Helicopter Sikorsky HO4S-3 Serial 55-689 Register 138593 used by US Navy USN. Built 1954. Aircraft history and location Aircraft History 138593 US Navy 1954-04-07Sikorsky S-55 c/n 55-689, ff:? del USN as HO4S-3, 138593, 07Apr54. Send Updates Use APP to upload photo @ (optional) When Now? / / Send