Frequently Asked Questions

Amateur-Built Aircraft and the “51% Rule”

What is the 51% Rule?
Issued by the FAA in September 1952, the 51% Rule made amateur-built aircraft legal. It allowed ordinary people to design, build, and fly aircraft for their own recreation and education. It authorized the certification of “Experimental amateur-built aircraft,” defined as “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” [FAR Part 21.191(g)].

The first key phrase here is, “the major portion,” which the FAA interprets as meaning, at least 51% of the construction tasks of the aircraft project. The other key phrase is, “solely for their own education or recreation.” Commercial builder assistance — construction assistance in exchange for compensation — is allowed, but only if the amateur builder completes at least 51% of the fabrication/construction tasks. [See also FAA Aircraft Circular AC 20-139 ( 04/03/1996 ), “Commercial Assistance During Construction of Amateur-Built Aircraft.”]

What is the issue?
In the past two or three decades new materials and technologies have given rise to “homebuilt” aircraft and aircraft kits representing a full spectrum of sophistication, up to and including kits for aircraft featuring pressurization, retractable landing gear, and turbine or even jet powerplants. Many of these kits are of such complexity that they compel the amateur builder to seek substantial expert assistance from the factory or from third-party “builders-for-hire.”

The FAA argues that some of these kits, and the expert assistance they attract, can compromise compliance with the 51% Rule. The FAA also argues that some “quick-build” kits leave less than 51% of the construction tasks to the owner-builder. FAA officials have said repeatedly that the agency is committed to preserving the Experimental Amateur-Built Category. They readily admit that some of the violations and abuses of the 51% Rule have arisen from the agency’s own policies and enforcement practices. But they are also concerned that some in the kit-building community are using the experimental amateur-built rules “to circumvent the normal certification regulations and procedures applicable to serial production of duplicate aircraft.”

The FAA announced on 18 April 2008 that, under its new policies, it will not re-evaluate any previously approved aircraft kits. (See list of approved kits.) The agency’s announcement makes it clear that the FAA’s new policies will not disqualify any kits that have already been approved. This is a major victory for the EAA community in its ongoing efforts to work with the FAA to preserve the Amateur-Built Category and the spirit and intent of the amateur-built rules. (Read the full story on the FAA’s 18 April announcement.)

The FAA still has not published its new proposed comprehensive policy on the 51% Rule and amateur-built aircraft. That policy proposal is expected at any time.

What is being done to resolve this issue?
In July 2006, the FAA chartered an Aviation Rulemaking Committee (ARC), an advisory panel to study the issue and propose specific ways of addressing it — ways that could include new amateur-built regulations, policies, directives, advisory materials, and implementation strategies.

EAA has been at the center of that initiative. The ARC was co-chaired by the FAA, by Earl Lawrence , EAA vice president of government and industry relations, and by Dick VanGrunsven, of Van’s Aircraft. It included kit manufacturers, amateur builders, EAA technical advisors, and FAA officials.

At its final meeting in November 2007, the ARC issued these recommendations:

• The FAA should not adopt new policies, interpretations, or enforcement of the 51% Rule that would disqualify current kits.
• The FAA should not revise the language of the experimental amateur-built regulations or make changes to the Amateur-Built Category.
• The FAA should pave a more feasible and practical regulatory avenue enabling the participation of enthusiasts who want to build and fly their own aircraft without the requirement to perform more than half of the aircraft construction tasks.

The FAA has made a commitment to consider seriously and carefully the ARC’s recommendations before it issues its proposed new policy in early 2008.

What happens next?
Sometime in May or June 2008, the FAA will place a notice in the Federal Register — essentially a statement of its proposed policy for administering and enforcing the 51% Rule. After the notice is issued, there will a two- to three-month period for public comment. FAA officials tell us the agency hopes to finalize and publish the new policy sometime around AirVenture 2008.

As soon as the Federal Register notice appears, EAA will provide a detailed and objective analysis of the proposed policy, through our publications, chapters, and Web site.

What can EAA members and other aviation enthusiasts do to influence the outcome?

You can help right now, before the proposed policy notice is issued .If you are an amateur builder—if you are working on or have completed an amateur-built aircraft— write to the FAA today.

• Tell the FAA what you have gained from the experience of building your own aircraft.
• If you have used an aircraft kit, factory-built components, a quick-build kit, or commercial builder assistance in your amateur-built aircraft project, tell the FAA how your contribution to that project, in time, skills, and effort, upholds the spirit and intent of the Experimental Amateur-Built rules.
• Tell the FAA that you value the privilege of amateur building and the freedom to design, build, and fly the aircraft of your dreams.

More than anything we can say, your personal testimony can demonstrate to the FAA that most of the current amateur-building practices, including quick-build kits, are completely consistent with the spirit and the purpose of the Experimental Amateur-Built rules—as they were conceived more than 50 years ago and as they exist today.

After the FAA publishes its notice of proposed policies, the public will have 2 to 3 months to comment on the proposals before the final policies are issued. During that comment period EAA members and aviation enthusiasts will rally to contact the FAA, to comment on the proposal and express support for preserving the Amateur-Built regulations. And EAA members’ government-relations representatives will continue to carry concerns to the FAA and to fight for the widest possible participation in the dream of flight.

What is FAA’s position on the 51% Rule?
FAA officials have stated repeatedly that the agency is committed to preserving the Experimental Amateur-Built Category and the 51% Rule. The FAA’s concern, documented in its charter for the ARC, is that some in the kit-building community are using the experimental amateur-built rules “to circumvent the normal certification regulations and procedures applicable to serial production of duplicate aircraft.”

What changes are ahead in FAA’s administration of the 51% Rule?
The FAA wants to achieve administration and enforcement of the 51% Rule that will be consistent with the letter and the spirit of the Experimental Amateur-Built Category. That could mean stricter enforcement in some areas, as the FAA has suggested. It may also mean some changes in the ways in which manufacturers, builders, and inspectors of amateur-built aircraft are required to measure and document the amateur builder’s share of the construction tasks.

The FAA has stated officially that it will not re-evaluate or disqualify any aircraft kits that it has previously approved under the 51% rule. However, the agency may require changes in the way amateur builders account for their 51% of the construction tasks. If you are currently building or plan to build a previously approved kit, you must still show that you performed the work, in order to qualify your aircraft project for Experimental certification. The best way to do that is to adopt and maintain scrupulous record keeping practices.

Will the policy changes disqualify a lot of kits?
The FAA stated on 18 April 2008 , that it will not re-evaluate or disqualify any kits that it has previously approved under the current amateur-built rules and policies. New kits that the agency has not yet evaluated or approved will be disqualified if, by the FAA’s interpretation, they leave less than 51% of the construction to the amateur builder. These might include some “quick-build” kits, as well as some kits for complex, composite, or high-performance aircraft that, in the FAA’s view, present considerable construction challenges that cannot be achieved by an amateur builder without substantial commercial assistance.

Again, the FAA has given official notice that aircraft kits that the agency has already evaluated and approved under the amateur-built rules will not be re-evaluated or disqualified under whatever new amateur-building policies the FAA issues. (See list of approved kits.)

EAA maintains that most of the current amateur-built practices, including quick-build kits, do fall within the spirit and intent of the Experimental Amateur-Built rules, and that the FAA should avoid punishing the entire amateur-builder community for the abuses of a few.

Will some kits be “grandfathered”?
Yes. Any kit that has already been evaluated and approved by the FAA under the Amateur-Built Rules will be “grandfathered” under the agency’s still-to-be-announced new policies.

EAA has argued that any new policies should not “maroon,” in regulatory limbo, any amateur-built aircraft or aircraft project that its builder(s) have undertaken consistent with FAA’s past or present interpretation and enforcement of the 51% Rule. The FAA has accepted that position in its announcement that already-approved aircraft kits will not be re-evaluated or disqualified.

What about aircraft kits in progress by their amateur builders, or already flying?
Any kit that the FAA already evaluated and approved under the amateur-built rules will be grandfathered under the new policy. Amateur-built aircraft already flying can continue to fly under the new policy. The FAA has said it wants tighter enforcement of the 51% Rule, so builders with aircraft projects in progress should adopt and maintain scrupulous records in order to demonstrate to the FAA that they have completed “the major part” of the work.

Does grandfathering mean that kits on the approved list will automatically qualify for certification as Experimental Aircraft?
No. Certification of a completed aircraft project has never been a foregone conclusion—even for kits on the approved list. That fact will not change. The FAA’s 18 April 2008 notice reminded us that the FAA determines whether an amateur builder personally contributed enough to the construction of a particular aircraft, when the agency performs the airworthiness inspection. The builder still has to show that he or she did the work.

Theoretically, a kit could be on the approved list with the assumption that it qualifies only if the amateur builder personally performs all of the construction tasks that remain after the kit manufacturer prefabricates and pre-assembles certain components. The FAA has said it wants tighter enforcement of the 51% Rule. All amateur builders must be careful to fully understand the new enforcement criteria that the FAA will soon publish.

How will the FAA’s policy changes affect commercial builder assistance?
Commercial builder assistance — assistance in exchange for compensation — is allowed under the 51% Rule, but only if the amateur builder completes at least 51% of the fabrication/construction tasks. In some cases, and for some kits, commercial “builder assistance” and “builders-for-hire” have completed more than 49% of the construction tasks on an aircraft project. The FAA has said it wants stricter enforcement of the existing rule. The FAA will continue to allow commercial builder assistance, but has foreshadowed additional steps to ensure compliance with the 51% Rule. (See also FAA Aircraft Circular AC 20-139 (04/03/1996), “Commercial Assistance During Construction of Amateur-Built Aircraft.”)

What is double-checking, and how will it be affected?
An aircraft builder documents his or her compliance with the 51% Rule by checking off the construction tasks that he or she has done. When both the builder and the factory or commercial builder assistance provider check off the same task, it is called “double-checking.” For some complex or quick-build kits, double-checking has been commonly used to credit both parties equally for this work. However, some FAA statements have suggested that it may either prohibit double-checking or assign more accurate contribution proportions, such as 60/40, 80/20, etc.

What about quick-build kits?
Under the Experimental Amateur-Built rules, all kits, including quick-built kits, require the amateur builder to complete at least 51% of the construction tasks, as defined by the FAA. EAA maintains that most of the current amateur-built practices, including quick-build kits, do, indeed, fall within the spirit and intent of the Experimental Amateur-Built rules.

Will some kit manufacturers be adversely affected?
The ARC recommended that any new enforcement policies should not disqualify current kits and the FAA has adopted that position. But new kits evaluated under a new and tighter enforcement policy might be disqualified if they do not meet the FAA’s interpretation of the 51% Rule.

Why not just change the required builder contribution in the Amateur-Built Category?
The 51% Rule is the bedrock premise on which the Amateur-Built Category rests. If the factory or a commercial builder is allowed to complete more than 49% of an aircraft project, it’s no longer an “amateur-built” aircraft — rather, it’s a commercially built aircraft, built with some assistance (maybe) from an amateur builder. The FAA has underscored this position repeatedly and has asserted that commercially built aircraft do not belong in the Amateur-Built Category.

The FARs provide many categories and regulatory avenues for commercially-built aircraft. However, they provide only one category for amateur-built aircraft. Through EAA’s efforts, the Amateur-Built Category has remained intact and vibrant for more than half a century. EAA is committed to preserving the special privileges and freedoms that the category provides.

As long as an aircraft is built solely for recreation or education, and the amateur builder completes the majority portion of the construction tasks, the Amateur-Built Category embraces everything from a Pober Pixie to a Rutan Voyager and beyond. EAA believes that it is essential to preserve that freedom for amateur builders to innovate, experiment, and dream. That is why the ARC recommended that the FAA make NO changes to the regulations that define the Amateur-Built Category.

Why not change the way the 51% requirement is measured and administered?
It is not EAA’s place to tell the FAA how to interpret the 51% Rule or how to measure “the major portion” of an amateur-built aircraft project. We maintain that most of the current amateur-built practices, including quick-build kits already fall within the spirit and intent of the Experimental Amateur-Built rules. And we have urged that the FAA, in interpreting the 51% Rule, and evaluating future kits, should give prime consideration to the spirit and the intent of those rules.

I’m a Warbird/Vintage/Ultralight enthusiast. Why should I care about the Amateur-Built Category?
Today, homebuilt aircraft make up roughly one fifth of the active single-engine general aviation (GA) fleet. Homebuilders have launched many innovations in aircraft design and composition, including materials, building techniques, electronic instrumentation, flight systems, and more. Innovations introduced on homebuilt aircraft are found today in certified GA, commercial, and military aircraft — even spacecraft. The entire aviation community, and general aviation in particular, benefits from the technological advances fostered by the Amateur-Built Category. And a growing, dynamic homebuilt community helps make aviation more affordable and more accessible to everyone.

Uncertainty over what new policies the FAA might propose is already hurting some manufacturers and builders of kit aircraft. Isn’t this discussion adding to the damage?
Preserving the Amateur-Built Category and the 51% Rule is a critical goal for all of general aviation. While FAA officials are deciding what policy changes to enact, some uncertainty is unavoidable and we sympathize with the builders and the companies affected by that uncertainty. But EAA has a responsibility to its members to provide open, honest, and timely information about issues like this.

We also believe that hiding from such issues only fuels the “rumor mill,” and that providing accurate, up-to-date information is the best and most responsible way to serve the interests of our members and of the aviation community at large.