Eurocopter AS355 Écureuil 2

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AS355 Écureuil 2/Twin Squirrel/TwinStar
A AS355 departs Toulouse–Blagnac Airport
Role Light utility helicopter
National origin France
Manufacturer Aérospatiale
Airbus Helicopters
DaimlerChrysler Aerospace
First flight 28 September 1979
Status In service
Produced 1975–2016
Developed from Eurocopter AS350 Écureuil
Developed into Eurocopter AS555 Fennec 2

The Eurocopter (now Airbus Helicopters) AS355 Écureuil 2 (or Twin Squirrel) 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. In 2016, shortly after Eurocopter's rebranding as Airbus Helicopters, the group ended production of the Écureuil 2.

Design and development[edit]

During the early 1970s, Aérospatiale initiated a development programme to produce a replacement for the aging Aérospatiale Alouette II.[1] 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.[1]

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. Both Aérospatiale's Production and Procurement departments were heavily involved in the design process.[1] 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.[1]

Helibras-built AS355 Écureuil 2

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.[1][2] 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.[3]

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.[4][5][6] 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.[7] During the 2000s, Eurocopter was reportedly in talks to open up an additional AS355 production line in China.[8]

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, was introduced to service.[9] 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.[10][11]

In addition to Eurocopter's internal efforts to enhance the Écureuil 2, third parties developed their own modifications and upgrades specifically for the type.[12] 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.[13]

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.[14] Despite the termination of the AS355 programme, production of its AS350 siblings has continued and even been expanded around the same timeframe.[15][16]


Twin engine[edit]

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 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) Maximum weight.
AS355 F2
Powered by two Allison 250-C20F engines, 2,540 kg (5,600 lb) 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
Version 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 better single engine performance, tail rotor strake added along starboard side of 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).[9]
HB.355F Esquilo Bi
Assembled in Brazil by Helibras (part of Eurocopter).
HB.355N Esquilo Bi
Assembled in Brazil by Helibras.

Aftermarket conversions[edit]

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.


The AS355 Écureuil 2 is used by both private individuals and companies, helicopter charter and training organizations as well as law enforcement and government use.

Military and government operators[edit]

West Midlands Police's G-WMPA
 United States

Former operators[edit]

 New Zealand

Accidents and incidents[edit]

  • On 8 May 1992, the Western Australian Police Polair One helicopter crashed while attempting to land on a sports oval for a public display in Kelmscott. The helicopter was destroyed after a fire started in the engine bay following ground impact. The Bureau of Air Safety Investigation report determined "The helicopter probably entered a vortex ring state during the final approach".[32] The pilot and crewman received minor injuries, and the two passengers serious injuries, as a result of the accident.
  • On 22 October 1996, an AS355 F1 Squirrel, registration G-CFLT, crashed in bad weather near Middlewich, Cheshire, England, killing all five on board. The people on board included Matthew Harding, a businessman and vice chairman of English football club Chelsea F.C. (the flight was returning to London from a Chelsea match in Bolton). The UK's Air Accidents Investigation Branch found that the pilot had insufficient qualifications and experience to fly in such poor conditions;[33][34] the agency also recommended a ban on commercial VFR helicopter night flying.[35]
  • In July 1998, the Kent Air Ambulance, an AS355 F1 Squirrel, crashed in good weather after colliding with power cables near Burham whilst returning to Rochester Airport following an aborted call to attend a road accident.[36] All three crew – the pilot, Graham Budden, and two paramedics, Tony Richardson and Mark Darby – were killed on impact.[37]
  • On 2 May 2007, Chelsea Football Club Vice President Philip Carter, founder of training company Carter and Carter, crashed in his part-owned Twin Squirrel registration G-BYPA returning from Liverpool John Lennon Airport after watching Chelsea play Liverpool F.C.[38]
VH-NTV in December 2010
  • On 18 August 2011, an AS-355F-2 (reg No/ VH-NTV) crashed near Lake Eyre in South Australia, resulting in three fatalities.[39] The helicopter was owned by the Australian Broadcasting Corporation. On board were Gary Ticehurst (ABC chief helicopter pilot for 25 years), John Bean (cameraman) and Paul Lockyer (journalist).[40] In response to the accident, Australia tightened the rules governing helicopter night flights.[41]
  • On 20 October 2011, a Belarus border patrol Eurocopter twin-engine helicopter crashed close to the village of Vileity near the Lithuanian border and burst into flames, killing all five people on board, including three members of a television crew.[42]
  • On 29 March 2017, a Eurocopter AS-355F-1 Ecureuil 2 was lost over the Snowdonia National Park in Wales whilst en route from Luton to Dublin, carrying five people on board.[43]

Specifications (AS355F2)[edit]

Cockpit of AS355 F1 Ecureuil 2

Data from Jane's All The World's Aircraft 1988–89[44]

General characteristics

  • Crew: 1
  • Capacity: 6 /
  • Length: 12.94 m (42 ft 5 in) inc. main and tail rotors
10.93 m (36 ft) fuselage and tail rotor only
  • Height: 3.14 m (10 ft 4 in)
  • Empty weight: 1,305 kg (2,877 lb)
  • Max takeoff weight: 2,540 kg (5,600 lb) internal load
2,600 kg (5,732 lb) with max. slung load
  • Fuel capacity: 730 L (190 US gal; 160 imp gal) usable, in two tanks
  • Powerplant: 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[45]


  • Cruise speed: 224 km/h (139 mph, 121 kn) (max cruise)
  • Never exceed speed: 278 km/h (173 mph, 150 kn)
  • Range: 703 km (437 mi, 380 nmi) with max fuel no reserve
  • Service ceiling: 3,400 m (11,200 ft)
  • Rate of climb: 6.5 m/s (1,280 ft/min)

See also[edit]

Related development

Aircraft of comparable role, configuration, and era

Related lists



  1. ^ a b c d e "1974: AS350/355 Ecureuil/AStar- AS550/555 Fennec – EC130." Archived 26 December 2015 at the Wayback Machine Eurocopter, Retrieved: 25 December 2015.
  2. ^ Jackson 2003, p. 244.
  3. ^ Taylor 1988, p. 61.
  4. ^ "Eurocopter Unit Inaugurates Chopper Plant in Brazil.[dead link]", defensenews, 2 October 2012.
  5. ^ "Eurocopter’s Helibras Subsidiary to Modernize 36 AS350 Ecureuil Helicopters Operated by the Brazilian Army Aviation Command. Archived 17 June 2015 at the Wayback Machine", Helicopter Maintenance Magazine, 1 February 2011.
  6. ^ "Zentech to support Brazilian aircraft carrier São Paulo’s upgrade programme. Archived 14 June 2015 at the Wayback Machine", naval-technology, 7 May 2015.
  7. ^ Wastnage, Justin (19 April 2005). "Buoyed in Brazil". Flight International.
  8. ^ Derby, Paul (25 February 2004). "Western firms wrestle for Chinese market". Flight International.
  9. ^ a b "Eurocopter Upgrades Its Most Affordable Twin, The AS355 Ecureuil/TwinStar." Eurocopter. Archived 23 December 2008 at the Wayback Machine
  10. ^ "Eurocopter launches heavier Twin Squirrel and EC135 variants". Flight International. 1 March 2006.
  11. ^ "Bell launches Honeywell HTS900-powered 417 to rival Eurocopter Squirrel". Flight International. 27 February 2006.
  12. ^ "Away from the wires". Flight International. 23 May 2007.
  13. ^ Lombardi, Frank. "AStar Evolution. Archived 26 December 2015 at the Wayback Machine", Aviation Today, 12 May 2015.
  14. ^ Perry, Dominic. "Airbus Helicopters ditches AS355 light twin." Archived 5 September 2015 at the Wayback Machine Flight International, 4 September 2015.
  15. ^ "First US-made Airbus Helicopters AS350 certified. Archived 6 July 2015 at the Wayback Machine", Aerospace Manufacturing and Design, 3 March 2015.
  16. ^ Forrest, Ben. "Airbus aims to ramp up H125 production in Mississippi." Archived 26 December 2015 at the Wayback Machine Vertical Magazine, 22 December 2015.
  17. ^ a b c d e f g "World Air Forces 2016". Flightglobal Insight. 2016. Archived from the original on 19 January 2016. Retrieved 28 May 2016.
  18. ^ "Argentine Coast Guard Receives its First Ecureuil". Air International. Vol. 80, no. 3. March 2011. p. 28. ISSN 0306-5634.
  19. ^ "Austrian Federal Ministry of Internal Affairs". Archived from the original on 5 September 2018. Retrieved 5 September 2018.
  20. ^ "Государственный пограничный комитет вооружается европейскими вертолетами". Archived from the original on 17 May 2013. Retrieved 1 March 2013.
  21. ^ "Парк воздушных судов". Archived from the original on 13 October 2018. Retrieved 13 October 2018.
  22. ^ "Aircraft – ITPS Canada". Retrieved 9 October 2020.
  23. ^ "Ontario Provincial Police upgrade from AS355F2 to EC135P2+". 4 February 2011. Archived from the original on 4 June 2013. Retrieved 1 March 2013.
  24. ^ "Ontario Provincial Police AS-355F". Demand media. Archived from the original on 4 March 2016. Retrieved 1 March 2013.
  25. ^ "World Air Forces 2022". Flightglobal. 2022. Retrieved 14 July 2022.
  26. ^ "JDF AS-355". Archived from the original on 24 December 2013. Retrieved 1 March 2013.
  27. ^ "Royal Malaysian Police wants more helicopters". 23 October 2012. Archived from the original on 3 June 2013. Retrieved 1 March 2013.
  28. ^ "AS355 NP Overview". Archived from the original on 19 September 2012. Retrieved 1 March 2013.
  29. ^ "World's Air Forces 1987 pg. 28". Archived from the original on 16 May 2013. Retrieved 1 March 2013.
  30. ^ "About the Air Support Unit". Archived from the original on 22 February 2012. Retrieved 1 March 2013.
  31. ^ "NZ Civil Aircraft". nzcivair .com. 16 November 2009. Archived from the original on 4 March 2016. Retrieved 1 March 2013.
  32. ^ "Aerospatiale AS355F1, VH-NJL, Kelmscott WA, 8 May 1992". Australian Transport Safety Bureau: Aviation safety investigations & reports. Australian Transport Safety Bureau. Retrieved 27 January 2021.
  33. ^ "Pilot disorientated on impact". BBC News. Retrieved 17 September 2007.
  34. ^ "Aircraft Accident Report 4/97" (PDF). Retrieved 7 December 2019.
  35. ^ "AAIB advises ban on VFR night flights". Flight International. 3 December 1997.
  36. ^ "Bulletin No:2/2000 Aerospatiale AS355 F1 Ecureuil II G-MASK" (PDF). Air Accident Investigation Board. Archived from the original (PDF) on 17 March 2009. Retrieved 14 May 2009.
  37. ^ "UK Helicopter crash kills three". BBC News. 27 July 1998. Retrieved 4 January 2010.
  38. ^ "Wealthy fan and son die in crash". 2 May 2007.
  39. ^ "Collision with terrain – Aérospatiale Industries helicopter, VH-NTV, near Lake Eyre, SA, 18 August 2011". Australian Transport Safety Bureau. 19 August 2011. Archived from the original on 21 August 2011. Retrieved 20 August 2011.
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  41. ^ Learmount, David (25 November 2013). "Australia tightens rules for helicopter night flying". Flight International.
  42. ^ Helicopter crash in Belarus kills 5[permanent dead link]
  43. ^ "Missing helicopter: Police launch Snowdonia ground search". BBC News. Retrieved 22 June 2018.
  44. ^ Taylor 1988, pp. 60–62.
  45. ^ Lednicer, David. "The Incomplete Guide to Airfoil Usage". Retrieved 16 April 2019.


  • Elliott, Bryn (May–June 1999). "On the Beat: The First 60 Years of Britain's Air Police, Part Two". Air Enthusiast (81): 64–69. ISSN 0143-5450.
  • Jackson, Paul, ed. (2003). Jane's All The World's Aircraft 2003–2004. Coulsdon, Surry, UK: Jane's Information Group. ISBN 0-7106-2537-5.
  • Taylor, John W.R., ed. (1988). Jane's All the World's Aircraft 1988–89 (79th ed.). London: Jane's Information Group. pp. 60–62. ISBN 0-7106-0867-5.

Further reading[edit]

External links[edit]