Helicopter Sikorsky S-55 Serial 55-772 Register HS-6 used by Royal Thai Air Force. Built 1954. Aircraft history and location Aircraft History For HS-6 see also mi-8ps 133 06 HS-6 Royal Thai Air Force 1954-10-01Sikorsky S-55 c/n 55-772, ff:? del RTAF as HS-6, 01Oct54. H3-6/97 Send Updates Use APP to upload photo @ (optional) When Now? / / Send