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Airbus Helicopters Écureuil 2

The AS355 Écureuil 2, also known as the Twin Squirrel, is a light utility helicopter with twin engines that was developed and originally produced by Aérospatiale in France.

Derived from the single-engined AS350 Écureuil, the Écureuil 2 made its first flight on September 28, 1979, and entered into service soon after.

Marketed as the TwinStar in North America, this helicopter continued to be manufactured by Eurocopter after Aérospatiale merged its helicopter operations into the consortium.

However, production of the Écureuil 2 was discontinued in 2016 following Eurocopter’s rebranding as Airbus Helicopters.

In the early 1970s, Aérospatiale launched a development program to create a successor to the ageing Aérospatiale Alouette II.

Despite the success of the Aérospatiale Gazelle with military customers, commercial sales were lower than expected, prompting the need for a civil-oriented replacement.

Led by Chief Engineer René Mouille, the development of the new rotorcraft aimed to produce an economical and efficient aerial vehicle.

Aérospatiale’s Production and Procurement departments played a significant role in the design process, implementing measures such as a rolled sheet structure inspired by the automotive industry and the innovative Starflex main rotor.

Additionally, plans were made to develop both civil and military versions of the helicopter to meet various military requirements.

The first prototype of the AS350C, powered by a Lycoming LTS101 turboshaft engine, took its inaugural flight on June 27, 1974, in Marignane, France.

The second prototype, equipped with a Turbomeca Arriel 1A engine, followed suit on February 14, 1975.

On September 28, 1979, the twin-engined version of the rotorcraft completed its maiden flight and was later introduced to the market under various names, such as Écureuil 2, Twin Squirrel, and TwinStar.

Overseas production of this model began shortly after.

Helibras, a Brazilian helicopter manufacturer, has had great success with the Eurocopter AS350 Écureuil, which has been one of their most popular products.

The company has been assembling both the AS350 and AS355 under licence, using kits shipped from Eurocopter’s main production line in Marignane, France.

The Brazilian AS355 models also feature some locally developed components.

In the early 2000s, Eurocopter was reportedly considering the possibility of establishing an additional AS355 production line in China.

In 2001, the Eurocopter EC130 was introduced, but production of the AS350 and AS355, along with their militarised counterparts AS550 and AS555 Fennec, continued for a period.

The AS355 NP variant, a more capable version, was launched in 2007.

Eurocopter’s development of the AS355 NP was in response to Bell Helicopter’s Bell 417, targeting corporate transport and utility operators.

Various third parties have also made modifications and upgrades to the Écureuil 2, with many aftermarket specialists offering conversion programs and addons for the AS350 family, incorporating digital systems like the Garmin G500H avionics suite.

In September 2015, Airbus Helicopters made public its decision to cease production of the AS355 in order to concentrate on more popular rotorcraft models.

The manufacturing of the AS355 persisted until 2016 to fulfil existing orders.

However, the production of the AS350 series, which is related to the AS355, has not only continued but also grown during the same period.

Twin engine

AS355N Twin Squirrel

Royal Malaysian Police Air Wing’s Twin Squirrel.

AS355 Ecureuil 2

Prototype of the twin-engined Écureuil 2 or Twin Squirrel.
AS355 E
Initial production version, with single hydraulics, powered by two Allison 250-C20F turboshaft engines.
AS355 F
Improved version, with dual hydraulics and an increased maximum weight of 2,300 kg (5,070 lb).
AS355 F1
Powered by two Allison 250-C20F engines, 2,400 kg (5,291 lb) is the maximum weight.
AS355 F2
Powered by two Allison 250-C20F engines, 2,540 kg (5,600 lb) of maximum weight, and a yaw compensation system.
AS355 M
Initial armed version of AS355 F1.
AS355 M2
Armed version of AS355 F2.

Superseded by AS555 Fennec.
AS355 N Ecureuil 2
The version is fitted with two Turbomeca Arrius 1A engines and a Full Authority Digital Engine Control (FADEC) system for better M.T.O.W (2,600 kg or 5,732 lb) and single engine performance, tail rotor strake is added along the starboard side of the tail boom for better yaw authority.
AS355 NP Ecureuil 2
Introduced in 2007, this version is fitted with two Turbomeca Arrius 1A1 turboshaft engines and a new AS350 B3-based main gearbox, increasing maximum take-off weight to 2,800 kg (6,173 lb).
HB.355F Esquilo Bi
Assembled in Brazil by Helibras (part of Eurocopter).
HB.355N Esquilo Bi
Assembled in Brazil by Helibras.
Aftermarket conversions
Heli-Lynx 355FX1
Powered by the Allison C20F engine. FAA, TC, and EASA approved.
Heli-Lynx 355FX2
Powered by the Allison C20F engine. FAA, TC and EASA approved.
Heli-Lynx 355FX2R
Powered by the Allison C20R engine. FAA and TC approved.
Starflex AS355F1R
AS355 F1 powered by the Allison C20R engine. FAA, TC and EASA approved.
Starflex AS355F2R
AS355 F2 Powered by the Allison C20R engine with optimised tail rotor blades. FAA, TC and EASA approved.






12.94 m (42 ft 5 in) inc. main and tail rotors
10.93 m (36 ft) fuselage and tail rotor only

3.14 m (10 ft 4 in)
Empty weight

1,305 kg (2,877 lb)
Max take-off weight

2,540 kg (5,600 lb) internal load
2,600 kg (5,732 lb) with a maximum slung load
Fuel capacity

730 L (190 US gal; 160 imp gal) usable, in two tanks

2 × Allison 250-C20F turboshaft engines,

313 kW (420 hp) each
Main rotor diameter

10.69 m (35 ft 1 in)
Main rotor area

89.75 m2 (966.1 sq ft)
Blade aerofoil section

ONERA OA211-root

ONERA OA209/OA207-tip

Cruise speed

224 km/h (139 mph, 121 kn) (max cruise)
Never exceed speed

278 km/h (173 mph, 150 kn)

703 km (437 mi, 380 nmi) with max fuel and no reserve
Service ceiling

3,400 m (11,200 ft)
Rate of climb

6.5 m/s (1,280 ft/min)

Helicopters: An Illustrated History of their Impact-S S McGowen.
How the Helicopter Changed Modern Warfare-W Boyne.
National Air and Space Museum of France.

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