The twin engined member of the Ecureuil (= Squirrel) family, the AS-355 Ecureuil 2 offers greater performance, carrying capability and the increased safety benefits of twin engines compared to the single engined AS-350.
Development of the first twin engine Ecureuil began early in the model's development life, with the first flying on September 28 1979. This prototype was powered by two Allison 250-C20F turboshafts, supplying power to the main and tail rotors through a combining gearbox. Put into production as the AS-355E, it was essentially a twin engined version of the AS-350 with detail changes made to the fuselage structure, fuel system, transmission and main rotor blades to support the twin engine configuration. In common with the AS-350, the AS-355 features the maintenance free Starflex main rotor hub, while the main rotor blades are of composite construction.
The AS-355F replaced the AS-355E from early 1982, and introduced new wider chord main rotor blades and a higher max takeoff weight. The AS-355F was followed by the AS-355F-1 in January 1984 and AS-355F-2 in December 1985, which introduced progressively higher maximum takeoff weights.
The current production model is the AS-355N Ecureuil 2 which introduced twin Turbomeca TM-319 Arrius turboshafts. It was certificated in 1989 and first deliveries took place from early 1992. It is marketed in North America as the TwinStar. As with the single engined AS-550, the twin engine military AS-555 is marketed as the Fennec (the AS-555SN is fitted with a chin mounted search radar for ASW).
Aerospatiale's helicopter division was integrated into Eurocopter in January 1992.
The AS-355 is built under licence in Brazil as the Helibras HB-355 Esquilo.
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