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Piasecki H-21 Workhorse

Cargo /Passenger Transport Tandem-Rotor Helicopter

United States | 1953

"The awkward-looking Piasecki H-21 Workhorse series of tandem-rotor transport helicopters was aptly-nicknamed the Flying Banana."

Authored By: Staff Writer | Last Edited: 03/08/2020 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
The Piasecki H-21 tandem-rotor helicopter was born from a line of Piasecki products that began with the HRP-1. The HRP-1 utilized a tandem-rotor arrangement and first flew in 1945 before eventually being adopted by the United States Navy, Marine Corps and the Coast Guard. Twenty-eight examples were completed with service beginning in 1947. With this framework came the H-21 in the late 1940s, developed along the lines of cold weather rescue service. The United States Air Force contracted for thirty-two of the type and knew it as the H-21 "Workhorse". Due to its unique shape, the H-21 - and its predecessors - were nicknamed the "Flying Banana". A first flight was had in April of 1952, its design attributed to Frank Piasecki himself.

The H-21 was based on the HRP-1 but incorporated more modern elements to its construction for a more robust end-product. The cockpit was heavily glazed for excellent vision by the crew and positioned at the extreme front end of the fuselage. The fuselage was pulled downward aft of midships, giving the cockpit a "nose up" appearance and driving the tail upwards as well - providing the H-21 its most unique look. At the lowest point of the fuselage were the fixed main landing gear legs (wheeled) while a wheeled leg was held under the nose. Each main rotor consisted of three-blade assemblies and the collapsed nature of the fuselage center ensured that the main rotor blades did not interact at any one point - reducing the chance of a fatal accident occurring. Their rotation was counter to reduce inherent torque and maximize control/stability. Vertical tail fins were situated outboard of the rear main rotor position. Internally, the H-21 was crewed by two in the cockpit and held space for up to 20 fully-laden combat troops or up to twelve medical litters with accompanying medical staff. Performance included a maximum speed over 130 miles per hour and a range out to 400 miles.

H-21A marked the early Search and Rescue (SAR) models for the USAF and these came fitted with a Curtis-Wright R-1820-103 "Cyclone" supercharged air-cooled radial engine of 1,150 horsepower. The mark numbered 32 in all and were followed by the "H-21B" which was developed into an assault transport through 163 examples. The engine was changed over to a Wright 103 model outputting at 1,425 horsepower for improved performance. Additionally, the main rotor blades saw an increase to their diameter as the blades were lengthened some six inches. The Royal Canadian Air Force (RCAF) soon joined the USAF in operation of the H-21 series (both A- and B-models).

In the early 1950s, the USMC shared interest in the H-21 and several H-21A models were used for evaluations. During 1957, an H-21B arrived and was used as a ship tug. The H-21C was a United States Army designation which carried the name of "Shawnee" and featured the Wright 103 engine. These were later redesignated under the "CH-21" model marker.

Production of H-21s spanned from 1952 until 1959 and their operational service ran into 1967. Beyond the United States and Canada, global operators included France, West Germany, Japan, and Sweden. New York Airways operated a civilian form as several models of the line were designed with passenger-hauling capabilities in mind. The French pressed their H-21C models into combat service during the Algerian War (1954-1962) in the gunship role armed with rockets and machine guns though this exposure was far from a complete success. Nevertheless the helicopter continued on in its given transport roles through to the end of the French commitment.

American H-21s were deployed during the Vietnam War (1955-1975) from December 1961 on and these were typically armed through trainable machine guns of 7.62mm and 12.7mm caliber for defensive purposes. However, their service in the conflict was relatively short-lived as the line was superseded in its over-battlefield roles by the new Bell UH-1 "Huey" and Boeing CH-47 "Chinook" series helicopters. The former excelled in the assault /gunship roles while the latter continued the tandem-rotor tradition and was cleared for heavy hauling. The war showcased several deficiencies in the H-21 design - slow performance and susceptibility to ground fire as well as below average hot weather operation. Their services in the war was greatly reduced from 1964 on.

A U.S. Army H-21C became the first American helicopter to cross the country non-stop on August 24th, 1954. In-flight refueling made this feat possible.

In 1959, Vertol Aircraft acquired the Piasecki concern, later becoming Boeing Vertol. A heavy-lift H-21 version was contemplated that featured conjoined H-21 airframes hauling very-heavy loads (the number of H-21s involved could vary based on cargo subject weight). This idea was not finalized into an in-service form.

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Power & Performance
Those special qualities that separate one aircraft design from another. Performance specifications presented assume optimal operating conditions for the Piasecki CH-21C Workhorse Cargo /Passenger Transport Tandem-Rotor Helicopter.
1 x Wright R-1820-103 radial engine delivering 1,425 horsepower to 2 x three-blade main rotors.
127 mph
204 kph | 110 kts
Max Speed
9,449 ft
2,880 m | 2 miles
Service Ceiling
265 miles
426 km | 230 nm
Operational Range
City-to-City Ranges
Operational range when compared to distances between major cities (in KM).
The nose-to-tail, wingtip-to-wingtip physical qualities of the Piasecki CH-21C Workhorse Cargo /Passenger Transport Tandem-Rotor Helicopter.
52.5 ft
16.00 m
O/A Length
44.0 ft
(13.40 m)
O/A Width
15.7 ft
(4.80 m)
O/A Height
8,946 lb
(4,058 kg)
Empty Weight
15,196 lb
(6,893 kg)
Design Balance
The three qualities reflected below are altitude, speed, and range. The more full the box, the more balanced the design.
Available supported armament and special-mission equipment featured in the design of the Piasecki H-21 Workhorse Cargo /Passenger Transport Tandem-Rotor Helicopter .
7.62mm or 12.7mm machine guns on fixed or trainable mountings; rockets fitted to some gunship models.
Notable series variants as part of the Piasecki H-21 Workhorse family line.
XH-21 - USAF designation of single prototype.
YH-21 "Workhorse" - Service Test Designation; 18 examples produced.
H-21A "Workhorse" Model 42 - Based on the YH-21 evaluation models; fitted with 1 x Wright R-1820-102 engine of 1,250 horsepower; 38 examples produced; redesignated to CH-21A in 1962.
H-21B "Workhorse" Model 42 - Based on H-21A production models; fitting 1 x Wright powerplant of 1,425 horsepower; 20-seat internal passenger capacity; standardized autopilot system; provision for external fuel tanks; armor protection; redesignated to CH-21B from 1962 onwards; 183 examples produced.
H-21C "Shawnee" Model 43 - Based on the H-21B production model for use by the US Army; 464 examples produced locally and under license in Germany; redesignated to CH-21C in 1962.
XH-21D "Shawnee" Model 71 - Proposed General Electric T58 turboshaft-powered model; 2 examples modified from -21C production models; never produced.
CH-21A - 1962 designation change of H-21A production models.
CH-21B - 1962 designation change of H-21B production models.
CH-21C - 1962 designation change of H-21C production models.
SH-21B - Based on the H-21B production model; modified as a rescue platform; redesignated to HH-21B in 1962.
HH-21B - Redesignation of SH-21B production model.
Model 42A - Vertol Aircraft of Canada conversions of H-21 military models for civilian operation; 19-passenger seating.
Model 44A - Civilian conversion model of military H-21B models.
Model 44B - Civilian 15-passenger seating conversion model of H-21B military models.
Model 44C - Civilian 8-passenger VIP transport version of the H-21B military model.
Global customers who have evaluated and/or operated the Piasecki H-21 Workhorse. Nations are displayed by flag, each linked to their respective national aircraft listing.

Total Production: 500 Units

Contractor(s): Piasecki Helicopter / Boeing Vertol - USA
National flag of Canada National flag of France National flag of modern Germany National flag of modern Japan National flag of Sweden National flag of the United States

[ Canada; France; Germany; Japan; Sweden; United States ]
Relative Max Speed
Hi: 150mph
Lo: 75mph
Aircraft Max Listed Speed (127mph).

Graph Average of 113 MPH.
Era Crossover
Pie graph section
Showcasing Aircraft Era Crossover (if any)
Max Alt Visualization
Small airplane graphic
Production Comparison
Entry compared against Ilyushin IL-2 (military) and Cessna 172 (civilian) total production.
MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030
Aviation Timeline
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Image of the Piasecki H-21 Workhorse
Image from the National Museum of the United States Air Force, Dayton Ohio, USA.

Mission Roles
Some designs are single-minded in their approach while others offer a more versatile solution to airborne requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
The Piasecki H-21 Workhorse Cargo /Passenger Transport Tandem-Rotor Helicopter appears in the following collections:
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