In 2017, the FAA updated Federal Order 8900.1, adding a section of phrases that cannot be brought into an MEL from the MMEL.  Here’s an excerpt:

A. Must be Defined. In an MEL, the operator must expand on MMEL general “Remarks or Exceptions” and include specific procedures in accordance with the requirements of the operating rules (e.g., parts 91K, 121, 135) under which the operator conducts their operation. The procedures must address what is required when a particular item is inoperative. The following phrases are examples of MMEL general “Remarks or Exceptions” that may not be included in an MEL. POIs may not approve an MEL that contains these phrases:

1) “May be inoperative provided procedures do not require its use.”
2) “May be inoperative or missing if alternate procedures are established and used.”
3) “May be inoperative unless required by 14 CFR” or “As required by 14 CFR.”

The Phrase “As Required by 14 CFR” or Any Similar Statement is Prohibited in an MEL. This phrase (or similar ones) may appear in the MMEL general “Remarks or Exceptions”. Operators may never carry this phrase over to an MEL.

So, don’t be surprised when your MEL is a bit lighter on words than its’ parent MMEL.  Oh…and you might think that since this directive came out of Vol 4, Chapter 4, Section 3 (applicable to Pts 135, 121, 125, etc) that it doesn’t apply to Part 91 operators.  Surprise!  Here’s the directive from the 1st page of Vol 4, Chapter 4, Section 3 that makes it applicable when building a Part 91 MEL:

1. Scope. This section applies to all parts 91K, 121, 125, 125 Letter of Deviation Authority Holder (LODA), and 135 operations. Portions of this section related only to MEL revision, format, and content (with the exception of repair categories) also apply to parts 91, 137, and 142 MEL requirements.

1) Limited Applicability to Parts 91, 137, and 142 Operators Using an FAA-Approved MEL. Volume 4, Chapter 4, Section 2 contains the majority of information related to parts 91 (with the exception of part 91K), 137, and 142 operators. However, information contained in this section regarding MEL format, content, and revision may also apply to parts 91, 137, and 142 operators who have been issued a Letter of Authorization (LOA) to use an MEL (D095 for parts 137 and 142, and D195 for part 91).

So there you go…oodles of tweaks to the MEL have to be accomplished by both Part 135 AND Part 91 operators.  Painful?  Yes…but we knock this out of the park for you,…no sweat!