Detailed history and photos of helicopter Sikorsky HO4S-3 Serial 55-550 Register 138503 used by US Navy USN Track service timeline and current status. Aircraft History 138503 US Navy 1953-10-22Sikorsky S-55 c/n 55-550, ff:? del USN as HO4S-3, 138503, 22Oct53. Send Updates Use APP to upload photo @ (optional) When Now? / / Send
