Amateur Built
Design and Construction Requirements


To be eligible for an experimental airworthiness certificate, satisfactory evidence must be presented to show that the aircraft was not assembled from completely prefabricated parts or kits. The FAA recognizes that amateur builders cannot be expected to have fabricated every part that makes up the aircraft and that some parts will be acquired from commercial sources.

Items such as engines, engine accessories, propellers, rotor blades, rotor hubs, tires, wheel and brake assemblies, instruments, and standard aircraft hardware, including pulleys, bell cranks, rod ends, bearings, bolts, rivets, hot air balloon burners, and fuel tanks, are acceptable and may be procured on the open market. The use of these items is not counted against the amateur builder or kit manufacturer when the FAA determines whether the amateur-built aircraft has met the major portion requirement.


The use of used or salvaged assemblies (for example, landing gear, horizontal stabilizer, and engine mount) from type-certificated aircraft is permitted, as long as they are in a condition for safe operation.

No credit will be given to the amateur builder(s) for any work on these salvaged assemblies when determining whether the amateur-built aircraft has met the major portion requirement. This would include any “rebuilding” or “restoring” activities to return these components to an airworthy condition.

All fabrication, installation, and assembly tasks accomplished with used or salvaged assemblies will be credited to the “Mfr Kit/Part/Component” column on the Amateur-Built Aircraft Fabrication and Assembly Checklist (2009). However, assembly credit may given in those cases where used or salvaged parts and assemblies are mated to portions of the aircraft fabricated and assembled by the amateur builder.

Amateur built design and construction requirements prevent the builder from excessive use of prefabricated or salvaged assemblies when building their aircraft.

Using too many prefabricated or salvaged components may render the aircraft ineligible for amateur-built status.

The use of a significantly complete airframe or combination of major subassemblies such as wings and fuselage, tail plane assembly from a type-certificated aircraft, or a compilation of aircraft, would most likely render the aircraft ineligible for amateur-built status.


Alterations, rebuilding, and repairs to a type-certificated part, component, or aircraft will be categorized as falling under FAR 43. The amateur builder will receive no credit for these actions toward fabrication or assembly.

The normal Supplemental Type Certificate (STC) process should be used for modifications to these aircraft. They need to be kept under their existing maintenance programs to ensure continued airworthiness.


The amateur builder will receive no credit toward fabrication or assembly for amateur built design projects where military surplus, spare parts, components, and assemblies are used. It might also compromise the builder’s ability to meet the major portion requirements.


An amateur built design that has been purchased and will be fabricated and assembled from a kit may be eligible for amateur-built certification, provided the major portion of the aircraft has been fabricated and assembled by the amateur builder(s) solely for their own education or recreation.

The applicant must have satisfactory evidence to support the major portion (greater than 50 percent) requirement and the education/recreation statement on Form 8130-12 . This evidence is typically in the form of a builder’s log or equivalent, and includes photographs that document the multitude of steps included in each of the listed tasks in the Amateur-Built Aircraft Fabrication and Assembly Checklist (2009). This checklist is contained in Appendix 8 of Advisory Circular (AC) 20-27. Click here to download a copy of this AC.

In addition, such documentation needs to include materials and techniques used, construction dates, locations, and detailed descriptions. If the builder’s log or equivalent does not provide sufficient detail, the FAA/DAR may not be able to find compliance with the major portion requirement.

All fabrication or assembly tasks contracted to another party (that is, for compensation or hire) or provided by a commercial assistance center, when added to the manufacturer’s total credits, must be less than the major portion of the construction project. An aircraft assembled from a kit composed entirely of completely finished prefabricated components and parts is not eligible for an experimental amateur-built airworthiness certificate.

The major portion of a kit should be composed of raw stock, such as lengths of wood, tubing, and extrusions, which may have been cut to an approximate length. A certain quantity of prefabricated parts, such as heat-treated ribs, bulkheads, or complex parts made from sheet metal, fiberglass, composites, or polystyrene would also be acceptable.

However, the kit must still allow an amateur builder to meet the major portion requirement, and the applicant must show to the satisfaction of the FAA/DAR that the completion of the aircraft was not simply an assembly operation. Caution is recommended for kits that provide large components, such as complete fuselages and wing structures requiring minimal supplemental fabrication and assembly.

Some kits may include aircraft-specific jigs, assembly tools and fixtures, templates, raw stock, or other means to simplify the fabrication and assembly process. If an amateur builder uses such items, the FAA/DAR will determine whether the amateur builder will still fabricate and assemble the major portion of the aircraft and advise the amateur builder accordingly.

Amateur builders should obtain a copy of the completed FAA kit evaluation from their respective kit manufacturer if available. Click the following link to find a list of FAA-evaluated kits.

Amateur Built Kit Listing

The completed evaluation will enable the amateur builder to determine how much fabrication and assembly remains to be completed by the amateur builder, and if any percentage of that work could be performed using commercial assistance.


The FAA performs kit evaluations to determine if an aircraft constructed from a prefabricated kit, following the manufacturer’s instructions, may meet the major portion requirement of FAR 21.191(g).

The FAA does not certify amateur built design aircraft kits or approve kit manufacturers. The outcome of these evaluations should not be construed as meaning the kit is FAA “certified,” “certificated,” or “approved,” and kit manufacturers should not represent their kits as such.

The placing of a kit on the FAA List of Amateur Built Design Aircraft Kits is not a prerequisite for issuance of an amateur-built airworthiness certification. If an aircraft is fabricated and assembled from a kit that does not appear on the List of Amateur Built Design Aircraft Kits, the FAA/DAR will make a major portion determination at the time of airworthiness certification.

The FAA has adopted a task-based approach when evaluating amateur built design kits. Other variables, like time needed to complete a task, are not to be used. For simple repetitive fabrication tasks (that is, riveting, measuring, cutting, trimming, sanding, drilling, gluing, and layup) there should be enough work for the amateur builder to learn proficiency in each of those tasks.

However, this does not mean that all the credit for the tasks may then be given on the Amateur-Built Aircraft Fabrication and Assembly Checklist (2009) to the amateur builder. Rather, an incremental percentage, resulting in partial credit, may be accounted for on the checklist.

Kit evaluations are performed at the manufacturer’s facility or its distributor, by the FAA’s National Kit Evaluation Team (NKET). The team is composed of FAA personnel with experience in the evaluation and certification of amateur-built aircraft.

Kit manufacturers desiring an FAA kit evaluation should read Advisory Circular 20-27 for further information.

Go from this Amateur Built Design and Construction Page to the Experimental Amateur Built Certification Page

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Aircraft Registration

Experimental Amateur Built Certification