Its unusual shape made it known as “the flying banana”. And designed for a purpose.
Since World ധąɾ II, new military doctrine emphasizes flexibility on the battlefield, helicopters have been developed as a multi-role combat vehicle that can operate in complex terrain. The H-21 was fairly early tandem-rotor helicopter from the 1950s. Its unusual shape made it known as “the flying banana”. And designed for a purpose.
The banana shape came from Piasecki’s attempts to streamline the helicopter for better cruising performance. While resting on the ground, the nose and cabin are inclined with a nose-up attitude. And the engine and main gear are located where the helicopter is bent at an incline to the rear. The rotors are nearly at the same height and orientation with this arrangement so the helicopter will hover with this attitude.
In forward flight, the helicopter must nose down to transform some of its vertical lift into horizontal thrust. Now thanks to the banana shape, the cabin is much more level with the ground for streamlining and comfort during long cruises. The aft rotor also rises higher than the front rotor to avoid its turbulent rotor wash.
CH-21 Shawnee, the Flying Banana http://www.historynet.com/ch-21-shawnee-the-flying-banana.htm#prettyPhoto By Carl O. Schuster 5/15/2012 Gear, Vietnam, Vietnam Arsenal, Vietnam War Click on image for expanded view. (Illustration by Gregory Proch) Click on image for expanded view. (Illustration by Gregory Proch) In 1952, the U.S. Air Force ordered 32 Piasecki H-21A Workhorse search and rescue (SAR) helicopters. These were essentially improvements on a late World War IIera U.S. Navy design, the HRP-1 Rescuer, which was the U.S. militarys first tandem-rotor helicopter. Nicknamed the Flying Banana because of its upcurved fuselage shape, the H-21 was optimized for Arctic operations, but its comparatively powerful engines made it suitable for operations anywhere in the world. The Air Force quickly upgraded its H-21As to Bs by installing more powerful engines.
The Army purchased that variant as the H-21C (later CH-21C) Shawnee troop transport, first deployed to Vietnam in December 1961. Its first combat service was with the U.S. Armys 8th and 57th Transportation companies, carrying Army of the Republic of Vietnam (ARVN) troops. Vietnam quickly exposed its vulnerabilities. The first Shawnee was shot down near the Laotian border in July 1962. Both the SAR and troop transport versions were unarmored, and although the helicopters engine proved resistant to fragments and small-arms fire, its control cables and fuel lines were easily damaged. The Army armed its Shawnees with either 7.62mm or .50-caliber door-mounted machine guns, and experimented with a gunship version fitted with a forward-firing .50-caliber machine gun in a remote-controlled turret under the nose. But its slow speed and lack of armor limited its utility in that role. More important, the introduction of more powerful gas-turbine engines rendered piston-engine helicopters obsolete. The Bell UH-1 Huey began to replace the CH-21 in 1964, reducing it to the logistics role until replaced by the CH-47
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.
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. The French pressed their H-21C models into combat service during the Algerian ധąɾ in the gunship role, armed with rockets and machine guns. Nevertheless the helicopter continued on in its given transport roles through to the end of the French commitment.
Piasecki H-21C Shawnee
American H-21s were deployed during the Vietnam ധąɾ 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 ¢σиƒℓι¢т 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 ωαя 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 ωαя was greatly reduced from 1964 on.
More study and development of tandem-rotor helicopters led to the changes that are present in today’s tandems, like the famous CH-47 Chinook. It still hovers with a nose-high attitude, but the banana shape has been eliminated since the cabin runs the length of the helicopter and since the engines are mounted externally in the rear. And the vertical rotor separation is achieved by making the fore and aft rotor masts different heights.
