I did an analysis of the FAA registration database to develop some statistics on what kind of engines are installed in homebuilts. Here's an overall summary:

About 4000 homebuilts in the registry are listed as having "AMA/EXP" engines. As part of this analysis, compared the "AMA/EXP" engine aircraft with the NTSB accident database, which almost always includes the engine type. I found about 550 of the AMA/EXP aircraft in the accident database, and from them, extrapolated the percentage of AMA/EXP aircraft that have specific aircraft engines. I used those percentages to add the appropriate number of engines to each of the main analysis engine categories.

This aspect isn't precise... it produced slightly more aircraft with Rotorway engines than there are Rotorway helicopters registered... but I think proportionately, the numbers are pretty good.

Ron Wanttaja