Helicopter Sikorsky H-19D Chickasaw Serial 55-1137 Register 56-4256 used by US Army Aviation Army. Built 1957. Aircraft history and location Aircraft History 56-4256 US Army Aviation 1957-10-30Sikorsky S-55 c/n 55-1137, ff:? del US Army as H-19D, 56-4256, 30Oct57. Send Updates Use APP to upload photo @ (optional) When Now? / / Send