Of conventional configuration but sturdy design, the Aerospatiale Alouette II was one of the first true light multi-purpose helicopters and excelled in a variety of roles. This adaptability was facilitated by its reliable turboshaft engine, easy maintenance, and landing gear which could be either of wheel or skid type, or floats, with provision for emergency flotation gear.

The Alouette II originated as the Sud-Est SE 3120 Alouette (Lark), a three seat light helicopter designed mainly for agricultural purposes. The first SE 3120 prototype was flown on 31 July 1952, powered by a 149kW Salmson 9NH radial engine, and a year later established a new international helicopter closed-circuit duration record of 13 hours 56 minutes. The basic airframe was then completely redesigned to take the 269kW Turbomeca Artouste I turboshaft, and the first of two prototypes, designated SE 3130, was flown on 12 March 1955, followed by three pre-production aircraft in 1956. The Alouette II was granted a French Certificate of Airworthiness on 2 May 1956, and was soon in demand on the international market. In 1957 Sud-Est merged with Sud-Aviation, at which time the designation of the Alouette II was altered to SE 313B, remaining unchanged after Sud's take-over by Aerospatiale.

From the beginning, the Alouette II proved a most successful design and was found particularly suitable for operations in higher altitudes. Thus, during the period 9-13 June 1958, an Artouste-powered Alouette II set up a helicopter altitude record of 10981m for all classes, and a height record of 9583m in the 1000/1750kg category. By September 1960 no fewer than 598 Alouette IIs had been ordered by customers in 22 different countries and the type was being assembled by Republic in the USA and Saab in Sweden. It also became the first French aircraft of any kind, and the first helicopter in the world, to be granted an American certification.

A development of the Alouette II with a 298kW Turbomeca Turmo II engine, with the designation SE 3140, was announced in May 1957 but did not reach the production stage. Another derivative, powered by the more economical Astazou IIA turboshaft engine and featuring a new centrifugal clutch, was far more successful. The first prototype, designated SA 3180, was flown on 31 January 1960 and after thorough trials an extension of the Alouette II French Certificate of Airworthiness was granted on 18 February 1964. Production, as the SA 318C, commenced in the same year, with first deliveries taking place in 1965. Of generally similar appearance and versatility, the SA 318C had a slightly higher level speed, longer range and was capable of lifting heavier loads, but is less suitable for operations in higher altitudes. The success of the basic Alouette II design was reflected in the growing number of civil and military customers: by 1 June 1967 a total of 988 Alouette IIs (including those with Astazous engines) had been ordered (and 969 delivered); by 21 May 1970 the total had increased to 1,200 (923 with Artouste and 277 with Astazou engines); this total included 450 Alouette IIs delivered to the French air force, army and navy as well as private customers. By the spring of 1975, when the production of this helicopter was terminated, the number of Alouette IIs sold had reached 1,300, and it was used by 126 civil and military operators in 46 countries.

The Alouette success story may be regarded as beginning with the SNCA du Sud-Est's SE.3101, the first all-French helicopter to be designed and built after World War 2. A single-seater, the SE.3101 was powered by an 85hp Mathis engine and flew for the first time in June 1948. There then followed the 2-seat SE.3110 (F-WFUE), which had a 200hp Salmson 9 NH piston engine. The first of the line to be named Alouette (Lark) was developed originally for an agricultural role. Two SE.3120 prototypes, F-WGGD and 'GE, were completed, also with the Salmson as powerplant, and this type established several world and national helicopter records in July 1953.

The production model, however, was turbine-powered. This was the SE.3130 Alouette II, two prototypes of which were built with Artouste II shaft turbine engines. The first flight of an SE.3130 occurred on 12 March 1955, and three months later the Alouette II set a new helicopter altitude record of 8209m. Three similar pre-series SE.3130's were completed, and the Alouette II gained its domestic certificate of airworthiness on 2 May 1957. Production aircraft were delivered initially to fulfil orders from the French forces and civilian customers, but when production ended nine hundred and twenty-three of the Artouste-powered Alouette II's had been built for customers in thirty-three countries. Three-hundred and sixty-three of these were built for the French services — particularly the Aviation Legere de I'Armee de Terre - and a further two hundred and sixty-seven were built for the Federal German Heeresfliegerei. Other large military operators of the Alouette II include the Belgian Army (thirty-nine), Swiss Army (thirty), all three Swedish air arms (total twenty-five), and Britain's Army Air Corps (seventeen). Alouette II's were also delivered to the air forces of Austria (sixteen), Cambodia (eight), Congo Leopoldville (three), Dominican Republic (two), Indonesia (three), Israel (four). Ivory Coast (two), Laos (two), Lebanon (three), Mexico (two), Morocco (seven), Netherlands (eight), Peru (six), Portugal (seven) and South Africa (seven). Primary military roles of the Alouette II are those of observation, photography, air/sea rescue, liaison and training, but the aircraft can be equipped for more belligerent duties. Alouettes of the ALAT have carried out firing trials using Nord AS.10 or AS.11 anti-tank missiles, while some of the Aeronavale's machines have been used to carry homing torpedoes.

Other uses to which the Alouette II is put include casualty evacuation (with two external stretcher panniers), crop-spraying and flying crane (with a 500kg external sling load). Wheel, skid or pontoon landing gear may be fitted as required to all versions. Licences to assemble and market the Alouette II were granted to Saab in Sweden and Republic in the United States, and in 1963 an Alouette became the first commercially operated turbine helicopter in the USA.

The French Alouette II has undoubtedly been one of the most successful civil and military light helicopters. It was derived from the SE.3120 built by Sud-Est soon after the war. The prototype had a three-blade rotor, and a 200hp reciprocating engine. Two other prototypes followed, one of which was a three-seater. The aircraft originally had no outstanding features, but the situation changed with the introduction of the Artouste II turbine. The SE.3130 made its first flight on 12 March 1955, as did a second model immediately afterwards. Just three months after its maiden flight, the aircraft achieved world fame by setting an altitude record of 8209m, showing its ability to operate in mountainous areas.

The structure of the Alouette II is very reminiscent of the early Bell models, in that it has a plexiglass cockpit and open-framework fuselage. Although suited to many commercial roles, it has been used above all for military operations such as observation, liaison, search and rescue, training and casualty evacuation, and (armed with wire-guided missiles and torpedoes) in primarily offensive roles.

Mass production started in response to an order from the French Aeronavale (Fleet Air Arm), followed by others from the Armee de Terre and Armee de I'Air (Army and Air Force), amounting to a total of 363 aircraft. By the end of 1962, more than 1000 of the Alouette II had been ordered, including 267 for the German armed forces. Other military customers for the Alouette II (redesignated SE.313B in 1967) included the Belgian Army (39), the Swiss Army (30) and the British Army Air Corps (17). Alouette IIs have also been delivered to the air forces of Austria (16), Belgian Congo (3), Cambodia (8), the Dominican Republic (2), Indonesia (3), Israel (4), Ivory Coast (2), Laos (2), Lebanon (3), Mexico (2), Morocco (7), the Netherlands (8), Peru (6), Portugal (7), South Africa (7), and Tunisia (8).

In 1964, production was switched to the SE.318C variant which differed only in the installation of an Astazou II turbine. The ALAT (Aviation Legere de I'Armee de Terre) ordered 15 helicopters of this type and many others were sold to foreign armed forces. Production ended in 1975, by which time over 1300 had been built.

One Alouette II Astazou was modified experimentally to test a rigid rotor with plastic blade parts, developed by the German Bolkow company. It flew in this configuration on 24 January 1966. A license to produce the Alouette II was also granted to Sweden, India and the United States, but few were built.

Technical data for Aerospatiale SE-313B "Alouette II"