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The Piasecki H-21 was a successor to a line of tandem helicopters used by the U.S. military dating back to the end of World War II. It differed from its predecessors by being an all metal design with the ability to carry a heavier payload. Prior Piasecki helicopters which were used by the U.S. Navy were fabric covered.
The Piasecki H-21, sometimes called the Shawnee, Workhorse, or flying banana, had a pair of three bladed main rotors in a tandem arrangement. These were driven by a single radial piston engine located behind the main cabin. It was generally fitted with non retractable landing gear, but could also be equipped with pontoons.
When fitted for air rescue, the H-21 could hold up to 12 stretchers and had accommodations for two medics.
Airline versions of the Piasecki H-21 generally had 15 seats, plus a rear cargo area. The helicopter could carry a 5,000 lb. payload. The rear door of the helicopter had built-in passenger steps and a hand rail to allow for easy loading.
The U.S. government contracted for 540 Piasecki H-21 helicopters in the early 1950's to be used by the army and air force. It is unclear how many other H-21 helicopters were produced. The military helicopters were well armored, and had a long range due to the mounting of external fuel tanks. They could carry up to 5,000 lbs. internally or 4,000 lbs. on a sling beneath the fuselage.
In 1956 the reliability of the Piasecki H-21 was demonstrated in a non-stop, 2,610 mile, 37 hour, U.S. coast to coast flight during which the helicopter was refueled in mid-air. This was the first such flight ever by a helicopter.
In late 1961 some Piasecki H-21 helicopters were sent to Vietnam as troop and light armor transports. These were armed with .30 and .50 caliber machine guns in their doors. They served through 1964.
Civilian versions of the helicopter were purchased by New York Airlines and other commercial carriers.
Piasecki H-21 helicopters were exported to Canada, France, Germany and Japan. They were also deployed with the Swedish Navy for anti-submarine warfare.
Most Piasecki H-21 helicopters were retired from service by the late 1960's. It appears that a single H-21 is still flying. It is located at the Classic Rotors Museum in Ramona, CA.