Westland Sea King AEW2 and ASaC.7

Westland Sea King HAS Mk6

The Sea King HC Mk 1 and later marks are all versions of the Sikorsky SH-3D Sea King helicopter built under licence by Westlands in Yeovil, Somerset. The Westland version differed from the US versions by using UK engines and avionics and served with great distinction for many years as the Royal Navy’s primary Anti-Submarine Warfare (ASW) helicopter, operating from their three small Invincible class carriers, Illustrious, Ark Royal and Invincible.

Fairey Ganney AEW Mk 3

However, the Falklands War in 1982 exposed all too clearly a glaring gap in the Royal Navy’s capability, where a complete absence of an effective Airborne Early Warning (AEW) capability cost the Navy dearly, leading directly to the loss of a number of ships and the death of many servicemen and civilians. The lack of AEW was a direct result of a government decision to scrap the RN’s last fixed-wing carrier, HMS Ark Royal, in 1978 without replacing the AEW capability provided by the then antiquated fixed-wing Fairey Gannet AEW Mk3 carrying a fairly basic AN/APS20F radar, a development of the AN/APS20A radar that came into service with the first US Navy AEW Avenger aircraft in May 1945 and the Bellhop data-link. The expectation was that, when the Gannet AEW Mk 3 aircraft retired, an AEW capability would be provided for the RN by land based RAF Shackleton AEW Mk2 aircraft, again equipped with the antiquated AN/APS20F radar recovered from the Gannet AEW aircraft, and then eventually its planned replacement, the Nimrod AEW Mk3. The Nimrod AEW Mk 3 fiasco is covered in detail elsewhere and it is suffice to say that thankfully the programme was eventually scrapped before the aircraft entered service, but not before the expenditure of probably about one billion pounds. Nevertheless, even if this aircraft had been available, given the immense distances involved, it is highly unlikely it, or any other land-based AEW aircraft could have contributed very much to the Falklands War, unless it had joined the other Nimrod aircraft the RAF operated covertly out of Chile.

The RNs urgent need for effective an AEW system that could operate from the Invincible class carriers, which lack and angled deck, steam catapults or arrestor wires, meant that only a helicopter could be considered for the task and the Sea King was the only choice available. In May 1982, even whilst the Falklands conflict was still underway, Westlands began converting two standard Sea King HAS Mk 2s, XV 650 and XV 704, to undertake the AEW role. A large inflatable radome containing the Thorn-EMI ARI 5930/3 Searchwater radar was mounted on the starboard side of the helicopter. The Searchwater AEW radar was an adaptation of the Searchwater radar carried by the RAF’s Nimrod maritime patrol aircraft. The radome was mounted on a swivel arm which could be rotated through 90°, enabling it to be clear of the ground for take-off and landing.

Westland Sea King AEW Mk2

After a crash development programme, assisted considerably by a handful of former observers from the AEW Gannets, the two development helicopters were converted and flying by the end of July 1982 and were given the designation Sea King HAS Mk 2 (AEW). These two helicopters formed D Flt of 824 NAS on HMS Illustrious when it sailed with its battle group to the South Atlantic in Aug 1982, replacing the two carriers HMS Hermes and Invincible that had conducted the Falklands War. Although these two helicopters were rushed into service and were not up to full production standard, they proved the concept and a contract was placed with Westlands to convert a further six Sea King HAS Mk 2 helicopters into AEW Mk 2s as well as bringing the two development helicopters up to full production standard.

Westland Sea King AEW Mk2

On 1 Nov 1984 at RNAS Culdrose in Cornwall, 849 NAS was reformed to operate the two development AEW helicopters. As more helicopters were converted they joined 849 NAS and in August 1985 the first three production Sea King AEW Mk 2s embarked on HMS Illustrious. With a maximum of two of the Invincible class carriers planned to be at sea at any one time, 849 NAS consisted of A and B operational flights with three helicopters, five pilots and ten observers each, together with a small headquarters flight which remained at Culdrose. Unlike the ASW Sea Kings which operate with two pilots and two observers, the AEW version operates with a single pilot and two observers. Because of the inflatable bag containing the Searchwater radar, the AEW helicopters were soon referred to as ‘bags’ and the crews soon acquired the nickname ‘baggers’ or ‘bagmen’.

Westland Sea King AEW Mk2

As well as the pre-production aircraft, a further seven Sea King HAS 1/2s were eventually converted into Sea King AEW 2A helicopters, XV649, XV656, XV664, XV671, XV672, XV697, XV707 and XV714. Later all these nine helicopters were upgraded to AEW 5 standard and given the designation AEW 2A. As the EHI Merlin ASW helicopter began to enter service, a further four Sea King HAS 5s, ZD636, ZE418, ZE420 and XV664 were converted into AEW helicopters – these four helicopters were given the AEW 2 designation and serve alongside the other AEW helicopters in 849 NAS.

Westland Sea King ASaC.7

However, the effectiveness of the Thorn-EMI ARI 5930/3 Searchwater radar was limited by clutter, caused by land and wave crests that got worse closer to the receiver. Climbing higher increased the range of the radar horizon, but also increased the clutter – descending lower reduced the clutter but also reduced the radar horizon, so a compromise height was usually selected for the task. In normal AEW operations, the helicopter flew as high as it needed to until it acquired the target, then slowly descended to keep the target out of clutter. As the Sea King AEW helicopters were not pressurised or carried oxygen, they could not operate above 10,000 and generally operated much lower. As in the Gannet and Shackleton, aircraft returns were tracked by drawing marks with a chinagraph pencil on the radar screen, hardly a sophisticated system, but one that worked, and with well trained observers acting as airborne fighter controllers, proved effective at providing Sea Harriers with sufficient information to intercept low-flying aircraft.

Westland Sea King ASaC.7

However, the limitations of the Thorn-EMI ARI 5930/3 Searchwater radar and the need for better data links and communications were obvious and in the early 1990’s Project Cerberus were formed to identify the capabilities needed in a replacement system. On 14 Feb 97 Thales was awarded a £90 million contract to build the replacement AEW system and then modify the helicopters as necessary – this contract was subsequently increased to £140 million. The new Cerberus system consists of the Searchwater 2000AEW X band radar, a modified version of the radar that will equip the new Nimrod MRA4. This pulse Doppler radar is much lighter than the old Thorn-EMI ARI 5930/3 Searchwater radar, but has 300% more transmitting power, as well as an integrated Mk XII IFF interrogator. This sophisticated radar has much better clutter suppression and can provide overland tracking, as well as air and surface tracking. The new radar scanner can change its tilt angle between each rotation, producing an elevated pulse envelope beam to locate high altitude contacts on its first rotation, followed by a pulse Doppler beam on its second rotation to track contacts within the radar horizon. A further scan in either littoral or open-sea mode can then track surface contacts. This flexibility gives the new system a capability that is a quantum leap ahead of the fairly primitive radar system on the AEW 2A.

Westland Sea King ASaC.7 cabin

The two black and white radar displays in the old system were replaced by two colour high-resolution flat panel displays, which allow the observers to set up their screens to suit themselves or the task they are undertaking. Two smaller touch panels in front of each operator act as totes or can be used to control the various sub-systems or radar mode settings. The advanced processing systems available allow up to 250 air and surface contacts to be automatically tracked, in addition, the system can also accept up to 300 further tracks over its Link 16 or JTIDS data-links. Communications improvements include two ARC 164 secure UHF HQ11 radios, an AD3400 secure V/UHF radio and a Collins 618T HF radio.

Westland Sea King ASaC.7

A completely new system interface, utilising the touch-screen panels, a standard keyboard and a ‘Windows’ based programme, was designed to be user-friendly and allows any function to be accessed in no more than three key strokes. One key labelled ‘WTFGO’ is known officially as the ‘Weapon Target Fighter Global Overview and when pressed shows data link control lines from C² units and their fighters, together with intercept vector lines to their respective targets. Unofficially this key is known as the ‘What the F***s Going On’ button, which is probably a much more accurate description of the facilities it provides. Probably the only real weakness of the new helicopters equipment is in the area of electronic surveillance, where it retains the aged ‘Orange Crop’ system of the older helicopter; given the other excellent capabilities of the Cerberus system, this weakness will probably soon be addressed and ‘Orange Crop’ replaced with a modern and much more sophisticated ESM package, further enhancing the Cerberus system.

Westland Sea King ASaC.7

To reflect the vastly greater capabilities of the new helicopter, the designation was changed from AEW 2A to Air Surveillance and Control (ASaC.7). A rolling programme commenced at Westlands to convert the old AEW 2A helicopters into the ASaC.7 and in March 2002 the first new helicopter was delivered by to 849 Sqn. All 13 AEW 2 and AEW 2A helicopters were converted into ASaC.7 helicopters by 2004 and were soon operational on the Invincible class carriers. The new helicopters saw action in Gulf War II, where their overland capabilities enabled them to operate as a mini ‘J-STARS’, giving commanders on the ground the ability to monitor activity at the front by viewing the Link 16 picture. The Sea King ASaC.7 helicopters are likely to remain in service until 2015 and possibly beyond, given the UK’s abysmal record in defence procurement. Eventually the Sea King ASaC.7 helicopters will be replaced by a new platform identified under the Maritime Airborne Surveillance and Control Project. Although the purchase of the E-2C Hawkeye 2000 as a replacement would probably be the preferred option, the chances are that the UK government will be unwilling to agree to the two new carriers planned for the RN to be equipped to operate fixed wing AEW aircraft. This leaves either an AEW version of the Bell-Boeing V-22 Osprey or an AEW version of the EHI Merlin – given the history of UK defence procurement; my money would be on the AEW Merlin, nevertheless only time will tell, but jobs in marginal constituencies and politics will always outweigh the preferred military choice.

There is also a tragic postscript to the Sea King ASaC.7 helicopter story. On 22 Mar 03, whilst operating from HMS Ark Royal in the northern Persian Gulf, two Sea King ASaC.7 helicopters of 849 A Flt collided, killing all seven crewmen on board. The incident occurred in darkness as one helicopter returning from a surveillance mission collided with its replacement on the same flight path. According to the official Board of Inquiry, the collision was compounded by the lack of Night Vision Goggles on either helicopter, reported problems with the Sea Kings exterior warning lights (which may have been turned off) and inadequate radar vigilance by controllers on HMS Ark Royal. In a strange twist of fate, the helicopters that collided were XV 650 and XV 704, the two original airframes that were hastily converted into Sea King HAS Mk 2 (AEW)s back in May 1982.