{"id":28277648,"date":"2026-10-16T16:29:32","date_gmt":"2026-10-16T14:29:32","guid":{"rendered":"https:\/\/migflug.com\/afterburner\/faa-51-percent-rule-amateur-built-aircraft-major-portion\/"},"modified":"2026-10-16T16:30:08","modified_gmt":"2026-10-16T14:30:08","slug":"faa-51-percent-rule-amateur-built-aircraft-major-portion","status":"publish","type":"post","link":"https:\/\/migflug.com\/afterburner\/faa-51-percent-rule-amateur-built-aircraft-major-portion\/","title":{"rendered":"FAA 51 Percent Rule: What \u201cAmateur-Built\u201d Actually Means"},"content":{"rendered":"\r\n<style>.et_pb_title_container h1.entry-title { padding-top: 40px !important; }<\/style>\r\n\r\n\r\n<!-- mfsh:top -->\r\n\r\n<style>\r\n.mfsh-trigger{display:inline-flex;align-items:center;gap:10px;height:44px;padding:0 18px;margin:0 0 26px;border:2px solid 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Not assembled it from a crate over a weekend. Built it, over several years, in a garage, with a rivet gun.<\/p>\r\n\r\n<p>That aircraft is legal, insurable, and free to fly across the United States, because the Federal Aviation Administration will certify an aeroplane that a private individual made at home, provided the individual did enough of the work. Everybody in general aviation calls the dividing line the \u201c51 percent rule\u201d.<\/p>\r\n\r\n<p>There is only one problem with that name. The regulation does not contain the number 51, or the word percent, anywhere at all.<\/p>\r\n\r\n\r\n<div style=\"background:#f1f3f6;border-left:4px solid #0d1117;padding:18px 22px;margin:26px 0 30px;font-size:15px;line-height:1.65\"><p style=\"margin:0 0 10px;font-weight:700;font-size:16px;color:#0d1117\">Quick Facts: Experimental amateur-built certification in the United States<\/p><p style=\"margin:4px 0\"><strong>The regulation:<\/strong> 14 CFR 21.191(g), which issues an experimental certificate for \u201coperating amateur-built aircraft\u201d<\/p><p style=\"margin:4px 0\"><strong>The actual test:<\/strong> The \u201cmajor portion\u201d of the aircraft must have been fabricated and assembled by amateur builders<\/p><p style=\"margin:4px 0\"><strong>Where 51 percent comes from:<\/strong> FAA Advisory Circular 20-27G, which defines major portion as more than 50 percent of fabrication and assembly tasks<\/p><p style=\"margin:4px 0\"><strong>The builder\u2019s purpose:<\/strong> The project must be undertaken \u201csolely for their own education or recreation\u201d<\/p><p style=\"margin:4px 0\"><strong>How it is measured:<\/strong> The Amateur-Built Aircraft Fabrication and Assembly Checklist, applied to kits by the National Kit Evaluation Team<\/p><p style=\"margin:4px 0\"><strong>The paperwork:<\/strong> A notarised FAA Form 8130-12 eligibility statement, plus builder\u2019s logs and photographs<\/p><p style=\"margin:4px 0\"><strong>Operating rules:<\/strong> 14 CFR 91.319: day VFR unless otherwise authorised, no congested areas without approval, no carrying persons or property for hire<\/p><p style=\"margin:4px 0\"><strong>Who may inspect it afterwards:<\/strong> The primary builder, via a repairman certificate under 14 CFR 65.104, or an FAA-certificated mechanic<\/p><\/div>\r\n\r\n\r\n<h2 style=\"padding-top:22px\">The regulation never says 51 percent<\/h2>\r\n\r\n<p>Here is the whole of the relevant paragraph. Section 21.191 lists the purposes for which the FAA issues experimental airworthiness certificates, and paragraph (g) covers amateur-built aircraft:<\/p>\r\n\r\n\r\n<div style=\"background:#f8f9fa;border-left:4px solid #5C91FF;padding:20px 22px;margin:18px 0 24px;font-size:16px;line-height:1.7\"><em>&ldquo;Operating an aircraft the major portion of which has been fabricated and assembled by persons who undertook the construction project solely for their own education or recreation.&rdquo;<\/em><div style=\"margin-top:10px;font-size:14px;color:#555\"><strong>14 CFR 21.191(g)<\/strong> &mdash; Issue of experimental airworthiness certificates, US Code of Federal Regulations<\/div><\/div>\r\n\r\n\r\n<p>Two things are doing the work in that sentence, and neither is a percentage.<\/p>\r\n\r\n<p>The first is <strong>major portion<\/strong>. The second, and the one people forget, is <strong>solely for their own education or recreation<\/strong>. That clause is why you cannot build an aeroplane this way in order to sell it, and why the category has never been a back door into cheap commercial manufacturing. The certificate is issued on the basis of why you built it as much as how much of it you built.<\/p>\r\n\r\n<p>The famous number arrives one level down, in guidance rather than regulation. FAA Advisory Circular 20-27G, <em>Certification and Operation of Amateur-Built Aircraft<\/em>, puts it in a note:<\/p>\r\n\r\n\r\n<div style=\"background:#f8f9fa;border-left:4px solid #1565c0;padding:20px 22px;margin:18px 0 24px;font-size:16px;line-height:1.7\"><em>&ldquo;The major portion of the aircraft is defined as more than 50 percent of the fabrication and assembly tasks, commonly referred to as the &ldquo;51-percent rule.&rdquo;&rdquo;<\/em><div style=\"margin-top:10px;font-size:14px;color:#555\"><strong>Federal Aviation Administration<\/strong> &mdash; Advisory Circular 20-27G, Certification and Operation of Amateur-Built Aircraft<\/div><\/div>\r\n\r\n\r\n<p>So the rule of thumb is accurate, and it is also second-hand. That distinction matters more than it sounds, because the thing being counted is not weight, not cost, not hours and not parts. It is <em>tasks<\/em>.<\/p>\r\n\r\n\r\n<figure class=\"wp-block-image size-large\" style=\"margin:0 0 24px;width:100%\"><img decoding=\"async\" class=\"skip-lazy\" data-no-lazy=\"1\" loading=\"eager\" width=\"1024\" src=\"https:\/\/migflug.com\/afterburner\/wp-content\/uploads\/sites\/4\/2026\/10\/zenith-stol-ch-701-unfinished-airframe.jpg\" alt=\"An unfinished bare-metal Zenith STOL CH 701 airframe on display at Sun n Fun 2024\" style=\"width:100%;height:auto;max-width:100%;display:block\"><figcaption style=\"font-size:13px;color:#777;text-align:center;margin-top:6px;font-style:italic\">An unfinished Zenith STOL CH 701 on the manufacturer\u2019s stand at Sun \u2019n Fun in 2024. Every rivet line here is a task, and tasks are the unit the FAA counts. Photo: ZLEA \/ Wikimedia Commons, CC BY-SA 4.0<\/figcaption><\/figure>\r\n\r\n\r\n<h2 style=\"padding-top:22px\">What the FAA counts as fabrication<\/h2>\r\n\r\n<p>The counting is done with a document called the Amateur-Built Aircraft Fabrication and Assembly Checklist. A kit manufacturer submits a kit, and the FAA\u2019s National Kit Evaluation Team works through the checklist deciding which tasks the kit has already done and which ones are left for the builder. Kits that pass go on the FAA List of Amateur-Built Aircraft Kits, and the published arithmetic is exactly what you would expect: a kit credited at 49 percent by the manufacturer leaves 51 percent for the amateur builder.<\/p>\r\n\r\n<p>The advisory circular is unusually precise about what fabrication means, and the definition is worth reading if you have ever wondered why builders talk about their aircraft in verbs:<\/p>\r\n\r\n<p><em>\u201cThe definition of fabrication is to perform work on any material, part, or component, such as layout, bending, countersinking, straightening, cutting, sewing, gluing\/bonding, lay-up, forming, shaping, trimming, drilling, deburring, machining, applying protective coatings, surface preparation and priming, riveting, welding, or heat treating, and transforming the material, part, or component toward or into its finished state.\u201d<\/em><\/p>\r\n\r\n<p>Deburring is on that list. So is priming. The rule is not asking whether you built something impressive; it is asking whether you did the work.<\/p>\r\n\r\n<p>There is a matching set of things you do not get credit for. Salvaged major assemblies taken off a type-certificated aeroplane earn nothing, and neither does the labour of restoring them. And converting a certificated aircraft into an amateur-built one is simply not permitted, a position the FAA traces back to 1952 and the Civil Aeronautical Manual, which warned even then that the provision was not meant to be used \u201cto avoid obtaining approval of major alterations to aircraft previously certificated in another category\u201d.<\/p>\r\n\r\n\r\n<div style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;margin:24px 0\"><iframe class=\"skip-lazy\" data-no-lazy=\"1\" loading=\"eager\" src=\"https:\/\/www.youtube.com\/embed\/QUnkCtEHaBo\" style=\"position:absolute;top:0;left:0;width:100%;height:100%;border:0\" allowfullscreen><\/iframe><\/div>\r\n\r\n\r\n<p style=\"font-size:13px;color:#777;text-align:center;margin:-14px 0 24px;font-style:italic\">The FAA\u2019s own short briefing on amateur-built certification, from the agency\u2019s Aviation Maintenance Safety Minute series.<\/p>\r\n\r\n\r\n<h2 style=\"padding-top:22px\">What you may buy, and who may help you<\/h2>\r\n\r\n<p>The most common misreading of the rule is that a builder must make everything. The advisory circular says the opposite in plain terms: the FAA does not expect you to fabricate every part of the aircraft. Engines, propellers, landing gear, wheels and brakes, instruments and standard aircraft hardware can all be bought on the open market, and none of it counts against you.<\/p>\r\n\r\n<p>Beyond that there is a whole category of work the FAA calls non-checklist items, on which you may have unlimited commercial help. Painting is one. Interior upholstery is another. So is avionics installation, which is why a homebuilt aeroplane can have a professionally fitted glass panel without its certificate being in any danger.<\/p>\r\n\r\n<p>Where the line bites is on the checklist tasks themselves. Commercial builder-assist centres are legal and widespread, but what they are allowed to sell is bounded, and the advisory circular draws the boundary with real force: commercial educational assistance \u201ccannot exceed a demonstration on how to perform the task\u201d, and the builder \u201cmust still perform the task to receive credit\u201d. Somebody may show you how to set a rivet. They may not set it for you and have it count.<\/p>\r\n\r\n<p>Any task genuinely contracted out, to a third party or to the kit manufacturer, cannot push the builder\u2019s share below the major portion. At the end of it all the builder signs a notarised FAA Form 8130-12 certifying that the major portion was fabricated and assembled for their own education or recreation, and declaring how much commercial assistance was used and where it came from. The evidence behind that signature is the builder\u2019s log: dated, sequential, photographed. The FAA may also turn up for a pre-cover inspection while the structure is still open, and it is explicit that it will never do any of the construction work itself.<\/p>\r\n\r\n<p>One quirk is worth knowing, because it saves unfinished projects. If a half-built aeroplane is sold on, the first builder\u2019s work counts toward the second builder\u2019s major portion. The catch is evidential rather than legal: without the original builder\u2019s documentation, the FAA may simply be unable to find that the rule was met.<\/p>\r\n\r\n\r\n<div style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;margin:24px 0\"><iframe class=\"skip-lazy\" data-no-lazy=\"1\" loading=\"eager\" src=\"https:\/\/www.youtube.com\/embed\/qxeeZ61XAPk\" style=\"position:absolute;top:0;left:0;width:100%;height:100%;border:0\" allowfullscreen><\/iframe><\/div>\r\n\r\n\r\n<p style=\"font-size:13px;color:#777;text-align:center;margin:-14px 0 24px;font-style:italic\">What the airworthiness inspection itself looks like when a builder uses a Designated Airworthiness Representative, from a builder-focused channel.<\/p>\r\n\r\n\r\n<h2 style=\"padding-top:22px\">What the certificate gives you, and what it costs you<\/h2>\r\n\r\n<p>An experimental amateur-built certificate buys remarkable freedom in the hangar and rather less in the air. The operating limitations come from 14 CFR 91.319, and they are real.<\/p>\r\n\r\n<p>You may not fly for any purpose other than the one the certificate was issued for. You may not carry people or property for compensation or hire in the operations the rule lists. You may not operate over a densely populated area or in a congested airway unless the FAA has authorised it in your operating limitations. You must fly day VFR unless specifically authorised otherwise, you must tell air traffic control that the aircraft is experimental when you use their services, and you must tell every person you carry that they are getting into an experimental aeroplane.<\/p>\r\n\r\n<p>In exchange, the builder gets something no certificated owner has. Under 14 CFR 65.104 the primary builder of the aircraft can hold a repairman certificate (experimental aircraft builder) and perform the annual condition inspection on the aeroplane they built. The privilege is deliberately narrow: that person, that aircraft.<\/p>\r\n\r\n\r\n<figure class=\"wp-block-image size-large\" style=\"margin:0 0 24px;width:100%\"><img decoding=\"async\" class=\"skip-lazy\" data-no-lazy=\"1\" loading=\"eager\" width=\"1024\" src=\"https:\/\/migflug.com\/afterburner\/wp-content\/uploads\/sites\/4\/2026\/10\/sonex-subsonex-jsx-1-experimental-jet.jpg\" alt=\"A yellow Sonex SubSonex JSX-1 single-seat homebuilt jet flying with smoke on, EXPERIMENTAL lettering visible on the fuselage\" style=\"width:100%;height:auto;max-width:100%;display:block\"><figcaption style=\"font-size:13px;color:#777;text-align:center;margin-top:6px;font-style:italic\">The Sonex SubSonex JSX-1, a single-seat jet built under the same rule. The word EXPERIMENTAL on the fuselage side is not decoration: 91.319 requires the aircraft to be identified, and every passenger to be told. Photo: FlugKerl2 \/ Wikimedia Commons, CC BY-SA 3.0<\/figcaption><\/figure>\r\n\r\n\r\n<h2 style=\"padding-top:22px\">The rule that keeps coming back<\/h2>\r\n\r\n<p>For something so settled, the 51 percent rule attracts an enormous amount of argument, and the most recent round is on the record.<\/p>\r\n\r\n<p>When the FAA published its Modernization of Special Airworthiness Certification final rule in July 2025, the rulemaking that the general aviation world knows as MOSAIC, at least one commenter used the opportunity to go after the rule directly, asking the agency either to eliminate it or to modify it. The FAA\u2019s answer was procedural rather than philosophical: it restated what 21.191(g) requires, noted that the proposal had not been part of the rulemaking, and declined.<\/p>\r\n\r\n<p><em>\u201cFAA disagrees with this recommendation as it is outside the scope of this rulemaking. Such a proposal would require appropriate notice to the public and opportunity for comment.\u201d<\/em><\/p>\r\n\r\n<p>Which is the regulatory way of saying: not today, and not without a proper argument in public. The rule survived.<\/p>\r\n\r\n<p>MOSAIC did change something adjacent, though, and it matters to anyone who owns a homebuilt they did not build. Until that rule, the condition-inspection privilege under 65.104 was effectively limited to the person who built the major portion, because there was no other way to demonstrate the necessary knowledge. The FAA concluded that this is no longer true, and that light-sport repairman training covers the same ground. A light-sport repairman may now inspect aircraft in the relevant category and class, which gives second and third owners of amateur-built aeroplanes a route that did not previously exist. The builder\u2019s own privilege stays exactly as narrow as it was.<\/p>\r\n\r\n<p>It is worth being clear that MOSAIC is a light-sport rule that happened to touch this corner. It did not rewrite what amateur-built means. The major portion test, the education-or-recreation purpose, the checklist and the notarised form are all still there, and a kit that wants to be on the FAA\u2019s list still has to leave the builder more than half the tasks.<\/p>\r\n\r\n<p>Which is, in the end, the quiet achievement of the whole arrangement. A regulator agreed to certify aircraft built by people with no manufacturing approval of any kind, on the strength of a checklist, a logbook and a notarised signature. Thousands of them are flying. One of them was over the Sonoran Desert at sunset, and somebody in a garage put every rivet in it.<\/p>\r\n\r\n\r\n<div style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;margin:24px 0\"><iframe class=\"skip-lazy\" data-no-lazy=\"1\" loading=\"eager\" src=\"https:\/\/www.youtube.com\/embed\/STiFvf7tkd4\" style=\"position:absolute;top:0;left:0;width:100%;height:100%;border:0\" allowfullscreen><\/iframe><\/div>\r\n\r\n\r\n<p style=\"font-size:13px;color:#777;text-align:center;margin:-14px 0 24px;font-style:italic\">A full-length documentary following a Van\u2019s RV-8 build from kit to first flight, which is the best available answer to the question of what \u201cmajor portion\u201d feels like in practice.<\/p>\r\n\r\n\r\n\r\n<p><em>Sources: 14 CFR 21.191, 21.193, 91.319 and 65.104 (eCFR); FAA Advisory Circular 20-27G, Certification and Operation of Amateur-Built Aircraft; FAA final rule, Modernization of Special Airworthiness Certification, 90 FR, 24 July 2025 (document 2025-13972); FAA Form 8130-12.<\/em><\/p>\r\n\r\n\r\n<!-- mfsh:bottom -->\r\n\r\n<button type=\"button\" class=\"mfsh-trigger mfsh-bottom\" data-mfsh-placement=\"bottom\" aria-haspopup=\"dialog\"><svg><use href=\"#mfsh-i-share\"\/><\/svg>Share this story<\/button>\r\n\r\n<!-- \/mfsh:bottom -->\r\n\r\n\r\n<style>.mfq{margin:34px 0 8px}.mfq h2{font:26px\/1.3 \"Gilroy semiBold\",Helvetica,Arial,sans-serif;color:#0d1117;padding-top:22px;margin:0 0 6px}.mfq .qa details{border-top:1px solid #5C91FF;margin:0;padding:0}.mfq .qa details:last-of-type{border-bottom:1px solid #e2e7ee}.mfq .qa summary{cursor:pointer;list-style:none;display:flex;justify-content:space-between;align-items:center;gap:16px;padding:22px 26px;font:18px\/1.7 \"Gilroy semiBold\",Helvetica,Arial,sans-serif;color:#0d1117}.mfq .qa summary::-webkit-details-marker{display:none}.mfq .qa summary::after{content:\"+\";font:24px Helvetica,sans-serif;color:#3568e0;flex:0 0 auto}.mfq .qa details[open] summary::after{content:\"\\2013\"}.mfq .qa details:hover summary{color:#3568e0}.mfq .qa .a{font:16px\/1.7 \"Gilroy regular\",Helvetica,Arial,sans-serif;color:#454e5e;padding:0 26px 24px}.mfq .qa .a a{color:#3568e0}@media(max-width:680px){.mfq .qa summary{padding:18px 14px;font-size:17px}.mfq .qa .a{padding:0 14px 20px}}<\/style>\r\n\r\n\r\n<section class=\"mfq\"><h2>Frequently Asked Questions<\/h2><div class=\"qa\"><details open><summary>What is the 51 percent rule in aviation?<\/summary><div class=\"a\">It is the common name for the requirement in 14 CFR 21.191(g) that the \u201cmajor portion\u201d of an amateur-built aircraft be fabricated and assembled by people building it solely for their own education or recreation. FAA Advisory Circular 20-27G defines major portion as more than 50 percent of the fabrication and assembly tasks, which is where the number comes from.<\/div><\/details><details><summary>Does the FAA regulation actually say 51 percent?<\/summary><div class=\"a\">No. The regulation, 14 CFR 21.191(g), says only \u201cmajor portion\u201d and never uses a percentage. The 51 percent figure appears in FAA guidance, specifically Advisory Circular 20-27G, which defines the major portion as more than 50 percent of fabrication and assembly tasks and notes that this is commonly called the 51-percent rule.<\/div><\/details><details><summary>What counts toward the 51 percent, and what does not?<\/summary><div class=\"a\">The FAA counts tasks on the Amateur-Built Aircraft Fabrication and Assembly Checklist, not weight, cost or hours. Buying an engine, propeller, wheels, brakes, instruments and standard hardware does not count against you. Work on salvaged major assemblies from certificated aircraft earns no credit at all.<\/div><\/details><details><summary>Can you pay someone to help build an amateur-built aircraft?<\/summary><div class=\"a\">Yes, within limits. You can have unlimited commercial help on non-checklist items such as painting, upholstery and avionics installation. On checklist tasks, Advisory Circular 20-27G says commercial educational assistance \u201ccannot exceed a demonstration on how to perform the task\u201d and that the builder must still perform the task to receive credit.<\/div><\/details><details><summary>Can you convert a certificated aircraft into an experimental amateur-built one?<\/summary><div class=\"a\">No. The FAA states that rebuilding or altering a previously type-certificated aircraft to obtain an amateur-built certificate is not authorised under 21.191(g), and that it will not accept applications for airworthiness inspections on such aircraft. The position dates back to the Civil Aeronautical Manual in 1952.<\/div><\/details><details><summary>What are the operating limitations on a homebuilt aircraft?<\/summary><div class=\"a\">Under 14 CFR 91.319 an experimental aircraft may only be flown for the purpose its certificate was issued for, may not carry persons or property for hire in the listed operations, and may not fly over densely populated areas or congested airways unless authorised. Flight is day VFR unless otherwise authorised, ATC must be told the aircraft is experimental, and every person carried must be informed.<\/div><\/details><details><summary>Who can inspect an experimental amateur-built aircraft?<\/summary><div class=\"a\">The primary builder can obtain a repairman certificate (experimental aircraft builder) under 14 CFR 65.104 and perform condition inspections on that specific aircraft. FAA-certificated mechanics and repair stations may also do them, and since the MOSAIC final rule a suitably trained light-sport repairman may inspect aircraft in the relevant category and class.<\/div><\/details><details><summary>Can you sell an aircraft you built under the 51 percent rule?<\/summary><div class=\"a\">You can sell the finished aircraft, but you cannot build it in order to sell it. The regulation requires that the project was undertaken solely for the builder\u2019s own education or recreation, and the builder certifies that on a notarised FAA Form 8130-12. Selling an unfinished project is different: the first builder\u2019s work counts toward the second builder\u2019s major portion, provided the documentation exists.<\/div><\/details><\/div><\/section>\r\n\r\n\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"What is the 51 percent rule in aviation?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"It is the common name for the requirement in 14 CFR 21.191(g) that the \u201cmajor portion\u201d of an amateur-built aircraft be fabricated and assembled by people building it solely for their own education or recreation. 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Selling an unfinished project is different: the first builder\u2019s work counts toward the second builder\u2019s major portion, provided the documentation exists.\"}}]}<\/script><div style=\"background:#f0f4ff;border-left:4px solid #5C91FF;padding:16px 20px;margin:32px 0 8px\"><p style=\"margin:0 0 8px;font-weight:600;color:#333\">Related Posts<\/p><p style=\"margin:4px 0\"><a href=\"https:\/\/migflug.com\/afterburner\/mosaic-rule-light-sport-aircraft-pipistrel-voyager-2026\/\">A New Class of Aircraft Just Became Legal<\/a><\/p><p style=\"margin:4px 0\"><a href=\"https:\/\/migflug.com\/afterburner\/sonex-aircraft-closes-its-doors-overnight\/\">Sonex Aircraft Closes Its Doors Overnight<\/a><\/p><p style=\"margin:4px 0\"><a href=\"https:\/\/migflug.com\/afterburner\/eaa-airventure-oshkosh-2026-record-attendance-734000\/\">Oshkosh Just Broke Its All-Time Record<\/a><\/p><p style=\"margin:4px 0\"><a href=\"https:\/\/migflug.com\/afterburner\/flying-flea-mignet-pou-du-ciel\/\">The Flying Flea: Henri Mignet\u2019s Aeroplane for Everyone<\/a><\/p><\/div>\r\n","protected":false},"excerpt":{"rendered":"<p>Share this story Somewhere over the Sonoran Desert there is a yellow and blue two-seater turning in the evening light, and the person who owns it also built it. Not assembled it from a crate over a weekend. Built it, over several years, in a garage, with a rivet gun. That aircraft is legal, insurable, [&hellip;]<\/p>\n","protected":false},"author":23,"featured_media":28277496,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"editor_notices":[],"footnotes":""},"categories":[665],"tags":[],"class_list":["post-28277648","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aviation-world"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>FAA 51 Percent Rule: What Amateur-Built Means | MiGFlug<\/title>\n<meta name=\"description\" content=\"The FAA 51 percent rule explained: what 14 CFR 21.191(g) really says, what counts as fabrication, how much help you may buy, and what MOSAIC changed.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" 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