AgustaWestland AW101
The AgustaWestland AW101 is a medium-lift helicopter in military and civil use. First flown in 1987, it was developed by a joint venture between Westland Helicopters in the United Kingdom and Agusta in Italy in response to national requirements for a modern naval utility helicopter. 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.
Prior to 2007, the aircraft had been marketed under the designation EH101. The original designation was EHI 01, from the name given to the Anglo-Italian joint venture—European Helicopter Industries—but a transcription error changed this to EH101. In 2000, Westland Helicopters and Agusta merged to form AgustaWestland, leading to the type's current designation.
The AW101 entered into service in 1999 and has since replaced several older helicopter types, such as the Sikorsky SH-3 Sea King, performing roles such as medium-sized transport, anti-submarine warfare, search and rescue, and ship-based utility operations. The Royal Canadian Air Force operates the CH-149 Cormorant variant for air-sea rescue. Another variant, the Lockheed Martin VH-71 Kestrel, was produced to serve in the United States presidential transport fleet before the program was cancelled and the aircraft sold off to Canada for parts. Civil operators use the AW101 for 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.
Development
Origins
In 1977, the UK Ministry of Defence issued a requirement for an anti-submarine warfare 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 was also considering the replacement of its fleet of Sea Kings, which had been built by the Italian company Agusta; Westland and Agusta soon began talks regarding the 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, 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.
In 1987, Canada selected the EH101 to replace its Sea Kings in the anti-submarine warfare and search and rescue roles. The EH101's third engine and increased range compared favourably with rival aircraft, such as the Sikorsky Seahawk. The range and de-icing capability were also seen as vital for North Atlantic operations. The fledgling EH101, of which up to 50 were on order to replace the Canadian Armed Forces's Sea Kings, found itself subject to a wider political battle between the country's Conservative and Liberal parties, the latter viewing the aircraft as too costly. Critics attacked the EH101 purchase as excessive and unnecessary after the Cold War's end in the early 1990s. Wide-ranging cost estimates were presented by both proponents and opponents of the EH101 procurement, with opponents backing life extensions of Sikorsky CH-124 Sea King and Boeing Vertol CH-113 Labrador helicopter fleets. The EH101 controversy was seen as a factor in the 1993 Canadian federal election. The order was cancelled by the new Liberal government in 1993 resulting in a $470 million cancellation fee.
Into production
Several pre-production aircraft were assembled during the late 1980s and early 1990s. The first pre-production aircraft had its first flight powered by General Electric CT7-2A engines on 9 October 1987. Flight tests were suspended for six months following the crash of the second pre-production aircraft on 21 January 1993. On 6 June 1993, the first EH101 took its maiden flight with the Rolls-Royce Turbomeca RTM322 turboshaft engine. Nine prototypes were built to explore military and civil applications, including a "heliliner" configuration. In February 1995, Britain formally placed its first order for a total of 22 EH101s; this was quickly followed by Italy's order for 16 EH101s in October 1995. The EH101 order was not without controversy, the RAF had declared its preference for an all-Chinook fleet; also, Boeing allegedly offered cheaper terms for the Chinook. RAF deliveries began in 1997; RN deliveries started the following year.Following the merger of Westland and Agusta to form AgustaWestland in 2000, there was no need for the separate EHI entity; the EH101 was formally re-branded as the AW101 in 2007. By April 2009, more than 180 AW101s had been sold worldwide; the combined operational fleet had also accumulated a total of 170,000 flying hours.
Further developments
In November 2007, Algeria signed a contract for six AW101 helicopters. In August 2012, it was reported that Algeria had signed an agreement with AgustaWestland for the provision of up to 80 helicopters, 42 of which were to be AW101s. Under the terms of this arrangement, early aircraft were to be manufactured by AgustaWestland, while Algeria was to commence the assembly of some AW101s later on.By September 2013 AgustaWestland was in the process of acquiring civil certification for the AW101; prospective customers include offshore oil platform operators and VIP clients. As of February 2014, AgustaWestland was considering adapting the AW101 as a heavyweight unmanned aerial vehicle, it is proposed that in this configuration an AW101 could be optionally crewed.
On 7 June 2010, it was announced that Boeing had acquired a manufacturing licence and the rights from AgustaWestland for US production of a localised AW101 variant, designated as the Boeing 101. In October 2012, the aircraft was submitted in a U.S. Air Force competition to replace the HH-60 Pave Hawk; however, the bid was dropped three months later.
Design
Overview
The AW101 follows a conventional design layout, but makes use of advanced technologies, such as the design of the rotor blades, avionics systems, and 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 and +50 °C. The aircraft's control systems allow the AW101 to maintain a stable hover in crosswinds.An active vibration control system, known as the active control of structural response system, reduces airframe vibration by up to 80%, increasing crew comfort and minimising 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 pilots' instrument displays include six full-colour high-definition screens and an optional mission display; a digital map or forward looking infrared display can also be installed.
Powerplant
The AW101 is powered by three turboshaft engines. Initially the Rolls-Royce Turbomeca RTM322 producing and the General Electric CT7 producing were the two available engine types, but by 2020 new aircraft were only being sold with the CT7-8E. The RTM322 powerplant was specifically developed for the AW101; it was subsequently adopted on the AgustaWestland WAH-64 Apache and the NHIndustries NH90 helicopters. According to Rolls-Royce, about 80% of AW101s use the RTM322The engines power an 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 acoustic signature. Improved BERP IV rotors have since been developed; when installed this increases the AW101's maximum take-off weight.
Each engine is supplied by a separate 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 fitted with a probe for aerial refuelling. Self-sealing fuel tanks are an optional item to be selected by the customer. An inlet particle separator system can be installed, protecting the engine when operating in sandy environments.
Armament and defensive systems
Most variants of the AW101 are equipped with self-defence systems, such as chaff and flare dispensers, directed infrared countermeasures, ESM, and a laser detection and warning system. British Merlins have been outfitted with protective armour against small-arms fire. A side-mounted forward looking infrared imaging sensor has been fitted to some variants.Two hardpoints are present in 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 five 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.