Not built to plan.

[Davecove]

Let's say I buy a set of plans for scratch building and decide to make the wings longer or the cockpit wider. Let's also say that I 'ran the numbers' and am confident that the changes are safe.

Or, even more extreme, I buy plans for two different aircraft and use the fuselage from one and the wings from the other.

Am I free to make the changes I want as long as I change the model designation on the paperwork so that the designer(s) safety record isn't put at risk? How much ownership does the designer retain regarding what I build and how I use it beyond the restriction to only build one primary unit of any part.

Dave

[Jim Hann]

Let's say I buy a set of plans for scratch building and decide to make the wings longer or the cockpit wider. Let's also say that I 'ran the numbers' and am confident that the changes are safe.

You can do that, no restrictions!

Or, even more extreme, I buy plans for two different aircraft and use the fuselage from one and the wings from the other.

Long EZ wings on a Pietenpol? Why not!

Am I free to make the changes I want as long as I change the model designation on the paperwork so that the designer(s) safety record isn't put at risk? How much ownership does the designer retain regarding what I build and how I use it beyond the restriction to only build one primary unit of any part.

Dave

They hold no ownership and most plans that you see today will have that stated in the license included with the plans, including a possible copy that you sign and is retained by said designer.

This is a great freedom we enjoy but must treat carefully!

[Frank Giger]

Am I free to make the changes I want as long as I change the model designation on the paperwork so that the designer(s) safety record isn't put at risk? How much ownership does the designer retain regarding what I build and how I use it beyond the restriction to only build one primary unit of any part.

Okay, let's talk license for use versus ownership.

When one purchases the plans for an aircraft one gets license to build an aircraft from them. This is different from ownership, as you can't start making copies of the plans and sell them. Usually the plans come with a waiver of liability about waist high, saying if one builds a plane from what they put down and dies, it ain't their fault.

Now, then, unless one is building an E-LSA, modification of the plans is pretty much expected; indeed, most plans have "blank" areas because the designer knows the builder is going to do whatever the hell they want to and they're wasting their time putting stuff on paper (my own plans/kit have a couple of those like the seat and fuel tank mounting).

Putting two sets of plans together to make an aircraft isn't all that unusual, either. Lots of folks mix the Graham Lee and Robert Baslee designs for the Nieuport 11, for example. Or use wing design or gear design from certified aircraft on their own experimentals.

So yeah, you can totally do what you're thinking, and name the resulting aircraft pretty much anything you want to....along with the serial number. "Almost" because if you name your aircraft a Boeing 747, the folks up by Seattle may have an issue with it, as they actually own that name. On my own aircraft, I'll call it a Nieuport 11 (though it isn't one other than by general appearance) and ditch the model/date/time serial number on the plans for one of my own choosing (since it's really a serial number for the plans for Airdrome Airplane's own tracking).

Prudence comes first, naturally, when modifying plans.