Helicopter Sikorsky HO4S-3 Serial 55-705 Register 138596 used by US Navy USN. Built 1954. Aircraft history and location Aircraft History 138596 US Navy 1954-05-10Sikorsky S-55 c/n 55-705, ff:? del USN as HO4S-3, 138596, 10May54. Send Updates Use APP to upload photo @ (optional) When Now? / / Send