View Full Version : Ala-Carte X-Cubs and the 51% Rule

Tom Tyson
01-05-2006, 11:46 AM
... and so it begins ...

I've been reading many of the threads here on SC and they have vastly widened my horizon about available parts and subassemblies I can choose from in building my Cub.

But the one question which continues to bother me is: With so many options pre-assembled (Smith wings just to name one example) how do you reconcile these with the FAA and the 51% rule for Amateur Construction.

- Tom Tyson

01-05-2006, 04:45 PM
No matter which route you take, believe me, you will be doing at least 51%. Even the kits take a tremendous amount of work. I don't think anyone has had problems with Smith kits getting approved. Maybe someone else can share their experience.

Tom Tyson
01-05-2006, 05:33 PM
Hi Buggs,

Yeah, I know what you mean - this will be my fourth homebuilt, but only the first where I'm not working from either a set of plans or an FAA "51% approved" kit.

I had originally planned to build a Wag Sport Trainer which is an FAA "accepted" kit, but the more I've learned about Cubs the last few months it's become obvious that I'm not going to be happy with anything less that a 150 horse PA-18 / L-21.

The problem (and my title for this thread) comes from the fact that there are hundreds of combinations of fuselages, wings and tailfeathers available, many with PMAs. If I use a Spraker tack welded frame (for instance) I'll obviously do much of the fuselage work myself between the finish welding and attaching all the fittings, but several of the wings I'm considering from other sources (Smith & Dakota) come preassembled and ready for covering. That effects the FAA calculus.

I thought someone here might have already worked through some of these issues with their local FAA and might have some guidance as to how to go about it, but maybe I'll just have to jump in myself and get together with my local DER or FSDO and try to get them to agree up front to what they will and won't accept.

LOTS of work ahead, no doubt about it.


- Tom Tyson

Ron B.
01-05-2006, 08:25 PM
In Canada the Smith's kit passes the 51% rule easily. We've got two and they were not even an issue. Hoping to be flying in the spring, believe me there is still plenty to do before flying once you recieve the kit. If you modify a part or sub-assembly you are now the manufacturer of that part, not the Smiths. So it all addes up. If I remember correctly the research also counts in the build process. I believe the US. has similar rules, as Canada probably copied!!!

01-05-2006, 08:51 PM
In the US, the Smith Kit easily passes the 51% rule. The FAA uses a strange set of rules to measure what they call 51%. 99% of all kits will easily pass.