The Eurocopter, later Airbus Helicopters, AS355 Écureuil 2, or Twin Squirrel, is a twin-engine light
utility helicopter
A utility helicopter is a multi-purpose helicopter capable of pursuing a wide array of tasks. They have proven useful in both civilian and military operations, with versatility being their defining trait.
Civilian
Helicopters play a crucial ...
developed and originally manufactured by
Aérospatiale
Aérospatiale () was a major French state-owned aerospace manufacturer, aerospace and arms industry, defence corporation. It was founded in 1970 as () through the merger of three established state-owned companies: Sud Aviation, Nord Aviation ...
in France.
The Écureuil 2 was directly derived from the single-engined
AS350 Écureuil, performing its
maiden flight
The maiden flight, also known as first flight, of an aircraft is the first occasion on which it leaves the ground under its own power. The same term is also used for the first launch of rockets.
In the early days of aviation it could be dange ...
on 28 September 1979 and introduced to service shortly thereafter. The type was marketed in North America as the TwinStar. During the 1990s, Aérospatiale merged its helicopter interests into the multinational
Eurocopter
Airbus Helicopters SAS (formerly Eurocopter S.A., trade name, trading as Eurocopter Group) is the helicopter manufacturer, helicopter manufacturing division of Airbus. It is the largest in the industry in terms of revenues and turbine helicopte ...
consortium; under this new entity, the Écureuil 2 continued to be manufactured. In 2016, shortly after Eurocopter's rebranding as
Airbus Helicopters
Airbus Helicopters SAS (formerly Eurocopter S.A., trading as Eurocopter Group) is the helicopter manufacturing division of Airbus. It is the largest in the industry in terms of revenues and turbine helicopter deliveries, holding 48% of the wo ...
, the group ended production of the Écureuil 2.
Design and development
During the early 1970s, Aérospatiale initiated a development programme to produce a replacement for the aging
Aérospatiale Alouette II
The Aérospatiale Alouette II (, "lark"; company designations SE 313 and SA 318) is a French light helicopter originally manufactured by Sud Aviation and later Aérospatiale. It was the first production helicopter powered by a gas turbine e ...
.
While the
Aérospatiale Gazelle
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 ...
, 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. 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
The automotive industry comprises a wide range of company, companies and organizations involved in the design, Business development, development, manufacturing, marketing, selling, Maintenance, repairing, and Custom car, modification of motor ve ...
; 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.
["1974: AS350/355 Ecureuil/AStar- AS550/555 Fennec – EC130."](_blank)
''Eurocopter'', Retrieved: 25 December 2015.
On 27 June 1974, the first prototype, an AS350C powered by a
Lycoming LTS101 turboshaft
A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the ex ...
engine, conducted its maiden flight at
Marignane
Marignane (; ) is a commune in the Bouches-du-Rhône department in the Provence-Alpes-Côte d'Azur region in southern France.
Geography
It is a component of the Aix-Marseille-Provence Metropolis, and the largest suburb of the city of Marsei ...
,
France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
; the second prototype, powered by a
Turbomeca Arriel 1A, following on 14 February 1975.
[Jackson 2003, p. 244.] 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
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, ''TwinStar''.
[Taylor 1988, p. 61.]
It was not long before overseas production of the type commenced. The
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
ian helicopter manufacturer
Helibras' most numerous product in its lineup has been the
Eurocopter AS350 Écureuil
The Airbus Helicopters H125, previously the Eurocopter AS350 Écureuil, or Squirrel, is a single-engine light utility helicopter designed and originally manufactured by the French corporation Aérospatiale, and later by Eurocopter, now Air ...
.
["Eurocopter's Helibras Subsidiary to Modernize 36 AS350 Ecureuil Helicopters Operated by the Brazilian Army Aviation Command.](_blank)
", ''Helicopter Maintenance'', 1 February 2011. The company had
licence-assembled both the AS350 and AS355 from kits shipped from
Eurocopter
Airbus Helicopters SAS (formerly Eurocopter S.A., trade name, trading as Eurocopter Group) is the helicopter manufacturer, helicopter manufacturing division of Airbus. It is the largest in the industry in terms of revenues and turbine helicopte ...
main production line for the family in
Marignane
Marignane (; ) is a commune in the Bouches-du-Rhône department in the Provence-Alpes-Côte d'Azur region in southern France.
Geography
It is a component of the Aix-Marseille-Provence Metropolis, and the largest suburb of the city of Marsei ...
, 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
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
.
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.
According to aerospace periodical ''
Flight International
''Flight International'', formerly ''Flight'', is a monthly magazine focused on aerospace. Published in the United Kingdom and founded in 1909 as "A Journal devoted to the Interests, Practice, and Progress of Aerial Locomotion and Transport", i ...
'', 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
Bell Textron Inc. is an American aerospace manufacturer headquartered in Fort Worth, Texas. A subsidiary of Textron, Bell manufactures military rotorcraft at facilities in Fort Worth, and Amarillo, Texas, United States as well as commercial heli ...
'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
Garmin Ltd. is an American multinational technology company based in Olathe, Kansas. The company designs, develops, manufactures, markets, and distributes GPS-enabled products and other navigation, communication, sensor-based, and information ...
-built G500H avionics suite.
[Lombardi, Frank]
"AStar Evolution.
", ''Aviation Today'', 12 May 2015.
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.
[Perry, Dominic]
"Airbus Helicopters ditches AS355 light twin."
''Flight International'', 4 September 2015. Despite the termination of the AS355 programme, production of its AS350 siblings has continued and even been expanded around the same timeframe.
Variants

;AS355
: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)
;
: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
;
:Version fitted with two
Turbomeca Arrius 1A engines and a
Full Authority Digital Engine Control
A full authority digital engine (or electronics) control (FADEC) is a system consisting of a digital computer, called an "electronic engine controller" (EEC) or "engine control unit" (ECU), and its related accessories that control all aspects of ai ...
(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
A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the ex ...
engines and a new AS350 B3-based main gearbox, increasing maximum take-off weight to 2,800 kg (6,173 lb).
["Eurocopter Upgrades Its Most Affordable Twin, The AS355 Ecureuil/TwinStar"](_blank)
''Eurocopter''.
;HB.355F Esquilo Bi
:Assembled in Brazil by Helibras (part of Eurocopter). Designated UH-13 by the
Brazilian Navy
The Brazilian Navy () is the navy, naval service branch of the Brazilian Armed Forces, responsible for conducting naval warfare, naval operations.
The navy was involved in War of Independence of Brazil#Naval action, Brazil's war of independence ...
. Cargo and VIP transport variants are respectively designated CH-55 and VH-55 by the
Brazilian Air Force
The Brazilian Air Force (, FAB) is the air branch of the Brazilian Armed Forces and one of the three national uniformed services. The FAB was formed when the Brazilian Brazilian Army Aviation (1919–1941), Army and Brazilian Naval Aviation, Nav ...
.
;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
Operators
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
;
*
Algerian Air Force
The Algerian Air Force (, ) is the aerial arm of the Algerian People's National Army.
History
The Algerian Air Force was created to support the fight of the People's National Army against the French occupying forces. It came as part of the ...
;
*
Argentine Naval Prefecture
The Argentine Naval Prefecture ( or PNA) is a service of Argentina's Security Ministry charged with protecting the country's rivers and maritime territory. It therefore fulfills the functions of other countries' coast guards, and furthermore acts ...
;
;*
Bernie Wainscott Helicopters
;*
Surf Life Saving South Australia
;
*
Austrian Federal Police
;
* Border Guard
*
Ministry of Emergency Situations
;
*
Brazilian Air Force
The Brazilian Air Force (, FAB) is the air branch of the Brazilian Armed Forces and one of the three national uniformed services. The FAB was formed when the Brazilian Brazilian Army Aviation (1919–1941), Army and Brazilian Naval Aviation, Nav ...
*
Brazilian Naval Aviation
The Brazilian Naval Aviation () is the air component of the Brazilian Navy, currently called ''Força Aeronaval''. Most of its air structure is subordinated to the Naval Air Force Command (''Comando da Força Aeronaval'', ComForAerNav), the milita ...
;
*
Royal Cambodian Air Force
;
*
International Test Pilots School
*
Ontario Provincial Police
The Ontario Provincial Police (OPP) is the State police, provincial police service of Ontario, Canada. The OPP patrols Provincial highways in Ontario, provincial highways and waterways; protects Government of Ontario, provincial government buil ...
;
*
Chilean Army
The Chilean Army () is the land arm of the Chilean Armed Forces. This 80,000-person army (9,200 of which are conscripts) is organized into six divisions, an army aviation brigade and a special operations brigade.
In recent years, and after sever ...
;
*
Djibouti Air Force
;
*
Jamaica Defence Force
The Jamaica Defence Force (JDF) is the combined military of Jamaica, consisting of an infantry Regiment and Reserve Corps, an Air Wing, a Coast Guard fleet and a supporting Engineering Unit. The JDF is based upon the British military model, with ...
;
*
Malawi Air Wing
;
*
Royal Malaysia Police
The Royal Malaysia Police (often abbreviated RMP) (; Jawi script, Jawi: ), is a (primarily) uniformed national and federal police force in Malaysia. The force is a centralised organisation, and its headquarters are located at Bukit Aman, Kuala ...

;
*
Ministry of Interior
An interior ministry or ministry of the interior (also called ministry of home affairs or ministry of internal affairs) is a government department that is responsible for domestic policy, public security and law enforcement.
In some states, th ...
;
*
National Navy of Uruguay
;
*
Massachusetts State Police
The Massachusetts State Police (MSP) is an agency of the Commonwealth of Massachusetts' Executive Office of Public Safety and Security, responsible for law enforcement and vehicle regulation across the state. As of 2024, it has 2,500 sworn troop ...
Former operators
;
*
Bophuthatswana Air Force
;
*
Garda Air Support Unit
;
*
New Zealand Police
Accidents and incidents
* On 8 May 1992, the
Western Australian Police
The Western Australia Police Force, colloquially WAPOL, provides police services throughout the state of Western Australia to a population of 2.66 million people, of which 2.11 million reside in the Perth Metropolitan Region. Western Australia h ...
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".
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
Middlewich is a town and civil parish in Cheshire East, Cheshire, England. It is located east of Chester, east of Winsford, south-east of Northwich and north-west of Sandbach. The population of the parish at the United Kingdom 2021 census, ...
, Cheshire, England, killing all five on board. The people on board included
Matthew Harding
Matthew Charles Harding (26 December 1953 – 22 October 1996) was a British businessman, vice-chairman of Chelsea F.C., Chelsea Football Club and a major financial supporter of New Labour.
Early years and education
Harding was born in Hay ...
, a businessman and vice chairman of English football club
Chelsea F.C.
Chelsea Football Club is a professional football club based in Fulham, West London, England. The club was founded in 1905 and named after neighbouring area Chelsea. They compete in the Premier League, the top tier of English football, pl ...
(the flight was returning to London from a Chelsea match in Bolton). The UK's
Air Accidents Investigation Branch
The Air Accidents Investigation Branch (AAIB) investigates civil aircraft accidents and serious incidents within the United Kingdom, its British Overseas Territories, overseas territories and crown dependencies. It is also the Space Accident I ...
found that the pilot had insufficient qualifications and experience to fly in such poor conditions; the agency also recommended a ban on commercial VFR helicopter night flying.
* 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.
All three crew – the pilot, Graham Budden, and two paramedics, Tony Richardson and Mark Darby – were killed on impact.
* On 2 May 2007,
Chelsea Football Club
Chelsea Football Club is a professional football club based in Fulham, West London, England. The club was founded in 1905 and named after neighbouring area Chelsea. They compete in the Premier League, the top tier of English football, pl ...
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
Liverpool John Lennon Airport is an international airport serving Liverpool, England, on the estuary of the River Mersey south-east of Liverpool city centre. Scheduled domestic, European, North African and Middle Eastern services are oper ...
after watching Chelsea play
Liverpool F.C.
Liverpool Football Club is a professional Football club (association football), football club based in Liverpool, England. The club competes in the Premier League, the top tier of English football league system, English football. Founded in ...
* On 18 August 2011, an AS-355F-2 (reg No/ VH-NTV) crashed near
Lake Eyre
Lake Eyre ( ), officially known as Kati Thanda–Lake Eyre, is an endorheic lake in the east-central part of the Far North (South Australia), Far North region of South Australia, some 700 km (435 mi) north of Adelaide. It is the larg ...
in South Australia, resulting in three fatalities. The helicopter was owned by the
Australian Broadcasting Corporation
The Australian Broadcasting Corporation (ABC) is Australia’s principal public service broadcaster. It is funded primarily by grants from the federal government and is administered by a government-appointed board of directors. The ABC is ...
. On board were Gary Ticehurst (ABC chief helicopter pilot for 25 years), John Bean (cameraman) and
Paul Lockyer (journalist). In response to the accident, Australia tightened the rules governing helicopter night flights.
* On 20 October 2011, a
Belarus
Belarus, officially the Republic of Belarus, is a landlocked country in Eastern Europe. It is bordered by Russia to the east and northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Belarus spans an a ...
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.
* On 29 March 2017, a Eurocopter AS-355F-1 Ecureuil 2 was lost over the
Snowdonia
Snowdonia, or Eryri (), is a mountainous region and National parks of the United Kingdom, national park in North Wales. It contains all 15 mountains in Wales Welsh 3000s, over 3000 feet high, including the country's highest, Snowdon (), which i ...
National Park in Wales whilst en route from
Luton
Luton () is a town and borough in Bedfordshire, England. The borough had a population of 225,262 at the 2021 census.
Luton is on the River Lea, about north-west of London. The town's foundation dates to the sixth century as a Saxon settleme ...
to
Dublin
Dublin is the capital and largest city of Republic of Ireland, Ireland. Situated on Dublin Bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, and is bordered on the south by the Dublin Mountains, pa ...
, carrying five people on board.
Specifications (AS355F2)
See also
References
Citations
Bibliography
*
*
*
Further reading
*
External links
AS355 page on manufacturer's website
{{AvN aircraft designations
Airbus Helicopters aircraft
Aérospatiale aircraft
1970s French helicopters
1970s French civil utility aircraft
Twin-turbine helicopters
Aircraft first flown in 1979