AW101 Merlin (EH101) military utility medium lift helicopter is manufactured by AgustaWestland (formerly EH Industries), a joint venture company formed by Agusta of Italy and the British company GKN. AgustaWestland is now wholly owned by Leonardo.
The EH101, now renamed the AW101, is also produced in naval and civil versions. 146 AW101 variants have been ordered and over 120 delivered.
The rugged modular structure incorporates crashworthy and damage-tolerant features, including a five-blade main rotor, four-blade teetering rotor and main lift frame, which includes multiple primary and secondary load paths.
The fuselage is mainly of aluminium-lithium construction. The aerodynamic rotor blades are constructed from carbon / glass with nomex honeycomb and rohacell foam. Active vibration control of the structural response (ACSR) uses a vibration-cancelling technique.
The helicopter operates in temperatures ranging from -40°C to 50°C.
An ice protection system allows operation in known icing conditions. An engine inlet particle separator system provides protection in sandy environments. High flotation tyres and efficient landing gear permit take-off from soft or rough terrain.
The cockpit is equipped with armoured crew seats able to withstand an impact velocity of 35ft/s. Dual flight controls are provided for the pilot and copilot, but the helicopter is capable of being flown by a single pilot.
The pilot’s mission display unit is supplied by Northrop Grumman (formerly Litton). The electronic instrument system includes six high-definition, full-colour displays, together with an optional mission display.
A forward-looking infrared (FLIR) system display and digital map can be installed. Portuguese and Danish Air Force helicopters have FLIR Systems Star SAFIRE thermal imagers. DRS Technologies of the USA supplies the flight control computers.
EH101s for Denmark and Italy are fitted with Selex Communications LOAM laser obstacle avoidance and monitoring system.
Military utility and naval weapons
Naval versions of the AW101 can be armed with two anti-ship missiles, or up to four torpedoes and depth charges.
Armament options for military utility variants include a chin turret for a 12.7mm machine gun or pintle-mounted machine gun. The stub wings provide the hard points for mounting of rocket pods.
The AW101 is equipped with infrared jammers, such as the Northrop Grumman Nemesis, directed infrared countermeasures, missile approach warners, chaff and flare dispensers, and a laser detection and warning system.
The military version AW101 has accommodation for 30 seated or 45 standing fully equipped combat troops. The cabin has room for a medical team and 16 stretchers or for palleted internal loads. The maximum ramp load is 3,050kg for vehicles such as Land Rovers.
The heavy-duty cabin floor and ramp are equipped with flush tie-down points, a roller conveyer for palleted freight and a cargo winch for non self-loading freight.
An underslung load hook is capable of carrying external loads up to 12,000lb, and the load measurement is displayed in the cockpit. A rescue hoist and a hover trim controller are fitted at the cargo door.
Avionics and mission systems
The AW101 is equipped with two military standard 1553B multiplex databuses, which link the helicopter management, avionics and mission systems. The Smiths Industries OMI SEP 20 automatic flight control system is a dual redundant digital system, which provides autostabilisation and four-axis auto-pilot operation.
The navigation system includes a global positioning / inertial navigation system, instrument landing system (ILS), VHF omnidirectional radio range (VOR), tactical air navigation (TACAN) and automatic direction finding.
The AW101 transport helicopter is armed with five general-purpose machine guns, two 960kg (2,116lb) anti-ship missiles, four homing torpedoes, depth charges, and rockets.
The military version of the AW101 is powered by either three General Electric CT7-6 turboshaft engines, rated at 1,491kW, or three Rolls-Royce Turbomeca RTM322 turboshaft engines, rated at 1,567kW.
Each engine is fed from a dedicated self-sealing fuel tank using dual booster pumps and a crossfeed system. The Rolls-Royce engine has been chosen by UK, Canada, Japan, Denmark and Portugal. The GE engine was selected by Italy.
The three tanks hold 3,222l of fuel. The fourth tank acts as a reservoir supply to top up the main tanks during flight. There is capacity for an additional transfer tank to increase the helicopter’s range.
The range can be extended by the hover in-flight refuelling (HIFR) capability. The crew are able to select pressure refuel, defuel, jettison and buddy-to-buddy refuelling.
The AW101 transport helicopter can fly at the rate of 10.2m/s. The maximum and cruise speed of the helicopter are 309km/h and 278km/h respectively.
The maximum range and service ceiling are 927km and 4,575m, and the maximum endurance is four hours 50 minutes. The helicopter weighs around 10,500kg and the maximum take-off weight is 15,600kg.
AW101 Merlin and Cormorant helicopter orders
The UK Royal Air Force has taken receipt of 22 AW101 Merlin HC3 medium support helicopters, with the first entering service in January 2001. A total of 44 have been delivered to the UK Royal Navy.
Italy ordered 20 AW101s with options for a further four. Nine ASW (anti-surface and anti-submarine) plus one optional with L-3 Communications HELRAS active dipping sonar (deliveries complete), four plus two optional AEW (airborne early warning), four utility and four amphibious support helicopters (ASH) were delivered between July 2000 and August 2009.
The Italian Navy took delivery of its 21st AW101 helicopter on 4 August 2009 during an official ceremony held at Maristaeli Luni naval base in Italy.
Canada ordered 15 AW101 Cormorant variants for search and rescue, which entered service in 2002. Denmark ordered 14 search and rescue and troop transport variants in September 2001. Deliveries began in January 2006. Portugal ordered 12 search and rescue and combat SAR in 2002. The first was delivered in December 2004 and deliveries were completed in July 2006. Kawasaki delivered the first licence-built AW101 to Japan in March 2007.
In September 2003, Japan ordered 14 AW101 utility helicopters for airborne mine countermeasures and Antarctic survey transport. Deliveries began in March 2006.
In July 2002, AgustaWestland signed an agreement with Lockheed Martin to jointly market and produce a version of the helicopter for the US market, the US101. In February 2005, the helicopter was chosen as the replacement helicopter for the US Marine One presidential transport fleet requirement. The helicopter was proposed by Team US101, led by Lockheed Martin.
First flight of a new, higher performance variant of the AW101 took place in September 2006. This variant is fitted with British Experimental Rotor Programme (BERP) IV composite main rotor blades, more powerful CT7-8E engines rated at 1884kW and a new integrated cockpit display system with five 10in x 8in LCD displays.
In March 2007, the UK Royal Air Force agreed to buy six new AW101 already delivered to Denmark. The helicopters were transferred to the RAF in June 2007. They were fitted with new BERP main rotor blades and entered service in 2008. Denmark received replacement helicopters.
Algeria signed a contract with AgustaWestland to purchase six AW101 helicopters in November 2007. A total of 170 AW101 helicopters were ordered by the customers worldwide by that time.
The Royal Norwegian Air Force (RoNAF) placed an order for 16 AW101 helicopters to meet their Norwegian All Weather SAR Helicopter (NAWSARH) requirement. Under the $1.58bn (€1.15bn) contract, AgustaWestland will also supply spares, technical support and training services for 15 years, which can be optionally extended for a further five years. The contract also includes an option to purchase six additional aircraft.
The first AW101 helicopter under the contract was delivered to the RoNAF in November 2017, while the remaining helicopters are expected to be delivered by the end of 2020.
In April 2019, the Polish Ministry of National Defence (MND) awarded a PLN1.65bn ($430m) contract to Leonardo for the delivery of four AW101 helicopters. Deliveries are scheduled to be completed by 2022.
- Model 110: Italian Navy ASW/ASuW variant, eight built. Powered by T-700-GE-T6A1 engines. Fitted with Eliradar APS-784 radar and Honeywell HELRAS dipping sonar. Armed with torpedoes or Marte anti-ship missiles.
- Model 111: Royal Navy ASW/ASuW variant, designated Merlin HM1 by customer. Powered by RTM322 engines and fitted with Blue Kestrel radar, Thomson Marconi FLASH dipping sonar and Orange Reaper ESM. 44 built.
- Model 112: Italian Navy early warning variant with same airframe as Model 110 but with Eliradar HEW-784 radar in large underfuselage radome. Four built.
- Series 200: Proposed military utility version with no rear-loading ramp.
- Series 300 Heliliner: Proposed civil transport with no ramp. In 2000, British International Helicopters conducted service trials using PP8; these did not lead to a commercial service.
- Series 310: Proposed version of Heliliner with full airline avionics for operation from oil platforms. No production.
- Model 410: Italian Navy transport variant with folding rotors and tail boom. Four built.
- Model 411: Royal Air Force transport variant, designated Merlin HC3 by customer, 22 built.
- Model 413: Italian Navy special forces and amphibious assault transport with more advanced avionics.
- Model 500: Proposed civil utility variant with rear-ramp.
- Model 510: Civil utility variant with rear ramp, two built. One used for Tokyo Metropolitan Police Agency and one used to support US101 bid.
- Model 511: Canadian military search and rescue variant, designated CH-149 Cormorant by customer.
- Model 512: Merlin Joint Supporter for Royal Danish Air Force. Eight acquired for search and rescue (512 SAR) and six for tactical troop transport (512 TTT). The six transports were sold to RAF (as Merlin HC3As) and replaced by six new-build Merlins.
- Model 514: Portuguese Air Force search and rescue variant, six built.
- Model 515: Portuguese Air Force fisheries protection variant, two built.
- Model 516: Portuguese Air Force combat search and rescue variant, four built.
- Model 518: Japanese Maritime Self-Defense Force mine countermeasures and transport variant, two built.
- Model 519: Presidential Transport variant for the United States Marine Corps as the VH-71 Kestrel, four test vehicles and five pilot production aircraft built.
- Model 610: Algerian Naval variant. 6 delivered.
- Model 611: Italian Air Force Combat Search and Rescue variant, powered by CT7-8E engines. 15 on order.
- Model 612: Norwegian search and rescue variant, operated by the Air Force. 16 ordered with option for 6 more.
- Model 640: Saudi Arabian VVIP variant, operated by the Air Force. 2 delivered.
- Model 641: Indian VVIP variant. (See 2013 Indian helicopter bribery scandal). Latterly delivered to Nigerian and Azerbaijani Air Forces.
- Model 642: Algerian VVIP variant, 2 delivered.
- Model 643: Turkmenistani VVIP variant, operated by the Air Force. 2 delivered.
- Merlin HM1: Royal Navy designation for the Model 111.
- Merlin HM2: Avionics retrofit of 30 HM1s for the Royal Navy.
- Merlin HC3: Royal Air Force designation for the Model 411.
- Merlin HC3A: Royal Air Force designation for six former Royal Danish Air Force Model 512s modified to UK standards.
- Merlin HC3i: Royal Navy will fit seven HC3 with folding rotor heads as an interim (3i) measure until the full HC4 upgrade is available.
- Merlin HC4/4A: The conversion of 25 RAF HC3/3A for RN use in hand with the first flight taking place in November 2016. HM2 cockpit, folding tail/blades and other adaptations for naval use.
- CH-148 Petrel: Ship-based anti-submarine helicopter for Canada. 35 originally ordered by the Canadian Forces, reduced to 28 and cancelled in 1993.
- CH-149 Chimo: Search and rescue helicopter for Canada. 15 ordered by the Canadian forces, but later cancelled.
- CH-149 Cormorant: Search and rescue helicopter for Canada, 15 ordered and delivered.
- Lockheed Martin VH-71 Kestrel: Cancelled USMC variant that was intended to serve as the US Presidential helicopter.
- SH-101A: Italian Navy designation for the MP variant.
- EH-101A: Italian Navy designation for the AEW variant.
- MH-101A: Italian Navy designation for the Amphibious Support Helicopter (ASH) variant.
- HH-101A: Italian Air Force designation for the CSAR variant.
- Kawasaki Heavy Industries MCH-101: Japan Defense Agency designation of Model 518.
Specifications (Merlin HM1)
|Crew||3 – 4|
|Capacity||– 26 troops (38 passengers) or 5 tonnes of payload or 4 stretchers (with sonar array removed) for Merlin HM1.
– 30 seated troops or 45 standing fully equipped combat troops, or 3,050 kg (6,724 lb) of internal payload, 5,520 kg (12,169 lb) of external payload, or 16 stretchers for AW101.
||19.53 m (64 ft 1 in) fuselage|
|Height||6.62 m (21 ft 9 in)|
|Main rotor diameter||18.59 m (61 ft 0 in)|
|Maximum weight||14,600 kg (32,187 lb)|
|Empty weight||10,500 kg (23,149 lb)|
|Maximum speed (Vne)||309 km/h (192 mph, 167 kn)|
|Cruising speed at sea level||278 km/h (173 mph, 150 kn)|
|Ascent speed at sea level|
|Ceiling in service||4,575 m (15,010 ft)|
|Passable distance at sea level with standard reserve||833 km (518 mi, 450 nmi)|
|Powerplant||3 × Rolls-Royce Turbomeca RTM322-01 turboshaft engines, 1,566 kW (2,100 hp) each (take-off power)|
|Avionics||– Smiths Industries OMI 20 SEP dual-redundant digital automatic flight control system
– Navigation systems: BAE Systems LINS 300 ring laser gyro, Litton Italia LISA-4000 strapdown attitude and heading reference system
– Radar: Selex Galileo Blue Kestrel 5000 maritime surveillance radar
– ECM: Racal Orange Reaper ESM
– Sonar: Thomson Marconi Sonar AQS-903 acoustic processor; Active/passive sonobuoys; Thomson Sintra FLASH dipping sonar array
|Armament||4× Sting Ray homing torpedoes or Mk 11 depth charges|
- Algerian Air Force
- Algerian Navy
- Canadian Air Force
- Danish Air Force
- Indonesian Air Force
- Japan Maritime Self-Defense Force
- Nigerian Air Force
- Norwegian Air Force
- Polish Navy – 4 on order
- Portuguese Air Force
- Royal Saudi Air Force
- Turkmen Air Force
- UK Royal Navy – 30 AW101 Merlin HM2 and 25 AW101 Merlin HC4/4A.