Helicopter Sikorsky HO4S-3 Serial 55-605 Register 138520 used by US Navy USN. Built 1953. Aircraft history and location Aircraft History 138520 US Navy 1953-11-30Sikorsky S-55 c/n 55-605, ff:? del USN as HO4S-3, 138520, 30Nov53. Send Updates Use APP to upload photo @ (optional) When Now? / / Send