The Sikorsky S-55 is a medium-lift helicopter designed by Sikorsky Aircraft Corporation in the 1950s. It features a single main rotor and a tail rotor, providing stability and control during flight. The S-55 was primarily used for military and civilian purposes, including transport, search and rescue, and utility missions. First flown in 1954, the S-55 was known for its reliability and versatility. It could carry up to 12 passengers or a significant payload, making it suitable for various applications. The helicopter was widely used by several military forces and commercial operators around the world.