the xron-i rotorcycle or yron-i rotorcycle (originally designated hog) was a tiny, single-seat helicopter designed under contract for the u.s. navy. in the mid-1950s. it later was designed for a united states marine corps requirement for a small personal helicopter that would fulfill a number of roles, including observation, liaison, small unit tactical maneuvers, and which could be dropped to downed airmen behind enemy lines to facilitate their escape.