Helicopter Sikorsky HO4S-3 Serial 55-688 Register 138592 used by US Navy USN. Built 1954. Aircraft history and location Aircraft History 138592 US Navy 1954-04-09Sikorsky S-55 c/n 55-688, ff:? del USN as HO4S-3, 138592, 09Apr54. Send Updates Use APP to upload photo @ (optional) When Now? / / Send