U.S . Department of Transportation Federal Aviation Administration Advisory Circular Subject: Minimum Equipment Requirements for General Aviation Operations Under 14 CFR Part 91, § 91.213 Date: 10/16/23 AC No: AC 91-67A Initiated by: AFS-800 Change:
This advisory circular (AC) describes acceptable methods for the operation of aircraft with certain inoperative instruments and equipment items, which are not essential for safe operations under Title 14 of the Code of Federal Regulations (14 CFR) part 91, 133, or 137 (including part 91 operations conducted by parts 141 and 142 certificate holders (CH )).
The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies.
This AC describes an acceptable means, but not the only means, to operate an aircraft with certain inoperative instruments and equipment items that are not essential. While using the means described in this AC is not mandatory, an operator that voluntarily elects to use the means described in this AC must follow, in all respects, the terms, conditions, and processes provided in the AC.
Robe rt M. Ruiz Acting Deputy Executive Director, Flight Standards Service
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CONTENTS Paragraph Page
Chapter 1. Introduction1-1
1.1 Purpose of This Advisory Circular (AC)1-1
1.2 Audience1-1
1.3 Where You Can Find This AC1-1
1.4 What This AC Cancels1-1
1.5 Related 14 CFR Sections1-2
1.6 Related Documents (current editions)1-2
1.7 Background1-2
1.8 Definitions and Terminology1-3
1.9 AC Feedback Form1-8
Chapter 2. Mas ter Minimum Equipment List (MMEL)2-1
2.1 General2-1
2.2 ATA/JASC Coded System Section Components2-1
2.3 Obtaining a Current MMEL2-3
2.4 Aircraft for Which No MMEL Has Been Developed2-3
2.5 MMEL PLs2-3
2.6 MMEL PL Global Change (GC) Designation2-4
Chapter 3. Minimum Equipment List (MEL)3-1
3.1 General3-1
3.2 Three Methods for Operating an Aircraft with Inoperative Equipment3-2
3.3 MEL LOA3-2
3.4 Aircraft Operated Under Multiple 14 CFR Parts3-3
3.5 F
leet MEL3-3
Chapter 4. Conducting Operations Without an MEL4-1
4.1 Operating Without an MEL4-1
4.2 Removal, Deactivation, and Placarding4-1
4.3 Continued Operation with Inoperative Items4-2
4.4 Safety Risk Analysis of Proposed Operation with Inoperative Equipment Items4-3
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Chapter 5. Conducting Operations With an MEL5-1
5.1 Operating with an MEL5-1
5.2 Documentation of Deferred Items5-2
5.3 Placarding5-2
5.4 Performing (M) and (O) Procedures5-2
5.5 Repair of Deferred Instruments or Equipment Items5-3
Chapter 6. Application for MEL Letter of Authorization (LOA)6-1
6.1 Application for an MEL Approval Issued Under LOA D0956-1
6.2 Application for an MEL Approval Issued Under LOA D1956-1
6.3 Request for Approval of an MEL That Does Not Conform to This AC6-1
6.4 Oversight6-1
Chapter 7. Content of a Procedures Document7-1
7.1 MEL Approval Under LOA D0957-1
7.2 Procedures Document Content7-1
7.3 Procedures Document Required Sections7-1
7.4 Procedures Document Optional Sections7-3
7.5 Example “As Required by 14 CFR” and (M) and (O) Procedures7-3
Chapter 8. Content of an Operator-Developed MEL8-1
8.1 MEL Approval Under LOA D1958-1
8.2 MEL Content8-1
8.3 MEL Required Sections8-1
8.4 MEL Optional Sections8-2
8.5
ATA/JASC Coded System Sections8-2
8.6 Example Proviso, “As Required by 14 CFR,” and (M) and (O) Procedures8-7
Chapter 9. MEL Revisions9-1
9.1 General9-1
9.2 FAA-Initiated MEL Revisions9-1
9.3 Operator-Initiated MEL Revisions9-4
9.4 Vertical Bar (Change Bar)9-4
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Chapter 10. MEL Relief for Items Installed After Type Certification10-1
10.1 General10-1
10.2 Operator NEF Items or Administrative Control Items (ACI)10-1
10.3 MEL Relief for Items Installed via a Change to a Type Design10-1
Chapter 11. Nonessential Equipement and Furnishings (NEF) Program11-1
11.1 Definition11-1
11.2 Background11-1
11.3 The NEF Program Under § 91.213(a)11-1
11.4 Deferral Authority11-2
11.5 NEF Program Development11-3
11.6 Required NEF Program Contents11-3
11.7 NEF Program Approval11-4
11.8 Criteria for Selection of NEF Items11-4
11.9 NEF Deferral Process11-5
Chapter 12. Configuration Deviation List (CDL)12-1
12.1 Purpose of the CDL12-1
12.2 Development12-1
12.3 CDL Versus MEL12-1
12.4 CDL Management Program12-2
List of Figures
Figure 2-1. Example MMEL ATA/JASC Coded System Section Page2-2
Figure 2- 2. Sample Global Change Header Box2-4
Figure 4-1. PI C Decision Sequence4-4
Figure 5-1. PI C Decision Sequence5-4
Figure 6-1. Sam ple LOA D095 Request Letter6-2
Figure 6-2. Sam ple LOA D195 Request Letter for an Operator-Developed MEL That Conforms
to the Content Described in AC 91-676-3
Figure 6-3. Sa mple LOA D195 Request Letter for an Operator-Developed MEL That Does Not
Conform to the Content Described in AC 91-676-4
Figure 7-1(a). Example MMEL “As Required by 14 CFR” Statement7-3
Figure 7-1(b). Example Procedures Document “As Required by 14 CFR” Regulatory
Reference or Requirement/Limitation7-4
v Figure 7-2(a). Example 1 MMEL Maintenance (M) and Operations (O) Symbols and
Provisos7-4
Figure 7-2(b). Example 1 Procedures Document Maintenance (M) and Operations (O)
Procedures7-4
Figure 7-3 (a). Example 2 MMEL Maintenance (M) Symbol and Proviso7-5
Figure 7-3(b). Example 2 Procedures Document Maintenance (M) Procedure7-5
Figure 8-1(a). Example MMEL General “As Required by 14 CFR” Statement8-8
Figure 8-1(b). E xample MEL Specific “As Required by 14 CFR” Regulatory Reference8-8
Figure 8-1(c). E xample MEL Specific “As Required by 14 CFR” Requirement/Limitation8-9
Figure 8-2 (a). Example 1 MMEL General Maintenance (M) and Operations (O) Symbols
and Provisos8-9
Figure 8-2(b). Example 1 MEL Specific Maintenance (M) and Operations (O) Symbols
and Provisos8-10
Figure 8-2(c). Example 1 MEL Specific Maintenance (M) and Operations (O) Procedures ... 8-10
Figure 8-3(a). Example 2 MMEL General Maintenance (M) Symbol and Proviso8-10
Figure 8-3(b). Example 2 MEL Specific Maintenance (M) Symbol and Proviso8-11
Figure 8-3(c). Example 2 MEL Specific Maintenance (M) Procedure8-11
Figure 8-4(a). Example 3 MMEL General Operation (O) Symbol and Proviso8-11
Figure 8-4(b). Example 3 MEL Specific Operations (O) Symbol and Proviso8-12
Figure 8-4(c). Example 3 MEL Specific Operations (O) Procedure8-12
Figure 11-1. Re quired NEF MEL Proviso for an Operator’s NEF Program11-4
Figure 11-2. NE F Item Selection Criteria Elements Flowchart11-7
1-1 CHAPTER 1. INTRODUCTION
1.1 Purpose of This Advisory Circular (AC). This AC describes acceptable ways in which an aircraft can be operated under Title 14 of the Code of Federal Regulations (14 CFR) part 91, 133, or 137 (including part 91 operations conducted by parts 141 and 142 certificate holders (CH)) with certain inoperative instruments and equipment items that are not essential for safe operations, in accordance with part 91, § 91.213. The methods described are not the only means to comply with § 91.213. The Federal Aviation Administration (FAA) will consider other means of compliance an operator may present.
1.1.1 Effects of Guidance. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies. While using the means of compliance described in this AC is not mandatory, an operator that voluntarily elects to use the means of compliance described in this AC must follow, in all respects, the terms, conditions, and processes described in the AC. The use of terms such as “shall” and “must” throughout the AC do not impose any regulatory requirement.
1.2 Audience. T his AC applies only to aircraft operated under parts 91, 133, and 137 (including part 91 operations conducted by parts 141 and 142 CHs) with certain inoperative instruments and equipment.
Note: Unless otherwise stated, the term “operator,” used throughout this AC, applies to part 91 operators, parts 133 and 137 CHs, and part 141 pilot schools or provisional pilot schools. This AC uses the singular term “operator” for simplicity.
1.2.1 Applicability. This AC does not apply to part 91 subpart K (part 91K) program managers or CHs under 14 CFR part 121, 125 (including part 125 Letter of Deviation Authority (LODA) holders), or 135. These operators are required to comply with their approved minimum equipment list (MEL), even when the operation is conducted under part 91.
Refer to § 91.213(c).
1.2.2 Foreign Air Carriers and Foreign Operators of U.S. Registered Aircraft Engaged in Common Carriage (14 CFR Part 129). Foreign air carriers and foreign operators of U.S. registered aircraft engaged in common carriage should refer to AC 129-4, Maintenance Programs for U.S. Registered Aircraft Operated Under 14 CFR Part 129, for information regarding their MELs.
1.3 Where You Can Find This AC. Y ou can find this AC on the FAA’s website at https://www.faa.gov/regulations_policies/advisory_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov.
1.4 What This AC Cancels. AC 91-67, Minimum Equipment Requirements for General Aviation Operations Under FAR Part 91, dated June 18, 1991, was canceled on November 3, 2017.
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1.5 Related 14 CFR Sections. All regulatory references in this AC are found in 14 CFR unless otherwise indicated. The following 14 CFR sections are related to this AC. You can download the full text of these regulations at the U.S. Government Publishing Office (GPO) Electronic Code of Federal Regulations (e-CFR) website at https://ecfr.gov. You can order a paper copy by sending a request to the U.S. Superintendent of Documents, U.S. Government Publishing Office; by calling the telephone number 202-512-1800; or by sending a request by facsimile at 202-512-2104.
• P art 21, §§ 21.19, 21.197, and 21.199.
• Part 43, §§ 43.3, 43.7, 43.9, 43.11, and 43.13.
• Part 91, §§ 91.7, 91.205, 91.213, 91.405, 91.417, and 91.501.
1.6 Related Documents (current editions).
• Master Minimum Equipment List (MMEL) Policy Letter (PL)-25, MMEL/M EL Definitions.
• M MEL PL -36, 14 CFR Part 91 MEL Approval and Preamble.
• AC 43-9, Maintenance Records.
• AC 43-12, Preventive Maintenance.
• AC 91-70, Oceanic and Remote Continental Airspace Operations.
1.7 Background. The airworthiness certification of an aircraft is conditioned on the aircraft conforming to its type certificate (TC) and being in a condition for safe operation. While items installed in an aircraft must be operative for the aircraft to conform to its TC, an approved MEL allows an operator to operate the aircraft with certain items inoperative.
An approved MEL, as authorized by a Letter of Authorization (LOA) under § 91.213(a), constitutes an approved change to the type design without requiring recertification.
1.7.1 A irworthiness. Under § 91.7, an operator cannot operate an aircraft unless it is in an airworthy condition. As noted above, to be airworthy, the aircraft must conform to its TC and be in a condition for safe operation. Except as provided in § 91.213(d) and (e), an inoperative item present on the aircraft would result in a violation of § 91.7, unless the inoperative item or equipment is listed on the operator’s approved MEL. As such, compliance with all applicable criteria of an MEL is necessary when taking advantage of the relief an MEL provides; in the absence of such compliance, the FAA would not consider the aircraft airworthy.
1.7.2 Acceptable Level of Safety (ALoS). The FAA developed the concept of the MEL after recognizing that under certain circumstances, a flight or series of flights might occur safely with certain inoperable instruments and equipment. In certain specific situations, an ALoS can be met because not all of an aircraft’s installed instruments and equipment are necessary for every type of operation. For example, a flight that is not being conducted in icing conditions would not require operable airframe deicing or anti-icing equipment. Similarly, an aircraft that will not operate at night may receive relief from the
1-3 requirement to have an operable landing light. In other words, the MEL requirements and related processes are independent from an aircraft’s operating requirements and an MEL cannot authorize a deviation from operating rules.
1.7.3 Requirement for Items to be Operative. All items related to the airworthiness of the aircraft that are not included in an approved MEL are required to be operative in accordance with the aircraft’s TC. An MEL does not include obviously required items, such as wings, rudders, flaps, engines, landing gear, etc. Except as provided in § 91.213(d) and (e), and described in Chapter 4, an aircraft is not airworthy when any item that is not included in the MEL is inoperative.
1.7.4 Repair Inoperative Items at Earliest Opportunity. T he 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 to return the aircraft to its design level of safety and reliability.
1.7.5 MEL Development. The M EL is developed from an MMEL for the aircraft type. The operator uses the MMEL as the baseline to develop the MEL and the operational and maintenance procedures and lists the items installed in the operator’s aircraft. The MEL is developed by the operator for their particular type of operation (i.e., instrument flight rules (IFR), visual flight rules (VFR), Category (CAT) II, over water, etc.). The MEL is approved by the responsible Flight Standards office.
1.8 Definitions and Terminology. For additional MMEL and MEL definitions, refer to M MEL PL-25.
1.8.1 Airworthiness Directive (AD). ADs are legally enforceable regulations issued by the FAA in accordance with 14 CFR part 39 to correct an unsafe condition in a product.
Part 39 defines a product as an aircraft, engine, propeller, or appliance.
1.8.2 Air Transport Association of America (ATA)/Joint Aircraft System/Component (JASC) Coded System Section Components. MMEL system sections are organized by aircraft system according to the ATA or JASC coded numbering system. MMEL system numbers use the ATA/JASC codes that are standardized for each aircraft system. The ATA/JASC numbering system provides an industrywide standard for numbering aircraft systems and is relevant for all aircraft. ATA changed its name to Airlines for America (A4A) in 2011;
however, the acronym “ATA” is still used for coded aircraft systems. The acronyms “ATA” and “A4A” are considered interchangeable. The alternate format for aircraft system coding is the JASC codes, which are a modified version of the ATA codes.
1.8.3 Aircraft Evaluation Division (AED). The inspectors in the AED serve as technical subject matter experts for operational and engineering activities of the FAA’s Flight Standards Service (FS). These inspectors coordinate and assist with aircraft certification and continued airworthiness programs and serve as a liaison with the responsible Aircraft Certification Service office during the initial certification of an aircraft and throughout the service life of the aircraft.
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1.8.4 C onfiguration Deviation List (CDL). A CDL is a list of externally exposed aircraft parts that may be missing for flight. A CDL allows continued operation with missing externally exposed nonstructural parts by defining restrictions, limitations, or performance penalties, while the aircraft remains airworthy. See Chapter 12 for additional information on the CDL.
1.8.5 Deferral. The term “deferral” is used to describe the authorization for an operator to delay repair and continue operating with a required item inoperative, under the authority of their FAA-approved MEL. Authority to defer an inoperative item is subject to specific conditions and limitations, as described in the associated proviso.
1.8.6 Dynamic Regulatory System (DRS). DRS is an FAA website that contains regulatory, policy, and guidance information. DRS can be accessed at https://drs.faa.gov.
1.8.7 Flight Operations Evaluation Board (FOEB). An FOEB is comprised of technically qualified specialists, engineering representatives, and aviation safety inspectors (ASI) responsible for developing MMELs from the proposed MMEL provided by the aircraft manufacturer. An aircraft MMEL is usually developed during initial aircraft certification.
FOEBs are also responsible for developing MMEL revisions. FOEBs coordinate with internal and external stakeholders, such as the responsible Aircraft Certification Service office, Flight Standards offices, aircraft and engine manufacturers, operators, and private-sector groups.
1.8.8 Global Change (GC). A GC is newly developed or changed relief for an item, usually applicable to numerous MMELs (hence “global”) to allow operators to obtain MEL relief prior to the release of a revised MMEL. Incorporation of a GC into an operator’s MEL is optional until the GC is incorporated in the aircraft’s MMEL. GCs may be used to provide immediate relief for items required by a new regulatory requirement, policy change, or new technology.
1.8.9 K inds of Operations Equipment List (KOEL). Aircraft certificated under 14 CFR part 23 or 27 may have a KOEL. The KOEL specifies the kinds of operations (e.g., VFR, IFR, day, or night) in which the aircraft can be operated. The KOEL also indicates the installed equipment that may affect any operating limitation. Although the certification rules require this information, there is no standard format; consequently, the manufacturer may furnish it in various ways. Inoperative equipment, when required by the KOEL for a particular type of operation (e.g., VFR, IFR, day, or night), may not be deferred for that operation under § 91.213.
1.8.10 Letter of Authorization (LOA). The term “LOA,” used throughout this AC, refers to an operator-specific LOA, which is the MEL-authorizing document containing conditions and limitations the operator must comply with in order to conduct aircraft operations with specific inoperative items. When used in this AC, the term “LOA” refers to all LOAs issued under the provisions of § 91.213(a) to part 91 operators, part 133 rotorcraft external-load operators, part 137 agricultural aircraft operators, and part 141 pilot schools or provisional pilot schools.
1-5 Note: The part 142 training specification (TSpec) D095 has been decommissioned. Part 142 training centers holding TSpec A003, Aircraft Authorization, and seeking MEL authorization must do so under the appropriate operating rule (e.g., part 91, 121, or 135).
1.8.11 Maintenance (M) Procedure. The (M) symbol indicates a specific maintenance procedure that must be accomplished prior to operation with the listed item inoperative. Normally, (M) procedures are accomplished by qualified maintenance personnel; however, other personnel may be qualified and authorized to perform certain functions. Procedures requiring specialized knowledge or skill, or requiring the use of tools or test equipment, should be accomplished by maintenance personnel. The satisfactory accomplishment of all (M) procedures, regardless of who performs them, is the responsibility of the aircraft operator. Appropriate procedures are required as a part of the aircraft operator’s MEL.
See paragraph 5.4, Performing (M) and (O) Procedures.
1.8.12 Master Minimum Equipment List (MMEL).
1.8.12.1 The term “MMEL,” used throughout this AC, means an FAA-approved, aircraft make, model, and series (M/M/S)-specific master list of aircraft instrument and equipment items that may be inoperative under certain operational conditions, while maintaining the airworthiness of the aircraft and providing an ALoS. An MMEL is the baseline document used by operators to develop their own aircraft-specific MEL. Operators may download MMELs from the “MMELs and AED Guidance Documents” section in DRS at https://drs.faa.gov.
1.8.12.2 The United States may enter a Bilateral Aviation Safety Agreement (BASA) with a foreign government when there is a need for technical cooperation with the foreign government’s Civil Aviation Authority (CAA), and if the foreign authority’s civil aviation safety oversight is substantially comparable to the FAA’s. BASAs are carried out through associated implementation procedures.
Refer to country-specific BASAs for MMEL considerations relating to foreign type-certificated aircraft validated under Implementation Procedures for Airworthiness (IPA). The BASAs and associated IPAs may be found at https://www.faa.gov/aircraft/air_cert/international/bilateral_agreements/.
1.8.13 Minimum Equipment List (MEL). The term “MEL,” used throughout this AC, means a document listing items that may be inoperative during flight for a specific aircraft or a fleet of aircraft. Operation of the aircraft under the MEL is authorized by an operator-specific LOA. As provided in § 91.213(a)(2), an MEL and the associated LOA constitute a Supplemental Type Certificate (STC) for the aircraft. Operators will base their MEL on the MMEL applicable to the aircraft M/M/S. An operator’s MEL may be more restrictive than the MMEL, but it will not be less restrictive. Unless specified otherwise, the term “MEL,” used throughout this AC, refers to both: (1) the MEL approval under LOA D095, MMEL Used as an MEL, consisting of an MMEL and a procedures document, and (2) the MEL approval under LOA D195, Minimum Equipment List (MEL), consisting of an operator-developed MEL. When required for clarity, this
1-6 AC will distinguish between an MEL approval under LOA D095 or D195 by using the terms “procedures document,” or “operator-developed MEL,” respectively.
Note: MEL approvals under LOA D095 meet the International Civil Aviation Organization (ICAO) MEL requirements of Annex 6, Parts II and III. However, some CAAs may not accept LOA D095 as a valid MEL approval.
1.8.14 MMEL Policy Letters (PL). P Ls clarify FAA MMEL policy regarding specific kinds of equipment that may be deferred. While developing its MEL, an operator may need to refer to one or more aircraft or equipment-specific PLs with a GC designation, as these PLs may provide additional relief for items until the MMEL is revised. Operators may download PLs from the “MMELs and AED Guidance Documents” section in DRS at https://drs.faa.gov.
1.8.15 Make, Model, and Series (M/M/S). M/M/S is a common abbreviation used when referring to a manufacturer’s particular model or type and series of given aircraft.
1.8.16 Nonessential Equipment and Furnishings (NEF) Program. An operator’s MEL program may also include an NEF program that allows relief for nonessential items. An NEF program allows operators to use the authority granted by their MEL LOA to provide relief for nonessential items located throughout the aircraft. See Chapter 11 for additional information on an NEF program.
1.8.17 Operational Control. As defined in 14 CFR part 1, § 1.1, operational control, “with respect to a flight, means the exercise of authority over initiating, conducting or terminating a flight.”
1.8.18 Operations (O) Procedure. The (O) symbol indicates a specific operations procedure that must be accomplished prior to operation with the listed item inoperative. Normally, these procedures are accomplished by the flightcrew; however, other personnel may be qualified and authorized to perform certain functions. These procedures may be required for flight planning purposes, or they may require action by the flightcrew. Additionally, MEL items affecting the aircraft Weight and Balance (W&B) and cargo loading may require procedures for additional personnel, such as those involved with aircraft load control. The satisfactory accomplishment of all (O) procedures, regardless of who performs them, is the responsibility of the aircraft operator. Appropriate procedures are required as a part of the aircraft operator’s MEL. See paragraph 5.4.
1.8.19 Procedures Document. The procedures document is based on the MMEL applicable to the aircraft M/M/S. The procedures document, the MMEL, and the MEL LOA D095 together constitute an approved MEL. The procedures document contains:
• The name of the operator,
• The aircraft serial and registration numbers (or “Fleet”),
• The aircraft M/M/S,
• The MMEL revision number on which the MEL is based,
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• (M) and (O) procedures that correspond with the (M) and (O) symbols and/or provisos listed in the MMEL,
• A list of all MMEL items that contain the statement “as required by 14 CFR,”
• All applicable definitions, per MMEL PL-25, and
• The preamble, per current MMEL PL-36.
1.8.20 Principal Base of Operations. The term “principal base of operations” used throughout this AC is the physical address where an operator or pilot school conducts business or resides. It is a physical location where the FAA can contact the operator (i.e., a post office box is not an acceptable principal base of operations). While the principal base of operations may coincide with the place where the aircraft is located, this is not always the case. Depending upon the applicable 14 CFR part, this location may be an operator’s residence, business address, home base of operations, or a pilot school’s principal business office. For simplicity, this AC uses the singular term “principal base of operations” to refer to all these locations.
1.8.21 Principal Inspector (PI). P Is are FAA personnel, within the operator’s responsible Flight Standards office, who are assigned primary responsibility for oversight of an operator’s safety of operations. PIs specialize in the three general areas of aircraft operations according to their qualifications, either as a Principal Avionics Inspector (PAI), Principal Maintenance Inspector (PMI), or Principal Operations Inspector (POI). PIs have FAA administrative authority to evaluate and approve an operator’s manuals, including the MEL.
1.8.22 Responsible Flight Standards Office. The term “responsible Flight Standards office,” used throughout this AC, refers to the Flight Standards office responsible for issuance and oversight of all LOAs for the operator. This is typically the Flight Standards office with a Service Area (SA) covering the location of the operator’s principal base of operations. FAA office locations are available at https://www.faa.gov/about/office_org/field_offices/fsdo/ and https://www.faa.gov/about/office_org/field_offices/ifo.
1.8.23 Responsible Person (Part 91 Only). The term “Responsible Person,” used throughout this AC, is the person who has legal authority to sign the LOA on behalf of a part 91 operator.
Such person should have ongoing knowledge of the operations of the aircraft. The Responsible Person may be the individual who acts as operator or, if the operator is a legal entity, an officer, employee, or person duly designated to act on behalf of the operator. The person assumes responsibility for ensuring the operator complies with all applicable regulations, requirements, limitations, and provisions. If the Responsible Person relinquishes responsibility, the LOA is no longer valid.
1.8.24 Supplemental Type Certificate (STC). An S TC is a TC issued by the FAA to a person who applies for a major change to a type design when the proposed change does not require an application for a new TC under § 21.19. The STC, which incorporates by reference the related TC, approves not only the modification but also how that modification affects the original design.