Helicopter Sikorsky HO4S-3 Serial 55-687 Register 138591 used by US Navy USN. Built 1954. Aircraft history and location Aircraft History 138591 US Navy 1954-04-22Sikorsky S-55 c/n 55-687, ff:? del USN as HO4S-3, 138591, 22Apr54. Send Updates Use APP to upload photo @ (optional) When Now? / / Send