ThePiasecki H-21 Workhorse/Shawnee is an American helicopter, the fourth of a line oftandem rotor helicopters designed and built byPiasecki Helicopter (laterBoeing Vertol). Commonly called "the flying banana", it was a multi-mission helicopter, capable of being fitted with wheels, skis or floats.

H-21 Shawnee/Workhorse
AUS Army Piasecki H-21
General information
Type	Military transport helicopter
National origin	United States
Manufacturer	Piasecki Helicopter
Status	Retired
Primary users	United States Air Force United States Army French Army Light Aviation
History
Manufactured	1952–1959
First flight	11 April 1952
Retired	1967
Developed from	Piasecki HRP Rescuer

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.

Piasecki Helicopter designed and successfully sold to theUnited States Navy a series of tandem rotor helicopters, starting with theHRP-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-21Workhorse, 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-cylinderCurtis-Wright R-1820-103 Cyclone supercharged 1,150 hp (858 kW)air-cooledradial 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 1,425shaft horsepower (1,063 kW) and featured rotor blades extended by 6 inches (152 mm). With its improved capabilities, theH-21B could carry 22 fully equipped infantrymen or 12 stretchers, plus space for two medical attendants, as amedevac 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 serviceDistant Early Warning Line (DEW) radar installations stretching from theAleutian Islands andAlaska across theCanadian Arctic toGreenland andIceland.

In 1952, some H-21As were evaluated by USMC helicopter squadronHMX-1 for air assault.^[2] In 1957, an H-21B was loaned to theUnited 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 anLST 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-21CShawnee) 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]

In 1956, seeking a way to use helicopters for ground-attack in theAlgerian War, the French Air Force and French Army Aviation (Aviation Légère de l'Armée de Terre) experimented with arming theSikorsky S-55, then being superseded in service by the more capable Piasecki H-21 andSikorsky 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]

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. ArmyU-1A Otter, a H-21C known asAmblin' 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.

One experimental version was tested with aBoeing B-29 Superfortress .50 cal. remote turret mounted beneath the nose. The H-21C (later designated CH-21C) was first deployed toSouth Vietnam in December 1961 with the Army's 8th and 57th Transportation Companies, in support ofArmy 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 theVietcong, who 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 theVietnam 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 theBell UH-1 Huey. In 1965, theBoeing 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.

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 1250hpWright 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 forJapanese Self-Defense Forces; 10 H-21B built for theFrench 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 theFrench Air Force andFrench Army Aviation (ALAT).

XH-21D Shawnee (Model 71).

Two H-21Cs re-engined with twoGeneral 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 theSwedish Air Force, 9 for theSwedish 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

  Canada

• Royal Canadian Air Force^[12]

  France

• French Air Force^[13]
• French Army^[14]

• French Navy^[15]

  Japan

• Japan Air Self-Defense Force^[16]
• Japan Ground Self-Defense Force^[16]

  Sweden

• Swedish Navy^[17]

  United States

• United States Air Force^[18]
• United States Army^[19]

  West Germany

• WestGerman Army^[20]

  Zaire

• Zairean Air Force^[21]

  United States

• New York Airways^[22]

• 642 – On display at theMusée de la Défense aérienne ofCFB Bagotville,Quebec^[23]
• 641 – On display at the Heritage Air Park of theComox Air Force MuseumCFB Comox,British Columbia^[24]

• FR94 – H-21C on static display at the Musée de l'Aviation Légere de l'Armée de Terre et de l'Hélicoptère inDax, Landes.^[25]
• FR106 is on display at the "Ailes Anciennes" Museum at Toulouse-Blagnac Airport.^[26]

• 83+07 – H-21C on static display at theHubschraubermuseum Bückeburg inBückeburg, Lower Saxony.^[27][28]
• 83+08 – H-21C on static display at theMilitärhistorisches Museum Flugplatz Berlin-Gatow inBerlin, Berlin.^[29]
• 83+11 – H-21C on static display at theFlugausstellung Hermeskeil inHermeskeil, Rhineland-Palatinate.^[30]
• 83+17 – XH-21D on static display at theAuto & Technik Museum Sinsheim inSinsheim, Baden-Württemberg.^[31]

• JG-0001 – Model 44A on static display at theBihoro Aviation Park inBihoro, Hokkaido.^[32]
• JG-0002 – Model 44A on static display at theTokorozawa Aviation Museum inTokorozawa, Saitama.^[33][34][32]
• 02-4756 – H-21B on static display at the JASDF Air Park inHamamatsu, Shizuoka.^[35][36]

• N74056 – Model 44A on static display atCentral Air Force Museum inMonino, Moscow.^[37]

• 01001 – HKP 1 on static display at theSwedish Air Force Museum inLinköping, Östergötland.^[38]
• 01009 – HKP 1 on static display at the Gotland Museum of Defence inTingstäde,Gotland.^[39]

Airworthy

• 54-4001 – CH-21B airworthy at theClassic Rotors Museum inRamona, California. This is the last H-21 still flown.^[40][41]

Static Display

• 51-15857 – CH-21B on static display at theNational Museum of the United States Air Force atWright-Patterson AFB inDayton, Ohio. It was obtained fromEglin Air Force Base in January 1965.^[42]
• 51-15859 – CH-21B on static display atBattleship Memorial Park inMobile, Alabama.^[43][44]
• 51-15886 – CH-21C on static display at theAerospace Museum of California atMcClellan Airport (formerMcClellan AFB) inMcClellan, California.^[45]
• 51-15892 – CH-21B on static display at theQuonset Air Museum at the formerNaval Air Station Quonset Point inNorth Kingstown, Rhode Island.^[46]
• 52-8676 – CH-21B on static display at theStrategic Air Command & Aerospace Museum nearOffutt AFB inAshland, Nebraska.^[47]
• 52-8685 – CH-21B on static display at theMuseum of Aviation atRobins AFB nearWarner Robins, Georgia.^[48]
• 52-8688 – CH-21B on static display at theTravis Air Force Base Heritage Center nearFairfield, California.^[49]
• 52-8691/52-8706 – CH-21B on static display atKirtland Air Force Base inAlbuquerque, New Mexico. This airframe is a composite of two different airframes and is painted as 53-4343.^[50]
• 52-8696 – CH-21B on static display atJoint Base Elmendorf-Richardson nearAnchorage, Alaska.^[51]
• 53-4323 – HH-21B on static display at Berryman War Memorial Park inBridgeport, Washington.^[52]
• 53-4324 – CH-21B on static display at theVintage Flying Museum inFort Worth, Texas.^[53] This airframe was previously on display at the Pate Museum of Transportation inCresson, Texas.^[54]
• 53-4326 – CH-21B on static display at theMarch Field Air Museum atMarch Air Reserve Base (formerMarch AFB) inRiverside, California.^[55]
• 53-4347 – CH-21B on static display at thePueblo Weisbrod Aircraft Museum inPueblo, Colorado.^[56][57]
• 53-4354 – CH-21C on static display at theArkansas Air & Military Museum inFayetteville, Arkansas.^[58]
• 53-4362 – SH-21B on static display at the Alaska Museum of Transportation and Industry inWasilla, Alaska.^[59]
• 53-4366 – CH-21B on static display at theMuseum of Flight inSeattle, Washington.^[60]
• 53-4367 – CH-21B on static display at theMid-Atlantic Air Museum,Reading, Pennsylvania.^[61]
• 53-4369 – CH-21B on static display at theUnited States Army Aviation Museum nearFort Novosel inDaleville, Alabama.^[62]
• 53-4389 – CH-21B on static display at thePima Air & Space Museum adjacent toDavis-Monthan AFB inTucson, Arizona.^[63]
• 54-4404 – CH-21B on static display at theAlaska Aviation Heritage Museum inAnchorage, Alaska.^[64]
• 55-4140 – CH-21C on static display at the American Helicopter Museum & Education Center in West Chester, Pennsylvania.^[65] This airframe was previously on display at theIntrepid Sea, Air & Space Museum inNew York, New York.^[66]
• 55-4218 – CH-21C on static display at theEvergreen Aviation & Space Museum inMcMinnville, Oregon.^[67] This airframe was previously on display at theWings Over the Rockies Air and Space Museum at the formerLowry AFB inDenver, Colorado. It is painted as 53-4379.^[68]
• 56-2040 – CH-21C on static display at the United States Army Aviation Museum at Fort Novosel, near Daleville, Alabama.^[69]
• 56-2077 – CH-21C on static display at theU.S. Army Transportation Museum ayFort Eustis nearNewport News, Virginia.^[70]

• 56-2142 – CH-21C on static display at theHill Aerospace Museum atHill AFB nearOgden, Utah. This airframe is painted as 54-4002.^[71]
• 56-2159 – CH-21C on static display at thePima Air & Space Museum adjacent toDavis-Monthan AFB inTucson, Arizona.^[72]

Stored or under restoration

• 52-8623 – CH-21B in storage at theAir Force Flight Test Museum atEdwards AFB inEdwards, California.^[73]
• 52-8683 – H-21B in storage withBasler Turbo Conversions inOshkosh, Wisconsin.^[74]
• 53-4329 – CH-21B under restoration at theMuseum of Flight Restoration Center atPaine Field inEverett, Washington.^[75]
• 54-4003 – CH-21B in storage at theAmerican Helicopter Museum & Education Center inWest Chester, Pennsylvania. This airframe was previously on display at theFlorence Air & Missile Museum inFlorence, South Carolina.^[76]
• c/n 438 – Model 44B in storage in unrestored condition at theGillespie Field Annex of theSan Diego Air & Space Museum inEl Cajon, California.^[77]

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

General characteristics

• Crew: 3–5 (Pilot, co-pilot, crew chief and one or two gunners in Vietnam)
• Capacity: ** 20 troopsor
  • 12 stretchers
• Length: 52 ft 6 in (16.00 m)
• Height: 15 ft 9 in (4.80 m)
• Empty weight: 8,950 lb (4,060 kg)
• Gross weight: 15,200 lb (6,895 kg)
• Powerplant: 1 ×Wright R-1820-103 Cyclone 9-cylinder air-cooled radial piston engine, 1,425 hp (1,063 kW)
• Main rotor diameter: 2 × 44 ft 0 in (13.41 m)
• Main rotor area: 3,041 sq ft (282.5 m²) *Blade section: –NACA 0012^[79]

Performance

• Maximum speed: 127 mph (204 km/h, 110 kn)
• Cruise speed: 98 mph (158 km/h, 85 kn)
• Range: 265 mi (426 km, 230 nmi)
• Service ceiling: 9,450 ft (2,880 m)
• Disk loading: 5 lb/sq ft (24 kg/m²)
• Power/mass: 0.09 hp/lb (0.15 kW/kg)

Armament

• Varying, but usually one or two.50 (12.7 mm) machine-guns, or 7.62 mmM60machine guns.

Related development

• Piasecki HRP Rescuer
• Piasecki H-25
• Boeing Vertol CH-46 Sea Knight
• Boeing CH-47 Chinook

Aircraft of comparable role, configuration, and era

• Bristol Belvedere
• Yakovlev Yak-24

Related lists

• List of military aircraft of the United States

• Arkell, Basil."Helicopters in Contrast: (2) Flying the American Vertol 44".Flight, Vol. 71, No. 2526. pp. 844–846.
• Bridgman, Leonard.Jane's All the World's Aircraft 1952–53. London: Sampson Low, Marston & Company, Ltd., 1952.
• Duke, R.A.,Helicopter Operations in Algeria [Trans. French], Dept. of the Army (1959).
• Harding, Stephen.U.S. Army Aircraft Since 1947. Shrewsbury, UK:Airlife Publishing, 1990.ISBN 1-85310-102-8.
• Swanborough, F. G. andBowers, Peter M.United States Military Aircraft since 1909. London: Putnam, 1963.
• "The World's Air Forces".Flight, Vol. 67, No. 2416, 13 May 1955. pp. 615–668.
• "World Helicopter Market".Flight, Vol. 94, No. 3096, 11 July 1968. pp. 48–60.
• United States Air Force Museum (1975 edition)

• H-21 US Army Aviation history fact sheet