Aerospatiale AS350/AS355 Ecureuil/Ecureuil 2

_IGP0153 Aerospatiale AS-350B Ecureuil D-HCOR Flughafen Berlin Brandenburg

Aerospatiale AS350 Ecureuil (Squirrel) is a single engined Medium Utility helicopter,  The AS355 Ecureuil 2 is a twin engined variant, while the Eurocopter EC130 is a derivative of the AS350 airframe. Both single and twin engined versions are now built by Eurocopter and under licence by Helibras in Brazil. The AS355 is marketed in North America as the TwinStar. AS 355 in military duty are designated AS 555 Fennec.

Developing nation: France.
Number built: .
Type aircraft: Medium Utility helicopter.
First flight: AS350 27 June 1974, AS355 3 October 1979.
State: in service.
Primary user: Gendarmerie France.


Aerospatiale’s development of the AS350 Ecureuil in the early 1970s culminated in the first flights of the Avco Lycoming LTS-101 powered prototype on June 27 1974 and the Turbomeca Arriel powered prototype on February 14 1975. Customer deliveries began in April 1978.

A high-performance workhorse with hot and high capabilities. The high-performance variant of the AS350 Ecureuil (Squirrel/AStar) series, the single-engine B3 outclasses all other 6 seat helicopters for power, flexibility, safety and low acquisition and maintenance costs. The AS350 B3 is made to measure for hot conditions and very high altitudes. In fact, a standard production model recently made history by landing on Mount Everest!


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.  In common with the AS350, the AS355 features the maintenance free Starflex main rotor hub, while the main rotor blades are of composite construction.

AS355 NP

With excellent handling, robustness and ease of maintenance, the AS355 NP incorporates twin-engine added reliability and performance – making it ideal for police and parapublic missions, as well as demanding operations over water, rugged terrain and urban areas.
Renowned for its low operation and maintenance costs, this helicopter benefits from the reliability and safety of its two Turbomeca Arrius 1A1 engines, and is equipped with a full authority digital engine control (FADEC) system.


Single engine

AS350 – Prototype.
AS350 Firefighter – Fire fighting version.
AS350B – Powered by one Turbomeca Arriel 1B engine.
AS350 B1 – Improved version of the original AS350B, which is powered by one Arriel 1D engine, type also fitted with AS355 main rotor blades, AS355 tail rotor with tabs and a tail rotor servo.
AS350 B2 – Higher gross weight version powered by one Arriel 1D1 engine over the B1 version with aerodynamic strake fitted to tail boom along the starboard side and angled engine exhaust duct for better yaw control.
AS350 B3 – High-performance version, is powered by a Arriel 2B engine equipped with a single channel (DECU) Digital Engine Control Unit with a mechanical backup system. This helicopter is the first ever to land on Mount Everest. Recently introduced AS350 B3/2B1 variant introduces enhanced engine with dual channel (FADEC) Full Authority Digital Engine Control, dual hydraulics and a 2,370 kg (5,225 lb) Maximum Take Off Weight.
AS350 BA -Powered by a Arriel 1B engine and fitted with wider chord AS355 main rotor blades and tail rotor servo.
AS350 BB – AS350 B2 variant selected to meet rotary-wing training needs of UK MoD, through its Defence Helicopter Flying School in 1996. Powered by a derated Arriel 1D1 engine to improve the helicopters’ life cycle.
Eurocopter Squirrel HT.1
Designation of AS350BB in operation with British RAF as a training helicopter.
Eurocopter Squirrel HT.2
Designation of AS350BB in operation with British Army Air Corps as a training helicopter.
AS350 C – Initial variant of Lycoming LTS-101-600A2 powered version developed for the North American market as the AStar. Quickly superseded by AS350D.
AS350 D – Powered by one Lycoming LTS-101 engine for the North American market as the AStar. At one stage marketed as AStar ‘Mark III.’
AS350 L1 – Military derivative of AS350 B1, powered by a 510kW (684shp) Turbomeca Arriel 1D turboshaft engine. Superseded by AS350 L2.
AS350 L2 – Military derivative of AS350 B2, powered by a 546kW (732shp) Turbomeca Arriel 1D1 turboshaft engine. Designation superseded by AS550 C2.
HB350 B Esquilo -Unarmed military version for the Brazilian Air Force. Brazilian designations CH-50 and TH-50. Built under licence by Helibras in Brazil.
HB350 B1 Esquilo – Unarmed military version for the Brazilian Navy. Brazilian designation UH-12. Built under licence by Helibras in Brazil.
HB350 L1 – Armed military version for the Brazilian Army. Brazilian designation HA-1. Built under licence by Helibras in Brazil.

Twin engine

AS355 – Prototype of the twin-engined Ecureuil 2 or Twin Squirrel.
AS355 E – Initial production version, powered by two Allison 250 turboshaft engines. Known as the Twin Star in the United States and Canada.
AS355 F – Improved version, fitted with improved rotor blades and systems.
AS355 F1 – Powered by the Allison C20F engine. 2,400 kg (5,291 lb) M.T.O.W.
AS355 F2 – Powered by the Allison C20F engine with uprated engine and transmission for higher M.T.O.W. (2,540 kg or 5,600 lb), and hydraulic accumulator for better tail rotor control.
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. Known as the TwinStar in the United States, 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).
HB.355F Ecureuil 2 – Licence built in Brazil by Helibras.
HB.355N Ecureuil 2 – Licence built in Brazil by Helibras.

Specifications AS350 B3

General characteristics

  • Crew: 1
  • Capacity: 6
  • Length: 10.93 m (35 ft 10½ in)
  • Rotor diameter: 10.69 m (35 ft 1 in)
  • Height: 3.14 m (10 ft 3½ in)
  • Disc area: 89.75 m² (966.1 sq ft)
  • Empty weight: 1,174 kg (2,588 lb)
  • Max takeoff weight: 2,250 kg (4,960 lb)
  • Powerplant: 1× Turbomeca Arriel 2B turboshaft, 632 kW (847 shp)


  • Never exceed speed: 287 km/h (155 knots, 178 mph)
  • Cruise speed: 245 km/h (132 knots, 152 mph)
  • Range: 662 km (357 nmi, 411 mi)
  • Endurance: 4.1 hrs
  • Service ceiling: 4,600 m (15,100 ft)
  • Rate of climb: 8.5 m/s (1,675 ft/min)

Vehicle and Engine Multifunction Display (VEMD) with First Limit Indicator (FLI) fitted as standard.

Specifications AS355 F3

General characteristics

  • Crew: 1
  • Capacity: 6
  • Length: 12.94 m (42 ft 5½ in)
  • Rotor diameter: 10.69 m (35 ft 0¾ in)
  • Height: 3.14 m (10 ft 3½ in)
  • Disc area: 89.75 m² (966 sq ft)
  • Empty weight: 1,305 kg (2,877 lbs)
  • Max takeoff weight: 2,600 kg (5,732 lbs)
  • Powerplant: 2× Allison 250-C20F turboshaft, 313 kW (420 shp) each


  • Never exceed speed: 278 km/h (150 knots, 172 mph)
  • Cruise speed: 224 km/h (121 knots, 139 mph)
  • Range: 703 km (380 nm, 437 mi)
  • Service ceiling: 3,400 m (11,150 ft)
  • Rate of climb: 6.5 m/s (1,280 ft/min)

All pictures courtesy of Zijde Aviation Photo and Publishing, Rob Vogelaar and Marcel van Leeuwen