Builder Assistance:
Common term for commercial assistance (as defined by the FAA), performed at a Builder Center (as defined by the FAA).

Builder Center:
A place where amatuer-builders can obtain instruction, help, and support during construction of their aircraft.

Commercial Assistance:
Assistance in the building of an amateur-built aircraft in exchange for compensation

Unacceptable Builder Assistance:
Any commercial assistance that reduces the work performed by the amateur builder to less than the "major portion" of the aircraft construction

Amateur Built Aircraft:
An aircraft, the "major portion" of which has been fabricated and assembled by person(s) who undertake the construction project solely for their own education or recreation

Person:
An individual, firm, partnership, corporation, company, association, joint-stock association, government entity, trustee, receiver, assignee, or similar representative of any of them

Major Portion:
...when the aircraft is completed, the majority of the fabrication and assembly operations have been performed by the amateur builder(s) who submit the application for certification (See AC 20-139 Appdx 1 -- FAA form 8000-38, Fabrication/Assembly Operations Checklist)

How Do I Know If I've Built the Major Portion?
(It has nothing to do with the number of hours required to build!)
The following fabrication & assembly operations are listed on FAA Form 8000-38 - these are the parts of the aircraft that FAA Airworthiness Inspectors are concerned with when determining the major portion status of your amateur-built experimental aircraft. When you perform any of these operations, you earn "credit" towards the major portion for having performed these operations and toward establishing amateur-built status for your plane:

Thus, in the case of a standard fixed-wing aircraft, being involved in performing at least 60 of the applicable 119 Fabrication & Assembly Operations (51%) establishes your plane's amateur-built status and your eligibility to apply for a Repairman's Certificate.

Some of those 119 operations are easier than others. Some are less critical to safety. Some require fewer special tools to complete expertly. AirCrafters can pick the operations you do for your particular kit that will guarantee adherence to the 51% rule, and reduce the amount of time you spend, if that's your goal.

Documentation is Important:
The Amateur Builder(s) must be able to show that they have performed at least 60 of the 119 operations (in the case of a fixed-wing aircraft) in order to qualify for the repairman certificate, and to register their aircraft in the experimental category. You will be required to sign and notarize an affidavit (FAA Form 8130-12) attesting to the fact that you have completed at least 51% of the operations required.

What if you bought the project from a previous owner who never finished it?
It does not matter how many previous owners a project may have had - as long as each owner intended to build the aircraft for their own education or recreation - if you can document or show documentation of the work that each did, it is as if YOU did the work!

Things that don't count toward the Major Portion rule:
Engines, Propellers & Accessories, Avionics & Instruments, Interior Items, Hardware, Landing Gear, Exterior Finish and related items.

Which Kits have been evaluated by the FAA and found "OK" to build?
The FAA maintains a listing of amateur-built aircraft kits found to be eligible under the Major Portion Rule.  This List is available at:
http://www.faa.gov/aircraft/gen_av/ultralights/amateur_built/kit_listing/Complete_mfr_model_listing/
The FAA does NOT "certify" amateur-built kits.

Things to Think About When Shopping for Builder Education and Assistance:

1. Get it in writing (proposal, contract, etc.)
2. Get references and check them out
3. Visit the Facility and Meet the People
4. Gauge the Experience and Workmanship
5. Beware the Low Bidder... Quality, Speed, and Low Price don't go together!

Reference Materials:

• http://www.faa.gov/aircraft/gen_av/ultralights/amateur_built/ Links to amateur built data as well as ultralight data
• FAR 21.191, Certification of Experimental Aircraft
• AC 20-27E, Certification/Operation of Amateur-Built Aircraft
• AC 20-139, Commercial Assistance During Construction Of Amateur-Built Aircraft
• AC 21-12A, Application for U.S. Airworthiness Certificate, FAA Form 8130-6
• AC 39-7C, Airworthiness Directives
• AC 65-23A, Certification of Repairmen (Experimental)
• AC 90-89A, Amateur-Built Aircraft and Ultralight Flight Testing Handbook
• AC 103-7, The Ultralight Vehicle
• http://www.faa.gov/aircraft/gen_av/ultralights/amateur_built/kit_listing/Complete_mfr_model_listing/ Revised Listing of Eligible Amateur-Built Aircraft Kits
• Excerpt from FAA Order 8130.2D, Airworthiness Certification of Aircraft and Related Products (Procedures for Experimental Certification - Internal Guidance for FAA)

We hope this is an educational and informative site. Please call or write with comments to:

AirCrafters: Builder Education and Assistance in Custom Aircraft Construction and Repair
140 Aviation Way
Watsonville, CA  95076
Phone 831.722.9141  Fax 831.722.9142