I'm not sure why they call it a minimum equipment list. The title makes me think of a list of all the equipment that must be installed in the aircraft. For what this document really is, a better title would be "stuff that doesn't have to work." For our purposes here, and since the FAA will not likely change the name anytime soon, we will just stick with "minimum equipment list" or "MEL." In this issue we will look at the regulations that govern the operation of an aircraft when instruments and or equipment are inoperative and talk about how a minimum equipment list is created.
An aircraft is a machine that is made up of several systems and system components. It is inevitable that sooner or later a component or two is going to stop working properly and need to be repaired. The question is can we continue to operate that aircraft with the component inoperative? Lets start with 14 CFR Part 91.213.
14 CFR Part 91.213, like so many other regulations, is disjointed and without flow leaving it very difficult to grasp with just one look. This one really takes some study to get the full picture. The answer is, yes, we can continue to operate the aircraft with inoperative instruments and or equipment as long as it is done within the provisions outlined by 14 CFR Part 91.213.
First of all, it is important to understand that the FAA, specifically, the division of the FAA called the Aircraft Evaluation Group, develops and maintains Master Minimum Equipment Lists (MMEL). An MMEL is used as an MEL for Part 91 aircraft or as a guide or template by Part 135 operators in developing an MEL for their specific aircraft. An MMEL is specific to an aircraft make, model, or series and is designed to cover the most common configurations of an aircraft. The familiar Air Transportation Association (ATA) numbering system is used to organize individual equipment and instrument items within an MMEL providing a consistent look between MMEL's regardless of aircraft model. Most importantly, the MMEL is the Aircraft Evaluation Group's method of relaying to us which items of equipment are more critical to the safety of flight than others by their inclusion or exclusion from the list contained in the MMEL.
Simplified, if you are operating a turbine-powered airplane, Part 91.213 requires that you have an MEL in your aircraft and that you comply with the restrictions contained in your MEL. Your MEL actually becomes a Supplemental Type Certificate (STC) for your aircraft and must be carried within the aircraft at all times. However, not all aircraft must have an MEL in order to operate with inoperative instruments or equipment. The following regulation excerpts explain (Ref. 14 CFR Part 91.213 (d)):
Aircraft Type or Size: 14 CFR Part 91.213 (d)(1)
(d) Except for operations conducted in accordance with paragraph (a) or (c) of this section, a person may takeoff an aircraft in operations conducted under this part with inoperative instruments and equipment without an approved Minimum Equipment List provided -
(1) The flight operation is conducted in a -
(i) Rotorcraft, nonturbine-powered airplane, glider, or lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft, for which a master minimum equipment list has not been developed; or
(ii) Small rotorcraft, nonturbine-powered small airplane, glider, or lighter-than-air aircraft for which a Master Minimum Equipment List has been developed; and ...
This first section means that if an MMEL has been developed for a large aircraft or a large rotorcraft, it must be used to develop an MEL for the aircraft in order to fly with inoperative instruments or equipment. However, even if an MMEL has been developed for a small rotorcraft, small aircraft, glider, or lighter-than-air aircraft, its use is optional. Let's continue.
Instrument or Equipment Function:
Operating an Aircraft With inoperative instruments or equipment Joe Hertzler The MMEL is the Aircraft Evaluation Group’s method of relaying to us which items of equipment are...
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