AC 91-67A

Advisory circular · Minimum Equipment Requirements for General Aviation Operations Under 14 CFR Part 91, § 91.213

Approved
October 16, 2023
Last reviewed
October 17, 2023
Family
AC 91-67 · 2 versions
Revision
A
14 CFR parts
21, 43, 91

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed August 14, 2026.

Show pages 35–46
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8.6.1.3 If there are operator procedures that rely on the item listed in the MMEL, but there is alternate equipment that could be used, then the MEL remark notes the use of that equipment (and thus, must be operative). For example, "HDG HOLD Mode. May be inoperative provided HDG SEL or LNAV autopilot/flight director mode(s) is operative."

8.6.1.4 There may be cases where the dispatch decision needs to be made by the PIC based on conditions at the departure or destination airport, or along the route of flight. These conditions could result from Notice to Air Missions (NOTAM) information or ground-based equipment outages. These situations would be known only to the pilot when preparing for specific flights;

therefore, a more general proviso would be appropriate. For example, "May be inoperative provided departure, en route, or arrival/approach procedures do not require its use."

8.6.1.5 Where the MMEL contains an unconditional statement, such as, "May be inoperative or missing," the MEL may leave the statement unmodified, or even omit the statement if the operator's procedures or operations do not require the item's use.

8.6.2 Example "As Required by 14 CFR" Statements.

Figure 8-1(a). Example MMEL General "As Required by 14 CFR" Statement

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT: 2. NO. INSTALLED (insert aircraft make and model)

3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

33. LIGHTS Change Sequence No. Item 1 2 4 Bar 33-07 Landing Light C As required by 14 CFR Figure 8-1(b). Example MEL Specific "As Required by 14 CFR" Regulatory Reference (The operator must ensure the applicable 14 CFR section is accessible on board the aircraft.)

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT:

2. NO. INSTALLED (insert aircraft make and model) 3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

33. LIGHTS Sequence No. Item 1 2 4 Change Bar 33-07 Landing Light 14 CFR Reference: 14 CFR 91.205(c)(4) and

91.205(d)(1).

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Figure 8-1(c). Example MEL Specific "As Required by 14 CFR" Requirement/Limitation

TABLE KEY

1. REPAIR CATEGORY (insert aircraft make and model) AIRCRAFT: 2. NO. INSTALLED 3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

33. LIGHTS Sequence No. Item Change Bar 33-07 Landing Light The landing light must be operative for night flight operations if the aircraft is being operated for hire.

Note: Illustrated in the examples above, the MEL will: (1) list the specific 14 CFR part and section (and the operator must ensure the applicable 14 CFR section is accessible on board the aircraft), or (2) specify the requirements and/or limitations to conduct the flight in accordance with the appropriate 14 CFR regulations.

8.6.3 Example (M) and (O) Symbols and Procedures.

Figure 8-2(a). Example 1 MMEL General Maintenance (M) and Operations (O) Symbols and Provisos

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT:

2. NO. INSTALLED (insert aircraft make and model)

3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

78. Engine Exhaust Sequence No. Item Change Bar -30-01 Thrust Reverser 0 (M)(O) May be inoperative provided:

a) Affected thrust reverseris locked in the forward thrust position, and

b) Appropriate performance penalties are applied.

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Figure 8-2(b). Example 1 MEL Specific Maintenance (M) and Operations (O) Symbols and Provisos

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT: 2. NO. INSTALLED (insert aircraft make and model) 3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

78. Engine Exhaust Sequence No. Item → 28 MO) Maybe Change Bar -30-01 Thrust Reverser (M)(O) May be inoperative provided:

a) Affected thrust reverseris locked in the forward thrust position, and

b) Appropriate performance penalties are applied.

Figure 8-2(c). Example 1 MEL Specific Maintenance (M) and Operations (O) Procedures 78-30-01:

Maintenance (M) Procedure Lock affected thrust reverser in the forward thrust position in accordance with AMM 78-30-12.

Operations (O) Procedure Refer to AFM Performance Section, Thrust Reverser inoperative for applicable takeoff and landing penalties.

Note: AMM 78-30-12 and the AFM in the above example are FAA-approved or FAA-accepted manuals.

Figure 8-3(a). Example 2 MMEL General Maintenance (M) Symbol and Proviso

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT:

2. NO. INSTALLED (insert aircraft make and model) 3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

28. FUEL Sequence No. Item 2 4 Chang e Bar 28-21-25 XBP Crossfeed Valve 2 (M) One or more may be inoperative in closed position provided:

a) All Booster Pumps are operative,

b) Affected XBP Crossfeed Valve is secured in closed position, and

c) Repairs are made within 3 consecutive calendar-days.

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Figure 8-3(b). Example 2 MEL Specific Maintenance (M) Symbol and Proviso

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT:

2. NO. INSTALLED (insert aircraft make and model) 3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

28. FUEL Sequence No. Item 1 3 4 Change Bar 28-21-25 XBP Crossfeed Valve 2 (M) One or more may be inoperative in dosed position provided:

a) All Booster Pumps are operative,

b) Affected XBP Crossfeed Valve is secured in closed position, and

c) Repairs are made within 3 consecutive calendar-days.

Figure 8-3(c). Example 2 MEL Specific Maintenance (M) Procedure 28-21-25:

Maintenance (M) Procedure CROSSFEED VALVE IN CLOSED POSITION:

1. Open the door 170AB.

2. Check that the inoperative XBP crossfeed valve (400QS/410QS) is in close position ("C").

NOTE: If not, set the valve to close ("C") using the lever.

3. Disconnect the electrical connector.

4. Close the door 170AB.

NOTE: Place inoperative placard near MDU.

Figure 8-4(a). Example 3 MMEL General Operation (O) Symbol and Proviso

TABLE KEY

1. REPAIR CATEGORY AIRCRAFT:

2. NO. INSTALLED (insert aircraft make and model)

3. NO. REQUIRED FOR DISPATCH

4. REMARKS OR EXCEPTIONS

23. COMMUNICATIONS Sequence No. Item 1 2 4 Change Bar -43-01 Flight Deck to Ground B (O) May be inoperative provided Interphone System alternative procedures are established and used.

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8-12 Figure 8-4(b). Example 3 MEL Specific Operations (O) Symbol and Proviso F igure 8-4(c). Example 3 MEL Specific Operations (O) Procedure 23-43-01:

Operations (O) Procedure May be inoperative provided:

1. Verify to ground crew personnel before main cabin door is closed that ECAM message NW STRG DISC is displayed.

2. Use company hand signals as required. Refer to Ramp Operations Manual, Chapter 1, for a complete list of company hand signals.

Note 1: The Ramp Operations Manual in the above example is an FAA-approved or FAA-accepted manual.

Note 2: The proviso in the above MEL example was changed from the MMEL proviso because alternative procedures “are established.”

9-1 CHAPTER 9. MEL REVISIONS

9.1 General. MEL revisions may be initiated by either the FAA or the operator. The revision to an operator’s MEL must comply with the conditions and limitations of the operator’s MEL LOA.

• MEL revisions for an MMEL used as an MEL under LOA D095 consist of using the latest mandatory MMEL revision and revising the procedures document, as required.

• MEL revisions for an operator-developed MEL under LOA D195 consist of revising the operator-developed MEL.

9.1.1 O perator Responsibility to Obtain MMEL Revisions. It is the responsibility of an operator to obtain the latest revisions to their MMEL, applicable STC Relief Approval Letter, and applicable MMEL PLs. Operators may download these documents from the “MMELs and AED Guidance Documents” section in DRS at https://drs.faa.gov.

Note: Operators may keep informed of MMEL revisions by subscribing to receive automatic email notifications for their aircraft. To subscribe, visit https://service.govdelivery.com/accounts/USFAAMMEL/subscriber/new.

9.1.2 Submission of Revised Operator-Developed MEL to the FAA for Approval. Operators must submit revisions to an operator-developed MEL under LOA D195 to the responsible Flight Standards office for approval. An electronic copy is preferred. The revised MEL may not be used prior to FAA approval. Holders of LOA D095 are not required to submit a revised procedures document to the FAA.

Note: M EL revisions solely for the purpose of documenting the inappli cability of a mandatory MMEL revision, or to incorporate revised MMEL PL-25 or PL-36 content, are not required to be submitted to the FAA. If the control page is revised, the operator will retain the previous FAA-signed MEL control page(s) or LEP within the MEL.

9.2 F AA- Initiated MEL Revisions. An FAA-initiated MEL revision may be due to an MMEL revision, MMEL PL revision, AD, or deficiencies discovered in the MEL.

9.2.1 MME L Revision. There are two types of MMEL revisions: nonmandatory/interim, and mandatory/standard.

9.2.1.1 N onmandatory/Interim MMEL Revision. A nonmandatory/interim MMEL revision means that revision to an operator’s MEL is optional and not required. If the relief granted by the nonmandatory/interim MMEL revision is applicable to an operator’s aircraft operations, then it is advisable the operator revise their MEL to incorporate the MMEL revision. If the nonmandatory/interim MMEL revision is not applicable to an operator’s aircraft operations, they may disregard the MMEL revision altogether. For example, a nonmandatory/interim MMEL revision is issued to provide for optional equipment such as logo lights, which are not installed on all aircraft

9-2 of a particular type. Operators operating an aircraft without logo lights may simply ignore the MMEL revision. Operators operating an aircraft with logo lights may choose to incorporate the MMEL revision if the operator would like MEL relief for inoperative logo lights.

1. A nonmandatory/interim MMEL revision is identified by the current standard revision number plus a lowercase letter. For example, a nonmandatory/interim revision following revision 5 will be identified as revision 5a. There may be subsequent interim revisions to the same standard revision. These subsequent revisions carry the next lowercase letter (e.g., 5b, 5c, or 5d).

2. The operator’s MEL revision number does not have to match the MMEL revision number. Operators may use their own revision numbering system.

3. If an MMEL revision results in a change to the system number, sequence item number, repair interval, or proviso, the operator does not need to modify or close an open MEL item and reinitiate it. Instead, the item may continue to be tracked under its original deferral until the item is repaired and the deferral cleared.

9.2.1.2 Mandatory/Standard MMEL Revision. A mandatory/standard MMEL revision means that revision to an operator’s MEL is required. A mandatory/standard MMEL revision includes changes applicable to all operators using an MEL for a specific aircraft type.

9.2.1.2.1 A mandatory/standard MMEL revision is identified by the next successive change to the basic MMEL revision number. For example, the next mandatory/standard revision following nonmandatory/interim revision 6a, 6b, or 6c is revision 7. The next mandatory/standard revision following revision 7 is revision 8.

9.2.1.2.2 The operator is required to review the mandatory/standard MMEL revision to determine if the more restrictive revised content is applicable to their aircraft and operation. If so, the operator must revise their MEL as follows:

1. For an MMEL used as an MEL under LOA D095: Within 90 calendar days of the date of the MMEL revision, the operator must revise their procedures document. The revision must address (M) and (O) or “as required by 14 CFR” procedures, as applicable. If no changes are determined to be applicable to the aircraft or operator, then the operator is not required to update the procedures document. However, the FAA recommends the operator make a statement in the procedures document that the mandatory revision has been reviewed and determined not to apply. Regardless, the procedures document must contain the MMEL revision number on which the MEL is based.

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2. For an operator-developed MEL under LOA D195:

a. If the revised content of the mandatory/standard MMEL revision is applicable, the operator must revise their MEL and incorporate applicable changes and submit it to the responsible Flight Standards office for approval within 90 calendar days of the date of the MMEL revision. The revised MEL may not be used prior to FAA approval.

b. If the revised content of the mandatory/standard MMEL revision is not applicable, within 90 calendar days of the revision, the operator must document its inapplicability. Revise the MEL control page(s) or LEP to indicate the MEL is in compliance with the required MMEL revision. The operator will retain the previous FAA-signed MEL control page(s) or LEP within the MEL.

c. Irrespective of applicability, the operator-developed MEL must contain the MMEL revision number on which the MEL is based.

9.2.1.2.3 If an MMEL revision results in a more restrictive proviso, the operator does not have to close and reinitiate an existing open MEL item affected by the revision. Existing MEL items may remain open in accordance with the original proviso under which the item was initially deferred until such time as the item is repaired or replaced and the MEL item is closed.

9.2.1.2.4 If an MMEL revision results in a change to the system number or sequence item number, the operator does not need to modify or close an open MEL item and reinitiate it under its new number. Instead, the item may continue to be tracked under its original item number until the item is repaired and the deferral cleared.

9.2.2 Revisions as a Result of an MMEL PL with a GC Designation. An operator may revise their MEL based on relief available in an MMEL PL with a current GC designation. An operator is not required to include GC designation relief in their MEL. See paragraph 2.6 above for detailed information on MMEL PLs with a GC designation.

9.2.3 R evisions Initiated by the Responsible Flight Standards Office. The responsible Flight Standards office may initiate an MEL revision for reasons such as the issuance of an AD, upon discovery of deficiencies in the operator’s MEL (including (M) and (O) procedures), or upon discovery that the operator has modified their aircraft.

9.2.3.1 The responsible Flight Standards office will inform the operator of the need to revise their MEL in writing and provide the reasons why the revision must be accomplished.

9.2.3.2 The responsible Flight Standards office will allow the operator 90 calendar days to complete the revision process. An operator may request an extension for developing an MEL revision. If the responsible Flight Standards office determines the safety of flight could be affected (e.g., AD), they may specify a shorter period of time.

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9.2.4 M MEL PL-25 (Definitions) or MMEL PL-36 (Preamble) Revision. A revision to MMEL PL-25 does not necessitate immediate revision of the operator’s MEL. However, the current revision to MMEL PL-25 should be incorporated in the next FAA or operator-initiated MEL revision. A revision to MMEL PL-36 would necessitate a revision to a procedures document under LOA D095 or an operator-developed MEL under LOA D195. MEL revisions solely for the purpose of incorporating revised MMEL PL-25 or PL-36 content need not be submitted to the FAA.

9.3 O perator- Initiated MEL Revisions. An operator may revise their MEL for a number of reasons. An operator-initiated MEL revision will not be, in any way, less restrictive than the MMEL.

9.3.1 M ajor Aircraft Modifications . An operator may elect to initiate an MEL revision due to major aircraft modifications, such as an STC, a major alteration (refer to FAA Form 337), or a modification to the TC.

9.3.2 Installation of Additional Items. An operator may initiate a change based on the installation of additional items. An operator may add an item to their MEL only if it is listed in:

1. Th e MMEL,

2. An applicable STC Relief Approval Letter, or

3. An applicable MMEL PL with a current CG designation.

Note: See Chapter 10 for information on how to obtain relief for an item not listed in items 1–3 above.

9.3.3 Changes in Operational Complexity. An operator may need to revise their MEL due to changes in their operational complexity, such as adding a type of operation

(e.g., Reduced Vertical Separation Minimum (RVSM), CAT II/III landing minimums, etc.). An operator may need to revise their MEL for the purpose of adding or revising (M) and (O) procedures based on operational complexity.

9.4 V ertical Bar (Change Bar). A vertical bar denotes a change in content. For MMELs, a vertical bar is placed in the right margin; location in the operator’s MEL is a matter of choice. A change due to copy editing (e.g., punctuation, spelling, or grammatical structure) does not need a vertical bar in an MMEL or MEL. All vertical bars applicable to the previous revision of the MMEL are removed at the next revision. It is permissible to issue an MMEL or MEL revision without vertical bars when the revision affects most or all relief items. In which case, in lieu of vertical bars, a note is added to the “Highlights of Change” page instructing operators to consider all content revised and indicating that vertical bars are not used. Other alternate means of compliance may be used if approved by the Administrator.

10-1 CHAPTER 10. MEL RELIEF FOR ITEMS INSTALLED AFTER TYPE

CERTIFICATION

10.1 General. The aircraft design approval holder (DAH) determines the configuration of the aircraft, the items installed, and the official parts listed during the initial aircraft type certification process conducted at the time of manufacture. Subsequent installation or removal of items may be accomplished through an STC, an Engineering Order (EO), a field approval, or other FAA-approved methods, as appropriate.

10.2 Operator NEF Items or Administrative Control Items (ACI). Items listed on an operator’s NEF program are excluded from the requirements in this chapter. With respect to ACIs, relief is listed elsewhere in the operator’s manual system, and they are also excluded from the guidance in this chapter.

10.3 MEL Relief for Items Installed via a Change to a Type Design. Operators may add relief for items resulting from changes to type design to their MELs, and may exercise MEL relief for such items, when that relief has been evaluated by the operator’s responsible Flight Standards office or the AED, and the operator’s MEL is approved by the POI. Requested relief must meet or exceed the original level of safety.

10.3.1 An operator may add relief for an STC or for another design change to an MEL through the normal MEL revision process, when:

1. The change in type design is specifically listed in the applicable aircraft’s MMEL

(i.e., STC XXX, etc.);

2. An approval letter from the AED is in DRS at https://drs.faa.gov (or a paper copy) for the specific change in type design; or

3. A n MMEL PL with a current GC designation contains relief for the item(s).

Note: Upon evaluation and approval of a design change, the AED will submit an approval letter directly to DRS. Operators may download STC Relief Approval Letters from the “MMELs and AED Guidance Documents” section in DRS at https://drs.faa.gov. Paper copies of the AED approval letter are also acceptable in lieu of the DRS database. The approval letter will contain the allowed relief, including conditions and provisos, along with remarks or exceptions. Approval letters will be dated and have revision numbers. Operators may amend their MEL(s) with the relief for the STC(s) in accordance with the AED approval letter.

MMEL PL-109 provides additional information on how to obtain MMEL/MEL relief for items associated with STCs.

10.3.2 I f the operator is unable to obtain relief as described above, they should submit a request to the responsible Flight Standards office and include enough supporting information to allow for a thorough evaluation of the risk associated with operating the aircraft with the item inoperative. For a detailed list of the information required, operators should contact their responsible Flight Standards office. Once a request is received, PIs will first determine if relief for the unevaluated item requires AED evaluation. If required, PIs will coordinate with the applicable AED office before approving MEL relief. Requested or

10-2 pending MEL relief for items associated with recent or imminent changes to the type design may not be added to an operator’s MEL, or exercised by the operator, until the relief has been approved by the POI.

11-1 CHAPTER 11. NONESSENTIAL EQUIPMENT AND FURNISHINGS (NEF)

PROGRAM

11.1 Definition. NEF are those items installed on the aircraft as part of the original TC, STC, EO, or other form of alteration that have no effect on the safe operation of flight and would not be required by the applicable certification or operational rules. These are items that, if inoperative, damaged, or missing, have no effect on the aircraft’s ability to be operated safely under all operational conditions. NEF items are not items already identified in the MEL or CDL of the aircraft. NEF do not include items that are functionally required to meet the certification rule or for compliance with any operational rule.

11.2 Background. The NEF program originated from an earlier form called Passenger Convenience Items (PCI) program. PCIs were items related to passenger convenience, comfort, or entertainment located in the passenger compartment, galley, and lavatory areas. The PCI program did not allow for nonessential items that were missing or inoperative located elsewhere in the aircraft. Due to the limited nature of PCI, the FAA replaced the PCI title in ATA/JASC code 25 in all MMELs with the acronym NEF. An NEF program allows operators to use the deferral authority granted by virtue of their MEL LOA to provide deferral relief for nonessential items located throughout the aircraft.

11.3 The NEF Program Under § 91.213(a). An operator’s MEL approved under the provisions of § 91.213(a) may include an NEF program that allows relief for nonessential items. An NEF program is supplemental to the MEL approval under § 91.213(a); it is not a standalone program. An NEF program is developed by an operator to meet their individual needs. An operator’s NEF program is a supplement to the operator’s MEL.

The NEF program encompasses: (1) an (optional) list of NEF items located in the operator’s MEL, (2) a process for evaluating an item in accordance with NEF requirements, and (3) policies and procedures for repair and/or replacement. Operators may choose to use the recommended method of evaluation shown in Figure 11-2, NEF Item Selection Criteria Elements Flowchart, or they may use an alternative method that is acceptable to the FAA. If an operator’s NEF program is insufficient or systemically problematic, the FAA may cancel, rescind, or revoke the operator’s MEL LOA.

11.3.1 NEF items are:

• Items installed on the aircraft that have no effect on the safe operation of the aircraft.

• Items installed as part of the original TC, STC, EO, or other form of alteration, not required by certification or operational rules.

• Items that if inoperative, damaged, or missing, have no effect on the safe operation of the aircraft under all operational conditions.