# Bell H-13 Sioux

The Bell H-13 Sioux is an American single-engine light helicopter built by Bell Helicopter and manufactured by Westland Aircraft under license 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 (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.
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 dispenses 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 at 90° beneath and 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 stabilising 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 175 hp (130 kW) 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-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 (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.

#### Texas Helicopter M74 Wasp

    Texas Helicopter Corporation single-seat conversion of OH-13E helicopters for agricultural use, powered by 200 hp (150 kW) 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 240 hp (180 kW) 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 270 hp (200 kW) for 5 minutes.

#### Texas Helicopter M79T Jet Wasp II

    Texas Helicopter Corporation conversion of Bell 47G helicopters for agricultural use, powered by 420 hp (310 kW) Soloy-Allison 250-C20S engines.

## Operators
### Argentina

* Argentine Army
* Argentine Navy
* Argentine Naval Prefecture

### Australia

* Australian Army

### Austria

* Austrian Air Force

### Brazil

* Brazilian Air Force

### Canada

* Royal Canadian Navy
** VX-10 Squadron

### Chile

* Chilean Navy

### Colombia

* Colombian Air Force

### Cuba

* Air Defense Force

### Ecuador

* Ecuadorian Air Force

### France

* French Air Force
* National Gendarmerie

### Germany

* Bundesgrenzschutz
* German Army
* German Air Force

### Greece

* Hellenic Air Force

### Honduras

* Honduran Air Force

### Iceland

* Icelandic Coast Guard

### Indonesia

* Indonesian Air Force

### India

* Indian Air Force

### Italy

* Italian Air Force
* Italian Army
* Italian Navy

### Jamaica

* Jamaica Defence Force

### Japan

* Japan Ground Self Defence Force
* Japan Maritime Self Defence Force

### Malaysia

* Royal Malaysian Air Force

### Malta

* Maltese Air Wing

### Mexico

* Mexican Air Force
* Mexican Navy

### New Zealand

* Royal New Zealand Air Force

### Norway

* Royal Norwegian Air Force

### Paraguay

* Paraguayan Air Force

### Pakistan

* Pakistan Army Aviation Corps

### Peru

* Peruvian Air Force
* Peruvian Navy

### Philippines

* Philippine Air Force

### Senegal

* Senegalese Air Force

### South Vietnam

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

### South Yemen

* People's Republic of Yemen Air Force

### Spain

* Spanish Air Force
* Spanish Army
* Spanish Navy
Sri Lanka
* Sri Lanka Air Force
** No.5 Squadron

### Taiwan

* Republic of China Army

### Thailand

* Royal Thai Air Force

### Turkey

* Turkish Air Force

### United Kingdom

* British Army Army Air Corps

### United States

* United States Air Force
* United States Army
* United States Navy
* United States Coast Guard

### Uruguay

* Uruguayan Air Force
* Uruguayan Naval Aviation

### Venezuela

* Venezuelan Air Force

### Zambia

* 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

* 58-1520 – South Dakota Air and Space Museum in Box Elder, South Dakota.

   #### OH-13H

* 59-4949 - in use as instructional airframe at Portland Community College in Portland, Oregon.

   #### UH-13H

* 56-2217 – Castle Air Museum in Atwater, California.

   #### OH-13S

* 63-9085 – Texas Air & Space Museum in Amarillo, Texas. It wears a "M*A*S*H" paint scheme and is on loan from Amarillo College.
* 64-15338 – Flying Leatherneck Aviation Museum in San Diego, California.
* 64-15393 – Intrepid Sea, Air & Space Museum in New York, New York.

   #### TH-13T

* 67-15963 – Pueblo Weisbrod Aircraft Museum in Pueblo, Colorado. It has a "M*A*S*H" paint scheme.
* 67-17053 – Hill Aerospace Museum in Ogden, Utah.

   #### HTL-2

* 122952 – Pima Air & Space Museum in Tucson, Arizona.

   #### HTL-4

* 128911 – National Museum of Naval Aviation in Pensacola, Florida.

   #### HTL-6

* 142377 – National Museum of Naval Aviation in Pensacola, Florida.
* 142394 – Flying Leatherneck Aviation Museum in San Diego, California.

   #### HTL-7

* 145842 – Pima Air & Space Museum in Tucson, Arizona.

   #### Unknown

* Fantasy of Flight in Polk City, Florida has an airworthy XH-13F.
* U.S. Veterans Memorial Museum, Huntsville, Alabama has an H-13D on display.

## Specifications (Sioux AH.1)

Data from Newark Air Museum, Britains Small Wars.
General characteristics
* Crew: 1
* Capacity: 3
* Length: 31 ft 7 in (9.63 m)
* Height: 9 ft 8 in (2.95 m)
* Gross weight: 2,952 lb (1,339 kg)
* Powerplant: 1 × Lycoming TVO-435-A1A six-cylinder, horizontally opposed piston, 260 hp (190 kW)
* Main rotor diameter: 37 ft 0 in (11.28 m)
Performance
* Maximum speed: 105 mph (169 km/h, 91 kn)
* Cruise speed: 84 mph (135 km/h, 73 kn)
* Range: 273 mi (439 km, 237 nmi)
* Service ceiling: 16,100 ft (4,900 m)
Armament Twin .30 in (7.62 mm) Machine guns

## 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 (1972–1983) and the film of the same name (1970), 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 (1957–1959).