By Mark Albertson
The CH-21 Shawnee is rooted in the Piasecki HRP-1, an ungainly contraption featuring a tandem rotor configuration. The pedigree was the XHRP-X, an experimental platform devoid of an outer skin . . . a rotary wing skeleton which first took to the air in 1945. AKA the “Dogship,” it attained a speed of 95 mph. The following year it hoisted a log weighing 1,800 pounds.1 The XHRP-1 prototype followed. The Navy and Coast Guard accepted twenty production copies of the HRP-1. Due to the rear upward slope of the fuselage, the HRP soon earned the nickname “Flying Banana.” Early applications were search and rescue, anti-submarine duties, heavy transport, mine sweeping and amphibious assault.
Twelve HRP-1s joined the Marine Corps, put to work in developing the Vertical Assault Concept, flying off the light carrier Saipan (CVL-48)2 and the escort carrier Palau (CVE-122).3 The HRP-1 remained in Navy service till 1953.
ARMY AVIATION MAGAZINE FILE PHOTO
The HRP-2 was an improvement over the HRP-1. More streamlined with an all-metal fuselage and a cockpit positioned just forward of the front rotor for improved visibility, featuring a side-by-side arrangement for the pilot and co-pilot. Upwards of ten passengers could be accommodated in the helicopter which was slated for transport duties, such as in the development of the Vertical Assault Concept of the Marine Corps and rescue operations.
The H-21 “Work Horse” is a product of the HRP lineage. Improvements engendered into the H-21 saw a rotor of 44 feet in lieu of the earlier 41 foot blades. The Pratt & Whitney R-1340 power plant of 600 hp was replaced by the Wright R-1820 of 1,425 hp.4 Maximum speed went from 109 to 125 mph; while cruising went from 92 to 101 mph. Gross weight increased from 7,225 to 14,700 pounds.
The H-21A earned top honors in an Air Force design competition, fashioned as a high altitude rescue helicopter, carrying capacity of 14 troops or 12 litter patients. B and C versions of the H-21 accommodated 20 troops. Landing gear was of the tricycle type with the tail assembly adorned with twin vertical fins.
In 1953, Air Force H-21s set two world records: Speed record of 146.7 mph and an altitude mark of 22,110 feet. On August 24, 1956, a U.S. Army H-21 made the first non-stop cross-country flight in a helicopter, traversing the United States via in-flight refueling in 37 hours.
French counterinsurgency forces used the H-21 in its war against guerrillas seeking to evict the French from Algeria. The Work Horse hauled troops and stores. Others were turned into gunships, mounting .50 caliber machine guns; a door-mounted 20 mm cannon was fashioned in a few models in an effort to boost firepower. However the Sikorsky H-34 was found to be a better gunship. The H-21 was used primarily as a troop transport and rotary wing supply wagon.
In 1956, Piasecki became the Vertol Aircraft Company.5 Model number 42 was assigned to the A and B models of the H-21. H-21Bs were used in a variety of functions along the DEW Line.6 The SH-21B filled an important role for MATS7 as a rescue helicopter.8
The major production Model 43 or H-21C (later the CH-21C) first took to the air in 1956. To the Army it was the Shawnee, built as a troop transport and cargo carrier. The CH-21C carried much of the load in the Army’s opening phase of involvement in South Vietnam. Army aviators were laying the groundwork for later Army use of airmobility by hauling ARVN9 troops to and from battle zones.
In Vietnam, Vertol’s tandem rotor trucks were equipped with wheels, floats or skies, so as to accommodate a multi-role mission; however, the Shawnee was sluggish and therefore made a presentable target for Viet Cong gunners. Attempts to arm the Shawnee saw .50 caliber machine guns mounted in the nose and doorways. A pair of .50 caliber machine guns was fashioned on skis beneath the fuselage. Another attempt at armament featured a ball turret from a B-29 mounted into the ventral side of the fuselage. The blast effect was reputed to have damaged the undersides of the Shawnee and the idea was dropped. To limit potential losses, UH-1 Huey gunships were assigned as escorts.
Total production amounted to 707 copies, of which 334 were C models. Some 150 copies of the production run were sold to foreign interests: Canada, France, West Germany,
Sweden and Japan. In 1963, the Shawnee was phased out of service, replaced by the UH-1, Huey and CH-47, Chinook. z
- See page 5, “Model XHRP-X,” The Piasecki Story of Vertical Lift.
- USS Saipan (CVL-48) was the lead vessel of a two-ship class of light carriers. Sister ship was USS Wright (CVL-49). Built upon a Baltimore-class-type heavy cruiser hull, Saipan was commissioned into the fleet after World War II, July 14, 1946. On March 30, 1963, she entered the Alabama Drydock and Shipbuilding Company for conversion to a communications ship. And on April 8, 1965, she became the USS Arlington (AGMR-2). Arlington was decommissioned on January 14, 1970 and consigned to the inactive fleet at San Diego.
- USS Palau (CVE-122) was a Commencement Bay-class escort carrier. She was commissioned into the fleet on January 15, 1946. She was decommissioned at the Philadelphia Navy Yard on June 16, 1954. She remained as a unit of the Atlantic Reserve Fleet until April 1, 1960. She was sold for scrapping to Jacques, Jr. and Sons, New York.
- Power plant was later down rated to 1,150 hp.
- Vertol in turn was gobbled up by Boeing in 1960.
- DEW or Distant Early Warning Line was a chain of radar and communication centers that stretched from the Aleutian Islands, across the Canadian Arctic to Greenland. Construction began in December 1954 in response to the growing strategic threat posed by the Soviet Union. The Soviets exploded their first atomic bomb in 1949 followed by an H-bomb in 1953. As a rival to the USAF Strategic Air Command, Soviet Long-Range Aviation was viewed as a potential strategic threat as a delivery system for Soviet nuclear weaponry.
- Military Air Transport Service of the United States Air Force.
- In 1962, designations for the Shawnee were changed: H-21A/H-21B/SH-21 became the CH-21A/CH-21B/HH-21B.
- Army of the Republic of Vietnam. z
Mark Albertson is an award winning historian and contributing editor to ARMY AVIATION magazine.
H-21 C Shawnee Cargo, Personnel
- Manufacturer: Boeing-Vertol, Morton, PA
- Power plant: One Curtiss-Wright
- R-1820-103, 1,425 hp
- Rotor system: Tandem three-bladed
- Rotor diameter: 44 feet
- Length: 52 feet 7 inches
- Height: 15 feet 9 inches
- Gross weight: 15,200 pounds
- Weight empty: 8,950 pounds
- Complement: Crew of three plus 20 troops
- or 12 litters
- Max speed – sea level: 127 mph
- Cruising speed – sea level: 98 mph
- Service ceiling: 18,600 feet
- Max range: 281 nautical miles
- Endurance: 2 hours 41 minutes