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. The H-13 Sioux is named after the eponymous Native American ethnic group.
Development
In 1947, the United States Army Air Forces (later the United States Air Force) 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.Donald, David, ed. "Bell Model 47". The Complete Encyclopedia of World Aircraft. Barnes & Nobel Books, 1997. .
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 (similar to the HTL-4 but powered by a Franklin O-335-5 engine) 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 (as its designer Arthur M. Young termed it), 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 (149 kW) 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 (Turbomeca Artouste) 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 (186 kW) 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 (168 kW) 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-13QOriginally the HUL-1G, it was used by the U.S. Coast Guard for search and rescue. UH-13RPowered by an Allison YT63-A-3 turboshaft engine. Original US Navy designation HUL-1M. OH-13SThree-seat observation helicopter based on 47G-3B to replace the OH-13H. 265 received by US Army. TH-13TTwo-seat instrument trainer for the U.S. Army based on the 47G-3B-1, powered by 270 hp (201 kW) Lycoming TVO-435-D1B. 411 purchased. Sioux AH.1 General purpose helicopter for the British Army, 50 built by Agusta (Agusta-Bell 47G-3B1) and 250 built by Westland (Westland-Agusta-Bell 47G-3B1). A small number also used by 3 Commando Brigade Air Squadron of the Royal Marines. Sioux HT.2 Training helicopter for the Royal Air Force, 15 built by Westland. H.7 () Royal Thai Armed Forces designation for the OH-13H.
Civil Texas Helicopter M74 Wasp Texas Helicopter Corporation single-seat conversion of OH-13E helicopters for agricultural use, powered by Lycoming TVO-435-A1E engines. Certified 1976. Texas Helicopter M74A Texas Helicopter Corporation single-seat conversion of OH-13H helicopters for agricultural use, powered by Lycoming TVO-435 engine rated at for 2 minutes. Certified 1977. Texas Helicopter M79S Wasp II Texas Helicopter Corporation conversion for agricultural use, with tandem seating and stub wing fuel tanks. Powered by Lycoming TVO-435 engine rated at for 5 minutes. Texas Helicopter M79T Jet Wasp II Texas Helicopter Corporation conversion of Bell 47G helicopters for agricultural use, powered by Soloy-Allison 250-C20S engines.
Operators
Argentine Army Argentine Navy Argentine Naval Prefecture
Australian Army
Austrian Air Force
Brazilian Air Force
Royal Canadian Navy VX-10 Squadron
Chilean Navy
Colombian Air Force
Air Defense Force
Ecuadorian Air Force
French Air Force National Gendarmerie
Bundesgrenzschutz German Army German Air Force
Hellenic Air Force
Honduran Air Force
Icelandic Coast Guard
Indonesian Air Force
Indian Air Force
Italian Air Force Italian Army Italian Navy
Jamaica Defence Force
Japan Ground Self Defence Force Japan Maritime Self Defence Force
Royal Malaysian Air Force
Maltese Air Wing Retired as of 2026.
Mexican Air Force Mexican Navy
Royal New Zealand Air Force
Royal Norwegian Air Force
Paraguayan Air Force
Pakistan Army Aviation Corps
Peruvian Air Force Peruvian Navy
Philippine Air Force
Senegalese Air Force
South Vietnam Air Force operated several helicopters since April 1956. 1st Helicopter Squadron 2nd Helicopter Squadron
People's Republic of Yemen Air Force
Spanish Air Force Spanish Army Spanish Navy Sri Lanka Sri Lanka Air Force No.5 Squadron
Republic of China Army
Royal Thai Air Force
Turkish Air Force
British Army Army Air Corps
United States Air Force United States Army United States Navy United States Coast Guard
Uruguayan Air Force Uruguayan Naval Aviation
Venezuelan Air Force
Zambian Air Force
Surviving aircraft Canada RCN 1387 – HTL-6 on static display at the Canada Aviation and Space Museum in Ottawa, Ontario.
Germany 58-5348 – OH-13H on static display at the Hubschraubermuseum Bückeburg in Bückeburg, Lower Saxony. XT548 – Sioux AH.1 on static display at the Flugausstellung Hermeskeil in Hermeskeil, Rhineland-Palatinate.
New Zealand H-13 Sioux (Bell 47-G3) registration NZ3705 Sioux on display at the Royal New Zealand Air Force Museum at Wigram. The aircraft is displayed in its RNZAF colour scheme when it was retired from service in 2012. NZ3705
Pakistan OH-13 on static display at the Pakistan Army Museum in Rawalpindi, Punjab.
South Africa XT562 – Bell 47 on static display at Port Elizabeth Branch of the South African Air Force Museum in Port Elizabeth, Eastern Cape.
South Korea
H-13 on static display at the War Memorial of Korea in Seoul.
Spain OH-13H on static display at the Aeronautical Laboratory of the School of Industrial and Aeronautical Engineering of the Polytechnic University of Catalonia in Terrassa, Barcelona.
Taiwan 1101 – OH-13H on display at Aviation Education Exhibition Hall, a subsidiary of the Republic of China Air Force Academy.
2110 – OH-13H on display at Longtan Sports Park at Taoyuan City, Taiwan.
Thailand 56-2182/H7-9/15 – OH-13H on display at the Royal Thai Air Force Museum in Bangkok, Thailand.
United Kingdom Airworthy XT131 (G-CICN) - Sioux AH.1 airworthy with the Historic Army Aircraft Flight based at AAC Middle Wallop. On display XT148 – Sioux AH.1 under restoration at the North East Land, Sea and Air Museums in Sunderland, Tyne and Wear. XT190 – Sioux AH.1 on static display at The Helicopter Museum in Weston-super-Mare, Somerset. XT200 – Sioux AH.1 on static display at the Newark Air Museum in Newark, Nottinghamshire.
United States
Airworthy OH-13H 58-1528 – operated by Ocean Air Inc. of Eugene, Oregon. TH-13T 65-8040 – based at the Cavanaugh Flight Museum in Addison, Texas. It is painted as a H-13D. Removed from public display when the museum indefinitely closed on 1 January 2024. To be moved to North Texas Regional Airport in Denison, Texas. 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 48-0845 – United States Army Aviation Museum in Enterprise, Alabama. OH-13D 51-2456 - United States Army Medical Department Museum located on base at Fort Sam Houston, in San Antonio, Texas. OH-13E 51-13934 – Evergreen Aviation & Space Museum in McMinnville, Oregon. 51-14010 – U.S. Army Transportation Museum at Joint Base Langley–Eustis near Newport News, Virginia. 51-14062 or 51-14077 – Aviation Hall of Fame and Museum of New Jersey in Teterboro, New Jersey. 51-14175 – Yanks Air Museum in Chino, California. 51-14193 – United States Army Aviation Museum in Enterprise, Alabama. 51-14218 – United States Army Aviation Museum in Enterprise, Alabama. OH-13G 52-7833 – Wings of Freedom Aviation Museum in Horsham, Pennsylvania. H-13H