The Fine Line...Can someone explain to me...

[JDD]

Hi all,

Lets say I want to build an airplane that is a VERY close clone of one that exists. I do want it to be experimental so I can update a number of things. This would be a open three place biplane.

I may start with a couple of parts from another aircraft for patterns and the like.

Where is the bright line?

In the end I wish to end up with what amounts to in the classic car world as a "resto-rod". It would look like a 1929 design, but have things like regular rudder pedals as opposed to a rudder bar, a engine with a 1500 TBO and not a 400 TBO, a mix of steam and electric gauges. You get the idea.

Can someone educate me on this?

Thanks, JD.

[rwanttaja]

The design doesn't matter, as long as you meet the 51% rule in its construction. Your inspector might be suspicious that you used more manufactured parts than you should, so be prepared to prove your actual labor.

Ron Wanttaja

[Dana]

If you're building from scratch, it doesn't matter. It can be a 100% exact copy of an existing aircraft if you want. Or you can change anything you want. The only way you might have trouble is if your plane incorporates too many used parts from another aircraft.

[WLIU]

Builders these days write a construction log that includes pictures of you working on the project. Pictures of you cutting tubing and sheet, welding, riveting, and gluing create the record that says your building work satisfies the 51% requirements. And the checklist for the 51% may be found in one of the FAA advisory circulars on experimental amateur built aircraft. Track that AC down and give it a read.

Best of luck,

Wes
N78PS

[planecrazzzy]

FAA will check your weight and balance figures ( 170 lb pilots and passengers ) That'll be three for you...
They'll check wing loading figures...
I know what your saying.... does it need to be on an established print for you to get away with it...

Most people modify their plane during building.... a little or a lot...

Mine is two planes in one...Tailwind and Buttercup

I might call it a Buttwind
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Gotta Fly...
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PS I would have modified my first plane more... But wanted it to Fly during a better build...
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[cub builder]

As previously mentioned, just comply with the 51% rule for amateur built. If that is in question, go through AC 20-27G Appendix 8 and add up the parts you plan to buy, vs the amateur built parts and see if it comes out to 51%. If not, then modify your plan to ensure you make 51%.

-Cub Builder

[FlyingRon]

It's not 51% of the parts, it's 51% of the tasks.
The rule isn't really a rule anyhow. The rule just says constructed primarily for recreation or education. The 51% guidance was established to indicate how much manufacturered kit components could be used and still consider the fabrication to be done for those purposes.