U .S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Flight Standardization Board Evaluations Date: 9/11/25 AC No: 120-53C Initiated by: AFS-100 Change:
This advisory circular (AC) provides guidance to those persons applying for a Flight Standardization Board (FSB) to have new or modified aircraft types and models evaluated for the purpose of determining minimum flightcrew training, checking, and currency recommendations;
determining and establishing pilot type ratings; developing recommended aircraft type-specific training; and determining the scope of differences training and related aircraft differences training. This AC applies to aircraft manufacturers, type certificate (TC) holders, and aircraft modifiers seeking to use the FSB process.
Use of this AC enhances the safety of flight operations by providing a standard method of relating pilot training and qualification requirements to fleet characteristics, operating concepts, and pilot assignments; providing a consistent standard for determining necessary training resources or devices; encouraging aircraft manufacturers to design with the goal of developing common characteristics between related aircraft; and providing a recommended framework for application of suitable credits or constraints to address new technology and future safety enhancements.
This revision reformats the AC and replaces the appendices with chapters; adds new and revised definitions and acronyms; clarifies Aircraft Evaluation Division (AED) responsibilities;
incorporates human factors (HF) considerations; revises references; clarifies pilot training, qualification, and type rating evaluation; updates rating and level tests planning and proposals;
and removes operator Differences Tables (DT) and related principal inspector responsibilities.
R obert Reckert for Lawrence Fields Executive Director, Flight Standards Service
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CONTENTS Paragraph Page
Chapter 1. General1-1
1.1 Purpose of This Advisory Circular (AC)1-1
1.2 Audience1-3
1.3 Where You Can Find This AC1-3
1.4 What This AC Cancels1-3
1.5 Related 14 CFR Parts1-4
1.6 Definitions1-5
1.7 Related Reading Material (current editions)1-10
1.8 Background1-11
1.9 Discussion1-11
Chapter 2. T-Tests Used to Evaluate Type Ratings and Pilot Training, Checking,
and Currency2-1
2.1 Preparation2-1
2.2 Type Rating Determination Through Analysis—Level A or B Training Only2-5
2.3 Functional Equivalence—Level A or B Test 1 (T1)2-6
2.4 Handling Qualities Comparison Between Aircraft—Test 2 (T2)2-7
2.5 System Differences Test and Validation of Training and Checking—Test 3 (T3)2-8
2.6 Currency Validation—Test 4 (T4)2-10
2.7 Initial Type Rating Training/Checking or Transition Training/Checking
Validation—Test 5 (T5)2-11
2.8 Common Takeoff and Landing Credit (CTLC)—Test 6 (T6)2-12
Chapter 3. FSB Evaluation and Development of Report Recommendations3-1
3.1 Introduction3-1
3.2 Concepts3-3
3.3 Formulation of FSBRs, MDRs, and Determination of Type Ratings3-16
3.4
FSBR Requirements3-29
3.5 FSTD Approval3-29
3.6 Review and Approval3-30
3.7 Appeal of FAA Decisions3-30
Appendix A. A dministrative ParagraphsA-1
iii List of Figures
Figure 2-1. Sample Flight Standardization Board Compliance Checklist With Examples2-3
Figure 3-1. Master Differences Requirements Table3-6
Figure 3-2. MDR Table Example for Make/Model [XXX] on FSBR Cover Page3-6
Figure 3-3. Differences Tables—Design3-14
Figure 3-4. Differences Tables—Maneuvers3-15
Figure 3-5. Master Differences Requirements Formulation3-21
Figure 3-6. Test Definitions3-22
Figure 3-7. Training Differences Legend3-23
Figure 3-8. Checking Differences Legend3-24
Figure 3-9. “T” Tests T1 Through T53-25
Figure 3-10. Standard Method and Flight Simulation Training Device (FSTD)3-27
1-1 CHAPTER 1. GENERAL
1.1 Purpose of This Advisory Circular (AC). This AC describes standard systems, processes, and tests used by the Flight Standardization Board (FSB), managed by the Federal Aviation Administration’s (FAA) Aircraft Evaluation Division (AED), to evaluate aircraft to determine minimum pilot training, checking, and currency; to determine type rating designations; to recommend aircraft type-specific training, and to establish minimum requirements for differences training and related aircraft differences training. It further provides guidance to applicants seeking FSB review.
1.1.1 When to Use This AC. This AC describes FSB evaluation of the following:
1.1.1.1 Newly Manufactured Aircraft, Modified Aircraft or Aircraft Not Previously Evaluated. It provides procedures for evaluating new or modified aircraft types and models or an aircraft with unique flight or handling characteristics to determine the appropriate pilot type rating1 and recommend pilot training, checking, and currency for the applicable type rating.2 1 Title 14 of the Code of Federal Regulations (14 CFR) § 61.31(a) requires a person to hold a type rating to act as pilot in command (PIC) of the following aircraft: (1) large aircraft (except lighter-than-air), (2) turbojet-powered airplanes, (3) powered-lift, and (4) other aircraft specified by the Administrator through the type certificate (TC) procedures. The FSB is the mechanism the Administrator uses to make a type rating designation.
2 Title 14 CFR §§ 61.63(d) and 61.157(b) contain the training requirements for a type rating. The Airman Certification Standards (ACS) or practical test standards (PTS) establish the required tasks and maneuvers for the practical test for a type rating. The FSB Report (FSBR) recommends the training necessary to satisfy 14 CFR §§ 61.63(d) and 61.157(b) and is used by training providers to obtain training program approval.
1.1.1.2 S ystems or Equipment, Separately or as Part of an Aircraft/System Combination. It provides procedures for evaluating new and novel aircraft/systems, amended aircraft/systems, or Supplemental Type Certificates (STC) in accordance with FAA Order 8110.4, Type Certification, FAA Order 8110.48, How to Establish the Certification Basis for Changed Aeronautical Products, and FAA Order 8900.1, Volume 3, Chapter 19, Flightcrew Member Training and Qualification Programs, as applicable.
1.1.1.3 Differences and Related Aircraft Differences Training and Qualification Between Aircraft or Equipment. It describes procedures to determine the scope of differences in training and qualification between aircraft with the same type certificate (TC). It further describes an acceptable means for determining related aircraft differences training and qualification in Title 14 of the Code of Federal Regulations (14 CFR) part 121 between aircraft with different TCs that have been designated by the Administrator as related. Both of these processes result in an FSB Report (FSBR) that becomes the basis for the approval of training and qualification for pilots serving in operations in 14 CFR parts 91 subpart K (part 91K), 121, and 135.3
3 Refer to 14 CFR §§ 91.1097(b), 121.418, and 135.341(b).
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1.1.2 Safety Enhancement Through Use of This AC. Use of this AC enhances safety by:
1.1.2.1 Providing a standard method of assessing applicant proposals.
1.1.2.2 Directly relating pilot training and qualification to fleet characteristics, operating concepts, and pilot assignments.
1.1.2.3 Permitting better industry planning and management by outlining what training resources or devices are needed and what alternatives are possible.
1.1.2.4 Providing efficiencies in developing training between aircraft types with similar design and flight handling characteristics.
1.1.2.5 Providing a recommended framework for application of suitable credits or constraints to better address new technology and future safety enhancements.
1.1.3 General.
Note: This is a guidance document. Its content is not legally binding in its own right and will not be relied upon by the Department as a separate basis for affirmative enforcement action or other administrative penalty.
Conformity with the guidance document is voluntary only. Nonconformity will not affect rights and obligations under existing statutes and regulations.
1.1.3.1 The terms “must” and “will” in this AC indicate a mandatory requirement established by regulation that is to be followed when using the guidance in this AC. The term “should” is used in this AC to indicate a recommendation and not a requirement when using the guidance in this AC.
1.1.3.2 This AC describes a means to apply for operational evaluation of new or modified aircraft types by the FAA. This AC further explains how the Administrator exercises discretion under the regulations to evaluate aircraft to determine aircraft operational suitability, determine and recommend pilot type rating designations, recommend training for a type rating, and establish pilot training and qualification requirements for differences and related aircraft differences. If you use the means described in this AC, you should follow it in all important respects. While this is nonbinding guidance, you still must comply with the applicable regulations.
1.1.3.3 Since this AC represents an accepted means of compliance, an applicant seeking an alternative to any requirement or recommendation within this AC may need to discuss other means of compliance with the responsible AED branch in order to achieve compliance with applicable regulations for pilot training and qualification.
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1.1.4 Summary of Revision. This revision incorporates multiple Air Carrier Training Aviation Rulemaking Committee (ACT ARC) recommendations4 and is responsive to the applicable portions of sections 105, 115, 119, 124, and 128 of Public Law 116-260, Consolidated Appropriations Act, 2021, Division V, Aircraft Certification, Safety, and Accountability (ACSAA). It reformats the AC, moves the former appendices to the body of the AC, and reorders the chapters for more logical flow between technical data and process descriptions. The audience has been clarified to include aircraft to be operated under other than 14 CFR part 121. It adds emphasis to operational suitability for new or derivative aircraft and establishes flight criteria for FSB operational suitability assessments. It describes the use of non-FAA pilots and clarifies pilot training and rating determination in the FSB. This AC also (1) amends the FSB process for pilot training and checking and differences level tests and planning and proposals; (2) expands previously approved Master Differences Requirements (MDR); (3) clarifies nuances on T-Test discussions; and (4) revises T-Test subject descriptions and experience prerequisites. In response to ACSAA section 124(b), this revision incorporates human factors (HF) considerations in the FSB process. Additionally, definitions have been added or revised, including clarification of related aircraft terminology and operational use. The description of AED FSB responsibilities has been expanded and a new feedback form for the FSBR has been added. All figures have been updated, and the Simulator Differences Table (DT) has been removed. Finally, the AC has been retitled to reflect its content and purpose more accurately.
4 The ACT ARC recommendations can be obtained at https://www.faa.gov/about/office_org/headquarters_offices/av s/offices/afx/afs/afs200/afs280/act_arc.
1.2 A udience. The primary audience for this AC includes aircraft manufacturers, TC holders, and aircraft modifiers who design, test, and certificate under 14 CFR and are seeking to use the FSB process managed by the FAA AED to determine pilot training and qualifications for new or modified aircraft types and models. The original version of this AC was for aircraft intended for operation by an air carrier under 14 CFR part 121. While some provisions such as the term “related aircraft” are defined and applicable only under 14 CFR part 121 regulations, training and qualification provisions also extend to variations of aircraft operated under 14 CFR parts other than part 121. Original Equipment Manufacturers (OEM), TC holders, and modifiers of aircraft to be operated under 14 CFR parts other than part 121 may also request an evaluation from the AED.
The secondary audience for this AC includes air carriers, operators, and training providers who use FSB recommendations to develop training, checking, and currency programs, manuals, checklists, and training curricula.
1.3 Where You Can Find This AC. You 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 120-53B, Guidance for Conducting and Use of Flight Standardization Board Evaluations, dated November 5, 2013, is canceled.
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1.5 Related 14 CFR Parts.
1.5.1 Aircraft Certification and Airworthiness:
• Part 21, Certification Procedures for Products and Articles.
• Part 23, Airworthiness Standards: Normal Category Airplanes.
• Part 25, Airworthiness Standards: Transport Category Airplanes.
• Part 27, Airworthiness Standards: Normal Category Rotorcraft.
• Part 29, Airworthiness Standards: Transport Category Rotorcraft.
1.5.2 Training and Simulation:
• Part 60, Flight Simulation Training Device Initial and Continuing Qualification and Use.
• Part 61, Certification: Pilots, Flight Instructors, and Ground Instructors.
• Part 141, Pilot Schools.
• Part 142, Training Centers.
1.5.3 Air Carriers and Air Operators:
• Part 91, General Operating and Flight Rules.
• Part 91 Subpart K, Fractional Ownership Operations.
• Part 121, Operating Requirements: Domestic, Flag, and Supplemental Operations.
• Part 125, Certification and Operations: Aircraft Having a Seating Capacity of 20 or More Passengers or a Maximum Payload Capacity of 6,000 Pounds or More; and Rules Governing Persons On Board Such Aircraft.
• Part 129, Operations: Foreign Air Carriers and Foreign Operators of U.S.-Registered Aircraft Engaged in Common Carriage.
• Part 133, Rotorcraft External-Load Operations.
• Part 135, Operating Requirements: Commuter and On Demand Operations and Rules Governing Persons On Board Such Aircraft.
• Part 137, Agricultural Aircraft Operations.
1.5.4 Other:
• Part 1, Definitions and Abbreviations.
• Part 97, Standard Instrument Procedures.
• Part 117, Flight and Duty Limitations and Rest Requirements: Flightcrew Members.
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1.6 Definitions. The terms in this AC are defined for use exclusively in this AC.
1.6.1 Air Carrier. Refer to 14 CFR § 1.1.
1.6.2 Aircraft Evaluation Division (AED) Summary Report. A report developed by the AED which provides a record of the operational evaluations conducted in accordance with the Type Inspection Authorization (TIA) or Letter of Authorization (LOA) to provide a record of the aircraft configuration presented for the evaluation.
1.6.3 Applicant. For the purposes of this AC, an applicant is an aircraft OEM, modifier, TC holder, or any person who can provide the means to justify the request (e.g., an aircraft and/or device necessary to perform the test).
1.6.4 Base Aircraft. The first aircraft of a type or model, or an aircraft identified by the applicant, to use to compare differences with the candidate aircraft.
1.6.5 Candidate Aircraft. The aircraft that will be subjected to the FSB evaluation process outlined in this AC.
1.6.6 Check. An assessment of crewmember proficiency during which limited training or practice is allowed. The assessment is of knowledge and skill in tasks to the standards identified by the FAA. If the check is given for the purpose of pilot flightcrew member certification, it will be considered a practical test and must be administered by the FAA or a designated examiner. Failure of checks conducted during an FSB evaluation will not constitute negative consequences to the participating airman’s pilot certificate.
1.6.6.1 Types of Checks.
1.6.6.1.1 Full Proficiency Check (FPC). An FPC is a knowledge and skill assessment in accordance with 14 CFR part 61 and the appropriate Airman Certification Standards (ACS)/practical test standards (PTS).
1.6.6.1.2 Partial Proficiency Check (PPC). A PPC is conducted on a variation of the aircraft covering all pertinent differences.
1.6.6.1.3 Systems Check. An oral or written check conducted on a variation of the aircraft covering all pertinent differences.
1.6.7 Common Takeoff and Landing Credit (CTLC). CTLC is a proposal/process that identifies 14 CFR part 121 recency-of-experience credit between related aircraft (same make) with different TCs that can be demonstrated to have an equivalent level of safety during takeoff and initial climb, and approach and landing, including the establishment of final landing configuration. Refer to 14 CFR § 121.434(a)(4).
1.6.8 Compliance Checklist. A worksheet used to determine the applicable operational requirements of 14 CFR and whether the aircraft meets them to operate in the National Airspace System (NAS). (See Chapter 2, Figure 2-1, Sample Flight Standardization Board Compliance Checklist with Examples.)
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1.6.9 Configuration. Aircraft physical features, which are distinguishable by pilots, with respect to differences in systems, cockpit geometry, visual cutoff angles, controls, displays, aircraft geometry, and/or number of required pilots.
1.6.10 Currency. Currency is the experience necessary, within a specified period of time, for the safe operation of aircraft, equipment, and systems. Currency may include, but is not limited to, recency of experience.
1.6.11 Device. See the definition for “Flight Simulation Training Device (FSTD)” below.
1.6.12 Differences Levels. For the purpose of an FSB, training and checking differences levels are determined by training and checking methods that satisfy difference requirements between related aircraft or aircraft variations. A range of five differences levels in order of increasing rigor are identified as A through E. See Chapter 3, paragraph 3.2.3 for an explanation of differences levels.
1.6.13 Differences Tables (DT). Tables within the FSBR that describe the differences between the base and candidate aircraft and the minimum levels of training an operator (under 14 CFR part 91K, 121, or 135) may use to conduct differences training and checking of crewmembers. These tables have been validated by the FSB; if not, the table will state “not evaluated” (see Chapter 3, Figure 3-3, Differences Tables—Design, and Figure 3-4, Differences Tables—Maneuvers). DTs are determined by the FAA as a product of a successful FSB evaluation.
1.6.14 Differences Training. The training required for crewmembers who have qualified and served on a particular type aircraft, when the Administrator finds differences training is necessary before a crewmember serves in the same capacity on a particular variation of that aircraft (refer to 14 CFR §§ 91.1063(d)(4), 121.400(c)(5),5 and 135.321(b)(4)).
5 Under 14 CFR § 121.418(a), differences training must consist of the same training as required for initial training on the type of aircraft unless the Administrator finds that subjects, maneuvers, or procedures are not necessary.
1.6.15 Evaluation Plan. A proposal submitted for validation by the applicant and accepted by the AED to outline FSB operational activities, including determining minimum flightcrew training, checking, and currency recommendations; determining pilot type rating;
recommending aircraft type-specific training; and determining the scope of differences training, as applicable.
1.6.16 Flight Characteristics. The aerodynamic or performance characteristics perceivable by a pilot relating to the natural response of an aircraft to system inputs (e.g., primary flight control surfaces, various types of landing gear, effects of external accessories, etc.), as affected by changes in configuration and/or flightpath parameters (e.g., lift or drag devices, pitch/yaw/roll inputs, power settings, airspeed change, etc.).
1.6.17 Flight Simulation Training Device (FSTD). Per 14 CFR § 1.1, a full flight simulator (FFS) or a flight training device (FTD).
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1.6.18 Flight Standardization Board (FSB). A group of FAA personnel responsible for evaluating aircraft to: determine the appropriate type rating required; recommend the appropriate training for a type rating; determine minimum flightcrew training, checking, and currency recommendations; and establish the minimums for differences and related aircraft differences training and checking. The board members are selected by the FSB Chair and may include representatives from the Office of Safety Standards (OSS), the Aircraft Certification Service (AIR), or Flight Standards (FS) Operations inspectors.
1.6.19 FSB Chair. The person appointed by the AED manager of the appropriate AED branch responsible for conducting the FSB and Flight Operations Evaluation Board (FOEB) for an aircraft fleet. The FSB Chair is usually an AED Operations inspector assigned to the aircraft certification project. A Co-chair may serve as alternate FSB Chair. This term is synonymous with the outdated terms “Chairperson” or “Chairman” used in other contexts.
1.6.20 FSB Members. Individuals identified by the FSB Chair based on size, scope, and specific requirements necessary to complete the evaluation, which may include Operations inspectors, FAA test subjects, OSS representative(s), and Technical Advisors.
1.6.21 FSB Report (FSBR). An FSBR is a published report written by FSB members, identifying the recommended training, checking, and currency for a type rating, and minimum training required for differences between the base, candidate, and related aircraft, if applicable.
1.6.22 Flight Training Device (FTD). Per 14 CFR § 1.1, a replica of aircraft instruments, equipment, panels, and controls in an open flight deck area or an enclosed aircraft cockpit replica. It includes the equipment and computer programs necessary to represent aircraft (or set of aircraft) operations in ground and flight conditions having the full range of capabilities of the systems installed in the device as described in 14 CFR part 60 and the Qualification Performance Standards (QPS) for a specific FTD qualification level.
1.6.23 Full Flight Simulator (FFS). Per 14 CFR § 1.1, a replica of a specific type; or make, model, and series (M/M/S) aircraft cockpit. It includes the assemblage of equipment and computer programs necessary to represent aircraft operations in ground and flight conditions, a visual system providing an out-of-the-cockpit view, a system that provides cues at least equivalent to those of a three-degree-of-freedom motion system, and has the full range of capabilities of the systems installed in the device as described in 14 CFR part 60 and the QPS for a specific FFS qualification level, Level A, B, C, or D.
1.6.24 Function and Reliability (F&R) Flight Testing. The flight tests conducted by AIR after the applicant shows compliance with the applicable type certification regulations and requirements. For more details regarding F&R testing, refer to 14 CFR §§ 21.35 and 21.39, and Order 8110.4, Subparagraph 2-6w, Function and Reliability (F&R) Flight Testing.
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1.6.25 Handling Characteristics. The manner in which the aircraft responds with respect to rate and magnitude of pilot-initiated control inputs to the primary flight control surfaces
(e.g., the ailerons, elevator, rudder, spoilers, cyclic, collective, etc.).
1.6.26 Handling Qualities. The qualities or characteristics of an aircraft that govern the ease and precision with which a pilot is able to perform the tasks required of an aircraft role.6 This includes handling characteristics and flight characteristics.
6 Cooper, G.E. and Harper, R.P., “The Use of Pilot Rating in the Evaluation of Aircraft Handling Qualities,” NASA TN D-5153. April 1969.
1.6.27 H uman Factors (HF). HF is a multidisciplinary field that generates and compiles information about human capabilities and limitations, and applies it to design, development, and evaluation of equipment, systems, facilities, procedures, jobs, environments, staffing, organizations, and personnel management for safe, efficient, and effective human performance (refer to FAA Order 9550.8, Human Factors Policy).
1.6.28 Line-Oriented Flying (LOF). A phase of the T3 test used at the discretion of the FSB to validate the proposed training and checking. This LOF fully assesses particular difference areas, examines implications of Mixed Fleet Flying (MFF), assesses special circumstances such as the Master Minimum Equipment List (MMEL) effects, and evaluates the effects of pilot errors potentially associated with the differences.
1.6.29 Master Differences Requirement (MDR). MDRs are those requirements applicable to pilot training and qualifications that pertain to differences between related aircraft.
1.6.30 Mixed Fleet Flying (MFF). MFF is the operation of a base aircraft and one or more related aircraft for which credit may be taken for training, checking, and/or currency events. The FSB process defines minimum training, checking, and currency differences levels between related aircraft.
1.6.31 Operational Evaluation. A process to determine pilot type rating, recommend training for a type rating and unique or special airman training (e.g., specific flight characteristics or handling qualities such as a no-flap landing or the addition of new technology), and establish the minimum requirements differences and related aircraft differences training.
1.6.32 Operational Suitability. The extent to which an aircraft or system is acceptable for its intended operations, meets the applicable regulatory requirements, and can be operated safely in the NAS.
1.6.33 Operator. An air carrier or air operator conducting operations under 14 CFR part 91K, 121, 125, 129, 133, 135, or 137. The FSBR designates 14 CFR applicability for its recommendations.
1.6.34 Operator Differences Requirements (ODR). If differences exist within an operator’s fleet that affect pilot knowledge, skills, or abilities pertinent to systems or procedures, ODR tables provide a uniform means for operators to comprehensively manage differences or
1-9 related aircraft differences training programs and provide a basis for FAA approval of MFF.
1.6.35 Production Equivalent Aircraft or FFS. A new or candidate aircraft (or FFS) as determined by the FAA National Simulator Program (NSP), which represents the TC M/M/S aircraft to be operated in the NAS at the completion of the FSB and TC project, in accordance with Order 8110.4, Chapter 2, Type Certification Process.
1.6.36 Qualification. In the context of an operator, the process by which a flight crewmember completes an operator’s FAA-approved program, including all training, testing, and checking requirements, for the aircraft type and duty position.
1.6.37 Related Aircraft. Title 14 CFR § 121.400(c)(10) defines “related aircraft” as “any two or more aircraft of the same make with either the same or different type certificates that have been demonstrated and determined by the Administrator to have commonality to the extent that credit between those aircraft may be applied for flightcrew member training, checking, recent experience, operating experience, operating cycles, and line operating flight time for consolidation of knowledge and skills.” Related aircraft differences training defined in 14 CFR § 121.400(c)(11) applies when used as part of a 14 CFR part 121 training and qualification program.
1.6.38 Safety Pilot. For the purposes of the FSB, the pilot serving as pilot in command (PIC) as applicable based on aircraft design and AED risk management whose primary role is to intervene to prevent damage to the aircraft or to limit maneuvers which endanger the flight.
1.6.39 Seat-Dependent Tasks. Maneuvers or procedures using controls that are accessible or operable from only one flightcrew member seat.
1.6.40 Special Emphasis Area. Training unique to the aircraft, based on a system, procedure, or maneuver, which requires additional highlighting during training. It may also require additional training time or a specialized FSTD or training equipment.
1.6.41 Specific Flight Characteristics. A maneuver or procedure with unique handling or performance characteristics that the FSB has determined the pilot must be trained in and checked for competency or proficiency as referenced in FAA-S-ACS-11, Airline Transport Pilot and Type Rating for Airplane Airman Certification Standards;
FAA-S-8081-20, Airline Transport Pilot and Aircraft Type Rating Practical Test Standards for Rotorcraft Category Helicopter Rating; FAA-S-ACS-17, Airline Transport Pilot and Type Rating for Powered-Lift Category Airman Certification Standards; and/or 14 CFR part 121 appendix F.
1.6.42 Supervised Line Flying (SLF). Supervised experience associated with the introduction of equipment or procedures requiring postqualification skill enhancement during which a pilot occupies a specific pilot position and performs particular assigned duties for that pilot position under the supervision of a qualified company check airman (e.g., new systems, new operations, experience for a particular pilot position, or special characteristics).