AW101

The AgustaWestland AW101 is an Anglo-Italian three-engined medium-lift helicopter developed by Westland Helicopters and Agusta as the EH101 and built at Yeovil, England, and Vergiate, Italy. First flown on 9 October 1987 and in service since 1999, it replaced the Sea King in anti-submarine warfare, search and rescue, troop transport and ship-based utility roles, and is named Merlin by Britain, Denmark and Portugal. It serves the Royal Navy, the Italian Navy and Air Force, Canada, Norway, Poland, Algeria, several VIP customers and Japan, where Kawasaki assembled it under licence.

Development

In 1977 the UK Ministry of Defence issued a requirement for an anti-submarine helicopter to replace the Royal Navy's Westland Sea Kings against improving Soviet submarines; Westland proposed the three-engined WG.34. Agusta, whose Italian Navy customer was also replacing Sea Kings, joined Westland in EH Industries Limited to develop the design; Britain confirmed its participation on 12 June 1981 and the two governments signed the main funding agreement in 1984. The first prototype, PP1, flew on 9 October 1987 on General Electric CT7-2A engines; the loss of the Agusta-built PP2 to a rotor-brake malfunction on 21 January 1993 halted flight tests for six months, and the first flight on Rolls-Royce Turbomeca RTM322 engines followed on 6 June 1993.

Canada selected the EH101 in 1987 for up to 50 anti-submarine and search-and-rescue helicopters, but the incoming Liberal government cancelled the order in 1993. Britain ordered 22 transports for the RAF in February 1995 and Italy ordered 16 in October 1995. After Westland and Agusta merged into AgustaWestland in 2000 the EHI joint venture was wound up and the type was renamed AW101 in 2007. By April 2009 more than 180 had been sold.

Design

The AW101 is of conventional layout with a modular aluminium-lithium alloy fuselage, a de-icing system and clearance to operate between −45 and +50 °C. An active control of structural response system cuts airframe vibration by up to 80 % and a dual-duplex digital automatic flight control system provides a four-axis autopilot. Three turboshafts drive the 18.59 m (61 ft) five-bladed main rotor: the RTM322, developed for the type, rated at 1,517–1,611 kW (2,035–2,160 shp), or the General Electric CT7 at 1,462–1,737 kW (1,960–2,329 shp); according to Rolls-Royce about 80 % of AW101s use the RTM322, though by 2020 new aircraft were sold only with the CT7-8E.

The cabin is 6.5 m (21 ft 4 in) long, 2.3 m (7 ft 7 in) wide and 1.91 m (6 ft 3 in) high and carries 24 seated or 45 standing troops, 16 stretchers or pallets; the rear ramp takes 3,050 kg (6,720 lb) and the cargo hook 5,440 kg (11,990 lb). The Merlin HM1 has an empty weight of 10,500 kg (23,150 lb) and a maximum take-off weight of 15,600 kg (34,390 lb); it cruises at 278 km/h (150 kn) with a range of 1,389 km (750 nmi). Sensors vary by customer: the HM1 carried the Blue Kestrel 5000 radar, detecting small targets at 46 km (25 nmi), the FLASH dipping sonar, the AQS903 acoustic processor and Orange Reaper ESM.

Armament

Most variants carry chaff and flare dispensers, directed infrared countermeasures, radio-frequency electronic support measures and laser warning receivers, and British Merlins received armour against small-arms fire, fully fitted by July 2010. Two underside hardpoints let the Merlin HM1 carry four Sting Ray torpedoes or Mk 11 Mod 3 depth charges, and Italian Model 110s carry torpedoes or Marte anti-ship missiles. The Mk1, Mk3 and Mk3A can mount general-purpose machine guns in up to five cabin door and window positions.

Operational History

The Royal Navy took 44 Merlin HM1s, the type entering service on 2 June 2000 with the Culdrose-based squadrons 814, 820, 824 and 829 NAS. Thirty were rebuilt to HM2 standard under the £750 million Merlin Capability Sustainment Programme, with a new mission system and digital cockpit; initial operating capability came on 30 June 2014 and the last was delivered on 11 July 2016. HM2s can also carry the Thales Crowsnest airborne early warning pod, which replaced the Sea King ASaC7; it deployed with the 2021 carrier strike group, reached initial operating capability in July 2023 and was at full operating capability when nine HM2s of 820 NAS, six for ASW and three for AEW, embarked in HMS Prince of Wales for the 2025 Indo-Pacific deployment. The HM2's out-of-service date was moved to 2040 in June 2021.

The RAF's 22 Merlin HC3 transports entered service with No. 28 Squadron at RAF Benson in January 2001 and served in Iraq from 2004 as the main medevac asset around Basra until June 2009. Merlins flew in Afghanistan from 2009 until June 2013. Command passed to the Royal Navy's Commando Helicopter Force on 30 September 2014, and the £454 million Merlin Life Sustainment Programme converted 25 HC3/3As into naval HC4/4As, the first delivered to RNAS Yeovilton on 25 May 2018 and the last by the end of 2022. A Mk4 ditched in the English Channel on 4 September 2024 while exercising with HMS Queen Elizabeth, killing one crew member, and another crashed near Sourton on 3 June 2026, killing three.

The Italian Navy received 22 in all: eight ASW/ASuW SH-101As, four EH-101A early-warning aircraft with the HEW-784 radar and ten MH-101A amphibious support helicopters; three deployed to Afghanistan in 2010. The Italian Air Force chose the type in June 2011 to replace its HH-3Fs and received 15 HH-101A combat SAR helicopters between 2016 and 2020. Canada bought 15 CH-149 Cormorants after its 1997 SAR competition and in December 2022 announced a C$1.24 billion contract for three more aircraft and an upgrade of the existing fleet, bringing it to 16. Denmark received 14 by March 2007, eight for SAR and six transports later sold to Britain and replaced by new-builds; Portugal bought 12 under a €446 million contract, the first delivered on 22 December 2004, and its 751 Squadron flies them from Montijo, Lajes and Porto Santo; Japan's Kawasaki-assembled MCH-101 was delivered from 3 March 2006; Norway's 16 SAR Queens began rescue duty on 1 September 2020; and the Polish Navy has received four ASW/CSAR Model 614s. Algeria took six naval and two VIP aircraft.

Variants

• Merlin HM1 / HM2 (Model 111): Royal Navy ASW variant, 44 built; 30 rebuilt as HM2 by 2016, some also able to carry the Crowsnest AEW pod.
• Merlin HC3 / HC3A (Model 411 / 512): RAF transports, 22 new-build plus six ex-Danish aircraft bought in 2007.
• Merlin HC4 / HC4A: Conversion of 25 HC3/3As for the Commando Helicopter Force with HM2 cockpit and folding tail and rotor head.
• SH-101A / EH-101A / MH-101A (Models 110, 112, 410/413): Italian Navy ASW, early-warning and amphibious-support versions.
• HH-101A (Model 611): Italian Air Force combat search and rescue variant on CT7-8E engines, 15 delivered 2016–20.
• CH-149 Cormorant (Model 511 / 615): Royal Canadian Air Force search and rescue variant, 15 delivered, with three more and a fleet upgrade announced in 2022.
• MCH-101 (Model 518): Kawasaki-assembled JMSDF mine countermeasures and transport variant with the AQS-24A mine-hunting sonar.