- Feb 13, 2010
- Fort Walton Beach, Florida, USA
An ultralight can always be registered as an experimental, amateur-built if it meets the usual criteria for doing so, there is no lower limit on weight or horsepower or speed. A good example would be the Stits SA-8 Skeeto (https://en.wikipedia.org/wiki/Stits_SA-8_Skeeto), first flown in 1957 long before Part 103 was even a glint in the FAA's eye. It fits well within the modern Part 103 definition but it was N-numbered then and could just as easily be N-numbered today.
Another point....,Is there any reason why you can't register an ultralight as an LSA? In which case you would need a valid N number.