Bell H-13 Sioux


The Bell H-13 Sioux is an American single-engine light helicopter built and produced by Bell Helicopter for the military and licence-produced by Westland Aircraft for the British military as the Sioux AH.1 and HT.2. It was the first helicopter to be certified for civil use.

Development

In 1947, the United States Army Air Forces ordered the improved Bell Model 47A. Most were designated YR-13 and three winterized versions were designated YR-13A. The United States Army first ordered Bell 47s in 1948 under the designation H-13. These would later receive the name Sioux.
Initially, the United States Navy procured several Bell 47s, designated HTL-1, between 1947 and 1958. The United States Coast Guard evaluated this model, and procured two HTL-1s for multi-mission support in the New York Harbor. The most common U.S. Navy version of the 47 was designated the HTL-4, and dispensed with the fabric covering on the tail boom. The U.S. Coast Guard procured three HTL-5s in 1952 and used these until 1960. The Coast Guard procured two of Bell's Model 47G and designated them HUL-1G in 1959.
The H-13 was one of the principal helicopters used by the U.S. Army during the Korean War, with the H-13D variant being the most prevalent. During the war it was used in a wide variety of roles including observation, reconnaissance, and medevac. From its role in medevac flights, it gained the nickname "Angel of Mercy". It was also used as an observation helicopter early in the Vietnam War, before being replaced by the Hughes OH-6 Cayuse in 1966.
The Bell 47 was ordered by the British Army as the Sioux to meet specification H.240, with licensed production by Westland Helicopters. In order to comply with the terms of its licence agreement with Sikorsky Aircraft, which prevented it building a U.S. competitor's aircraft, Westland licensed the Model 47 from Agusta, who had purchased a license from Bell. the first contract was for 200 helicopters. The first 50 helicopters of the contract were built by Agusta at Gallarate in Italy followed by 150 built by Westland at Yeovil. The first Westland Sioux made its maiden flight on 9 March 1965.

Design

The Sioux is a single-engine, single-rotor, three-seat observation and basic training helicopter. In 1953, the Bell 47G design was introduced. It can be recognized by the full "soap bubble" canopy, exposed welded-tube tail boom, saddle fuel tanks and skid landing gear. In its UH-13J version, based on the Bell 47J, it had a metal-clad tail boom and fuselage and an enclosed cockpit and cabin.
The H-13 and its military variants were often equipped with medical evacuation panniers, one to each skid, with an acrylic glass shield to protect the patient from wind.
The development of the Sioux was helped greatly by Bell's implementation of a short weighted gyro-stabilizer bar beneath and perpendicular to the main rotor. It had streamlined counterweights at both tips and was linked so it determined which plane the rotor was in and kept it horizontal. The stabilizer, which was connected to the cyclic pitch control, acted as a hinged flywheel using gyroscopic inertia to keep the rotor blades in plane and independent of fuselage movement due to wind. It ensured that the system had enough inertia due to flight as well, so autorotation would function in case of engine failure.
A single 260 hp Lycoming VO-435 piston engine was fitted to the 47G variant. Fuel was fed from two high-mounted external tanks. A single two-bladed rotor with short inertial stabilizing minor blades was used on the Sioux.

Variants

Military

;YR-13: 28 Bell 47A helicopters procured by the United States Army Air Forces for evaluation. The YR-13 was powered by a Franklin O-335-1 piston engine. 10 of the aircraft were transferred to the U.S. Navy for evaluation as the HTL-1, with two HTL-1s later transferred to US Coast Guard.
;YR-13A: 3 YR-13 aircraft winterized for cold-weather testing in Alaska. Redesignated YH-13A in 1948.
;HTL-2: US Navy equivalent of the commercial Model 47D. 12 built.
;HTL-3: US Navy equivalent of the commercial Model 47E, powered by a 200 hp Franklin 6V4-200-C32 engine. Nine built.
;H-13B: 65 aircraft ordered in 1948 by the U.S. Army. All Army versions were later named Sioux.
;YH-13C: One H-13B used as engineering testbed. Fitted with skid undercarriage and open, uncovered tailboom.
;H-13C: 16 H-13B aircraft converted to carry external stretchers in 1952, with skid landing gear and open tail boom of YH-13C.
;H-13D: Army two-seat version based on commercial model 47D-1, with skid landing gear, stretcher carriers, and Franklin O-335-5 engine. 87 built.
;OH-13E: H-13D configuration with three-seat aircraft with dual controls. 490 built.
;XH-13F/Bell 201 : Modified Bell 47G powered by a Continental XT51-T-3 turboshaft. The first Bell helicopter powered by a turbine engine.
;OH-13G: Three-seater based on commercial model 47-G. Introduced a small elevator on the tailboom. 265 delivered to US Army.
;OH-13H/UH-13H: Based on 47G-2. Equipped with a 250 hp Lycoming VO-435 engine. At least 453 acquired by US Army. UH-13Hs were used by the U.S. Air Force.
;UH-13J: Two Bell 47J-1 Rangers acquired by the U.S. Air Force for VIP transport of the U.S. President. Originally designated H-13J.
;OH-13K: Two converted H-13Hs with a larger diameter rotor and a 225 hp Franklin 6VS-335 engine for test evaluation.
;TH-13L: Originally designated as the Navy HTL-4.
;HTL-5: Utilized a Franklin O-335-5 engine.
;TH-13M: Incorporated a small movable elevator. Originally designated as the Navy HTL-6.
;HH-13Q:Originally the HUL-1G, it was used by the U.S. Coast Guard for search and rescue.
;UH-13R:Powered by an Allison YT63-A-3 turboshaft engine. Original US Navy designation HUL-1M.
;OH-13S:Three-seat observation helicopter based on 47G-3B to replace the OH-13H. 265 received by US Army.
;TH-13T:Two-seat instrument trainer for the U.S. Army based on the 47G-3B-1, powered by 270 hp Lycoming TVO-435-D1B. 411 purchased.
;Sioux AH.1
;Sioux HT.2
;H.7

Civil

;Texas Helicopter M74 Wasp
;Texas Helicopter M74A
;Texas Helicopter M79S Wasp II
;Texas Helicopter M79T Jet Wasp II

Operators

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  • South Vietnam Air Force operated several helicopters since April 1956.
  • *1st Helicopter Squadron
  • *2nd Helicopter Squadron
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Sri Lanka

Canada

Airworthy
On display
;Airworthy
;;OH-13H
;;TH-13T
;On display
;;H-13B
  • 48-0796 – South Carolina Military Museum in Columbia, South Carolina. It is the first H-13B airframe, serial number 101, and came off the production line in mid-July 1948.
;;H-13D
;;OH-13D
;;OH-13E
;;OH-13G
;;H-13H
;;OH-13H
;;UH-13H
;;OH-13S
;;TH-13T
;;HTL-2
;;HTL-4
;;HTL-6
;;HTL-7
;;Unknown

Popular culture

The H-13 has appeared, and played key roles, in many film and television productions. It has been associated with both the M*A*S*H TV series and the film of the same name, prominently featuring the H-13 in its opening credits, and played a central role in the series finale, which still holds the
record as the highest rated single episode broadcast in America. The series helped popularize the H-13 as the helicopter most people now associate with the Korean War. The H-13 also played a key role in the Whirlybirds TV series.