An EN-A wing is considered to be a beginner wing, in that it's very stable, slower and most often somewhat self correcting. An EN-B wing is an intermediate wing and sometimes people start off with a B wing. A EN-C, or C wing is for a more advanced pilot and it's faster and more maneuverable. An EN-D wing is considered to be for a very advanced pilot. There are also Unrated wings as well. My wing is an EN-A and considered as a high A due to it's capabilites exceeding that of many other A wings. Many of those collapses you mention were probably on C & D wings. I hope that helps and thanks for asking. Cya