To: Manager, Aircraft Evaluation Division
All Aircraft Evaluation Group Managers
All General Aviation Safety Assurance Offices (AFG)
From: Manager, Air Transportation Division (AFS-200)
SUBJECT: 14 CFR Part 91 MEL Approval and Preamble
MMEL CODE: 00 (GENERAL)
REFERENCE: PL-36, Revision 2, dated August 15, 1997
PL-36, Revision 1, dated July 5, 1990
The purpose of this Policy Letter (PL) is to standardize the Preamble so that all Title 14 of the Code of Federal Regulations (14 CFR) part 91 minimum equipment lists (MEL) use the same Preamble and also to provide reference to guidance for the approval of MELs for part 91 operations issued under the provisions of part 91, § 91.213.
• Describes the two methods the Federal Aviation Administration (FAA) provides for issuing MEL approvals for part 91 operations.
• Preamble has been revised to incorporate wording for both methods of MEL approval for part 91 operations.
• Detailed policy has been removed and replaced with reference to FAA guidance in the Flight Standards Information Management System (FSIMS).
• An operator may request additions or changes to the MMEL by notifying its responsible Flight Standards office. If the additions or changes will be incorporated in the next MMEL revision, the operator will ensure its MEL aligns with the revised MMEL.
• Clarified the operator requirements to develop maintenance (M) and operations (O) procedures for the items listed in the MEL, as appropriate conditions and limitations for the use of the MEL.
• Removed “and deferred” from the following language in the Preamble: “Inoperative equipment in all cases must be repaired, replaced, removed, or inspected by qualified maintenance personnel at the next required inspection per § 91.405(c).” This language was removed to align with the language in § 91.405(c).
• Added “D” to the following language in the Preamble: “The repair category intervals indicated by the letters A, B, C, and D in column 1 of the MMEL are NOT applicable to this MEL, but operators must comply with any provisos, conditions, limitations, or restrictions defining a repair interval (flights, flight legs, cycles, hours, days, etc.).”
NOTE: The following bulleted information provided below under Revision 2 has been superseded by Revision 3 and is listed here for historical information only and should not be considered current policy.
• Reformats Policy Letter 36 with no change to policy.
• To alleviate delays involved with the approval process for part 91 MELs, and to provide relief for field inspectors with respect to time and work expenditure, the following procedural changes were instituted in the previous issues of this Policy Letter. The key changes are as follows:
o Inspectors are no longer required to review the operator’s M and O procedures prior to issuing the letter of authorization (LOA).
o Operators are required to countersign the LOA prior to its issuance.
o LOAs are to be issued without an expiration date.
o When operators relocate, the LOA is not required to be reissued.
• Field offices will issue part 91 MEL applicants the MMEL for their specific aircraft type with the accompanying new part 91 Preamble and LOA. This new preamble will also be available in the Flight Standards Information Management System (FSIMS) in the near future. The operator is authorized to use the MMEL in place of an MEL when the new Preamble and other listed requirements are complied with. The LOA and the Preamble clarify that the burden of compliance is on the operator. It is not necessary to review the operator’s M and O procedures prior to issuance of the letter.
The FAA provides two methods for issuing MEL approvals for part 91 operations:
• LOA D095 This method is used by the FAA to approve/authorize the operator to use the MMEL and the operator’s procedures document as an approved MEL.
• LOA D195 This method is used by the FAA to approve/authorize the operator to use an operator‑developed MEL as an approved MEL.
The attached Preamble must be included in all part 91 MELs.
PART 91 PREAMBLE
FEDERAL AVIATION ADMINISTRATION
MINIMUM EQUIPMENT LIST (AIRCRAFT TYPE)
This Preamble is applicable to, and will be included in, a part 91 approved minimum equipment list (MEL). An operator may be authorized to use the Master Minimum Equipment List (MMEL) along with a separate procedures document as its FAA-approved MEL under Letter of Authorization (LOA) D095. This Preamble must be incorporated in the operator’s procedures document, which must be carried in the aircraft along with the MMEL and LOA D095. An operator-developed MEL, rather than the MMEL, may be authorized for use as the operator’s FAA-approved MEL under LOA D195. This Preamble must be incorporated within the operator‑developed MEL. Both approved MELs under LOA D095 and LOA D195 are issued under the provisions of Title 14 of the Code of Federal Regulations (14 CFR) part 91, § 91.213(a)(2). This Preamble is not applicable to MELs issued under the provisions of 14 CFR parts 91 subpart K (part 91K), 121, 125, 129, and 135. Except as provided in § 91.213, or under the provisions of an approved MEL, all equipment installed on an aircraft in compliance with the airworthiness standards or operating rules must be operative. Experience has shown that, with the various levels of redundancy designed into modern aircraft, operation of every system or component installed may not be necessary when the remaining equipment can provide an acceptable level of safety.
An MMEL is developed by the Original Equipment Manufacturer (OEM), with participation by the aviation industry and the FAA, to improve aircraft utilization and, thereby, provide more convenient and economic air transportation for the public. The FAA-approved MMEL is the basis for the individual operator’s MEL for its particular operation and aircraft. The MMEL includes those items of equipment related to airworthiness and operating regulations and other items of equipment, which may be inoperative, and yet maintain an acceptable level of safety by appropriate conditions and limitations; it does not contain obviously required items such as wings, flaps, and rudders. The Supplemental Type Certificate (STC) MMEL/MEL relief process is described in MMEL Policy Letter (PL) 109, Supplemental Type Certificate (STC) MMEL/MEL Relief Process. Other than relief for items installed under an STC, an operator may request additions or changes to the MMEL by notifying its responsible Flight Standards office, which will make a request of the Flight Operations Evaluation Board (FOEB) to convene and consider the requested additions or changes to the MMEL. If the FOEB determines the additions or changes will be incorporated in the next MMEL revision, the responsible Flight Standards office may approve the operator to incorporate the additions or changes into its MEL until the next MMEL revision, at which time the operator will ensure its MEL aligns with the revised MMEL. An individual operator’s MEL may differ in format from the MMEL, but cannot be less restrictive than the MMEL or FOEB approval. The individual operator’s MEL, when approved and authorized, permits operation of the aircraft with inoperative equipment. Equipment not required by the operation being conducted and equipment in excess of 14 CFR requirements are included in the MEL with appropriate conditions and limitations. Except where authorized by law or another provision in 14 CFR, operators are not permitted to conduct operations with any inoperative or missing equipment that is not included in the MEL (or other FAA-approved program (e.g., nonessential equipment and furnishings (NEF))). The operator must develop maintenance (M) and operations (O) procedures for the items listed in the MEL, as appropriate conditions and limitations for the use of the MEL. Procedures must comply with all 14 CFR requirements and must not deviate from the aircraft flight manual limitations, emergency procedures, or with Airworthiness Directives (AD), all of which take precedence over the MEL and those procedures. When a manufacturer recommended procedure exists, the operator may use it as published, or develop equivalent procedures for its MEL.
Suitable conditions and limitations in the form of placards, maintenance procedures, crew operating procedures, and other restrictions, as necessary, are required to be accomplished by the operator to ensure that an acceptable level of safety is maintained. Those procedures should be developed from guidance provided in the manufacturer’s aircraft flight and/or maintenance manuals, manufacturer’s recommendations, engineering specifications, and other appropriate sources. Procedures must not be contrary to any 14 CFR requirement. Wherever the statement “as required by 14 CFR [or FAR]” appears in the MMEL, the operator must either list the specific 14 CFR by part and section and carry the 14 CFR on board the aircraft or specify the requirements and/or limitations to conduct the flight in accordance with the appropriate 14 CFR.
The MEL is intended to permit operations with inoperative items of equipment for the minimum period of time necessary until repairs can be accomplished. It is important that repairs be accomplished at the earliest opportunity in order to return the aircraft to its design level of safety and reliability.
Inoperative equipment in all cases must be repaired, replaced, removed, or inspected by qualified maintenance personnel at the next required inspection per § 91.405(c). The repair category intervals indicated by the letters A, B, C, and D in column 1 of the MMEL are NOT applicable to this MEL, but operators must comply with any provisos, conditions, limitations, or restrictions defining a repair interval (flights, flight legs, cycles, hours, days, etc.). The MEL provides for release of the aircraft for flight with inoperative equipment. When an item of equipment is discovered to be inoperative, it is reported by making an entry in the aircraft maintenance records. The item is then either repaired or deferred per the MEL or other approved means acceptable to the Administrator prior to further operation. In addition to the specific MEL conditions and limitations, determination by the operator that the aircraft is in condition for safe operations under anticipated flight conditions must be made for all items of inoperative equipment. When these requirements are met, the aircraft may be considered Airworthy and returned to service. Operators are responsible for exercising the necessary operational control to ensure that an acceptable level of safety is maintained. When operating with multiple inoperative items, the interrelationship between those items, and the effect on aircraft operation and crew workload, must be considered. Operators are expected to establish a controlled and sound repair program, including the parts, personnel, facilities, procedures, and schedules to ensure timely repair.
WHEN USING THE MEL, COMPLIANCE WITH THE STATED INTENT OF THE PREAMBLE, DEFINITIONS, CONDITIONS, AND LIMITATIONS SPECIFIED IN THE MEL IS REQUIRED.
ORIGINAL SIGNED by
/s/ Thomas F. Malone
Manager, Air Transportation Division