XH-26, a super lightweight (under 300 lb) helicopter designed to be able to be assembled by two men in 30 min. It was powered by ramjets, resulting in unacceptable noise levels, a problem the similar Hiller Hornet also suffered from. And, of course, during the start up process before the ramjets lit you had what amounted to a gigantic lawn sprinkler spraying kerosene in a wide circle. A friend of mine one watched Kermit Weeks starting up his Hiller Hornet; it was horrifying.