page_title: Eurocopter AS355 Écureuil 2
section_title: Design and development
hierarchical_section_title: Eurocopter AS355 Écureuil 2 / Design and development
caption_attribution_description: Português: helicóptero da força aérea
context_page_description: The Eurocopter AS355 Écureuil 2 is a twin-engine light utility helicopter developed and originally manufactured by Aérospatiale in France
  The Écureuil 2 was directly derived from the single-engined AS350 Écureuil, performing its maiden flight on 28 September 1979 and introduced to service shortly thereafter. The type was commonly marketed in North America as the TwinStar. During the 1990s, Aérospatiale merged its helicopter interests into the multinational Eurocopter consortium; under this new entity, the Écureuil 2 continued to be manufactured. Shortly after Eurocopter's rebranding as Airbus Helicopters, the group decided to discontinue production of the Écureuil 2 during 2016, however, production of its single-engined siblings has continued since then.
context_section_description: During the early 1970s, Aérospatiale initiated a development programme to produce a replacement for the aging Aérospatiale Alouette II. While the Aérospatiale Gazelle, which had been developed in the 1960s and 1970s, had been met with numerous orders by military customers, commercial sales of the type had been less than anticipated, thus the need for a civil-oriented development was identified.
  The development of the new rotorcraft, which was headed by Chief Engineer René Mouille, was focused on the production of an economic and cost-effective aerial vehicle, thus both Aérospatiale's Production and Procurement departments were heavily involved in the design process. One such measure was the use of a rolled sheet structure, a manufacturing technique adapted from the automotive industry; another innovation was the newly developed Starflex main rotor. It was also decided that both civil and military variants of the emergent helicopter would be developed to conform with established military requirements.
  On 27 June 1974, the first prototype, an AS350C powered by a Lycoming LTS101 turboshaft engine, conducted its maiden flight at Marignane, France; the second prototype, powered by a Turbomeca Arriel 1A, following on 14 February 1975. On 28 September 1979, a twin-engined version of the rotorcraft made its first flight; it was subsequently released and marketed under the names Écureuil 2, Twin Squirrel, and (in North America) TwinStar.
  It was not long before overseas production of the type commenced. The Brazilian helicopter manufacturer Helibras' most numerous product in its lineup has been the Eurocopter AS350 Écureuil. The company had licence-assembled both the AS350 and AS355 from kits shipped from Eurocopter main production line for the family in Marignane, France; Brazilian AS355s contain a level of indigenously-developed content as well. During the 2000s, Eurocopter was reportedly in talks to open up an additional AS355 production line in China.
  Despite the introduction of the Eurocopter EC130 in 2001, production of both the AS350 and AS355, and of their AS550 and AS555 Fennec militarized counterparts, was continued for some time. During 2007, the more capable AS355 NP variant, which was powered by Full Authority Digital Engine Control (FADEC) engines, was introduced to service. According to aerospace periodical Flight International, the decision to develop the AS355 NP, which Eurocopter stated was aimed at the corporate transport and utility operators, had been the firm's response to American competitor Bell Helicopter's launch of the Bell 417.
  In addition to Eurocopter's internal efforts to enhance the Écureuil 2, third parties developed their own modifications and upgrades specifically for the type. Conversion programs and addons for the AS350 family have been produced and are offered by numerous 'aftermarket' specialists; many upgrade and refit programmes have involved the increasing use of digital systems, such as the Garmin-built G500H avionics suite.
  During September 2015, Airbus Helicopters announced that the company had decided to terminate the manufacture of the AS355 as part of an effort to focus on stronger-selling rotorcraft. Production of the AS355 continued through 2016 until the existing order backlog had been fulfilled. Despite the termination of the AS355 programme, production of its AS350 siblings has continued and even been expanded around the same timeframe.
caption: Helibras-built AS355 Écureuil 2
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