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Sikorsky CH-37 Mojave

The S-56 helicopters featured a 68 foot (later increased to 72 foot) 5 bladed fully articulated main rotor and a 4 bladed tail rotor powered by the Pratt and Whitney Double Wasp R-2800-50, 1,900 hp (later R-2800-54, 2,100 hp), 18 cylinder, twin row, air cooled radial engine.

The S-56 was a giant step forward in helicopter design. It was four times larger than the S-58 model and comparable in size to the Douglas DC-3 twin engine transport. At the time of its introduction it was the largest and fastest helicopter in the western world. It was also Sikorsky’s first multi-engine, retractable main landing gear helicopter and is the largest piston-engine helicopter ever built. It was also the first Sikorsky helicopter with Automatic Main Rotor Blade folding (CH-37C), and an Auxiliary Power Unit which provided electrical power for the Cargo Winch to allow self-loading

In 1956 a Marine HR2S-1 helicopter set 3 World records: a speed record without payload of 162.7 mph (141.4 kts); an altitude record of 12,100 ft (3688.1 meters) with a 11,023 lbs (5000 kg) load; and a load carrying record of 13,227 lbs (6000 kg) to 6,561 feet (2000 meters).

More at http://www.sikorskyarchives.com/S+56%20HR2S-1H-37.php