Helicopter Sikorsky H-37A Mojave Serial 56-073 Register 55-638 used by US Army Aviation Army. Built 1958. Aircraft history and location Aircraft History 55-638 US Army Aviation 1958-03-10Sikorsky S-56, c/n 56-073, ff:? del US ARMY as H-37A, 55-638, 10Mar58 redesig CH-37A, Oct 62 conv CH-37B, unk wfu & soc unk. Send Updates Use APP to upload photo @ (optional) When Now? / / Send