Advisory Circular (AC) No. 549-002

Amateur-built aircraft major portion evaluation

Issuing Office: Civil Aviation, Standards Doument No.: AC 549-002
File Classification No.: Z 5000-34 Issue No.: 01
RDIMS No.: 18795193-v10 Effective Date: 2025-11-25

Table of contents

1.0 Introduction

1.1 Purpose

  1. (1) The purpose of this Advisory Circular is to explain the major portion requirement and its application, particularly when major assemblies of existing aircraft are used to construct an amateur-built aircraft. Professional assistance is defined and addressed.

1.2 Applicability

  1. (1) This document is to inform and advise Transport Canada Civil Aviation (TCCA) personnel and Minister’s Delegates – Recreational Aviation (MD-RA) evaluating an amateur-built aircraft or project’s eligibility for issue of a Special Certificate of Airworthiness - Amateur-built. This document also provides guidance for builders of amateur-built aircraft and applicants for a Special Certificate of Airworthiness - Amateur-built.

1.3 Description of Changes

  1. (1) Not applicable

2.0 References and requirements

2.1 Reference documents

  1. (1) It is intended that the following reference materials be used in conjunction with this document:
    1. (a) Aeronautics Act (R.S.C., 1985, c. A-2)
    2. (b) Part V Subpart 7 of the Canadian Aviation Regulations (CARs)—Flight Authority and Certificate of Noise Compliance;
    3. (c) Standard 507 of the CARs—Flight Authority and Certificate of Noise Compliance;
    4. (d) Section 549.01 of the CARs and Chapter 549 of the Airworthiness Manual (AWM)– Airworthiness Standards - Amateur-Built Aircraft;
    5. (e) Exemption from Section 549.01 of the CARs and Chapter 549 of the AWM – Airworthiness Standards - Amateur-Built Aircraft.

2.2 Cancelled documents

  1. (1) Not applicable.
  2. (2) By default, it is understood that the publication of a new issue of a document automatically renders any earlier issues of the same document null and void.

2.3 Definitions and abbreviations

  1. (1) The following definitions are used in this document:
    1. (a) Amateur: an individual who engages in an activity on an unpaid, non-commercial basis.
    2. (b) Amateur-built aircraft: an aircraft, the major portion of which is constructed or assembled individually by an amateur, as a non-commercial activity and as a unique project, either from raw materials or by completion of a kit.
    3. (c) Assemble: to fasten parts or assemblies together using reversible means of attachment such as screws, bolts, nuts, rivets or other mechanical fasteners.
    4. (d) Builder, amateur-builder: in the context of issue of a Special Certificate of Airworthiness - Amateur-built, the individual or group of individuals who constructs or assembles an amateur-built aircraft, or who oversees the construction or assembly by other persons, of an amateur-built aircraft; excludes commercial entities.
    5. (e) Builder of Record: the individual who informs TCCA of their intention to build an amateur-built aircraft and identifies themselves as the builders of the aircraft.
    6. (f) Commercial: an activity or enterprise conducted for hire or reward.
    7. (g) Construct/construction: to make a finished product by alteration of raw materials or extensive re-work of parts, using permanent methods such as cutting, drilling, milling, bending, forming, welding, soldering, gluing, bonding, crimping, sewing or swaging.
    8. (h) Exemption: the Exemption to CAR 549, Appendix A, Standards of Design and Construction for Amateur-Built Aircraft.
    9. (i) Existing aircraft: an aircraft or ultralight aeroplane that is or was capable of flight; includes but is not limited to: aircraft that were commercially produced, type certified or not type certified; destroyed or removed-from-service aircraft, and ultralight aeroplanes.
    10. (j) Letter of intent. the notification to the Minister (Transport Canada Civil Aviation) of the builder’s intention to build an amateur-built aircraft, required by both of Standard 549 and the Exemption.
    11. (k) Maintenance: the overhaul, repair, required inspection or modification of an aeronautical product, or the removal of a component from or its installation on an aeronautical product.
    12. (l) Major portion: means more than 50% of the total number of items constructed or assembled to complete the project of constructing an amateur-built aircraft, calculated in accordance with a checklist acceptable to Transport Canada.
    13. (m) Major assembly: a primary structure such as a spar assembly, a wing or lifting surface, a fuselage, horizontal or vertical stabilizer, tail boom or empennage, a landing gear assembly or float.
    14. (n) Oversee: to personally watch over, direct, physically inspect, and accept tasks performed by another individual.
    15. (o) Professional assistance: labour or services provided to the amateur-builder of an amateur-built aircraft in exchange for hire or reward.
    16. (p) Professional assistant: the person or entity providing professional assistance.
  2. (2) The following abbreviations are used in this document:
    1. (a) AME: Aircraft Maintenance Engineer
    2. (b) CAR:Canadian Aviation Regulations
    3. (c) TCCA: Transport Canada Civil Aviation

3.0 Background

  1. (1) Paragraph 507.03(b) of the Canadian Aviation Regulations (CAR) provides that a Special Certificate of Airworthiness in the Amateur-built classification shall be issued by the Minister for an aircraft which is constructed in conformity with the requirements of Subpart 549 of the CARs along with its associated standards or the related exemption.
  2. (2) A Special Certificate of Airworthiness - Amateur-built cannot be issued for an aircraft that was constructed in a way that does not meet the major portion requirements of CAR Subsection 549.01 or the Exemption to CAR Subsection 549.01.
  3. (3) The commonly used expressions “major portion rule” and “51% rule” are references to the application of CAR subparagraph 549.01(a)(iii), which says in part “…that the major portion of the aircraft will be constructed from raw material and assembled by an individual…”.
  4. (4) “Major portion rule” and “51% rule” also come from these two definitions in the Exemption to CAR 549, Appendix A, Standards of Design and Construction for Amateur-Built Aircraft:
    1. (a) “amateur-built aircraft” means an aircraft, the major portion of which is constructed or assembled individually as a unique project, either from raw materials or from a kit;
    2. (b) “major portion” means more than 50% of the total number of items constructed or assembled during the project;
  5. (5) Taken together, the two definitions express the major portion requirement; that the builder of an amateur-built aircraft must perform more than 50% of the total amount of construction and assembly tasks required to complete the aircraft.

4.0 Circumstances for refusal to issue

  1. (1) A Special Certificate of Airworthiness - Amateur-built cannot be issued for an aircraft if an amateur did not perform or personally oversee the major portion of the construction and assembly tasks required to complete the aircraft.
  2. (2) The applicant for the Special Certificate of Airworthiness - Amateur-built has the responsibility to demonstrate that the aircraft meets the major portion requirement.
  3. (3) A Special Certificate of Airworthiness - Amateur-built cannot be issued if
    1. (a) a person constructed or assembled the aircraft or a major portion of the aircraft in exchange for payment or any other form of compensation,
    2. (b) a person constructed or assembled the aircraft or a major portion of the aircraft, and the builder of record did not directly oversee the construction,
    3. (c) the applicant is an employee of the kit manufacturer,
    4. (d) the major portion the aircraft is an assembly of major structures or aerodynamic surfaces sourced from one or more previously existing aircraft, or
    5. (e) the processes involved were overhaul, repair, inspection or modification, and the aircraft is not significantly different from its origin as a previously existing aircraft or part.
  4. (4) An existing aircraft or its major assemblies, whether airworthy, damaged, scrapped or removed from service, cannot be converted or changed into an amateur-built aircraft by disassembly and re-assembly, repair, inspection, or any actions that in other circumstances would be considered normal maintenance actions on the aircraft or major assembly.
  5. (5) An aircraft that has sustained damage cannot be converted into an amateur-built aircraft by repairing the damage.

5.0 Evaluation of compliance with the major portion requirement; construction and assembly

  1. (1) A major portion evaluation will be performed when doubt exists about the portion of the project constructed or assembled by the amateur-builder. A major portion evaluation can be performed or repeated at any appropriate time in the construction process.
  2. (2) Major portion evaluations are carried out by persons with the delegation to issue a Special Certificate of Airworthiness - Amateur-built. They will use the latest version of a Major Portion Evaluation form provided by TCCA.
  3. (3) The purpose of the major portion evaluation is to determine the total number of construction and assembly tasks listed on a Major Portion Evaluation form that apply to the project, and of that total how many can be credited to the builder.
  4. (4) An amateur-builder will receive credit against the major portion rule for construction or assembly tasks that the amateur-builder performed themselves.
  5. (5) To ensure that they are given all the credit due, an amateur-builder should consider documenting the entire construction and assembly process. This may be done in many ways, such as:
    1. (a) Builder’s logs, logbook entries.
    2. (b) Photographs or video, drawings or engineering data,
    3. (c) Inventory lists of aircraft components and parts, receipts, invoices and catalogues.
    4. (d) Documentation referring to assistance of professionals.
    5. (e) Relevant documentation and references (e.g.: plans and handbooks).
  6. (6) The buyer of a partially constructed amateur-built aircraft project can become the builder of record for the project and be the applicant for the Special Certificate of Airworthiness - Amateur-built for the completed aircraft. It is their responsibility to show that the portion of the aircraft that they did not construct or assemble themselves was constructed or assembled by an amateur.
  7. (7) Overhaul, repair, inspection, removal, or fabric re-covering of airframe parts obtained from an existing aircraft is maintenance, and cannot be credited to the construction portion of the major portion requirement.
  8. (8) The opening up and subsequent closure of existing major assemblies for internal inspection is maintenance, not construction or assembly, and cannot be credited to the major portion requirement.
  9. (9) Use of major assemblies or parts from existing aircraft will not be granted construction credit. Construction credit may be granted only for work performed to alter the assembly or part in a manner necessary and beneficial to the completed aircraft. Credit will be granted only if the construction required by the alteration of the major assembly or part is accurately documented.
  10. (10) Only assembly credit can be granted for the incorporation of un-altered parts of existing aircraft, and the amount of assembly credit will depend on the documented number of tasks carried out.
  11. (11) No construction credit can be granted for the use of completely assembled ready-to-install mass-produced or commercially produced parts such as engine(s), propeller(s) or rotor blades and hubs, complex curved windows, accessories, wheels and brakes, standard aircraft hardware, or welded components. Assembly credit may be granted, and the amount of credit will depend on the number of tasks carried out and documented.

6.0 Professional assistance:

  1. (1) The builder of an amateur-built aircraft must perform more than 50% of the total amount of construction and assembly tasks required to complete the aircraft. However, the builder may contract for professional assistance from an individual or group of individuals, a commercial entity or a teaching facility to assist them with the completion of tasks involved in building the aircraft, such as construction or assembly of parts of the aircraft or construction of specific items.
  2. (2) The expectation is that professional assistance might be used to safely and efficiently accomplish complex or difficult tasks for which the builder chooses not to develop the competency or acquire the equipment to perform. Aircraft Maintenance Engineers (AME) and Approved Maintenance Organizations (AMO) may be able to perform specific tasks for the amateur-builder.
  3. (3) Tasks performed by a professional assistant must be directly overseen by the amateur-builder to be credited towards the major portion requirement. Construction or assembly tasks performed by a professional assistant without the amateur-builder’s actual physical presence and decision-making authority will not be credited to the amateur-builder.
  4. (4) The amateur-builder may claim full credit for tasks requiring two or more people when the amateur-builder hires another person to assist but the amateur-builder is personally present and directs the task.
  5. (5) Professional assistance does not refer to a person helping an amateur-builder without compensation.
  6. (6) A builder intending to employ professional assistance should declare it on their letter of intent. A major portion evaluation may be necessary to ensure the aircraft meets the conditions of issue of a Special Certificate of Airworthiness - Amateur-built.

7.0 Non-qualifying aircraft

  1. (1) If the construction of an aircraft fails to meet the major portion requirements, it cannot be issued a Special Certificate of Airworthiness - Amateur-built.
  2. (2) On a case-by-case basis, some non-qualifying aircraft may be eligible for a Flight Permit – Specific Purpose.

8.0 Information management

  1. (1) Not applicable.

9.0 Document history

  1. (1) Not applicable.

10.0 Contact us

For more information, please contact:

Jeffrey Phipps
Chief, Operational Airworthiness, Standards Branch (AARTM)
Telephone: 343-999-8145
E-mail: jeff.phipps@tc.gc.ca

We invite suggestions for amendment to this document.
Submit your comments to:
AART Documentation Services
E-mail: AARTDocServices-ServicesdocAART@tc.gc.ca

Original signed by

Jamie-Lee MacDermid
Executive Director, Standards Branch
Civil Aviation

AC 549-002 - Amateur-built aircraft major portion evaluation
(PDF, 314 KB)

Date modified: