The Merlin family in UK service

The Merlin helicopter is a big and powerful machine. A top class helicopter which not many countries can afford: yet, its formidable performances have gained it orders from all over the world, from the UK and Italy to Canada, Japan, India, Portugal, Algeria, and others. The Merlin is considered both the best ASW and the best medium utility helicopter, and had a solid recognition of these two titles by being chosen for the US President transport helicopter, an absolute first since it is not an american helicopter. It was also a strong contender for the USAF CSAR-X requirement, and much as both programmes were killed in budget cuts and restructurings, the point remains. 

Yet, there's a strong base of people online who mercilessly bash at the Merlin helicopter all the time. I wanted to understand why, and see if i could find any evidence that might support their bashing against the "industry's hype". 

Here is the result of my long investigation. I welcome further info from whoever can give me more data or first-hand experience. Of course, if is 'solid' data and not personal claims. I've personally tried to provide the source or evidence of all my points in this article.

HM1/HMA2: the best submarine hunter out there

The AW101 Merlin is well known for its extensive use of composite materials (a good 18% of the airframe, which was pretty much a world first when the Merlin appeared). The modular alluminium-lithium alloy fuselage structure is damage and crash resistant, with multiple primary and secondary load paths. Alluminium and composites also have the advantage of both being materials resistant to sea corrosion. (The Sea Harrier used lots of alluminium) The AW101 is fitted with Health and Usage Monitoring (HUM) equipment, which will monitor aspects of rotor head, transmission and mission performance, and warn the pilot of any problems. HUM and the mission systems combine to reduce crew workload, an essential requirement given the long and complex missions which the helicopter undertakes.

Active vibration control of the structural response (ACSR) uses a vibration-canceling technique to reduce the stress on the airframe. The AW101 is rated to operate in temperatures ranging from −40 to +50 °C. High flotation tyres permit operation from soft or rough terrain. The main rotor blades are a derivative of the BERP rotor blade design, which improves the aerodynamic efficiency at the blade tips, as well as reducing the blade's noise signature. The BERP IV was fitted to the HC3 fleet in 2008, and the new rotor design, alone, allows for 650 kg increase in payload thanks to its much higher lift, and also added 10 knots to the speed.

Excepting the naval/military mission equipment, the EH101 cockpit is common to all versions.  Six 18x15cm multifunction colour displays replace the traditional dials. The avionics system is based on two MIL STD 1553B digital databuses which link the basic aircraft management system and mission systems.  The latter, based on dual redundant mission computers, handles all sensors and displays and controls the mission bus. 

The cockpit of the HC3 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 EH101 can be flown by a single person.

Several engine choices are available for the AW101. The subsidiary Rolls-Royce Turbomeca Ltd has developed and produced the RTM 322 that powers the three-engine AW101 Merlin as well as other military aircraft such as the twin-engine NH90 and the WAH-64 Apache from GKN Westland built under license from Boeing. The versions 01/8 and 02/8 power respectively the versions Merlin Mk1 and Mk3. Finally, the latest version, having begun production in 2003, the RTM322 Mk250, powers the AW101 Export (outside Europe) with a compressor that delivers more power for a compression ratio lower than its direct competitor with a reduced number of components to optimize costs.

GE (General Electric), meanwhile, powered the Italian, Canadian and Japanese models at the beginning with the CT7-6 turbine, and today, with the latest, more powerful CT7-8E. The series 6 and 6A have been exclusively used in the development of the AW101 fleet and have accumulated hundreds of hours of flight operations. This turbine powers the Canadian version of the AW101 (Cormoran) as well as the NH90, and especially its major competitor, the S- 92/H-92.

Each engine is supplied by a separate 1,074 litre self-sealing fuel tank using dual booster pumps. A fourth tank acts as a reservoir supply, topping up the main tanks during flight; while a fifth transfer tank can be added to increase range, as can airborne refuelling. Two standard of fuel tanks are available, offering increasing levels of protection/survivability:

The three main fuel tanks hold 3222 liters, with 938 eventually in the fourth. 1051 more can be added with the 5^th tank, and auxiliary fuel tanks to fit in the cabin are also available. A hover in flight refuelling (HIFR) unit is installed internally in the cabin of the HM1/HM2. The HC3 can be fitted with Air to Air refueling probe.

It is hard to get so detailed information, but for what I understand, the HM1 is fitted with 3 fuel tanks, and the HC3 has four. I will correct this if I find information about it. 

The AgustaWestland data about the fuel tanks combinations for the Merlin

The 180 gallons Robertson auxiliary fuel tank cabin installation weights 146 kg. The 400 Gallons one weights 258 kg. AgustaWestland offers, for the latest AW101 variants, the option of adding a sixth underfloor fuel tank, which only weights 45 kg and can hold up to 518 kg of useable fuel, and without stealing space in the cabin.

The HM1 is fitted with a Ferranti Blue Kestrel with 360° field of view radar in the radome under the front of the helicopter. British aircraft also carry "Orange Reaper" ESM equipment.  The ASQ903 acoustic processor processes data returned by dunking sonor or sonobuoys.

Royal Navy Merlins are equipped with the Thales Underwater Systems (formerly Thomson Marconi Sonar) FLASH (Folding Light Acoustic System for Helicopters) active dipping sonar.  This comprises a submersible unit with a low frequency transmitter, and a receiving array of 12 folding arms.

Flash can search to a maximum depth of 2,000ft.

The helicopter is equipped with a Normalier-Garrett mission recorder and two sonobuoy and flare dispensers, together with Chelton sonobuoy homers. The sonobuoys are Difar, Barra, Harp and VLA.

It has two hard points for weapon carriers, on which the HM Mk1 model can carry four Sting Ray torpedoes or Mk 11 Mod 3 depth charges, though at present cannot use the Sea Skua missile as no one has funded the integration and test firing. The Italian Merlin ASW uses Marte missiles from MBDA. Weapons payload can reach 960 kg.

On an anti-submarine warfare active dipping mission over a radius of operation of 50 nautical miles, there is sufficient fuel in the internal fuel tanks to provide 190 minutes on station with a 20-minute fuel reserve. Fully armed on an anti-submarine warfare passive sonobouy mission, the helicopter time on station is 210 minutes at a radius of operation of 100 nautical miles, and 90 minutes at a radius of operation 200 nautical miles.

In the anti-ship surveillance and tracking role, Merlin uses its tactical surveillance and over-the-horizon targeting radar to identify the positions of hostile ships and relay the data to the allied command ship. The electronic support measures system is the Kestrel (Royal Navy designation Orange Reaper) from Thales Defence. Using the Kestrel ESM and the BAE Systems Blue Kestrel search radar, the Merlin helicopter is able to search an area of approximately 200,000km² in a single four-hour sortie.

The EH101 Merlin/Type 23 Frigate weapon system has been designed to provide maximum operational efficiency by reducing crew workload while maintaining a very high state of readiness and aircraft availability.  Coupled with these attributes, the Royal Navy's reduced manning philosophy has driven the cockpit design towards operation by a single pilot.  From a pilot's standpoint, the aircraft is fully capable of being flown solo.  The handling qualities are exceptional throughout the flight envelope, the autopilot modes permit hands-off flight for most of the mission, and the avionics are in some cases triple redundant with benign failure modes.

EH101 can operate in sea state 6, in up to 50 kts cross winds, to allow its parent Type 23 frigate to continue monitoring its towed sonar array without the need to turn into wind.  Once on deck, the rotor system can generate negative thrust while the helicopter is made fast (while) by engaging a rapid securing device called PRISM which consists of a "harpoon" in a grid on the deck.  PRISM interfaces with a semi-automatic handling system for aircraft moves and weapon loading.

Without disembarking the consoles (but disembarking the sonobuoys launchers) and with full four men crew, the Merlin HM1 can lift a 3400 kg payload, or carry 8 stretchers plus paramedic personnel. It can carry ten equipped soldiers, and with a L118 Light Gun under slung at the cargo hook it can stay in the air for a good hour, deploying the gun up to 100 km away from the ship. Up to 16 men can be carried in transfer flights. Disembarking the dipping sonar to free up cabin space when ASW is not a priority, 8 seats plus a rack of 4 stretchers can be fitted.

In January 2006, Lockheed Martin UK was awarded the contract for the Merlin capability sustainment plus (CSP) upgrade programme. 30 Merlin helicopters are to be upgraded under the contract, with a further eight on option. The option is practically dead, however, and unless the HM1 airframes left are given new life in a new role (for example fitting them with the Cerberus radar system to take on MASC role), they will be retired early after being hard-worked to cover the requirements as the other airframes become unavailable for 9 to 10 months each as they are upgrade to HM2 standard. The CSP programme is planned to sustain capability until the planned 2030 out-of-service date.

Under the Merlin CSP, the helicopters were also to be fitted with AgustaWestland's helicopter electro actuation technology (HEAT), a fly-by-wire system that uses electrical actuators to replace the hydraulic systems. This would have added considerable savings in weight and, it was hoped, in mainteinance, but during tests the reliability of the actuators emerged as a concern and the technology was dubbed not mature, leading to HEAT being dropped in 2008. The money that had been allocated for it was diverted on other parts of CSP, and mainly on the acquisition of spares.

BAE Systems is supplying the dual-lane digital flight control computers.

 

A computer image of a Merlin fully kitted for ASW/ASuW mission. The console is clearly evident, as are the sonobuoys launchers, the weapon racks shown with SA80s at the ready, the SAR winch and the new, much smaller sonar electronics mount (in white). Three seats (one in grey) appear placed before the consoles, while three seats for passengers are provided, plus a stretcher for medevac/SAR role. Disembarking the sonobuoys and half of the console, 16 soldiers will be seated.  

Separated from the HM2 upgrade programme, LM UKIS was in January 2008 awarded a $10.8 million contract to design, develop, trial and certify the DAS system for the HM1, incorporating the BAE Systems AN/AAR-57 Common Missile Warning System, the same company’s AN/ALQ-157 IR jammer and an AN/ALE-47 Countermeasures Dispensing System to eject IR flares.

The DAS requirement was spurred by concerns about the risk of meeting portable SAM and MANPADs missiles during missions in the Gulf. Under a second UOR, selected aircraft have received a naval full motion video (FMV) capability which enables EO/IR imagery from the L-3 Wescam MX-15 system (a pool of which are rotated across the Merlin fleet) to be downlinked to remote platforms.

RN sources suggest four FMV kits and DAS kits have been delivered.

Other UORs introduced to the front line have  included a two-way Bowman radio communications system,

additional armour protection for aircrew, a fast roping system, and the M3M 0.50 calibre heavy machine gun for force protection. In addition, Teledyne Reynolds was in late 2008 contracted to manufacture a quantity of fittings to allow for the mounting of the MX-15 EO/IR system across the whole Merlin HM1

forward fleet. It is not clear if more DAS kits and MX-15 EO/IR cameras have been acquired/will be acquired as part of the Merlin CSP, but each and every HM2 will be able to use both kits, being fitted for them without any modification required.

The Merlin HM2 upgrade mainly brings up to date the  avionics, but also adds a new mission computer, map systems as well as new processors for the radar and acoustic sensors. These new systems and improvements in technology mean a smaller number of black boxes in the aircraft allowing the avionics compartments to be redesigned and shrunk. The Mk1's Sonics processor, described by some as like a 'small fridge' has been replaced by a considerably smaller unit. The changes mean that the Mk2 is a leaner machine than its predecessor. When weighed, the aircraft came in around 200 kg (440 lbs) lighter than a Mk1 even with test instrumentation onboard.

The helicopter gets its Data Link 11 upgraded and comes out of the HM2 upgrade fitted for, but not with the Link 16. It receives new secure V/UHF radios (SATURN and CRIPTO) and Raytheon’s latest Successor IFF (SIFF) plus, for the first time, the Search and Rescue Location System, which draws info from the satellite constellation SARSAT. 

In terms of embodiment, the key features of the MCSP comprise the installation of new NVG-compatible cockpit avionics (based on seven 1024x768 pixel XGA multifunction flatpanel displays), a new navigation suite (with dual attitude, heading and reference system, embedded GPS/inertial navigation system, standby GPS and a new air data computer), an open architecture mission system, a substantial uplift in tactical management system processing capability, and new tactical management software. In parallel, the Merlin HM2 is receiving an improved Blue Kestrel surveillance radar (incorporating a new digital signal processor

conferring SAR/ISAR modes and improved track-while-scan performance), a revised sonics processing suite from Thales (featuring new shallow-water detection and tracking algorithms, a common acoustic processor to handle both active dipping sonar and sonobuoy processing, and a digital VHF sonobuoy receiver), and a new solid-state DiRECT HR mass storage and recording system from Saab Avitronics.

The new cockpit of the HM2, with the new screens and digital equipment replacing large part of the older instrumentation

New tactical mission consoles are installed in the rear cabin, using large flat-panel colour screens, drop-down menus and Windows-style display formats to reduce operator workload and provide a far more intuitive HMI. The dual 30cm displays used in the current HM1 consoles are being replaced by a Barco

60cm (1920x1200 pixel) widescreen colour display, a 30cm (1024x768 pixel) interactive display unit and a 30cm (1024x768 pixel) touch-screen control unit. 

The HM2 new rear console

 

The rear mission console, designed to be operated by two air warfare officers, has the option to be split in half if the aircraft is required for non anti-submarine warfare missions. With half the console removed, the aircraft can carry 12 patients in the CASEVAC role, over the Mk1s eight, or up to 16 combat troops (against 10), with the area previously occupied by the console being used for 'bergen' or backpack storage.

Other changes to the aircraft include a new environmental control system, improved fast roping equipment and the fitting of a M3M 0.50 calibre machine gun for use out of the cabin door. The HM2 is also being equipped with an FN Herstal-supplied M3M 0.50cal machine gun at the cabin's starboard door. It remains possible to use the 7.62 stabilized GPMG mount at the port window too.

The HM2 programme also involves, of course, the upgrading of the Full full mission cockpit dynamic simulator, the cockpit procedural trainer and two (out of the three existing) Merlin HM1 rear crew trainers in Culdrose.

Merlin HM1 data: 

Overall Length 22.8m

Fuselage Length 19.5m

Width (Excluding Rotor) 4.5m

Overall Height 6.6m

Folded Length 15.7m

Folded Width 5.2m

Folded Height 5.2m

Main Rotor Diameter 18.6m

Tail Rotor Diameter 4m

All-Up Weight 14,600kg

Performance:

Cruising speed 296km/h (160kt), long range cruising speed 260km/h (140kt), best endurance speed 167km/h (90kt), recommended cruise speed 130 knots (135 knots for HC3 with BERP IV rotors and latest AW101 variants)  

Range (With Standard Tanks) Over 1,000km

Ferry range with auxiliary tanks 1853km (1000nm).

Endurance with max weapon load, 5hr on station. (HM1)

Indicative mission profiles: active dipping sonar search mission at 50 nautical miles from the ship, 190 minutes on station with a 20-minute fuel reserve.

anti-submarine warfare passive sonobouy mission, time on station is 210 minutes at 100 nautical miles, and 90 minutes at a radius of operation 200 nautical miles.

Crew: pilot, co-pilot, acoustic sensor operator and observer. (HM1)

Rate of Climb 10.16m/sec

Engines 3 x Rolls-Royce Turbomeca RTM 322 02/8

Weapons: 4 Stingray torpedoes or depth charges, one window-mounted GPMG 7.62 machine gun port side;

          one M3M .50 heavy machine gun at the starboard cargo door (HM2 and on HM1 as a UOR from 2009)

Mission suite: dipping sonar Thales Flash, Blue Kestrel radar, sonobuoys on two launchers, SAR winch, 3 passenger seats (HM1) and a stretcher. With UORs, an advanced electronic self defence DAS has been procured, plus Fast Rope kit and MX-15 EO/IR camera for surface search day and night.

Disembarking sonar and sonobuoy, 10 soldiers can be carried, or 8 stretchers, plus full console and crew. (HM1)

Removing sonobuoys and half of the console, 16 soldiers or  12 stretchers. (HM2)

3400 kg + payload slung from cargo hook

    

Costs & Major Milestones

• Merlin aircraft procurement = £2.5 billion 
• Spares and Support = £430 million 
• Training systems = £170 million 
• Support Equipment = £50 million 
• MERLIN TOTAL = £3.15 billion
• International Collaborative Programme (development and production infrastructure) = £1.5 billion
• OVERALL TOTAL = £4.65 billion approx.

Major Milestones:

• First flight by a production Merlin was on 6 December 1995
• First mission system fitted Merlin flew in January 1997
• First Merlin HM Mk1 Squadron, 700M Naval Air Squadron, commissioned on December 1998
• In Service Date (ISD) achieved on March 1999, 12 aircraft delivered
• Delivery of last aircraft, October 2003
• 44 aircraft procured by RN, 38 still in service today, 4 mothballed, 2 lost to accidents.

 
The Squadrons of the HM1/HM2

The Merlin HM1 fleet number originally 44. 2 airframes have been lost in accidents, and 4 airframes are in stowage. 38 Merlin remain, maintaining a frontline ready fleet of roughly 30 helicopters ready at all times. The HM2 upgrade will further bring the fleet down in numbers, to just 30, but availability is expected to rise considerably as partial compensation.

The Merlin was first employed in the 700M (Merlin) squadron as Operational Evaluation Unit, from 2000 to 2008. 700 Squadron now is reforming as 700W to guide the introduction into service of the Wildcat Lynx, as commonly done with each new machine. 700M flew three Merlin.

Next to form was 824 Squadron which commissioned in June 2000 with 8 aircraft and is responsible for training and converting crew to the Merlin. The Pilots, Observers and Aircrewmen work together as a crew during the 44 week course covering all aspects of Merlin operations. Having successfully completed the course, they are awarded 'Wings', and sent to front line squadrons. 

The 814° NAS, the “Flying Tigers”, reformed in October 2001 equipped with the Merlin Mk.1, designed to be deployed aboard ships or operate from shore. It has seen operational service aboard HMS Illustrious, Operation Telic in Iraq and in the Persian Gulf area. It should have 8 frontline available Merlins. Normally, when a flight of six Merlins deploy on a Uk carrier, it comes from this squadron, which is probably the most active ASW unit of the whole fleet.

The next squadron to rededicate with Merlin was 820 in December 2003. It should have a frontline strength of 9 Merlins. It often deploys helicopters on the big RFA units.

The final squadron to recommission with Merlin was 829, formed on 21 October 2004. It provides 6 Small Ship Flights for deployment on Type 23 frigates, from a total strength of 9 Merlin helicopters.

The Merlins of the Navy are all based in RNAS Culdrose, known in the navy as HMS Seahawk. Here is located the Merlin (HM1) Training Facility. The MTF is part of 824 Sqn, and is a first in that it encompasses Pilot, Observer, Aircrewman and Engineering training under one roof. The facility comprises of a Cockpit Dynamic Simulator (CDS), 3 Rear Crew Trainers (RCT), 6 Part Task Trainers (PTT), Computer Based Training (CBT) classrooms, a Mechanical Systems Trainer (MST) and a Weapon Systems Trainer (WST).

The CDS offers a full motion simulator, which is an exact copy of the cockpit of the aircraft. Its state of the art graphics allow a very realistic training environment for aircrew. The 3 RCT's again offer a realistic environment for crews to train in a tactical scenario, and can be linked to the CDS to provide a full crew realistic simulation in order to encourage tactical development and crew resource management.

The MTF also provides more academic instruction through the employment of the PTT's and CBT machines. These devices allow students to learn the technical aspects of the Merlin aircraft, as well as how to operate it's many systems in a controlled environment. This aspect of the course is mostly self-taught, and the students can work at their own pace, thus ensuring that all the necessary information is understood.

Also within the MTF is a MST, where the majority of engineering training is carried out. On the MST, trainees learn how to change engines and rotor blades, while instructors can inject malfunctions for the trainees to detect. The WST has fully functional landing gear, hydraulics, deck lock (a hydraulic arm which grabs hold of a grid on the ship's deck once the aircraft has landed), sonobouy dispenser and Active Dipping Sonar (ADS). The WST allows trainees to practise loading and unloading weapons in a realistic environment. 

Depth mainteinance of the whole Merlin fleet is done in Culdrose. 

 

Merlin for MASC

The Merlin has always been one of the strongest contenders for the Sea King ASaC replacement programme, for obvious reasons. An AEW variant of the Merlin, in number of 4, is operated by the Italian Navy, but it uses an air search radar mounted in the same radome of the HM1’s Blue Kestrel radar and is not seen as a solution on par with the “Baggers” Sea King.

In the summer of 2010 AgustaWestland and Thales made a joint proposal to the MOD for the much delayed MASC, unveiling an enhanced Airborne Surveillance and Control (ASaC) capability, at RNAS Yeovilton on 10th July during the Fleet Air Arm’s annual Air Day. The low cost, low risk capability builds upon the combat proven Sea King Mk7 ASaC Cerberus mission system and Searchwater 2000 radar, to provide enhanced operational effectiveness through the use of the next generation AgustaWestland AW101 helicopter. AgustaWestland and Thales have teamed to jointly explore the potential for this capability in advance of the keenly expected MoD requirement to replace the Sea King Mk7 ASaC aircraft after its planned retirement in 2016.

AW101 MASC in an AEW surveillance sortie in a concept art supplied by AgustaWestland/Thales. The AEW suite and radar would be an evolution of the Cerberus already in use on the Sea King MK7, but with the radome deployed in this fashion, the coverage would be improved compared to the ASaC, giving 360° view.

The palletised Searchwater 2000 radar is deployed through the rear ramp aperture when in operation and stows in the cabin when not in use, enabling rapid transit between tasking. Two aft-facing modernised mission crew stations are located at the forward end of the cabin. The following key features and benefits are also included:

• Long range, look up/look down air, land and sea capability
• Human Machine Interface optimised for two man operation
• Fully integrated Link 16 Command and Control capability
• Modern platform extends 360 deg radar horizon and significantly increases mission range and endurance

The palletised ASaC equipment also enables a front line re-role capability delivering greater aircraft utility. The ASaC equipment could be role fitted to all AW101 utility variants. A limited number of new AW101 helicopters might be procured for the role and to augment the number of Utility Merlins available, but due to budget shortages it is likely that the Navy would be hard pressed to fit the palletized radar onto some of the 25 ex-RAF HC3 and HC3A helicopters once these are navalized. Since a frontline strength of more than 18 airframes fit for ops at all times will be the most that can probably be squeezed out of 25 helicopters, the Navy would gladly find a solution that makes use of the 8 non-updated HM1 airframes.

The MASC palletized radar suite offered for use on the AW101 or for the navalized HC3/3A. Note the retracted radome: in this transport fashion, the impact of the "bag" on the performances of the helicopter will be next to none, compared to the effect of the bag used on Sea Kings. Six seats for passengers are also available.

A solution might be removing the ASW kit from these airframes and kit them all for troop transportation: no rear ramp, but still good capability, and already fully naval-capable. However, they would present their own, aging avionics system, reducing their commonality with the rest of the fleet, especially if the HC3 and 3A get an upgrade that brings their avionics on par to the HM2’s one. Ruin the through-fleet commonality would be a shame, and that would be a problem to tackle, perhaps by throwing the HM1 airframes into the tail of HC3 ones to navalize and upgrade, in order to have the avionics fixed.

Lockheed Martin made its own proposal, and its plan is looking at using a Northrop Grumman AESA radar adapted from a fighter application. Under the Lockheed plan, several radar arrays are believed to be dotted around the Merlin fuselage to give the 360-degree coverage demanded by the RN. This solution would also probably be less “damaging” in terms of drag and performances degradation than the famous Bag of the Cerberus suite. Lockheed said in a statement that it was “in discussions with industry partners, including Northrop Grumman, who can work with us to offer a proven yet technically superior design for the Crow’s Nest opportunity. (Note that, apparently, the MASC now is called Crow’s Nest project. Why? To try and hide the fact that the MASC has been delayed year after year after year before even starting for real…?)  The Lockheed proposal is a quite radical change from what is available now, but it would be easier to fit to the 8 leftover HM1 airframes, on the other hand.  

The U.K. arm of Lockheed Martin has been involved with the AgustaWestland-built Merlin for the last 18 years as the systems integrator. It is currently under contract to provide an extensive mid-life upgrade of avionics and other systems on the machine.

Crown’s Nest specifically looked at Merlin for the AEW role, but this was before the change from a STOVL to a CATOBAR carrier. The Hawkeye might return as a strong contender for the role, now that the carrier is going to be properly kitted and thus ready to take on the AEW.

Crown’s Nest indicated a requirement of around 10 airframes in order to support training and operational needs, and the machines were to be put into service between 2019 and 2022. Currently, the Sea King MK7 fleet is based on three Squadrons (one OCU and two frontline). It had originally been a single Squadron, the 849 NAS, with an HQ Flight (OCU) and two operational flights, A and B. These two Flights later assumed Squadron dignity, and now each of the two frontline squadrons has 3 Sea King MK7, 5 pilots, 10 observers, 1 air engineering officer and around 40 members of groundcrew and support. The RN aims to replace this on a like for like base, hence the 10 machines requirement.

Back in 2001, the MOD had been tempted by a 1 billion deal with Northrop Grumman for 6 Hawkeye, but the project was not pursued, particularly for the need of installing at least arrestor wires on carriers that, back then, were expected to be STOVL. The Hawkeye targeted at the UK, in fact, was trialed for STOBAR kind ops, taking off from the sky jump and landing with wires.

Trials were positive, but not entirely. Launching Hawkeyes from sky jumps is possible, but far from optimal.  
  

The HC3/3A

The most obvious difference between the HC3 and the HM1/2 is of course the rear cargo ramp, followed by the less visible but just as noticeable lack of foldability, which was not wanted, despite being available. It also differs from the Royal Navy version by having double-wheel main landing gear, whereas the RN version only has a single wheel on each of the main gears. 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 operation from soft or rough terrain.

The HC3 is equipped with a full set of infrared jammers, such as the Northrop Grumman Nemesis, directed infrared countermeasures, missile approach warners, six different chaff and flare dispensers, and a laser detection and warning system.

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 at 35° C and 4500 ft altitude (with CT7-8E engines providing 2527 sHP at take off). RTM322 is rated 2270 sHP at take off, 2231 shìHP continuous and can reach, in emergency for 30 minutes, 2996 sHP. Interestingly, Camp Bastion sits at around 4000 feet altitude. The UK helicopters use the RTM322 engine, which back at the time in which the helicopters were acquired, was the best possible solution: the rival GE turbines offered (and chosen for example by Italy) have performances inferior in the whole spectrum. The CT7E turbine changed this, but it was presented only in 2008. It remains a contender for a future engine substitution during the life of the Merlins of the RAF and RN. 

The cargo bay is 6,50 meters long, 1,83 meters high, 2,49 meters wide, and the rear cargo ramp is two meters wide, with a cleared height of 1,95 to ease embarkation of payloads. A 0,90 meter door (either sliding or airstair) for personnel access to the cabin is fitted on the port side, while a 1,80 meters wide and 1,55 meters tall cargo door is on starboard.    

The RAF HC3 uses a window-mounted GPMG on the right side, and another pintle-mounted GPMG is fitted at the cabin door on the left side. A third machine gun has been installed on the rear ramp, after Iraq experience. 24 seated troops can be carried along with this weapon fit. With the loss of two seats, the cabin door can be left clear and the machine gun mounted at the nearby window. 

In this image of a Merlin HC3 operating in Afghanistan, the GPMG mount at the window can be seen.

This other photo shows the GPMG mount at the crew door position. Alternatively, to keep the door clear, the machine gun can be installed at the first window nearby, but this requires removing a couple of seats.

(Note that at one point in the video, one of the machine guns in the image appears being an MG42 of German memory, judging from the barrel. The other machine guns showed are both GPMG. Was the MG42 “borrowed” from an allied contingent…? The UK does not use them, for what I know, differently from Italy, Germany and others)

27 seated soldiers can be carried if the machine guns at the window is sacrificed in favor of additional seats, and the starboard cargo door not used. A maximum of 40 soldiers can be fitted in “High Density” arrangement. All seats are crashworthy. 20 seats can be provided if the sliding cargo door is to be kept clear.

In medevac role 16 stretchers and 4 attendants can be carried. Each litter station can receive medical suite for advanced life support.  

Troop seats arrangements. Many combinations are possible, particularly because the machine guns can be mounted, as seen, in several different places.

Other possible configurations. Note the large Quadbike carrier along with the Special Forces group. A RHIB could also be carried. The Troop Transport configuration shows the machine gun mounted at the window and the crew door open. As we have seen, the RAF favors more seats, even sacrificing the door.

 

5 tons of cargo can be carried in place of soldiers, from RHIBs to vehicles (eg: Land Rover) to pallets. A pallet conveyor can be fitted on the cabin’s floor. The maximum ramp load is 3,050kg for embarking vehicles such as Land Rovers.

For the latest AW101, 6000 kg of internal payload are possible up to 15600 kg max weight at take off, for the HC3 5000, as reflected by the max take off weight of 14600 kg. A maximum payload of 4536 kg can be carried slung from the cargo hook. 3000-3400 kg are more common. The Merlin can deploy a L118 Light Gun over 100 km away, and the M777 155/39 Ultra Lightweight howitzer can also be carried (3745 kg). The Merlin can lift half of a Viking vehicle, which can be separated into front and rear cab with just 20 minutes of work.

The Utility variant of the Merlin can be fitted with a variety of kit: while the HC3 is “conservative” in this regard, the Danish EH101 Merlin Mk 512 Joint Supporter (6 of whom have been notoriously taken over by the RAF as HC3A) were procured in number of 14, some equipped for SAR/CSAR duty and some for troop transport. The troop transport variant has armour in the crew seats and in other vulnerable areas (added to the HC3 too before their deployment in Afghanistan), two “Fast Rope” kits at the cargo door and two more fitted by the rear ramp, plus a static monorail line for the overture of parachutes, as the Danish Merlin has been procured also to transport and deploy up to 20 para in war missions. The CSAR variant has two 270 kg-capable electric winches, FLIR, three stretchers with complete medical care kit, one launcher for smoke-signals and other kit.      

Armament options for military utility variants include a chin turret for a 12.7mm machine gun and pintle-mounted machine guns of various type and caliber. The stub wings provide the hard points for mounting of rocket pods (was offered for example for the HH-71 Merlin variant, a bidder for the USAF new CSAR-X helicopter). 

The Merlin can be fitted with a fixed refueling probe, and during 2008, the Merlin HC3 was certified for air-refuelling, with a flight test campaign which started on 12 february. The HC3 was supplied by the RAF, but flew with an AgustaWestland-supplied crew. The air tanker used for the flight tests was an Italian C130J. During the tests, the Merlin made both “Dry” and “Wet” contacts, from both the right and left hose of the tanker, while carrying different payloads and at altitudes variable from 4000 to 5000 feet. Earlier on, on the RAF Lyneham airbase, ground compatibility tests had been done, after the arrival of the C130J from the “Reparto Sperimentale Volo” (Experimental Flight Unit) of the Italian Air Force (AMI). The C130J was one of 12 in the AMI kitted for taking on the role of air tanker: Italy has acquired 6 conversion kits, each inclusive of a tank to mount in the cargo bay and two underwing refueling pods. 

The HC3 during refuelling trials with the italian AMI C130J air tanker. The yellow rotor is the BERP IV prototype: some of the test flights were used to test at once the new rotor and the AAR compatibility.

The RAF currently does not operationally use the Merlin AAR capability, mainly for the absence of a tanker aircraft suitable for the role: a Tristar or VC10 can’t exactly refuel helicopters at 5000 feet, and there’s no kit in the RAF for the C130J, nor is acquisition of such kit planned for the A400M. One has to hope that an order will be made, instead, maybe in collaboration with the French, that seem to have a wish for a number of kits. The AAR capability was fundamental in order to pursue the US CSAR helicopter programme (in which the Merlin ran as HH-71) and for other export contracts. The Italian Air Force had set as firm requirement the AAR capability of its new CSAR helo, and the qualification of the Merlin for it was indispensable. The Merlin has effectively been ordered for the CSAR/Special Forces role in the last few years: the Italian CSAR Merlin will have AAR capability, armour, 20 troops seats and 3 Oto Melara pintle mounts with M134D miniguns. Germany has a similar requirement, but has mandated 3 M3M machine guns as armament instead, and its transport requirement is for a team of 7 soldiers, plus space and limited medical facilities for the rescue of 7 more.    

Oto Melara offers Pintle Mounts armed with Dillon M134D gatling guns. The whole mount weights 150 kg, with up to 150 more kg coming from the 4400 rounds box. The Italian army aviation (AVES) mounts two mounts on its NH90 TTH helicopters, one mount at each side door. The mounts are Merlin-compatible too. 

Oto Melara M134D minigun pintle mount. Two are used on the italian army NH90 helicopters, and three mounts of this family will arm the CSAR AW101 for the italian air force. The mount weights around 300 kg complete with 4400 rounds of ammo.

 

The HC3 was used operationally in the Balkans, in Iraq and now is working in Afghanistan.

Jebel Sahara, a massive training exercise in Marocco back in 2008, provided some interesting evidence about the HC3. It was the first opportunity for the Merlin force to deploy the aircraft's ISO container-housed support system, which comprises flight planning, rectification and welfare units for squadron personnel, including around 20 engineers. One of the two aircraft deployed by 28 Sqn also tested the type's enhanced health and usage diagnostic system.

Using one laptop computer per aircraft, this links maintenance information back to the UK to support supply chain planning activities. The Merlin has been the UK's first support helicopter to use the EHUDS technology.

Desert operations proved particularly harsh on the Merlin, which must have its Rolls-Royce/Turbomeca RTM 322 engines inspected by boroscope after every 30 landings. An engine change can be performed in the field within 2-3h, if necessary. Both deployed aircraft had 120 flight hours available before their next periods of scheduled work at the start of the exercise, and were each expected to log around four flight hours a day.

The Merlins fit into the C-17s with just inches to spare when the rotor blades and part of the gearbox have been removed. The whole exercise takes two to three days to perform, and was notoriously indispensable to deploy the Merlins to Camp Bastion. Earlier, they had self-deployed to Iraq from the UK with a 3500 miles flight.

Even with after the challenges of a desertic environment, RAF Merlin's deployment to Iraq has confirmed many of the outstanding capabilities of this new helicopter and has helped to expand its operational potential but none more so than its reputation for reliability and serviceability. Returning 96% serviceability and performing 70% more missions than originally mandated in its first 30 days in Iraq, this facet of Merlin operations was initially established during its thirteen month tour in Bosnia in 2003/4. This has been reinforced twice since on extended and remote Merlin HC Mk3 deployments to the USA. Firstly during a US Navy evaluation at NAS Patuxent River from November 2003 to March 2004 and secondly during a coast-to-coast tour in October 2004. Whilst at Patuxent River the two aircraft flew over 200 hours and achieved 99.1% availability and more recently the coast-to-coast tour covered 6000 miles in 10 days during which the single aircraft was serviceable at all times. Now 1419 Flight provides MND (SE) and JHF (I) with Merlin HC Mk3s available for tasking at thirty minutes and sixty minutes notice for operations by day and by night 24 hours per day 365 days a year. The primary roles for 1419 Flight are assault, fire support, troop moves, airborne command post, reconnaissance and surveillance, convoy protection and Casevac.

The Merlin also has a comprehensive radio suite and a powerful FLIR chin mounted, so that one of its roles in Iraq ended up being that of Airborne Command Post. In an operation in support of Iraqi Security Forces saw a Battle Group Commander and his Staff used one of the Merlins as an Airborne, Battle Group Command Post running an operation involving several hundred troops, over 40 vehicles, two assault Merlins and other surveillance aircraft. In this harsh operational environment the Merlin has also proved to be reliable. Squadron Engineers have benefited enormously from their previous experience over recent years in maintaining the aircraft's high availability rates. Modern technology, including a Health and Usage Monitoring System (HUMS) and built-in test equipment has facilitated ease of maintenance and resulted in much reduced maintenance hours per flying hours.

Before going in Stan, the Merlin faced the “Merlin Vortex” training exercise in California, where it prepared for the “Hot and High” conditions of Afghanistan: after all, Iraq is nearly all at sea level, so there the problem was only the heat. In Afghanistan, most places are located at 4000 feet of altitude, Bastion included.

The RAF assessment of the HC3's first year of ops in Afghanistan was more than positive.  

The HC3/3A fleet is planned to transfer to the Commando Helicopter Force in the coming years, to replace the Sea King HC4 from around 2016. The fleet has been reduced to 25 airframes after 3 Merlins were badly damaged during ops in Stan and training exercises (one had a crash landing during Merlin Vortex). The transfer will require a "navalization" refit that will certainly include folding rotors, but that may or may not be ambitious enough to aim for a folding tail as well: it will depend on budget. The Navalization is expected to become part of the work of the first Mid Life Upgrade of the HC3/3A fleet, for which a plan is expected to be part of the Planning Round 2011 of the MOD.

Merlin HC3 data:

Maximum Take-Off Weight 14,600kg

Never-Exceed Speed, The Dash Speed 167kt (309km/h)

Normal Cruise Speed 150kt (278km/h)

Range With Four Fuel Tanks 1,100km (610km)

Range With Five Fuel Tanks 1,300km (750km)

Maximum Range 927km

Endurance 4 hours 50 mins

Service Ceiling 4,575m

Payload:  24 soldiers in crashworthy seats and three 7.62 mm machine guns. Up to 27 without machine guns, 20 with side-door clear, up to 40 in high density arrangement with central row of seats. The AW101 has been test-flown with 55 standing “evacuated” civilians to demonstrate capacity in this role. 3000 to 4536 kg of under slung payload, up to 6000 kg internally (AW101).  

The HC3/3A Squadrons

28 Squadron was reformed in 2001 at RAF Benson to operate the first Merlin HC3 helicopters. On achieving Initial Operating Capability, the first operational deployment commenced immediately with the Squadron deploying two aircraft to Bosnia in support of SFOR in Banja Luka. Since then the Squadron has gone from strength to strength, supporting helicopter operations worldwide including Operation TELIC in Iraq until 2009 alongside 78 Squadron as the Merlin Force. Following the drawdown from Iraq operations, the Merlin Force swiftly trained aircrew and modified the aircraft to cope with higher altitudes, and the Squadron deployed to Afghanistan in support of Operation HERRICK in November 2009 as 1419 Flight.

In it's format, 28(AC) Sqn has been the largest in the whole of the RAF for quite some time - comprising no less than 22 aircraft (that figure includes a small number of airframes on permanent loan to Boscombe Down and Westland) and 340 aircrew and ground support staff - made up of eight flights. A and B are the operational flights, which also have the RAF experience in joint personnel recovery (JPR) and Combat Search and Rescue (CSAR) role. C Flight is the embedded Operational Conversion Flight (OCF) and E Flight is responsible for the RAF Regiment element. There is also a HQ flight.

At the start, the 28 Squadron also had an ample Engineering Flight that supported the Merlins and kept them flying, but with the passage to a two-squadrons world a dedicated unit has been formed: the Engineering Squadron has grown from being the Engineering Flight on 28 (AC) Squadron, with 145 personnel, into its own distinct entity with the acquisition of the 6 Danish Multi-Role Helicopters (DMRH) and the establishment of a further 90 technicians in 2007. http://merlinforce.com/mfes.php

When the RAF acquired six additional Merlins from Denmark (the MK3A), it was judged that expanding the squadron even more would not be a viable solution, and so the Merlin Force gained the second squadron, the 78, which on 3 Dec 2007 relocated to RAF Benson and was re-equipped with Merlin HC Mk3/3a helicopters as a dedicated Support Helicopter Squadron, ‘inheriting’ an existing operational flight from its sister Merlin Squadron. Currently the 78 is organized on 3 operational Flights, A, B and C. There is also a Training, Development and Standards Flight (TDSF) which is responsible for all environmental training, Combat Ready(CR) work-up and Merlin HC3A differences training. 

In total, some 400 men of the RAF are connected to the Merlin Force, in all roles. All are based on RAF Benson. RAF Benson is a front line support helicopter base working within the Joint Helicopter Command (JHC).  Located in South Oxfordshire, the Station is home to Puma helicopers of 33 and 230 Squadrons, Merlin HC3 and HC3a helicopters of 28 (AC) and 78 Squadrons, and the Tutor T1 Aircraft of Oxford University Air Squadron.  RAF Reserve unit, 606 (Chiltern) Squadron Royal Auxiliary Air Force are also located here in the form of the Helicopter Support Squadron.  There are also numerous other lodger units based at Benson including Thames Valley Police helicopters of the Chiltern Air Support Unit.

One of the most important facilities of RAF Benson is the Medium Support Helicopter Aircrew Training Facility (MSHATF), which contains 6 full mission simulators and 4 computer based training classrooms. These are used to provide conversion and continuation training for RAF support helicopter crews. The facility is owned and operated by CAE Aircrew Training Services plc and training is provided through a Private Finance Initiative (PFI) arrangement with the Ministry of Defence. In addition to being used in a stand-alone mode, the single Puma simulator, 2 x Merlin and 3 x Chinook Simulators can also all be linked to a Tactical Control Centre via a local area network to provide realistic operational training in a synthetic environment.  CAE ATS plc also offer time slots that are not being used by the Royal Air Force to other worldwide Air Forces for training purposes. This facility is proven, in service and effective, so even after the HC3 move to the Navy, the flight simulators are likely to remain here, probably upgraded to include the simulation of the peculiar Commando and naval helicopter operations. After all, it is easier and cheaper to upgrade software and simulators than move the whole thing to Yeonvilton.

Mobile Air Operation Teams (MAOTs) are also based here: the Teams co-ordinate and control helicopter movements into and out of the helicopter landing sites (HLS), and provide communications between the supported unit and the aircraft. When deployed the Team Leader (TL) acts as the trouble-shooter for all helicopter matters with an overarching responsibility for Flight Safety. As a secondary duty, TLs are also responsible for maintaining and updating the information contained in the various HLS directories in use by all military helicopters. 

There are 13 Teams, each one consisting of an RAF Officer, Master Aircrew or Senior Non-Commissioned Officer and 2 Signallers from 21 Signals Regiment (Air Support) based at Colerne in Wiltshire.

When deployed abroad, the Merlin detachment is known as 1419° Flight. Currently the flight is part of the Joint Helicopter Force Afghanistan, along with 1310° Flight with Chinooks, and Army and Navy helicopters.

Mainteinance of the Merlin

The Merlin, in particular the HC3, is still relatively young. The In-Service-Date, with 6 helicopters, was hit in June 2000, with deliveries completed in November 2002 and Initial Operating Capability in April 2003.

Depth maintenance of both fleets is currently carried out at the Merlin Depth Maintenance Facility at RNAS Culdrose.

Scheduled mainteinance happens after a minimum contracted value of 200 flying hours, and the amount of mainteinance is valued at 1,7 hours for each flying hour. Normally, the RTM332 engine is reliable enough that it well overcomes the 1000 flying hours before being dismounted for mainteinance. Merlin helicopters are expected to fly for 600 hours, or roughly two years of standard-schedule operations, before major mainteinance periods, which take place in a nine-phases "pulse" line for the type at RNAS Culdrose in Cornwall. The Merlin facility works with personnel coming from RN, RAF, AgustaWestland, Serco and Lockheed Martin.

The depth maintenance facility is indicatively capable of completing work on each aircraft in 63 days, down from a previous total of up to 110 days.

The 9 phases are:

Cell 1 - Strip, all major components including gearboxes, engines and fuel tanks are removed from the aircraft.

Cell 2 - Inspect, airframe and all removed components are fully cleaned and inspected in order to ascertain the serviceability of the aircraft, and to produce a work-package for the rectification phases.

Cell 3 - CRF, aircraft is moved to the Composite Repair Facility building for all structural composite fault rectification.

Cell 4 - Rects A, first rectifications phase to clear faults identified during Inspect phase and embody any Modifications (Mods) and Technical Instructions (TIs) .

Cell 5 - Rects B, second rectifications phase.

Cell 6 - Rects C, third rectifications phase.

Cell 7 - Rebuild, components removed during strip are rebuilt.

Cell 8 - Functionals, all disturbed systems are fully tested for serviceability.

Cell 9 - Flight Test, aircraft is ground run and flown through the full flight test schedule, before being delivered to the receiving squadron.

The unified Depth Mainteinance facility has only come online in 2006, after the contractual base was put into place in 2005, with the agreement signed on 12 december: previously, there had been two support arrangements, one for the Naval Merlins in Culdrose and another on RAF Benson for the HC3. There was duplication and inefficiency, that was tackled by bringing the management of the Merlin fleet together, in one single location and under the same main contractor. There was also a shift in payment mode, from a “pay when it breaks down” to a “pay when it flies” concept in which the payment is dependent on the effective number of flying hours that the mainteinance allows.

The Integrated Merlin Operational Support (IMOS) contract is a single 25 year contract, with 5 year price breakpoints, to provide through-life support for the MoD EH101 Merlin fleet to its planned out of service dates of 2029 (Royal Navy Mk1) 2030 (RAF Mk3). On March 6, 2006, the first Five Years contract was signed, for a total of GBP 450 millions. The second 5 year period has been contracted on January 17, 2011, for a total of 570 millions, and it will run to 2016.

The IMOS contract currently sustains over 1,000 jobs, many of which are located at AgustaWestland’s facility in Yeovil, and at RNAS Culdrose in Cornwall where the Merlin Depth Maintenance Facility and the Royal Navy’s Merlin Training System are located.

Contracting from Availability is now the standard way to go for the MOD: it is being done with Typhoon, with Tornado, with Sea King (SKIOS) and Hawks, Harrier (until it was in service), but even Sea Wolf missiles etcetera. The NAO gave the thumb up to this practice and recognized the savings it allows with a report in 2007. 

An useful comparison is to put side to side the Sea King support contracts and the Merlin IMOS. The last 5-year SKIOS contract, place in 2007, was valued at 470 million pounds. Of these, 70 millions go to Selex Galileo for the avionics mainteinance, and other money goes to other subcontractors for all other parts of the helicopter. A separated, 10-years contract was then signed with Rolls Royce to ensure availability of the engines for the whole Sea King fleet, for 258 million pounds.

The cost of an aircraft fleet

There are two tables - Full and Marginal costs. Full cost is the annual cost of everything to do with that airframe including all the support staff, buildings, etc divided by the total number of hours flown in a year. i.e. all direct and indirect costs.

The marginal cost is the cost of one more hour in the air ignoring all the indirect (fixed) costs, i.e. fuel and maintenance. Full cost per hour will vary with the number of hours flown, marginal will not.

For example, the following figures were indicated in the 2009-2010 period for a number of platforms:

Typhoon - Full £68716 Marginal £3780
Harrier GR9 - Full £35762 Marginal £3945
C-130 J - Full £11587 Marginal £1888
C-130K - Full £9924 Marginal £2132
C-17 - Full £42068 Marginal £4870

For the Merlin HM1, the Treasury came up with an admortised figure, which has become sadly quite famous, of £41,588 in answer to a question in Parliament.

However, according to the Defence Aircraft Capitation Rates the operating cost for just the machine is £3,162 per funded flying hour. A Sea King, for comparison, is reported at £3,183 per flying hour.
The same document, however, then adds on the ancillary costs to each aircraft, eg aircrew, Unit admin, admortization, Westland storage costs for spare parts for a minimum of six months after servicing requests, the cost of RAF Benson and the cost of the still recent restructuring of the Depth Mainteinance process and facility, the cast of thousands in the MoD and the 1000 men at Westland, and with amazing accuracy comes up with £41,588 for the Merlin HM1, around 34.000 for Merlin HC3 and £16,723 for the Sea King 4 and 7.

As with the C130J, which has a full cost for airframe of 11587 pounds against the C130K’s 9924, the C130J IS cheaper to fly per hour than the predecessor, but it is weighted down by all sorts of other voices of expense that come on top of the proper airframe running expense. Absurdly, the more Full Cost figure would appear lower if there were more flown hours to spread the costs upon. As with the Typhoon, (in service from 2005) the Merlin is, absurdly, still a “young” type. Deliveries of the HM1 were completed only in 2002, and the logistics of the fleet have for long time been, quite honestly, a mess. It is only in 2006 that the situation was rectified, and now it is expected that the costs will steadily decrease.  

The Merlin is not a cheap machine, but it is not the money-swallowing pit that it is often depicted as, either. It offers world-beating performances under many points of view, and continues to provide precious service all over the world. Could the Merlin fleet be ran in a cheaper way? Probably, and surely there must be an accurate look into the possible improvements. Once navalized and re-based on Yeonvilton, it is probable that the cost of the Merlin utility will drop significantly as the many voices of expense relative to Benson base are taken off its shoulders. Of course, depending on the cost and depth of the navalization process, the Full Cost voice will have to deal with the cost of the upgrade/refit in the admortization voice.  It has been suggested that the Royal Navy might have to content itself with Merlins that will have foldable rotors but not foldable tails. The problem would be considerable on HMS Ocean or HMS Illustrious, but will be less damaging in the immense hangar of the CVFs.
Overall, the Merlin is and remains the best sub-hunter helicopter out there, and it is the best Medium utility helicopter too, if we consider the Chinook a member of the Heavy league, which is the case, particularly in the RAF where there are not bigger and more powerful machines than it.