It's a Sikorsky CH-37 or in civilian configuration, the S-56.
Ah, the joys of the twin radials, retractable gear, a 5 bladed, greased, crane main rotor and the fully articulated tail rotor!!!
That this monsterous behemoth took to the air so soon after the first practical helicopter is mindblowing. The projects that followed in its footsteps with the transition to turbine engines were equally mindblowing!
