Helicopter Sikorsky H-19B Chickasaw Serial 55-611 Register 52-7520 used by US Air Force USAF. Built 1953. Aircraft history and location Aircraft History 52-7520 US Air Force 1953-12-19Sikorsky S-55 c/n 55-611, ff:? del USAF as H-19B, 52-7520, 19Dec53. Send Updates Use APP to upload photo @ (optional) When Now? / / Send