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M O D E L YH-16, M O D E L YH-16A
In 1964, development of the H-16 was initiated in response to a U.S. Air Force requirement for a long range (1432 mi.) Rescue helicopter to pick up (1-1/2 way mission) bomber crews. The YH-16 became the largest helicopter in the world, having a rotor diameter of 82 feet and an overall length (rotors turning) of 134 feet. The fuselage was as large as that of a four-engine airliner and could accommodate three light trucks loaded through a rear ramp.
Initially powered with two P&W R-2180-11 radial engines (each in an engine room), the YH-16 was the first twin engine helicopter. Later, the YH-16 became the world’s first twin turbine helicopter.
The three blades in each rotor were all aluminum alloy step taper milled skins keeping a ± .002 inch tolerance through their 41 foot radius by a special process developed by Piasecki. The bonded blade was made in four pieces, with two outer skins, a honeycomb filler and a leading edge balance weight which was almost a mechanical fastener of the leading edges of the skins.
The first flight of the YH-16 was 23 October 1953. The slow turning speed of the rotors (125 rpm) almost made the blades visible in their rotation and in-flight vibration was loping in character.
The size of the YH-16A fit the power output of the existing 1800 HP Allison T-38 gas shaft turbine. However, the T-38 was not a free-wheeling turbine and thus not ideally suited for multi-turbine interconnection. A concept was developed to tune the two fixed shaft turbines to act in consonance. (This concept was later utilized in Air Geep II).
The U.S. Army saw the H-16 as an answer to several of its military transport missions and joined in the project. The tall landing gear version was of particular interest since it allowed the rapid attachment of external loads or pods.
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If God had wanted man to fly behind a flat motor, Pratt Whitney would've built one.
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