Why was 1320 pounds chosen? A number was wanted that would screen out the large majority of existing two-seat aircraft in order to reinvigorate (or recreate) light aircraft manufacturing.
The FAA likes nice round numbers and the U.S. is, after all, on the metric system. (We just translate official standards to the antique English system for those who can't cope with simple measuring units. <That's a joke, folks - at least 40%> 1320 lb. = 600 kg. (almost exactly) 1430 lb. = 650 kg. (almost exactly) 254 lb. = 115 kg. (almost exactly) I don't know why 115 kg. was chosen for ultralights. As I recall, 600 kg. matches some preexisting foreign standard. Ed
