Helicopter Sikorsky S-55 Serial 55-744 Register HS-1 used by Royal Thai Air Force. Built 1954. Aircraft history and location Aircraft History For HS-1 see also mi-8t 133 01 HS-1 Royal Thai Air Force 1954-06-25Sikorsky S-55 c/n 55-744, ff:? del RTAF as HS-1, 25Jun54. H3-1/97 Send Updates Use APP to upload photo @ (optional) When Now? / / Send