Operating an Aircraft: With inoperative instruments or equipment

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 more critical than others by their inclusion or...


Operating an Aircraft

With inoperative instruments or equipment

Joe Hertzler
Joe Hertzler




I'm not sure why we call it a Minimum Equipment List. The title makes me imagine a list of all the equipment that must be installed in an aircraft. A better title for what this document really is might be "permissibly inoperative instruments and equipment." For the purpose of this discussion and since the FAA won't likely change the name any time soon, we'll continue to refer to the document as a Minimum Equipment List or MEL. In this issue we'll look at the regulations that govern the operation of an aircraft with inoperative instruments and equipment and outline the makeup of a minimum equipment list.

An aircraft is a machine that is made up of several systems and system components and 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? Enter rule 14 CFR 91.213.

14 CFR Part 91.213, like so many other regulations, is disjointed and 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.

Initially, 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 actually used as an MEL for Part 91 aircraft or as a guide or template by Part 135 operators in developing their own MEL for their 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-a-like order 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 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 within 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 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 means that if an MMEL has been developed for a large aircraft or 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 . . .

This content continues onto the next page...

We Recommend

  • Article

    Do I Need to Have an MEL?

    In this issue we will look at the regulations that govern the operation of an aircraft when instruments and or equipment are inoperative.

  • Article

    Minimum Equipment Lists (MEL) Part 2

    Minimum Equipment Lists (MEL) Part 2 Development and utilization By Jack Hessburg February 2001 Continuing on from the last column regarding what an MEL is and why it’s...

  • Article

    MEL magic - is it really airworthy?

    MEL Magic — Is It Really Airworthy? By Stephen P. Prentice May-June 1998 Steve Prentice is an attorney whose practice involves FAA-NTSB issues. He has an Airframe and Powerplant...

  • Article

    Minimum Equipment Lists

    Minimum Equipment Lists Why they exist and what they cover By Jack Hessburg October 2000 Not every device installed on an airplane works all the time. Items of installed...