Design and development
Piasecki Helicopter designed and successfully sold to the US Navy a series of tandem rotor helicopters, starting with the HRP-1 of 1944. The HRP-1 was nicknamed the “flying banana” because of the upward angle of the aft fuselage that ensured the large rotors did not hit each other in flight. The name would later be applied to other Piasecki helicopters of similar design, including the H-21.
In 1949, Piasecki proposed the YH-21A Workhorse to the USAF, which was an improved, all-metal derivative of the HRP-1. Using two tandem fully articulated three-bladed counter-rotating rotors, the H-21 was powered by one 9-cylinder Curtis-Wright R-1820-103 Cyclone supercharged 1,150 hp (858 kW) air-cooled radial engine. After its maiden flight in April 1952, the Air Force ordered 32 H-21A SAR models and 163 of the more powerful H-21B assault transport variant. The H-21B was equipped with an uprated version of the Wright 103 engine, developing 1425 shaft horsepower (1063 kW), and featured rotor blades extended by 6 inches (152 mm). With its improved capabilities, the H-21B could carry 22 fully equipped infantrymen, or 12 stretchers, plus space for two medical attendants, in the medevac role. With its Arctic winter capabilities, the H-21A and H-21B were put into service by both the U.S. Air Force (USAF) and the Royal Canadian Air Force (RCAF) to maintain and service DEW (Distant Early Warning) radar installations stretching from the Aleutian Islands and Alaska across the Canadian Arctic to Greenland and Iceland.
The uprated 1425 hp Wright engine used in the H-21B was also used in subsequent variants sold to both the U.S. Army (as the H-21C Shawnee) and the military forces of several other nations. In 1962, the H-21 was redesignated the CH-21 in U.S. Army service.
In 1959 Vertol Aircraft, who had acquired Piasecki, came up with a concept for heavy lift over short distances where between two to six H-21Bs would linked by beams to lift heavy loads. It was considered to be unsafe, because if one helicopter had mechanical problems during the lift it could cause an unbalanced situation and cause all helicopters to crash.
The Piasecki H-21 Workhorse/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 degrees F, and could be routinely maintained in severe cold weather environments
|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 (16.01 m)|
|Rotor diameter:||44 ft 0 in (13.41 m)|
|Height:||15 ft 9 in (4.80 m)|
|Disc area:||3,041 ft² (282.6 m²)|
|Empty weight:||8,950 lb (4,058 kg)|
|Loaded weight:||15,200 lb (6,893 kg)|
|Max takeoff weight:||15,200 lb (6,609 kg)|
|Powerplant:||1 × Wright R-1820-103 radial engine, 1,425 hp (1,063 kW) driving 2 rotors|
|Maximum speed:||127 mph (110 knot, 204 km/h)|
|Cruise speed:||98 mph (85 knots, 158 km/h)|
|Range:||265 mi (230 nmi, 427 km)|
|Service ceiling:||9,450 ft (2,880 m)|
|Disc loading:||5 lb/ft² (24 kg/m²)|
|Power/mass:||0.09 hp/lb (150 W/kg)|
Varying, but usually one or two .50 (12.7 mm) or 7.62 mm M60 machine guns.
US Army Operations
The H-21C saw extensive service with the U.S. Army, primarily for use in transporting troops and supplies. On August 24, 1954, with the assistance of in-flight refueling provided by a U.S. Army U-1A Otter, a H-21C known as Amblin’ Annie became the first helicopter to cross the United States nonstop. Various experiments were made by the Army in arming the H-21C as a gunship; some Shawnees were armed with flex guns under the nose, while others were fitted with door guns. One experimental version was tested stateside with a Boeing B-29 Superfortress .50 cal. remote turret mounted beneath the nose. The H-21C (later designated CH-21C) was first deployed to Vietnam in December 1961 with the Army’s 8th and 57th Transportation Companies, in support of ARVN (Army Republic South Vietnam) troops. In Army aviation service, the CH-21C Shawnee could be armed with 7.62 mm (.308 in) or 12.7 mm (.50 in) flexible door guns. Relatively slow, the CH-21’s unprotected control cables and fuel lines proved vulnerable to the enhanced threat posed by NVA and Viet Cong ground forces, which were increasingly well supplied with automatic small arms and heavy (12.7 mm) AA machine guns. The shooting down of a CH-21 Shawnee near the Laotian-Vietnamese border with the death of four Army aviators in July 1962 were the U.S. Army’s first Vietnam casualties. Despite these events, the Shawnee continued in service as the U.S. Army’s helicopter workhorse in Vietnam until 1964 when it was replaced with the UH-1 Huey. In 1965, the CH-47 Chinook was deployed to Vietnam, and later that year, most CH-21 helicopters were withdrawn from active inventory in the U.S. Army and Air Force.
- Canada Royal Canadian Air Force operated H-21A and Model 44A helicopters.
- France French Air Force operated H-21C helicopters.
- French Army operated H-21B helicopters.
- French Navy operated H-21B helicopters.
- Germany German Air Force operated H-21C helicopters.
- German Army operated H-21C helicopters.
- Japan Japan Air Self-Defense Force operated 10 H-21B helicopters as rescue.
- Japan Ground Self-Defense Force operated 2 Model 44A helicopters for testing. Japan Self-Defense Forces called H-21B and Model 44A Hou-Ou(ほうおう, Fenghuang).
- Sweden Swedish Air Force operated HKP-1 helicopters.
- Swedish Navy operated HKP-1 helicopters.
- United States United States Army operated H-21C from 1949 to 1967.
- United States Air Force operated H-21A, H-21B and SH-21B helicopters.
- United States Coast Guard operated HRP-1, HRP-1G and HRP-2 helicopters.
- Canada Dominion Helicopters
- Mexico Electramex
- United States New York Airways