Eyes and Ears

As Ian Harding explains, Crowsnest is set to give the Royal Navy’s Merlins a major leap forward in airborne surveillance capabilities

Initial assessment phase testing ensured there were no gross effects on the Merlin flight profile with the radome attached.
Leonardo Helicopters


Work has commenced to evolve the Royal Navy’s Merlin HM2 submarine hunter by giving it an aircraft tracker capability. With the UK’s first new aircraft carrier, HMS Queen Elizabeth, scheduled to begin sea trails during Q2 2017, the Ministry of Defence (MoD) announced on January 16, 2017, that £269 million had been set aside to fund the Crowsnest programme.

This programme will provide the Royal Navy with a future maritime intelligence, surveillance, targeting acquisition and reconnaissance (ISTAR) capability. Crowsnest is an integral part of the Carrier Enabled Power Projection capability, which will deliver two Queen Elizabeth-class aircraft carriers and the Lockheed Martin F-35B Lightning II to operate from their decks, along with other maritime and battlefield rotary assets. Whilst most media attention is focused on the future aircraft carriers and fifth-generation fighters, Crowsnest’s importance has gone under the radar.

Akin to the Leonardo Helicopters AW101 Merlin HM2 upgrade programme, the primary contractor is Lockheed Martin UK, which has subcontracted Thales UK to complete the mission system and sensors design and Leonardo to undertake system installation and flight testing from its Yeovil facility in Somerset. The contract will see all 30 Merlin HM2s in service modified and fit to receive the Crowsnest role kit of which ten will be delivered.

The Advantage of Crowsnest

The primary role of any airborne surveillance and control (ASAC) platform is to look out as far as it can over the horizon using its radar and detect the smallest contact possible, thereby providing the greatest threat warning to the asset it is defending. To achieve this, the platform’s radar must incorporate a sufficiently large and sensitive and reliable antenna aperture to receive the tiny radar pulses returned and use the information emitted, and then integrate this with other onboard sensors, including electronic support measures (ESM) and automatic identification systems (AIS).

1 All 30 Merlin HM2s in service modified and fit to receive the Crowsnest role kit, of which ten will be delivered.

Whilst obvious airborne threats exist, recent exercises undertaken, including Exercise Unmanned Warrior held in the UK in October 2016, have increasingly focused defence company and military minds on the serious threat posed by other fast-moving and more stealthy maritime and land-based threats: for example, a jet-ski or motorbike packed with explosives.

The main advantage of an airborne capability like Crowsnest over a groundbased system is that it’s easier to detect contacts at extended range operating close to the horizon. The system then provides targeting information that can be used to counter threats. Following discussions with the main programme participants, AIR International understands the enhanced capabilities of Crowsnest are such it will become a joint asset available to a wider range of potential users. In service, this system will therefore not only act as the eyes and ears for maritime task groups, including the UK’s two future aircraft carriers, but also other fleet and deployed elements, providing them with long-range air, maritime and land detection. In all respects, Crowsnest represents a major leap forward from what has previously been known as airborne early warning (AEW), moving it to another plane by encompassing both airborne surveillance and battlespace management.

For the past 15 years, this responsibility has fallen on the Royal Navy’s unique fleet of Sea King Airborne Surveillance and Control Mk7 helicopters (SKASaC) based at Royal Naval Air Station Culdrose in Cornwall. Entering service in May 2002 following upgrade to Mk7 standard, the final seven SKASaC aircraft serving with 849 Naval Air Squadron from the Cornish base are scheduled to be withdrawn from service during Q3 2018 to be replaced by Crowsnest.

SKASaC has been proven a huge operational success in many global confiicts. All programme participants are wholly committed to providing the Royal Navy and MoD with a vastly superior version of that system and one they can use in a similar fashion to that currently in use. By mid-2020, the Royal Navy’s current fleet of 30 Merlin HM2s based at Culdrose will have two primary roles: anti-submarine warfare (ASW) and ASAC, incorporating AEW, ISTAR and command and control.


The MoD’s tendering process for the Crowsnest project and initial assessment phases began in early 2013, with the competitive process for the mission system itself under Lockheed Martin UK’s direction commencing later that year. During the final assessment phase, this process evaluated two radar solutions. Leonardo Helicopters conducted flight trials with the Thales Searchwater radar fitted to a converted Royal Navy Merlin HM1 at its Yeovil facility, whilst QinetiQ test flew another Merlin HM1 at Boscombe Down in Wiltshire with an Elta Vigilance radar system attached, which Lockheed Martin UK were promoting. Following the MoD decision in favour of the Thales system in May 2015, initial flight testing took place at Leonardo Helicopters’ Yeovil facility in December 2014 using a converted Merlin HM1 with a radome attached.

2 Crowsnest will support the UK’s new Queen Elizabethclass aircraft carriers and the Lockheed Martin F-35B Lightning IIs by providing longrange air, maritime and land detection.
Fleet Media/Royal Navy


The current Cerberus mission system, specifically designed for AEW and control over land and sea, incorporates a highpower pulse doppler radar integrated with AIS. These include identification friend or foe and ESM which aid threat detection and targeting, inertial navigation system/GPS navigation system, Link 16 Joint Tactical Information Distribution System data link, HaveQuick II secure radio communications system, video recorder unit and an AN/APX- 113(V) interrogator transponder. The system has multimission capability provided by its various radar modes, which include air-to-air, ground moving target indicator and maritime surveillance (ASW/anti-surface warfare/ littoral). Ground and maritime environments appear distinct but not to the radar.

3 The target is to achieve a nominal in-service date for Crowsnest by Q3 2019 with initial operating capability by Q2 2020 and full operating capability in 2022.
All photos Ian Harding unless stated

From an industry perspective, 2017 will be the year for system design with implementation and flight testing during 2018. Lockheed Martin UK confirmed they are operating a split design phase approach in order to allow the phased capability to be delivered to the Royal Navy earlier than a single-phase approach. System design reviews are scheduled to take place through to early autumn 2017 with initial flight trials commencing mid-2018. Leonardo Helicopters estimate the flight test phase will last approximately eight months before flight test results are handed over to the independent reviewers QinetiQ (based at Boscombe Down) and the Military Aviation Authority to assess before issuing their release to service.

The target is a nominal in-service date (ISD) by Q3 2019 with initial operating capability (IOC) by Q2 2020. Full operating capability (FOC) will follow approximately two years later, in 2022. Preparedness for future carrier operations has been underway for some years at Culdrose with the reinvigoration of the Carrier Air Wing. Some 849 Naval Air Squadron aircrew have started their transitional Merlin HM2 training with 824 Naval Air Squadron. This process will continue commensurate with the Sea King’s out-of-service date; 849 Naval Air Squadron expects to begin formal Crowsnest training (aircrew and engineering) from the ISD, with the capability growing out of 824 Naval Air Squadron in time for the IOC.

Thales UK System Design

It is important to note that the ASaC or AEW concept has been created organically from within the existing Merlin fleet for sound reasons. The Merlin HM2 will retain its primary ASW role along with its long list of secondary roles. Common observer training will take place across as many secondary roles as the Crowsnest role-fit allows, thereby offering flexibility to the Task Group across all Merlin HM2s.

The Thales solution, which draws on over 30 years’ experience as the mission system supplier to both the Sea King AEW2 and SKASaC, is an updated and repackaged role-fit version of the Cerberus tactical sensor suite in service with the SKASaC. Whilst the system is currently referred to as a Cerberus/Searchwater 2000 AEW system, this is only because Thales is focused on system design, rather than naming the system. This may well change.


The Merlin HM2 continues to receive upgrades to enhance its capabilities in addition to Crowsnest. These include a new traffic avoidance system and updates to the defensive aids suite. Leonardo Helicopters confirmed these programmes remain ongoing and will eventually merge, culminating in the Crowsnest upgrade and a mode 5 identification friend or foe (IFF) upgrade. The Merlin HM2 fleet has Link 11 tactical data link whilst Crowsnest will be Link 16. AEW is broadly considered an extension of the Merlin HM2’s existing capability.


The Merlin HM2 continues to receive upgrades to enhance its capabilities in addition to Crowsnest. These include a new traffic avoidance system and updates to the defensive aids suite.

1 Crowsnest will replace the seven Sea King Airborne Surveillance and Control Mk7 helicopters serving with 849 Naval Air Squadron, which are scheduled to be withdrawn from service during Q3 2018.

The Crowsnest design comprises a single Searchwater mechanically scanned radar head mounted to the fuselage on the port-side weapon station. The radar head deployment mechanism uses an innovative electromechanical system to deploy the scanner, giving 360o visibility from the underside of the air vehicle, and folds up to the side of the aircraft for take-off and landing. The onboard tactical systems retain a similar configuration to the existing Sea King equipment, but with enhanced touchscreen multifunction screens, additional radar modes, sensor functionality and upgraded hardware and software systems to complement the Merlin HM2 host platform.

Thales confirmed its approach is underpinned by the re-engineering, repackaging and upgrading of the existing mission system to improve performance, reduce risk, maximise reuse and support an early introduction to service. From the outset, Thales has been focused on building and designing the most capable system available. Utilising its extensive global research and development experience, its findings confirmed the most capable radar available was that already in service with the SKASaC fleet. The system had hidden potential; it just had to be taken to the next level. Thales confirmed its challenge was effectively to do three things:

Update and modernise the radar to drive out obsolescence;

Upgrade the system, introducing new modes, improving performance, processing capability and speed, etc.;

Adapt the system and mount it on the Merlin HM2, ensuring it was an integral part of the platform, within threshold times which were achieved.

Upgrading processing capability was imperative. Knowing the SKASaC system already produces a lot of information, the key was being able to access and use all the information contained within each pulse in a timely and effective manner. Thales confirmed this has enabled its engineers to access far more information than was previously being returned to the SKASaC platform and to look more deeply at the information contained within each pulse.

At the operational level, this translates into future observers gathering more information from each pulse than previously and being able to see and track more targets than before, extending range. Having upgraded processing capability, it was imperative observers could find their way around the system quickly and efficiently to manage and interpret the information produced. Thales confirmed its new system human machine interface (HMI) has been enhanced to such a degree that current observers should be able to transfer to Crowsnest in a very short time.

Whilst the system cannot be viewed at present, AIR International was informed the future design incorporates tabletstyle touchscreen technology with similar touchscreen panels in use aboard the Merlin HM2. For example, if an operative wants to zoom in on a contact, the screen can be pinched and zoomed in as on a tablet. If they want to move the screen, they will in future grab it and move it in the same fashion. Comparing this with the present SKASaC system, if the observer wants to hook on to a contact, for example, previously a tracker ball and hard keys would be used; it is now a simple matter of reaching up, touching it and holding for a few seconds to receive a pop-up menu with options of what to do with the contact.

The HMI aim of Crowsnest is that the working environment will be relatively more relaxed, with observers’ eyes focused on their screens increasing their ability to prioritise and make timely decisions, whilst interacting with their system and other sensors. The key to observers’ operational effectiveness is maintaining their situational awareness whilst trying to avoid them being overloaded with information. The systems upgraded HMI will help them as will the logic and artificial intelligence built in to ensure information not displayed on the screen is retained. This information could be previous track warnings or a notification to the observer to look more closely at information derived. The reality is that if an ASaC observer has to look away from the screen for too long something might be missed, which could be crucial.

Inside the upgraded Merlin HM2, observers will sit side by side as they do inside SKASaC, although they will be positioned facing backwards to the forward flight crew. Their workstation comprises enhanced mission consoles with large tactical screens, multifunction displays and touchscreen units. To enhance observers’ situational awareness further, Thales confirmed it has redesigned the workspace screen, making it larger than both the Merlin HM2 (optimised for ASW) and SKASaC (approximately 35% larger) screens. The number of touchscreen panels has increased. Thales also confirmed that observers will be able to share seamlessly the information gathered. Our discussions with all parties confirmed it will not be possible for a Merlin HM2 and its aircrew to undertake both ASW and AEW simultaneously.

Less obvious benefits of this new system include that the MoD and Royal Navy could potentially reuse elements of the equipment and the existing training, logistics and supply chain, which is also already understood by service personnel. These benefits should not be overlooked, especially given the extensive testing and development phase necessary prior to operational service entry.

Implementation and Flight Testing

Leonardo Helicopters’ role has two main phases. Phase one involves designing and building the system’s fixed fittings outside and inside the aircraft. This comprises predominantly cabling or permanent wiring looms, waveguide runs, supportive bracketing, break out panels for connectors, the deployment mechanism which hinges the external radar up and down on the Merlin’s port side, and a new mission console for the mission system.

Phase two is flight testing. Initial flight testing from Yeovil in late 2014 consisted of approximately ten flight hours. This initial assessment phase testing was primarily to ensure there were no gross effects on the Merlin HM2’s flight profile with the radome attached – which it did. Leonardo Helicopters confirmed that once the systems design is finalised it will complete more detailed load survey and handling quality assessment studies to codify the effect of carrying the system and radome from an airworthiness point of view.

The three-engine Merlin is a very powerful helicopter and provisional analysis confirms the platform meets all the mission requirements placed on it with the radome positioned. Hot and high operational capability will be unaffected by this modification. Positioned from the weapons carriage station, Leonardo Helicopters confirmed it foresees no load or stress issues from these hard points. It says the radar is a similar weight to the two torpedoes the aircraft is cleared to carry each side.

Inside the helicopter, the sonobuoy carousel, dipping sonor and ASW mission console will be replaced with the new mission console and a rack of other line replaceable units. Any weight differential will likely be marginal, with little effect on lift capabilities. The AEW mission console will be similar in appearance to the existing ASW console it replaces with the addition of a panel to lower/raise the radome.

Leonardo Helicopters confirmed the new deployment mechanism system will use electric actuators to raise and lower the radomes (unlike the SKASaC, which uses a hydraulic system), for reliability and ease of back-up from a replacement and safety perspective. From an operational perspective, Leonardo Helicopters considered its engineering upgrade tasking to be relatively simple. The aim of the role-fit is the same with blank panels fitted when the system is not in use. When required, the goal for all parties is that Royal Navy personnel can literally wheel the system up to the aircraft, remove the blank panels and ASW system, replace it with the AEW console, attach the radome, and it is ready to use within 24 hours. The intention is this role-fit could theoretically be carried out aboard the aircraft carrier if operational circumstances necessitated.

The factory time to complete the implementation upgrade work has not yet been finalised, but it is clear the upgrade is nothing like as complicated as the initial Merlin HM2 upgrade (approximately nine months) or the Merlin HC4 upgrade Leonardo Helicopters is currently undertaking for the Royal Navy and the Commando Helicopter Force, under the Merlin Life Sustainment Programme. Current estimates are 12–15 weeks per aircraft. The rate at which aircraft will be upgraded will ultimately depend on the rate at which the front line can release them.

The Royal Navy and MoD are a great kitemark for any product and all the commercial participants are 100% committed to providing both with an outstanding and world-class solution to this critical defence programme. The system is currently referred to as a combination of Cerberus and Searchwater, but the reality of the adaptations made and those proposed mean it is far more than that. The advantages of Crowsnest compared with the SKASaC system include the ability to manage a significantly greater number of simultaneous tracks, additional radar modes, greater integration with other sensors, improved HMI along with enhanced combat identification functionality and integrated ESM.

2 The solution being developed for Crowsnest is an updated and repackaged role-fit version of the Cerberus tactical sensor suite in service with the SKASaC.


If the SKASaC Q3 2018 out of service date (OSD) is met, the Westland Sea King will retire from UK service just a few months shy of the platform’s 50th anniversary (first flight May 7, 1969). Any decision to extend the OSD for any reason (a perceived capability gap, for example) rests with Naval Command. At this stage, sources confirmed the specified Crowsnest delivery timeline meets both ISD and IOC requirements. The financial cost of extending the Sea King’s service life plus the availability of spares will be important considerations should this be required.