Piasecki H-21

Last updated

H-21 Shawnee/Workhorse
Piasecki H-21 (modified).jpg
A US Army Piasecki H-21
General information
Type Military transport helicopter
National originUnited States
Manufacturer Piasecki Helicopter
StatusRetired
Primary users United States Air Force
History
Manufactured1952–1959
First flight11 April 1952
Retired1967
Developed from Piasecki 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, capable of being fitted with wheels, skis or floats.

Contents

The H-21 was originally developed by Piasecki as an Arctic rescue helicopter. The H-21 had cold-weather 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 H-21 cockpit Piasecki H-21 - Cockpit.jpg
Piasecki H-21 cockpit

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, which ensured that the large rotors could not strike the fuselage in any flight attitude. The name was later applied to other Piasecki helicopters of similar design, including the H-21.

In 1949, Piasecki proposed the YH-21 Workhorse, which was an improved, all-metal derivative of the HRP-1, to the United States Air Force (USAF). 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 the first flight of the YH-21 on 11 April 1952, the USAF ordered 32 H-21A SAR models and 163 of the more powerful H-21B assault transport variant. [1] The H-21B was equipped with an uprated version of the Wright 103 engine, developing 1,425 shaft horsepower (1,063 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, as a medevac helicopter. With its Arctic winter capabilities, the H-21A and H-21B were put into service by the USAF and the Royal Canadian Air Force (RCAF) to maintain and service Distant Early Warning Line (DEW) radar installations stretching from the Aleutian Islands and Alaska across the Canadian Arctic to Greenland and Iceland.

Piasecki H-21 cabin interior looking towards the cockpit Piasecki H-21 - inside.jpg
Piasecki H-21 cabin interior looking towards the cockpit

In 1952, some H-21As were evaluated by USMC helicopter squadron HMX-1 for air assault. [2] 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 kn (9.3 km/h; 5.8 mph) and a simulated tracked amphibious vehicle from the water to the beach. [3] 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 renamed the CH-21 in U.S. Army service.

In 1959 Vertol Aircraft, the new name for Piasecki Helicopters, 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 unbalance the structure and cause all helicopters to crash. [4]

Operational history

French service in the Algerian War

A Shawnee over rice paddies in Vietnam Color shawnee over rice paddies.jpg
A Shawnee over rice paddies in Vietnam

In 1956, seeking a way to use helicopters for ground-attack in the Algerian War, the French Air Force and French Army Aviation (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 found that the H-21C lacked the maneuverability and performance needed for ground-attack. 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) M2 Browning machine gun or the (ex-German) MG 151/20 20 mm aircraft autocannon, for defensive use when landing assault forces under fire. [5] [6] [7]

Though the H-21 had been removed from ground-attack, official U.S. Army evaluations at the time indicated that the type was actually more likely to survive 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 counterinsurgency operations. [5] [6] [7]

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 non-stop. [8] [9] 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.

H-21 Shawnees of the 8th Transportation Company, Ft Bragg, 1956. The company had 24 helicopters, 48 officers and warrant officers, and 246 enlisted men. H-21 Shawnees Fort Bragg 1956.png
H-21 Shawnees of the 8th Transportation Company, Ft Bragg, 1956. The company had 24 helicopters, 48 officers and warrant officers, and 246 enlisted men.

One experimental version was tested 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 South 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 Vietcong, which were increasingly well supplied with automatic small arms and heavy (12.7 mm) anti-aircraft 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 could lift only nine when operating in Vietnam. Pilots reported that engines that were rated for 600 hours of flying time were lasting only 200 hours or less in Vietnam. [10] 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 casualties in the Vietnam War. [11] 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.
CH-127
Vertol Canada Model 44
Piasecki HkP1
Piasecki model 44 for the Swedish Navy

Operators

A US Army H-21 in flight US Army H-21 in flight.jpg
A US Army H-21 in flight

Former military operators

Canadian Red Ensign (1921-1957).svg  Canada
Flag of France.svg  France
Hkp 1 in Swedish Navy markings Piasecki H-21 - left.jpg
Hkp 1 in Swedish Navy markings
Flag of Japan (1870-1999).svg  Japan
Flag of Sweden.svg  Sweden
Flag of the United States (1959-1960).svg  United States
An HH-21 with US Air Force USAF H-21 manual.jpg
An HH-21 with US Air Force
Flag of Germany.svg  West Germany
Flag of Zaire (1971-1997).svg  Zaire

Civil operators

Flag of the United States (1912-1959).svg  United States

Aircraft on display

Canada

France

A USAF CH-21B at the National Museum of the United States Air Force Vertol CH-21B Workhorse USAF.jpg
A USAF CH-21B at the National Museum of the United States Air Force

Germany

Japan

Russia

Sweden

United States

Airworthy
Static Display
Model 44A with the JGSDF at Bihoro Aviation Park, August 2009 JGSDF V-44A.JPG
Model 44A with the JGSDF at Bihoro Aviation Park, August 2009
CH-21 in RCAF markings at the Canadian Museum of Flight Musee defense aerienne - Vertol H-21B.jpg
CH-21 in RCAF markings at the Canadian Museum of Flight
Stored or under restoration

Specifications (CH-21C)

3-view line drawing of the Piasecki YH-21 Workhorse Piasecki YH-21 Workhorse 3-view line drawing.png
3-view line drawing of the Piasecki YH-21 Workhorse

Data from U.S. Army Aircraft Since 1947 [78]

General characteristics

Performance

Armament

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

Related Research Articles

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References

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  70. ↑ "Airframe Dossier – Piasecki CH-21C Shawnee, s/n 56-2077 US, c/n C.239". Aerial Visuals. AerialVisuals.ca. Retrieved 21 October 2016.
  71. ↑ "CH-21C "Workhorse"". Hill Air Force Base. 27 September 2007. Archived from the original on 19 October 2016. Retrieved 20 October 2016.
  72. ↑ "WORKHORSE". Pima Air & Space Museum. Pimaair.org. Archived from the original on 21 October 2016. Retrieved 20 October 2016.
  73. ↑ "Aircraft Inventory". Flight Test Historical Foundation. Archived from the original on 19 October 2016. Retrieved 21 October 2016.
  74. ↑ "Airframe Dossier – Piasecki H-21B Work Horse, s/n 52-8683 USAF, c/n B.45, c/r N57968". Aerial Visuals. AerialVisuals.ca. Retrieved 21 October 2016.
  75. ↑ "Airframe Dossier – PiaseckiH-21, s/n 53-4329 USAF, c/r N6794". Aerial Visuals. AerialVisuals.ca. Retrieved 21 October 2016.
  76. ↑ "Airframe Dossier – Piasecki-Vertol H-21B Work Horse, s/n FR09 AdT, c/n B.155". Aerial Visuals. AerialVisuals.ca. Retrieved 21 October 2016.
  77. ↑ "Airframe Dossier – Piasecki 44B, c/r N74058". Aerial Visuals. AerialVisuals.ca. Retrieved 17 November 2016.
  78. ↑ Harding 1990, p.262.
  79. ↑ Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
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