Piasecki H-21

H-21 Shawnee/Workhorse
USAF CH-21B at the National Museum of the United States Air Force.
Role Cargo helicopter
Manufacturer Piasecki Helicopter
First flight 1952
Retired 1967
Status retired from active service
Primary users United States Air Force
United States Army
French Army Aviation
Produced 1952-1959
Developed from HRP Rescuer

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 1,150 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.[1] 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.[2]

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 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.[3]

Operational history

French service in the Algerian War

A Shawnee over rice paddies in Vietnam.

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.[4][5][6]

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.[4][5][6]

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.[7] 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.[8] 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

Cockpit view of the H-21.
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.
CH-127
Vertol Canada Model 44
Piasecki HkP1
Piasecki modell 44 for the Swedish Navy

Operators

H-21C in German Army markings
Hkp 1 in Swedish Navy markings
CH-21C with 105mm howitzer as a slung load

Military operators

 Canada
 France
 Germany
 Japan
 Sweden
 United States

Civil operators

 United States

Aircraft on display

Germany

Japan

Model 44A JG-0001 in JGSDF markings at the Bihoro air park in Bihoro, Hokkaido in August 2009

Russia

Sweden

United States

H-21B Shawnee 53-4347 on display at the Pueblo Weisbrod Aircraft Museum in Pueblo, Colorado in November 2007
CH-21B 53-4366 in USAF markings at the Canadian Museum of Flight 1988
Airworthy
Static Display
H-21C at Wings Over the Rockies Museum
Stored or under restoration

Specifications (CH-21C)

Data from U.S. Army Aircraft Since 1947 [22]

General characteristics

Performance

Armament

See also

Related development
Aircraft of comparable role, configuration and era
Related lists

References

  1. ↑ "Here Comes the Leathernecks." Popular Mechanics, April 1952, p. 101, bottom of page.
  2. ↑ "Flying Salvage Craft Works on Land Or Sea." Popular Mechanics, July 1957, p. 106
  3. ↑ "Workhorses of the Air." Popular Mechanics, March 1959, p. 100.
  4. 1 2 France, Operations Research Group, Report of the Operations Research Mission on H-21 Helicopter (1959)
  5. 1 2 Riley, David, French Helicopter Operations in Algeria, Marine Corps Gazette, February 1958, pp. 21-26
  6. 1 2 Shrader, Charles R. The First Helicopter War: Logistics and Mobility in Algeria, 1954-1962 Westport, CT: Praeger Publishers (1999)
  7. ↑ The New Propwash, Fox Valley Sport Aviation Assoc., Vol.2, Issue 12, p. 5
  8. ↑ Harding 1990, pp. 261–262.
  9. ↑ Flight 13 May 1955, p. 621.
  10. ↑ Arkell Flight 21 June 1957, p. 844.
  11. 1 2 Flight 11 July 1968, p. 51.
  12. ↑ "aéronautique navale H-21". helis.com. Retrieved 5 January 2013.
  13. 1 2 Flight 11 July 1968, p. 53.
  14. ↑ Flight 11 July 1968, p. 55
  15. ↑ Swanborough and Bowers 1963, pp. 398–399.
  16. ↑ Flight 13 May 1955, p. 668.
  17. ↑ "Helicopters in Civil Operations pg. 388". flightglobal.com. 21 March 1958. Retrieved 10 February 2015.
  18. ↑ "Hkp 1 - Flygvapenmuseum". Flygvapenmuseum.se. 2010-04-21. Retrieved 2012-12-17.
  19. ↑ "FAA REGISTRY: N64606". Federal Aviation Administration. 11 November 2009. Retrieved 2009-11-12.
  20. ↑ Classic Rotors Museum (n.d.). "About Us". Retrieved 2009-11-13.
  21. ↑ United States Air Force Museum (1975 edition)
  22. ↑ Harding 1990, p.262.

External links

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