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 °F (−54 °C), and could be routinely maintained in severe cold weather environments.
Design and development
Piasecki Helicopter designed and successfully sold to the United States 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 strike 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-21 Workhorse to the United States Air Force (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 nine-cylinder Curtis-Wright R-1820-103 Cyclone supercharged 1,.50 hp (858 kW) air-cooled radial engine. After its maiden flight in April 1952, the USAF 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 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.
In 1952, some H-21As were evaluated by USMC helicopter squadron HMX-1 in the air assault role. In 1957, an H-21B was loaned to the United States Marine Corps (USMC) to evaluate the helicopter as an airborne tug to tow disabled landing ships and amphibious landing vehicles to the beach. During the evaluation, the H-21B towed an LST at 5 knots and a simulated tracked amphibious vehicle from the water to the beach.
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 and six H-21Bs would be 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.
French service in the Algerian War
In 1956, seeking a way to use helicopters in a ground-attack role in the Algerian War, the French Air Force and French Army Aviation (ALAT, Aviation Légère de l'Armée de Terre) experimented with arming the Sikorsky S-55, then being superseded in service by the more capable Piasecki H-21 and Sikorsky H-34 helicopters. Some French Air Force and Army aviation H-21C helicopters were subsequently armed with fixed, forward-firing rockets and machine guns. A few even had racks for bombs, but tests subsequently determined that the H-21C lacked the maneuverability and performance needed in the ground-attack role. The H-21C was far more successful as a troop transport, and most H-21Cs in service were eventually fitted with flexible door-mounted guns such as the .50 cal. (12.7 mm) Browning machine gun or the (ex-German) MG 151/20 20 mm aircraft cannon for defensive use when landing assault forces under fire.
Though the H-21 had been removed from the ground-attack role, official U.S. Army evaluations at the time indicated that the type was actually more likely to survive multiple hits by ground fire than was the Sikorsky CH-34; this was assumed to be a consequence of the location and construction of the CH-34's fuel tanks. By the close of the Algerian War, troop-carrying H-21C helicopters were being used in concert with H-34 ground-attack helicopters in large-scale counterinsurgency operations.
U.S. Army operations
The H-21C saw extensive service with the U.S. Army, primarily for use in transporting troops and supplies. On 24 August 1954, with the assistance of inflight 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 Army of the Republic of Vietnam troops. In Army 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 North Vietnamese Army and Vietcong ground forces, which were increasingly well supplied with automatic small arms and heavy (12.7 mm) AA machine guns. The H-21, which was designed for cold weather operations, performed poorly in the hot weather of Vietnam. Despite being capable of carrying 20 passengers, it carried only nine when operating in Vietnam. The shooting down of a CH-21 Shawnee near the Laotian-Vietnamese border with the death of four aviators in July 1962 were some of the U.S. Army's earliest 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 Bell UH-1 Huey. In 1965, the Boeing 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.
Variants
XH-21
USAF designation of the first H-21 prototype.
YH-21 Work Horse
USAF Search And Rescue (SAR) version of the HRP-2 for service test, eighteen built
H-21A Work Horse (Model 42)
Same as YH-21 with detailed changes and powered by one 1250hp Wright R-1820-102, re-designated CH-21A in 1962, 32 built for USAF, 6 for the Royal Canadian Air Force)
H-21B Work Horse (Model 42)
Same as H-21A but with uprated Wright engine (1425hp) and seats for 20 troops, autopilot as standard and limited armour protection and external fuel tanks, became CH-21B in 1962, 163 built for U.S. forces. 10 built for Japanese Self-Defense Forces; 10 H-21B built for the French Navy.
SH-21B Work Horse
Rescue conversion of the H-21B, became HH-21B in 1962.
H-21C Shawnee (Model 43)
US Army version of the H-21B, became CH-21C in 1962, 334 built for U.S. forces. 32 built under license by Weser Flugzeugbau for the West German Army. 98 built for the French Air Force and French Army Aviation (ALAT).
XH-21D Shawnee (Model 71).
Two H-21Cs re-engined with two General Electric T58 turboshaft engines in place of the Wright R-1820. Not placed into production.
CH-21A
H-21A redesignated in 1962.
CH-21B
H-21B redesignated in 1962.
CH-21C
H-21C redesignated in 1962.
HH-21B
SH-21B redesignated in 1962.
Model 42A
Conversion by Vertol Aircraft (Canada) of eight Royal Canadian Air Force H-21s for civilian use. Equipped to carry 19 passengers or 2,820lb (1,279kg) of internal cargo or a 5,000lb (2,268kg) slung load.
Model 44A
Commercial 19-passenger transport version of the H-21B. 11 total (Swedish military designation: Hkp 1), 2 for the Swedish Air Force, 9 for the Swedish Navy. 2 used for test/evaluation purposes by Japan Self-Defense Forces.
Model 44B
Commercial 15-passenger/freighter version of the H-21B.
Model 44C
Commercial eight-passenger executive version of the H-21B.
02-4756 – H-21B on static display at the JASDF Air Park in Hamamatsu, Shizuoka.
Russia
N74056 – Model 44A on static display at Central Air Force Museum in Monino, Moscow. U.S. Vice President Richard Nixon gave it as a gift to Soviet premier Leonid Brezhnev.
53-4354 – CH-21C on static display at the Arkansas Air & Military Museum in Fayetteville, Arkansas.
53-4362 – SH-21B on static display at the Alaska Museum of Transportation and Industry in Wasilla, Alaska.
53-4366 – CH-21B on static display at the Museum of Flight in Seattle, Washington. This airframe was previously on display at the Canadian Museum of Flight in Langley, British Columbia.
53-4389 – CH-21B on static display at the Pima Air & Space Museum in Tucson, Arizona.
54-4404 – CH-21B on static display at the Alaska Aviation Heritage Museum in Anchorage, Alaska.
55-4140 – CH-21C on static display at the American Helicopter Museum & Education Center in West Chester, Pennsylvania. This airframe was previously on display at the Intrepid Sea, Air & Space Museum in New York, New York.
54-4003 – CH-21B in storage at the American Helicopter Museum & Education Center in West Chester, Pennsylvania. This airframe was previously on display at the Florence Air & Missile Museum in Florence, South Carolina.
c/n 438 – Model 44B in storage in unrestored condition at the Gillespie Field Annex of the San Diego Air & Space Museum in El Cajon, California.
Specifications (CH-21C)
Data from U.S. Army Aircraft Since 1947
General characteristics
Crew: 3–5 (Pilot, co-pilot, crew chief and one or two gunners in Vietnam)
