from the deferred log within the allowed time for deferral.
So, it is possible to safely fix an airplane with a pencil.