SA.340 and SA.341 Gazelles
The joint French and UK SA.341 Gazelle helicopter originated from the desire of the French Army in the early 1960s to replace their Alouette IIIs initially for light-weight observation helicopter purposes. During the early design stages at Sud-Aviation it was decided to also attract the export market, leading to a larger five-seated vehicle with accordingly greater versatility. This decision quickly attracted British interests, resulting in an agreement in 1967 between the Société Nationale Industrielle Aérosptatiale and Westland Helicopters to jointly share the development work and production of the Gazelle.
In April 1967, a single SA.340 prototype made its first flight at Marseille Provence Airport with test pilot Jean Boulet at the controls. This prototype made use of many Alouette III components such as the landing skid, 353-kW Turboméca Astazou IIN engine, drive train and the conventional tail rotor. Based on the experiences with the MBB Bo105 glass-fiber rotor blades — the first flight Bo105 occurred on Feb. 16, 1967 — the SA.340 received new three composite blades and a semi-rigid rotor hub, the design of which caused some development delays. The request for a safer tail rotor design with respect to ground strike and personal danger of injury resulted in the introduction of the Fenestron shrouded tail rotor, which was tested on the prototype. It had 13 straight equally spaced rigid blades without a stator but three straight struts, leading to a characteristic circular saw noise; this eliminated the large tail rotor blade flapping in fast forward flight, when the cambered fin completely took over the anti-torque.
Production of the final design SA.341 Gazelle began in 1971 in both countries and in military and civil versions as the first helicopter certified for instrument flight rules with a single pilot. It is equipped with a duplex autopilot for workload reduction. The design significantly reduced maintenance efforts and resulted in low operating costs. Its main rotor of 17-ft (5.25-m) radius lifts the maximum takeoff mass of 3,968 lb (1800 kg), powered by a single Turboméca Astazou III engine with 440 kW power, allowing for a maximum speed of 167 kt (310 km/h), making it the fastest light helicopter in production at the time with an advance ratio of 0.41. It had a range of 224 miles (361 km), a ceiling height of 16,404 ft (5 km), and a payload of 132 lb (600 kg). Production of 1,775 SA.341 Gazelles ran until 1996 in many variants; it remains in operation with many countries due to several upgrade and modernization programs.
Prepared by Berend van der Wall.
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