First flown on 22 September 1947, the S-53, naval designation HJS, was a bigger development of the S-51. It was a failure as the centre of gravity shifted too much with heavier payloads carried all forward of the engine, and the twin-rotor Piasecki HUP Retriever became the US Navy's new rescue helicopter instead. Sikorsky solved the problem by putting the engine in the nose of the S-55. BuNo 30370 was the second of two S-53 airframes built. Photo from: Vertical Flight Society