The Aérospatiale Gazelle (company designations SA 340, SA 341 and SA 342) is a five-seat helicopter developed and initially produced by the French aircraft company Sud Aviation, and later by Aérospatiale. It is the first helicopter to feature a fenestron tail instead of a conventional tail rotor, as well as being the first helicopter to be adapted for single-pilot operations under instrument flight rules.
The Gazelle was developed during the 1960s as a successor to the Alouette II as well as to meet a French Army requirement for a new lightweight observation helicopter. The Gazelle is considerably larger than the preceding Alouette series, yet is still powered by a single Turbomeca Astazou turbine engine. Innovations in the design of the Gazelle, aside from the fenestron, included an emphasis on minimal maintenance requirements, the use of a articulated rotor system, (feather, drag and pitch hinges), and rotor blades manufactured with composite materials. The rotor blades took a considerable amount of time to develop. In February 1967, France and the United Kingdom inked a cooperation agreement, which would see Westland Aircraft produce the Gazelle on British soil and partner with Sud Aviation on future refinements and upgrades to the Gazelle. On 7 April 1967, the Gazelle performed its maiden flight.
The first operational Gazelles were introduced in 1971. Initially, manufacturing lines for the type were established in both France and Britain, but later on, it was also manufactured under license by SOKO in Yugoslavia and the Arab British Helicopter Company (ABHCO) in Egypt. Multiple armed variants, oriented towards roles such as anti-tank gunship (SA 342M), light support (SA 341F), and anti-air variants were promptly produced for various branches of the French armed forces. The Gazelle was flown by all branches of the British armed forces—the Royal Air Force, Royal Navy (including in support of the Royal Marines) and the British Army in a variety of roles. The Gazelle has been procured and operated by a wide range of export customers. While it has been typically operated in a military capacity to perform light transport, scouting, and light attack missions, the Gazelle has also seen use with civil operators as well.
During its lengthy service life, the Gazelle has participated in numerous conflicts around the world, including by Syria during the 1982 Lebanon War, by Rwanda during the Rwandan Civil War in the 1990s, and by numerous participants on both sides of the 1991 Gulf War. By the twenty-first century, many operators were in the process of replacing the Gazelle with newer rotorcraft; in French service, the Gazelle has been supplanted as an attack helicopter by the larger and more modern Eurocopter Tiger, but remained active for some time in the scout helicopter role. Numerous operators have elected to upgrade their rotorcraft for continued service, the type still being in use with multiple countries as of 2024. Production ended in 1996.
Development
In 1966, Sud Aviation began working on a light observation helicopter to replace its Alouette II with seating for five people. The Gazelle originated in a French Army requirement for a lightweight observation helicopter intended to replace the Aérospatiale Alouette III; early on in the aircraft's development, the decision was taken to enlarge the helicopter to enable greater versatility and make it more attractive for the export market.Air International December 1977, pp. 277–278.
Early on, the Gazelle attracted British interest, which resulted in a major production work share agreement between Sud Aviation and Westland. Under the terms of the agreement, Westland would have a 65% work share in the manufacturing of the units destined for the British military, and be a partner to Sud Aviation on further refinements and upgrades to the Gazelle. The deal, signed in February 1967, allowed the production in Britain of 292 Gazelles and 48 Sud Aviation SA 330 Puma medium transport helicopters ordered by the British armed forces. In return, Sud Aviation was given a work share in the manufacturing programme for the 40 Westland Lynx naval helicopters for the French Navy.McGowen 2005, p. 125.Field 1973, p. 585. Ultimately, Westland would produce a total of 262 Gazelles of various models, mainly for various branches of the British armed forces but Gazelles for the civil market were also produced.
The first prototype SA 340 flew for the first time on 7 April 1967, it initially flew with a conventional tail rotor taken from the Alouette II. The tail was replaced in early 1968 with the distinctive fenestron tail on the second prototype. Four SA 341 prototypes were flown, including one for British firm Westland Helicopters. On 6 August 1971, the first production Gazelle conducted its first flight.McGowen 2005, p. 124. On 13 May 1967, a Gazelle demonstrated its speed capabilities when two separate world speed records were broken on a closed course, achieving speeds of 307 km/h over 3 kilometres and 292 km/h over 100 kilometres.
In service with the French Army Light Aviation (ALAT), the Gazelle was used primarily as an anti-tank gunship (SA 342M) armed with Euromissile HOT missiles. A light support version (SA 341F) equipped with a 20 mm cannon is used as well as anti-air variants carrying the Mistral air-to-air missile (Gazelle Celtic based on the SA 341F, Gazelle Mistral based on the SA 342M). The latest anti-tank and reconnaissance versions carry the Viviane thermal imagery system and so are called Gazelle Viviane. The Gazelle is being replaced in frontline duties by the Eurocopter Tiger, but will continue to be used for light transport and liaison roles.
Four versions of the Gazelle were used by the British forces. The SA 341D was designated 'Gazelle HT.3' in RAF service, equipped as a helicopter pilot trainer (hence HT). The SA 341E was used by the RAF for communications duties and VIP transport as the 'Gazelle HCC.4'. The SA 341C was purchased as the 'Gazelle HT.2' pilot trainer for the Royal Navy; training variants were replaced by the Eurocopter Squirrel HT1. The SA 341B was equipped to a specification for the Army Air Corps as the 'Gazelle AH.1' (from "Army Helicopter Mark 1").
The Gazelle proved to be a commercial success, which led Aérospatiale, as Sud Aviation had become, to quickly develop and introduce the SA 342 Gazelle series, which was equipped with uprated powerplants. Licensed production of the type did not just take place in the UK, domestic manufacturing was also conducted by Egyptian firm ABHCO. Yugoslavian production by SOKO reportedly produced a total of 132 Gazelles. As the Gazelle became progressively older, newer combat helicopters were brought into service in the anti-tank role; thus those aircraft previously configured as attack helicopters were often repurposed for other, secondary support duties, such as an air observation post (AOP) for directing artillery fire, airborne forward air controller (ABFAC) to direct ground-attack aircraft, casualty evacuation, liaison, and communications relay missions.Crawford 2003, p. 35. According to David Oliver, 1,560 Gazelles had been produced in both France and Britain at the end of production.
Design
The Aérospatiale Gazelle was originally developed as a replacement to the popular Alouette helicopter series; various aspects of the Gazelle are shared with the Alouette, including its mission types, loose dimensions, and operational equipment. The Gazelle featured several key innovations, being the first helicopter with a fenestron or fantail; this is a shrouded multi-blade anti-torque device housed in the vertical surface of the tail in place of a conventional tail rotor. The fenestron, while requiring a small increase in power at slow speeds, has advantages such as being considerably less vulnerable to damage, safer for people in close proximity to the helicopter, and low power requirements at cruising speeds, and has been described as "far more suitable for high-speed flight".Fricker 1973, p. 73.Mouille, Rene'. "The "Fenestron", Shrouded Tail Rotor of the SA. 341 Gazelle." Journal of the American Helicopter Society, Vol. 15, No. 4. October 1970, pp. 31–37. The fenestron has been credited with helping the Gazelle to become the world's fastest helicopter in its class.Fricker 1973, p. 72.
The original main rotor system of the Gazelle was based upon the rigid rotor system developed by Messerschmitt-Bölkow-Blohm for the MBB Bo 105; however, due to control problems experienced while at high speeds upon prototype rotorcraft, the rigid rotor was substituted for a articulated rotor counterpart on production aircraft. The difficulties experienced with the early design of the main rotor was one of the factors contributing to the lengthy development time of the Gazelle.Field 1973, p. 194. The individual rotor blades were made from composite materials, primarily fiberglass, and had been designed for an extremely long operational lifespan; composite rotor blades would become common on later helicopters.Field 1973, p. 587. The main rotor is described as having a "wide range of tolerance" for autorotation.Fricker 1973, p. 76.
The Gazelle is capable of transporting up to five passengers and up to 1,320 pounds of cargo on the underside cargo hook, or alternatively up to 1,100 pounds of freight in 80 cubic feet of internal space in the rear of the cabin. Armed variants would carry up to four HOT (Haut subsonique Optiquement Téléguidé Tiré d'un Tube) wire-guided anti-tank missiles, or a forward firing 20mm cannon mounted to the fuselage sides with its ammunition supply placed in the cabin.Tucker 2010, p. 49. Various optional equipment can be installed upon the Gazelle, such as fittings for engine noise suppression, 53 gallon ferry tanks, a rescue winch capable of lifting up to 390 pounds, emergency flotation gear, particle filter, high landing skids, cabin heater, adjustable landing lights, and engine anti-icing systems.Fricker 1973, pp. 75–76. While the Gazelle had been developed under a military-orientated design programme, following the type's entry to service increasing attention to the commercial market was paid as well.Field 1973, p. 193. The type was marketed to civil customers; notably, civilian operator Vought Helicopters at one point had a fleet of at least 70 Gazelles.Field 1973, p. 589. Civil-orientated Gazelles often included an external baggage access door mounted beneath the main cabin.Field 1973, p. 588.
The docile flying abilities of the Gazelle are such that it has been reported as being capable of comfortably flying without its main hydraulic system operation at speeds of up to 100 knots.Fricker 1973, p. 75. The flight controls are highly responsive; unusually, the Gazelle lacks a throttle or a trimming system. Hydraulic servo boosters are present on all flight control circuits to mitigate control difficulties in the event of equipment failure. The Gazelle was the first helicopter to be adapted for single-pilot operations under instrument flight rules. An advanced duplex autopilot system was developed by Honeywell in order to allow the pilot to not be overworked during solo flights; the Gazelle was chosen as the platform to develop this capability as it was one of the faster and more stable helicopters in service at that point and had a reputation for being easy to fly.McClellan 1989, pp. 30–31.