Nniiden Piasecki H-21 Työhevonen/Shawnee is an American helicopter, the fourth of a line of tandem rotor helicopters designed and built by Piasecki Helicopter (later Boeing Vertol). Commonly called “the flying banana”, it was a multi-mission helicopter, utilizing wheels, skis, or floats.
The H-21 was originally developed by Piasecki as an Arctic rescue helicopter. The H-21 had winterization features permitting operation at temperatures as low as −65 °F (−54 °C), and could be routinely maintained in severe cold weather environments.
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The Piasecki HU-2 was a variant of the Piasecki HUP Retriever, a compact utility helicopter with twin overlapping tandem rotors. The HU-2 was designed for the US Navy to perform rescue and transport missions from ships and aircraft carriers. The HU-2 was powered by a single Continental R-975 radial engine and could carry up to four passengers or two stretchers. The HU-2 was also equipped with an autopilot and a winch that could lower a rescue sling through a door in the cabin. The HU-2 was one of the first helicopters to perform a loop, although this was unintentional. The HU-2 was produced from 1949 to 1954 and was later replaced by the Sikorsky H-34.