The S-55 helicopter, also known as the Sikorsky H-19 Chickasaw, is a medium-lift utility helicopter developed in the late 1940s. It was designed by Sikorsky Aircraft Corporation and first flew in 1949. The S-55 features a single main rotor and a tail rotor, providing stability and control during flight. It was widely used by military and civilian operators for various roles, including transport, search and rescue, and medical evacuation. The S-55 was notable for its innovative design and versatility, allowing it to carry up to 12 passengers or a significant payload. It served in various conflicts, including the Korean War, and was used by several countries around the world. Its reliability and performance made it a popular choice for many helicopter operators during its operational years.