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Homebuilt ‘51% Rule’ Clarified by FAA

Gemini Sparkle

Key Takeaways:

  • The FAA has released Advisory Circular (AC-20-27G) to clarify what constitutes a "homebuilt" aircraft for experimental/amateur-built registration.
  • The core of the new guidance addresses how much of the aircraft construction must be performed by the amateur builder, distinguishing it from kit parts or professional assistance.
  • Though advisory, these guidelines serve as critical standards for FAA inspectors and airworthiness representatives who approve aircraft for registration.
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Just what is a “homebuilt” is now clearer. A long-awaited FAA advisory circular (AC-20-27G) outlines the approval basis for an aircraft to be registered in the experimental/amateur-built category. At issue was how much of the building is done by the builder, as opposed to prefabricated kit parts and/or work performed by professionals at a builder-assistance center. Though the provisions of the FAA document are advisory in nature and not mandatory, they are considered guidelines for designated airworthiness representatives and FAA inspectors, whose signature is required for an aircraft to be registered in the experimental/amateur-built category.

Mark Phelps

Mark Phelps is a senior editor at AVweb. He is an instrument rated private pilot and former owner of a Grumman American AA1B and a V-tail Bonanza.

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