Wes has the right of it; the reporting criteria is in NTSB 830, but it can be open to a bit of interpretation. "Accident" is defined as an occurence in which any person suffered serious injury or death, on in which the airplane receives "Substantial Damage," which is defined as "damage or failure which adversely affects the structural strength, performance, or flight characteristics of the aircraft, and which would normally require major repair or replacement of the affected component."
If it's a homebuilt, it's probably easier for the owner to dance around whether the damage requires "major repair".... "It's just some dinged sheet metal, I can fix it in a weekend." NTSB 830 includes other criteria for reporting, of course, but they don't really arise in most accidents.
We had one rather nasty accident here ~20 years ago where one of the homebuilt's occupants had a lot of 3rd degree burns and required extensive skin grafting. The owner successfully kept it out of the NTSB records by arguing that it was a taxi test of a vehicle that had not yet received FAA airworthiness or registration...thus wasn't an aircraft.
I've tried to pin NTSB guys down on whether they're required to investigate homebuilt accidents, and no one gave me a yes or a no. Certainly they do, but if a Gulfstream or something subsequently has an accident, you can bet the investigator will shunt the homebuilt aside.
Bob, the accident you're thinking about might be in the FAA Incident database:
http://www.asias.faa.gov/portal/page..._home/datainfo
Select the "AIDS Database Query Tool" link on the right.
Bob, if you can post a location and a more-exact date, I could dig a bit.
Ron Wanttaja