Can You Modify the RV-12

Thought I would post this as it comes up in conversation quite a bit when builders gather.... (from the VAF forums)

Below is a reply from Joe Norris, Senior Aviation Specialist at EAA.

It's ALWAYS legal to modify an experimental aircraft. That's the nature of the experimental certification categories. The only time when it's not acceptable to modify an experimental aircraft is BEFORE the initial certification of an ELSA that's built from a Consensus Standard-compliant kit from an SLSA manufacturer. This certification category, under the authority of 14 CFR 21.191(i)(2) requires that the aircraft be assembled in accordance with assembly instructions provided by the manufacturer. Since this application requires a Statement of Compliance (FAA Form 8130-15) from the manufacturer, the only way that statement can be valid is if the aircraft is assembled strictly in accordance with the manufacturer's instructions.
However, once that ELSA gets its airworthiness certificate it is an EXPERIMENTAL aircraft just like any other, and you will find no regulation that restricts the modification of such aircraft. The only guiding document will be the aircraft's operating limitations (issued by the FAA as a part of the airworthiness certificate) which will require an approval process to be adhered to if a major change is made. This does not prohibit the change, but does put in place a specific procedure to approve the change.
There is no FAA document that specifically says an ELSA (or any other experimental aircraft) can be modified. The more important issue though, is that you can't find any regulation or guidance that would prohibit such modification. The maintenance and repair regulations found in 14 CFR Part 43 specifically do NOT apply to experimental aircraft, as stated in 43.1(b):
This part does not apply to any aircraft for which the FAA has issued an experimental certificate, unless the FAA has previously issued a different kind of airworthiness certificate for that aircraft.
This specifically states that the maintenance and repair regulations found in part 43 do not apply to an experimental aircraft. That being the case, there is no restriction on who performs maintenance, repair or modification.
I hope this helps to explain the situation. If not, let me know what further questions you have.

Joe Norris
EAA 113615 Lifetime
Homebuilders Community Manager
EAA—The Spirit of Aviation
www.eaa.org
See you at EAA AirVenture Oshkosh—July 27 – August 2, 2009