Helicopter Sikorsky H-19B Chickasaw Serial 55-540 Register 52-7500 used by US Air Force USAF. Built 1953. Aircraft history and location Aircraft History 52-7500 US Air Force 1953-10-21Sikorsky S-55 c/n 55-540, ff:? del USAF as H-19B, 52-7500, 21Oct53. Send Updates Use APP to upload photo @ (optional) When Now? / / Send