How to Write a Minimum Equipment List (part 1)

This post is the first in a series of posts that cover the process for developing an MEL.

Minimum equipment lists are one of the more difficult documents to develop since the FAA guidance for MELs is somewhat vague in terms of the details and individual FSDOs/inspectors can have varying preferences for how an MEL is written.

Read the recommended documents below thoroughly, and be prepared to ask some questions of your FAA inspectors. The basic steps for developing an MEL for you company involve downloading the FAA’s MASTER Minimum Equipment List (MMEL) and developing your company-specific MEL from that document. The FAA develops the MMEL, the operator develops their own MEL.

To begin, you are going to need some background information from the FAA website. You’ll need to review the FAA guidance documents that govern how the FAA approves an operator’s MEL.

Let’s first find the necessary guidance files:

  • Go to, or search Google for the term “fsims”.
  • Once you are on the fsims site, click the link on the left that says “8900.1 contents”. (or click here)
  • You should see several expandable links to the various volumes of the FAA’s main guidance document.
  • Expand the link for Volume 4, then expand the link for Chapter 4 inside Vol 4. These are the guidance documents for developing and approving an MEL. (see pic below)

For Part 91 Operators:

  • Download Section 2 – MEL Requirements for 14 CFR Parts 91, 137, and 142 Operations

For Part 135 Operators:

  • Download Section 3 – MEL Requirements for 14 CFR Parts 91 Subpart K (Part 91K), 121, 125, 125 LODA, 129, and 135 Operations.

The Nonessential Equipment and Furnishings (NEF) document will be dealt with later on.

The Configuration Deviation List (CDL) is not something that most 135 operators will need to deal with (the CDL deals with items like operating with missing external components such as landing gear doors, etc.).

We still have a few more documents to find:

  • Go back to the fsims and click the link on the left entitled “publications”. (or click here)
  • Look under the section “MMEL & AEG Guidance Documents”. (see pic below)
  • Click the link for Master Minimum Equipment List (MMEL) and download the appropriate version of the MMEL for your aircraft (see info below on that topic).
  • Returning to the publications page you will see a link right below the MMEL link entitled “MMEL Policy Letters”. These are a necessary but unpleasant part of making an MEL. Policy letters will be covered in a separate post.

Which MMEL should you download? First a little background: The FAA, through a review process updates the MMEL from time to time. When the MMEL changes to MORE restrictive version (they eliminate relief for a particular item), the FAA increases the revision number by one. When the MMEL becomes less restrictive, the FAA adds a letter (or increments the letter) to the revision number. Note that some older MMELs have a separate part 135 and part 91 version. They have been slowly removing these over time in favor of a single combined version.

Example 1: Assume that the current MMEL revision for the Cessna 310 is revision 3. The FAA revises the C-310 MMEL to eliminate the ability to defer certain item. The MMEL would change to revision 4.

Example 2: Assume that the C-310 MMEL is on revision 3. The FAA decides to allow the deferral of an item. The revision number changes to 3a.

When the MMEL revision number changes (more restrictive MMEL), you MUST update your company MEL accordingly. When a letter is added or incremented (less restrictive), it is OPTIONAL to update your company MEL.
Read these guidance documents very, very thoroughly. MELs are one of the trickier documents to develop and a little patience and effort will make you very proficient at the task. The first one is the hardest, then they get easier.

Part 2 of this series will discuss the various sections of the basic MEL format.