AgustaWestland AW101

The AgustaWestland AW101 is a medium-lift helicopter used in both military and civil applications. It was developed by joint venture between Westland Helicopters in the UK and Agusta in Italy in response to national requirements for a modern naval utility helicopter; until 2007, the aircraft had been marketed under the designation EH101. Several operators, including the armed forces of Britain, Denmark and Portugal, use the name Merlin for their AW101 aircraft. It is manufactured at factories in Yeovil, England and Vergiate, Italy; licensed assembly work has also taken place in Japan and the United States.

In 2000, Westland Helicopters and Agusta merged to form AgustaWestland, leading to the type's redesignation as AW101. The AW101 first flew in 1987, and entered into service in 1999. Since the AW101's introduction it has replaced several older helicopter types such as the Sikorsky S-61, performing roles such as medium-sized transport, anti-submarine warfare, and ship-based utility operations.

The Royal Canadian Air Force (RCAF) operates a variant of the AW101, designated CH-149 Cormorant, in the air-sea rescue role. Another variant, designated VH-71 Kestrel, was developed to serve in the US presidential transport fleet, however the program was cancelled. Civil operators also use AW101s in roles such as passenger and VIP transportation. The type has been deployed to active combat theatres, such as in support of coalition forces during the Iraq War and the War in Afghanistan.

Origins
In 1977, the UK Ministry of Defence issued a requirement for an anti-submarine warfare (ASW) helicopter to replace the Royal Navy's Westland Sea Kings, which were becoming inadequate in the face of advances in Soviet submarine technology. Westland Helicopters put together a proposal, designated WG.34, for a three-engined helicopter of similar dimensions to the Sea King; the WG.34 was to feature more autonomy and a greater range than its predecessor. At the same time, the Italian Navy (Marina Militare), was also considering the replacement of its fleet of Sea Kings built by the Italian company Agusta; Westland and Agusta soon began talks regarding joint development of a successor helicopter.

Agusta and Westland finalised an agreement to work on the project together, and formed a jointly-owned new company, EH Industries Limited (EHI), to pursue the development and marketing of the new helicopter to potential operators. On 12 June 1981, the UK government confirmed its participation in the project, allocated an initial budget of £20 million to develop nine pre-series examples. A major agreement, which secured funding for the majority of the EH101's development program, was signed by both the British and Italian governments in 1984. At the 1985 Paris Air Show, Agusta showed a mock-up of a utility version of the new helicopter, leading to a more generalised design that could be customised to meet the needs of various civilian or military customers. The first prototype flew on 9 October 1987.

Early Canadian interest
In 1987, at a time when the EH101's future was not yet certain as neither Britain nor Italy had placed orders for production aircraft, the fledgling helicopter found itself at the centre of a major political battle overseas. In Canada, the Conservative-led government had ordered up to 50 EH101s to replace the Canadian Armed Forces's (CAF) fleet of ageing search and rescue and anti-submarine warfare helicopters. The EH101's third engine and increased independence from naval platforms compared favourably to helicopters such as the Sikorsky Seahawk, and its additional range and de-icing capability were seen as vital for North Atlantic operations.

With the end of the Cold War in 1991, Canada faced a reduced threat to its security so costly military procurements such as the EH101 appeared excessive and unnecessary. The issue became the topic of a heated political debate over alleged costs of the order versus life extensions of existing Sikorsky CH-124 Sea King and Boeing Vertol CH-113 Labrador helicopters – such estimates widely fluctuated in favour of either option. Ultimately, the order was cancelled by the new Liberal government in 1993. The politics surrounding the EH101 order have been viewed as one of the factors in the 1993 electoral defeat of the Canadian government.

Into production
Flight testing continued until the crash of the second pre-production aircraft on 21 January 1993; testing resumed six months later. On 6 June 1993, the first EH101 outfitted with the Rolls-Royce/Turbomeca RTM322 turboshaft engine flew. Nine prototypes were built to explore both military and civil applications, including a "heliliner" configuration. In 1993, it was announced that the United States Marine Corps had conducted a study into the EH101 as a fallback option to the ambitious tiltrotor under development, the Bell-Boeing V-22 Osprey.

In February 1995, Britain made its first order for the production EH101, ordering a total of 22 helicopters; Italy also placed an order for 16 EH101s in October 1995. Britain's order for the RAF was not without controversy, as the RAF announced its preference for an all-Chinook fleet and Boeing had allegedly offered a cheaper deal providing the Chinook. In 1997, deliveries to the RAF of production EH101s began; in 1998 deliveries to the RN commenced. Westland and Agusta merged to form AgustaWestland International Limited in July 2000. Consequently, there was no need for EHI to exist as a separate entity; in June 2007, the EH101 was re-branded as the AW101.

In 2002, Westland made an unsolicited and unsuccessful offer to the British Ministry of Defence, proposing an enhanced variant of the Merlin intended to satisfy the UK's demand for additional lift capacity. In 2005, a team of AgustaWestland and Lockheed Martin was selected as the winners of the US VXX competition to provide a replacement fleet to serve as the President's Marine One helicopter. The US presidential helicopter was designated VH-71 Kestrel, but the contract was eventually cancelled in June 2009 as opposition grew over significant cost overruns.

Further developments
In 2008, South Korea was planning to modernise its airborne mine countermeasures (AMCM) helicopter fleet, the AW101 is one of the helicopters being studied for the role.

In 2008, it was reported that customer demand for the AW101 was at the point where production capacity for more than five years had already been allocated. By April 2009, more than 180 AW101s have been sold, the global operational fleet of which had accumulated a combined total of 170,000 flying hours.

In November 2007, Algeria signed a contract for 6 AW101 helicopters. In August 2012, it was reported that Algeria had signed an agreement with AgustaWestland for the provision of up to 80 helicopters, including 42 AW101s. Later deliveries of the AW101 are to be assembled locally.

Norway has expressed an interest in the AW101 as a candidate for the Norwegian All Weather Search and Rescue Helicopter (NAWSARH) programme that plans replacement of the Westland Sea King Mk.43B of the Royal Norwegian Air Force in 2015. The other candidates for the NAWSARH contract of 10–12 helicopters are Bell Boeing V-22 Osprey, Eurocopter EC225, NHIndustries NH-90 and Sikorsky S-92. Iceland had cooperated with Norway in this programme and was interested in 3–4 helicopters to replace its fleet of Super Puma helicopters. Iceland later cancelled its involvement in the programme due to the country's financial situation.

In October 2012, the AW101 was submitted in a competition for the U.S. Air Force for a new Combat Rescue Helicopter (CRH) to replace the HH-60 Pave Hawk. By December 2012, AW-Northrop Grumman had dropped out of the competition.

In September 2013, AW began an effort for civil certification of the AW101 for offshore oil platform crew transport in Europe.

Overview
The AW101 Merlin follows a conventional design layout but makes use of advanced technologies such as the design of the rotor blades, avionics systems, and the extensive use of composite materials. The fuselage structure is modular and comprises an aluminium-lithium alloy, designed to be both light and damage-resistant. The AW101 is designed for operating in extreme weather conditions; it is fitted with a de-icing system and rated to operate in temperatures ranging between −45 to +50 °C. The sophisticated control systems of the aircraft's three engines allow the AW101 to maintain a stable hover in crosswinds of over 75 km/h.

An active vibration control system, known as the active control of structural response system, reduces airframe vibration by up to 80% which increases crew comfort and minimises the buildup of stress on the airframe. The cockpit is fitted with armoured seats for the crew, and can withstand an impact velocity of over 10 m/s. Dual flight controls are provided, though the AW101 can be flown by a single person. The pilot's instrument displays include six full-colour high-definition screens and an optional mission display; a digital map or forward-looking infrared (FLIR) display can also be installed.

Propulsion


The AW101 is powered by three turboshaft engines. Two different types of engines available for operators, the Rolls-Royce/Turbomeca RTM322 used by the UK, Japan, Denmark and Portugal; or the General Electric CT7 used by Italy, Canada, and Japan. The Rolls-Royce RTM322 engine was specifically developed for the AW101 but was later applied to the WAH-64 Apache and the NHIndustries NH90 helicopters. According to Rolls-Royce about 80% of AW101s use the RTM322.

The engine can be fitted with an inlet particle separator system for protection when operating in sandy environments.

The engines power an 18.59 metre diameter five-bladed main rotor. The rotor blades are constructed from carbon/glass with nomex honeycomb and rohacell foam, edged with titanium alloy in a sandwich construction. The shaping of the main rotor blades is derived from the BERP rotor blades first used on the Westland Lynx. This blade design improves aerodynamic efficiency at the blade tip and reduces the noise signature. Improved BERP IV rotors have since been developed; when installed, this increases the AW101's maximum takeoff weight.

Each engine is supplied by a separate 1,074 litre (276 US Gallon, 230 Imperial Gallon) fuel tank using dual booster pumps. Optional fourth and fifth tanks can be added to act as a reservoir supply, topping up the main tanks during flight, increasing range or endurance. The AW101 can also be outfitted with a probe for aerial refuelling. Self-sealing fuel tanks can be installed on the request of the customer.

Armament and defensive systems


Most variants of the AW101 are equipped with self-defence systems such as chaff and flare dispensers, directed infrared countermeasures (infrared jammers), ESM (electronic support measures in the form of RF heads), and a laser detection and warning system. British Merlins have been outfitted with protective armouring against small-arms fire. A chin-mounted forward looking infrared (FLIR) imaging sensor has been fitted to some variants.

Two hardpoints are present on the underside of the airframe on which the HM1 model can carry four Sting Ray torpedoes or Mk 11 Mod 3 depth charges. Some customers have chosen to deploy the Marte anti-ship missile on the AW101; as of 2011, the Royal Navy is considering equipping their Merlin fleet with an anti-surface missile. The Mk1, Mk3 and Mk3A variants can mount general purpose machine guns in up to 5 locations in the main cabin, aimed out of both door and window apertures. AgustaWestland has examined the integration of rockets and additional ground-attack weapons.

Avionics
Westland and IBM formed a consortium in 1991 to perform the helicopter's complex systems integration. The AW101 features a network of helicopter management and mission systems designed to reduce pilot workload and enable the helicopter to undertake a wide variety of missions. A digital automatic flight control system (AFCS) is employed by the AW101. The AFCS allows the operation of a four-axis (pitch, roll, yaw and collective) autopilot and the automatic stabilisation system, and is linked in with the aircraft's flight management systems. The AFCS, manufactured by Smiths Aerospace, is a dual-duplex system using two flight computers to provide redundancy and fault-tolerance.

The AW101's navigation system includes a GPS receiver and inertial navigation system, VHF omnidirectional radio range (VOR), instrument landing system (ILS), TACAN, and automatic direction finding. The Mk1 and Mk3 are equipped with a Doppler velocity system (DVS) which provides relative ground velocities; the DVS is also linked into the AFCS as part of the autostabilisation system. For safety, the aircraft is equipped with obstacle and terrain avoidance warning systems, traffic collision avoidance system (TCAS), and both voice and flight data recorders.

The AW101 is equipped with the Blue Kestrel search and detection radar which is capable of 360 degree scanning and can detect small targets as far as 25 nautical miles. As part of the Royal Navy's Merlin HM2 upgrade program, Lockheed Martin implemented a series of improvements to the radar, notably allowing it to track 40 times the number of targets previously capable. Danish EH101s are fitted with the RDR-1600 search and weather radar. Royal Navy Merlins are equipped with the AQS901 anti-submarine system for processing sonographic data from sonobuoys to detect and target submerged submarines. The AQS901 was derived from the system on the earlier Hawker Siddeley Nimrod maritime patrol aircraft.

Crew and cargo
The AW101 is typically operated by a crew of three: a pilot, an observer, and a crewman/operator. The pilot is able to fly for the majority of a mission in a hands-off mode, enabled by the sophisticated autopilot. All crew members have individual access to management computers and tactical information.

The fuselage has a volume of 31.91 m3 and the cargo compartment is 6.5 m in length, 2.3 m wide and 1.91 m high. The military version of the AW101 can accommodate up to 24 seated or 45 standing combat troops and their equipment. Alternative loads include a medical team and 16 stretchers, and cargo pallets.

The ramp, 1.91 x, can take a 3050 kg load, allowing it to carry vehicles such as Land Rovers. The ramp and cabin floor are fitted with flush tie-down points. A cargo hook under the fuselage can carry external loads of 5440 kg via the use of a semi-automatic cargo release unit (SACRU). A rescue hoist and a hover trim controller are fitted at the cargo door. An optional cargo winch can be installed near to the rear ramp.

Royal Navy


The RN's final order was for 44 ASW machines, originally designated Merlin HAS.1 but soon changed to Merlin HM1. The first fully operational Merlin was delivered on 17 May 1997, entering service on 2 June 2000. All aircraft were delivered by the end of 2002, and are operated by four Fleet Air Arm squadrons: 814 NAS, 820 NAS, 824 NAS and 829 NAS, all based at RNAS Culdrose in Cornwall. 700 NAS was the Merlin Operational Evaluation Unit from 2000 to 2008.

In March 2004, RN Merlins were temporarily grounded following an incident at RNAS Culdrose when a tail rotor failed. Investigations revealed that this was due to tail rotor hub manufacturing defects. An improved tail rotor has since been designed and introduced on most AW101s; according to AgustaWestland the new rotor has also significantly reduced associated maintenance.

The Merlin HM1 has been cleared to operate from the Royal Navy's aircraft carriers, amphibious assault ships, Type 23 frigates and a number of Royal Fleet Auxiliary (RFA) vessels including the Fort Victoria class. The HM1 is to equip the Type 45 destroyers. 30 aircraft are being upgraded to the Merlin HM2 standard under the £850m Merlin Capability Sustainment Programme. Awarded in 2006, the MCSP adds a new mission system, sensor upgrades and a digital cockpit. The HM2 first flew from a ship in September 2012 to test the new inertial navigation system, and will enter service in 2013. It had been planned to upgrade the remaining 8 airframes but this has now been dropped for financial reasons. Alternative roles are being sought for these aircraft.



On 15 December 2009, the UK announced plans to move RAF Merlin HC3s and HC3As to the Commando Helicopter Force. The Merlins have been replacing the Sea King HC4 helicopters. The Sea King is also to be replaced in the SAR role, resulting in its retirement by 2016. After 2016 the Navy will operate the Lynx Wildcat and Merlin, the RAF will operate Puma and Chinook, and the Army will operate Lynx Wildcat and Apache.

The UK has been considering the Merlin as a replacement for the Sea King ASaC7 in the airborne early warning (AEW) role. In September 2011, Thales UK proposed the re-use of Sea King ASaC7 equipment, such as the Searchwater 2000, to provide an AEW AW101 variant, similar to that ordered by the Italian Navy. A rival proposal from Lockheed Martin would develop a new multi-functional sensor to be fitted either to the Merlin or other fixed-wing assets.

The Westland Lynx helicopter has been seen as a useful complement to the newer Merlins; in 1995 it was decided to phase out Lynx for an all-Merlin fleet in maritime use. It is intended that 846 NAS will reform with ex-RAF Merlin HC3s in 2015. 845 NAS will follow in 2017, operating the fully navalised Merlin HC4. The 2010 SDSR has however stated that the future Naval helicopters will be the Wildcat and the Merlin. In August 2013, several Merlins of the new variant Mk2 were handed over to 824 NAS and the Mk2 variant will begin operations in the summer of 2014.

Royal Navy Merlins have seen action in the Caribbean, on counter-narcotics and hurricane support duties, as well as maritime security duties in the Persian Gulf. Merlins have also seen active duty in Iraq, providing support to British and coalition forces based in the region.

Royal Air Force


The RAF ordered 22 transport helicopters designated Merlin HC3, the first of which entered service in January 2001 with No. 28 Squadron RAF based at RAF Benson. The type is equipped with extended-range fuel tanks and is capable of air-to-air refuelling; however as of 2012, aerial refuelling has not entered operational usage. The Merlin is frequently utilised for troop transport duties and for the transport of bulky objects, either internally or underslung, including vehicles and artillery. Depth maintenance of the Merlin HC3 is carried out at the Merlin Depth Maintenance Facility at RNAS Culdrose.

The Merlin's first operational deployment was to the Balkans region in 2003. RAF Merlins were first deployed to Iraq as part of Operation Telic in 2004/5 where they remained until withdrawal in 2009. During this time they supported coalition forces and were the main medevac asset in southern Iraq, with both Flight Lieutenant Kev Harris and Flight Lieutenant Michelle Goodman being awarded the DFC during this period. They were commonly deployed in the vicinity of the city of Basra until the British withdrawal in June 2009.

To alleviate a shortfall in operational helicopters and to allow Merlins to be deployed in Afghanistan, the British Ministry of Defence acquired six AW101s from Denmark in 2007; these were assigned to the RAF with the designation Merlin HC3A. In December 2007, a second Merlin squadron, No. 78 Squadron was formed at Benson.

Five Merlin Mk3s were operating in Afghanistan in 2009 to provide much-needed transportation of troops and supplies. The deployment to Afghanistan came under media criticism over allegations that they lacked Kevlar protective armour. As of July 2010, the Merlin fleet has been fully fitted with ballistic armour. The deployment of Merlins into Afghanistan allowed the detachment of Sea Kings to be withdrawn from the region in October 2011. As part of the UK drawdown in Afghanistan Merlins were withdrawn from theatre in June 2013.

As of mid-2012, the RAF Merlin Mk3s and Mk3As started a transition period to become part of the Royal Navy's Commando Helicopter Force, due to be finalised by 2016 after it undergoes modification to Royal Navy standard to be capable of extended maritime operations. Royal Navy personnel have already started working alongside the Royal Air Force at RAF Benson to build their experience on the aircraft before the Merlin fleet is handed over to the Commando Helicopter Force.

Italian Navy


In 1997, the Italian government ordered 20 EH101 helicopters with four options for the Italian Navy. These EH101s included 10 of the anti-surface/submarine (ASuW/ASW) version, 4 airborne early warning (AEW), 4 utility, and 4 amphibious support helicopters (ASH). As of June 2011, the AW101 has also been chosen to meet an Italian Air Force (Aeronautica Militare) requirement for up to 12 helicopters in the combat search and rescue role to replace several ageing Sea King HH-3F; deliveries are expected from 2014 onwards.

The first Italian Navy production helicopter (MM81480) flew on 4 October 1999 and was officially presented to the press on 6 December 1999. Italy accepted delivery of the 21st AW101, configured for anti-submarine warfare, on 4 August 2009. Italian EH101s have operated from a variety of ships and have seen service overseas; in 2009 the Italian Navy used its AW101 fleet as executive transports for visiting heads of state and officials during the 35th G8 summit.

In 2010, the Italian Navy deployed three AW101s to Afghanistan where they were flown in both the transport and utility roles. In 2011, it was reported that the Italian contingent in Afghanistan, consisting of AW101s, had been providing coverage of a wide area of the country.

Royal Canadian Air Force


In 1997, in light of the declining condition of its helicopter fleet, Canada launched the Canadian Search and Rescue Helicopter competition. It was won by the EH101 which was designated CH-149 Cormorant in Canadian service.

In 2004, the EH101 was entered into a Canadian competition to replace the shipboard Sea King fleet, but the Sikorsky CH-148 Cyclone was selected. In 2013, following difficulties with the CH-148 procurement, the Royal Canadian Air Force (RCAF) was reported to be seriously considering canceling the contract with Sikorsky and was investigating the possibility of procuring the AW101 instead.

Royal Danish Air Force
In 2001, the Royal Danish Air Force (RDAF) announced the purchase of 8 EH101s for SAR duties and 6 tactical troop transports for 722 Squadron. The last of the 14 AW101s was delivered in March 2007 and the first SAR AW101s became operational out of Karup Airport in April 2007. In 2007, the 6 troop transport AW101s were transferred to the British MOD; in exchange, the British government ordered 6 new-build AW101s as replacements for the RDAF.

Danish AW101s have a higher gross weight capacity of 15,600 kg and were, as delivered, coated in a paint designed to reduce the aircraft's infrared signature. In the SAR role, RDAF AW101s have a crew of six and were initially painted yellow to distinguish themselves from AW101 allocated to military duties.

On 28 January 2008, the drive shaft of a Danish AW101 broke, leading to an emergency landing at Billund Airport. Following the incident, the Danish fleet was grounded as a safety precaution and arguments regarding the future of the AW101 in Danish service broke out. In the first six months of 2008, RDAF reported that the operational availability was roughly 50%; however this was below an internal target of 80%, in part due to inadequate organisation of maintenance and staff shortages.

In January 2011, it was reported that the Danish Ministry of Defence could not afford the retrofitting of the AW101 fleet for service in Afghanistan, against earlier reports of a deployment in 2012. In February 2013, Aviation Week reported that earlier reliability issues has been resolved and that the Danish AW101s would now receive a full upgrade package, including the addition of electronic warfare pods and a new electro-optical system, in advance of a deployment in Afghanistan in 2014. A contract for "a minimum of eight" L-3 Wescam MX-15 electro-optical/infrared (EO/IR) sensors was announced in September 2013; the SAR aircraft already carry the FLIR Systems Star Safire II EO/IR sensor.

Portuguese Air Force


The Portuguese Air Force has operated Merlins since 24 February 2005 to conduct transport, search and rescue, and maritime surveillance missions. The 12 aircraft began to gradually replace the Aérospatiale Puma that previously conducted these missions. The AW101 aircraft were purchased for €446 million.

The main role of the Portuguese AW101 is search and rescue in Portugal's maritime zone. AW101s are operated by the 751 Squadron and are on constant alert at three bases: Montijo near Lisbon, Lajes Field on the Azores, and Porto Santo Island.

Japan Maritime Self-Defense Force


The Japan Maritime Self-Defense Force (JMSDF) ordered 14 aircraft in 2003 to use in both the airborne mine countermeasures (AMCM) and transport roles. The AW101 was modified by Kawasaki Heavy Industries, and the Japan Defense Agency designated the model MCH-101. Special features of the MCH-101 include the automated folding of the rotor and tail. The MCH-101 has also been outfitted with Northrop Grumman's AQS-24A for the mine-hunting role.

In 2002, AgustaWestland, Kawasaki and Marubeni entered a general agreement for cooperation; Kawasaki began the assembly of both the CH-101 and the MCH-101 in 2003. Kawasaki also began licenced production of the RTM322 engines in 2005. In a separate agreement between Marubeni and AgustaWestland, a supply depot was established in Japan to support the MCH-101 and CH-101 fleets. The first MCH-101 was delivered to the JMSDF on 3 March 2006.

The MCH-101 will replace the MH-53E (S-80-M-1) in the AMCM role. The CH-101 will operate in the transport/support role for Antarctic missions, replacing the Sikorsky S-61, and will be working in coordination with the Ministry of Education, Culture, Sports, Science and Technology.

VIP and other usage


AgustaWestland has developed a luxury variant of the AW101, the AW101 VVIP (Very Very Important Person, i.e. a head of state), aimed at business and VIP customers. As of April 2009, 15% of all AW101s sold have been for VIP purposes.

The United States Marine Corps began acquiring the AW101 as the intended replacement of its fleet of Marine One helicopters, used by the President and other key political figures, under the VXX program; designated VH-71 Kestrel, this aircraft was heavily customised with specialised equipment and defensive systems. However, on 6 April 2009, the VH-71 was abruptly terminated when funding was withdrawn. A large number of AW101 spare parts, left over from the VH-71's aborted development, were purchased by Canada. AgustaWestland teamed up with Boeing in 2010 to enter the AW101 in the restarted VXX program.

Other customers for the VIP variant have emerged; a Saudi Arabian order was placed in 2009, while Algeria and Nigeria has issued orders. Turkmenistan is operating VIP AW101s as of 2013.

In April 2009, India ordered 12 AW101 to serve as executive transport helicopters for the Indian President and Prime Minister. The Indian selection was made after assessing the AW101 and the Sikorsky S-92 in field trials in 2008. The purchase was put on hold following the 2013 Indian helicopter bribery scandal involving Finmeccanica, the Italian supplier of the AW101 to the Indian Air Force and stakeholder in AugustaWestland.

Variants

 * Pre-production
 * PP1 – Westland-built basic air vehicle prototype, first flown 9 October 1987.
 * PP2 – Agusta-built Italian basic air vehicle prototype first flown on 26 November 1987 and used for deck trials but was destroyed on 21 January 1993 following a rotor brake malfunction.
 * PP3 – Westland-built and the first civil configured Heliliner, used for engine vibration tests and icing trials in Canada.
 * PP4 – Westland-built British naval prototype, lost in an accident on 7 April 1995 after a drive train control rod failure.
 * PP5 – Westland-built Merlin development aircraft eventually equipped with Merlin avionics.
 * PP6 – Agusta-built development aircraft for Italian Navy variant first flown 26 April 1989.
 * PP7 – Agusta-built military utility aircraft with rear-loading ramp.
 * PP8 – Westland-built civil prototype.
 * PP9 – Agusta-built military utility prototype with rear-loading ramp.
 * 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 ranp.


 * 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 (with links to Skyfall).


 * Model 511
 * Canadian Forces search and rescue variant, designated CH-149 Cormorant by customer, 15 built.


 * Model 512
 * Merlin Joint Supporter for Royal Danish Air Force. Eight acquired for search and rescue (512 SAR) and six for tactical transport (512 TTT). Six transport Merlins sold to RAF (as Merlin HC.3As) and replaced by six new build helicopters.


 * 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.


 * 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 HC4/4A
 * Planned conversion of Ex RAF HC3/3A for RN use. Tail and blade folding plus (possible) avionics upgrade.


 * Merlin ASaC5
 * Planned conversion of 8 RN HM1 for use in carrier based airborne early warning role.


 * 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
 * USMC variant intended to serve as the US Presidential helicopter.


 * SH-101A
 * Italian military designation from 2012 for the MP variant.


 * EH-101A
 * Italian military designation from 2012 for the AEW variant.


 * UH-101A
 * Italian military designation from 2012 for the ASH variant.

Military operators

 * Algerian Air Force (2 on order)
 * Algerian Navy
 * Royal Canadian Air Force (see CH-149 Cormorant)
 * Royal Danish Air Force
 * Indian Air Force
 * Italian Navy
 * Italian Air Force
 * Japan Maritime Self-Defense Force
 * Portuguese Air Force
 * Saudi Air Force
 * Turkmenistan Air Force
 * Royal Navy
 * Royal Air Force
 * Japan Maritime Self-Defense Force
 * Portuguese Air Force
 * Saudi Air Force
 * Turkmenistan Air Force
 * Royal Navy
 * Royal Air Force
 * Turkmenistan Air Force
 * Royal Navy
 * Royal Air Force
 * Royal Air Force

Law enforcement operators

 * Tokyo Metropolitan Police Department
 * Tokyo Metropolitan Police Department

Notable accidents and incidents

 * 21 January 1993 – Italian development Merlin PP2 crashed near Novara-Cameri airfield in Italy after an uncommanded application of the rotor brake in flight. Four people were killed.


 * 7 April 1995 – British development Merlin PP4 (ZF644) crashed while in-flight from Yeovil, England. All four crew members escaped the helicopter during its descent before it hit the ground.


 * 20 August 1996 – Italian development Merlin PP7 (I-HIOI) was damaged in an accident when it turned over after the tail rotor drive failed on landing. The helicopter was repaired.


 * 27 October 2000 – Royal Navy Merlin (ZH844) ditched near the Isle of Skye, Scotland after a hydraulic fire caused by the rotor brake being partially engaged.


 * 30 March 2004 – Royal Navy Merlin (ZH859) crashed on take-off from RNAS Culdrose due to tail rotor hub cracking.


 * 15 November 2007 – During embarkation for a medical evacuation on São Jorge Island, Azores, a Portuguese Air Force Merlin caused injuries to five people when it unexpectedly climbed by one metre before the pilot recovered control. An Air Force spokesperson later stated that this kind of incident is unheard of.

Notable appearances in media
The Merlin is used by the villain in the 2012 James Bond movie Skyfall.