Frank Piasecki was born in Philadelphia in 1919, the son of an immigrant Polish tailor. He earned degrees in aeronautical and mechanical engineering by the age of 20 and in 1940, he gained the support of a few friends and started a small aeronautical company.

He built a single-person, single-rotor helicopter designated the PV-2 and test-flew it by 1943. Piasecki realized that Sikorsky was the favored helicopter manufacturer for the U.S. Army, so he made an appeal to the U.S. Navy with his PV-2. Navy leaders initially showed little interest in helicopters, but soon changed their minds. Piasecki also had an idea for a much larger helicopter capable of fulfilling various naval missions, such as rescuing sailors at sea. On January 1, 1944, he received a Navy contract for a single new heavy-duty transport helicopter.

Piasecki decided to build a helicopter that had two rotors, one at each end of a long, somewhat cylindrical fuselage. The two rotors were easier to manufacture and control than a single large rotor, and the long fuselage could be loaded with cargo or people, without much concern for even weight distribution.

Piasecki also simply did not like the idea of a tail rotor, which had given Igor Sikorsky problems with his VS-300 and which looked like a circular saw mounted right at head-chopping level—and robbed valuable horsepower from the lifting rotor.

The Piasecki H21 bringing back a drone

The Army became aware of the H-21's potential as a medium utility helicopter soon after the type's maiden flight, and in 1952 awarded Piasecki a contract for the production of the H-21C variant. This aircraft had extensive armor plating and the ability to carry two external fuel tanks, plus increased troop capacity and a 4000-pound capacity belly sling hook. The Army purchased 334 H-21C Shawnees, with deliveries beginning in August 1954.

In addition, the Army 'borrowed' at least sixteen H-21B aircraft from the USAF; the majority of these machines were ultimately brought up to H-21C standard, and all were known as 'Shawnees' despite their origins as USAF 'Work Horses'. The Army also funded Vertol's development of the XH-21D, which was essentially a standard H-21C whose single piston engine had been replaced by two General Electric T58 shaft turbines. Two H-21Cs were so modified and flight tested in 1957 and 1958, but the variant was not adopted for production. In 1962 the H-21B and H-21C were re designated as, respectively, the CH-21B and CH-21C.

Several additional aircraft were experimentally fitted with a variety of offensive weaponry and used as interim gun ships pending the arrival in Southeast Asia of the first units of armed UH-1 Iroquois in the summer of 1963. The H-21 remained the backbone of the Army's aviation effort in South Vietnam until finally supplanted by the UH-1 in 1964, and most Shawnees were withdrawn from the active inventory within the following year.

The H-21 was the last of the large, piston powered transport helicopters to see military service, being replaced by the turbine engine CH-47 'Chinook.'

Cockpit of the Piasecki H-21 Shawnee.

Specifications of the Piasecki H-21 Shawnee

Crew: 3–5 (Pilot, co-pilot, crew chief and one or two gunners in Vietnam) Capacity: 20 troops or 12 stretchers Length: 52 ft 6 in Rotor diameter: 44 ft Height: 15 ft 9 in Disc area: 3,041 ft² Empty weight: 8,950 lb Loaded weight: 15,200 lb Max takeoff weight: 15,200 lb Powerplant: 1× Wright R-1820-103 radial engine, 1,425 hp driving 2 rotors Performance Maximum speed: 127 mph Cruise speed: 98 mph Range: 265 mi Service ceiling: 9,450 ft Disc loading: 5 lb/ft² Power/mass: 0.09 hp/lb Armament Varying, but usually 1x or 2x .50 or 7.62 mm M60 machine guns.