The first prototype of the S-55, first flown on 10 November 1949. The S-55 was the first successful single-rotor helicopter capable of transporting significant loads. The key was to put the big piston engine in the nose, and the changeable payload and fuel in the centre of gravity. Initially 49-2012 had a half horizontal tailplane with endplate on this side instead of the two canted fins seen here. Print stamped June 1952.