Sons of Damien                      





Sea King HAS1

Sea King HAS2

Sea King AEW2

Sea King HAR3

Sea King HAR3a

Sea King HC-4

Sea King HAS5

Sea King HU5

Sea King HAS6

Sea King HAS6CR

Sea King ASaC7


On this page I will deal with the individual marks of aircraft as they were introduced into service.

Sikorsky S-61

There was one aircraft delivered in this configuration and a further three which were delivered as HAS1. XV370 to XV373.

Westland built

HAS1 - XV642 to XV714 (56 built)

HAS2 - XZ570 to XZ582, XZ915 to XZ922 (21 built)

HAR3 - XZ585 to XZ599 and ZA105, ZE368 to ZE370 (19 built)

HAR3a - ZH540 to ZH545 (6 built)

HC4 - ZA290 to ZA314, ZB506, ZB507, ZD625 to ZD627, ZE425 to ZE428, ZF115 to ZF124, ZG820 to ZG822 and ZG829 (38 built)

HAS5 - ZA126 to ZA137, ZA166 to ZA170, ZD630 to ZD637 (25 built)

HAS6 - ZG816 to ZG819 and ZG875 (5 built)

Total built and delivered - 170.

All these serial numbers refer to the aircraft as they were built many of them were subsequently converted to different marks throughout their life.






This was the basic standard of Sea King which entered service in 1969 and from which the whole range of the Westland product has evolved. It is in fact a very good example of the way in which Westland have always contrived to improve their licence built products, the introduction of electronic engine governing, AFCS and radar offered a substantial improvement over the original SH-3 and subsequent modifications have taken the Sea King either further.

The HAS Mk1 is easily distinguished by its five bladed tail rotor and the absence of the ‘Barn Door’ Intake Guard, most were modified to Mk2 standard and many have remained in service.

First Flight 7th May 1969 (XV642)




The main features which distinguished this version were the introduction of the six bladed tail rotor and the Gnome 1400-1 engine capable of 1660 shp. A total of 21 new aircraft were ordered and the Mk1’s were updated.

The avionic fit was fundamentally the same although a number of additional Naval Service Modifications (NSM’s) have been incorporated across the Sea King Fleet to become standard. The most significant external addition being the ‘Barn Door’ in front of the intakes, with the familiar pattern of fluid de-icing strips.

First Flight 18th June 1976 (XZ570)



The neglect of Airborne Early Warning capability will probably be long remembered as one of the most costly tactical mistakes. The loss of HMS Sheffield forced the lesson home decisively.

The speed with which the ‘Searchwater’ radar was installed in the Sea King was a great example of what can be achieved when driven by necessity. In the course of two months two modified aircraft were embarked, with 824 squadron, in HMS Illustrious. By the time they arrived in the Falklands the conflict was over.

During the next 12 months, the installation was productionised and six aircraft were subsequently converted. The AEW task was once again placed with 849 squadron which has maintained the role for the Royal Navy since 1952.

The AEW Mk2 is easily distinguishable from other Sea Kings by the presence of its massive inflatable radome which has to be deployed in flight into its vertical, dome down position and retracted through 90º for take off and landing.

One feature which has resulted from radome retraction is that because of the increased all up weight, the crew is limited to three, on Pilot and two Observers. One of the Observers comes forward to occupy the Co-pilots sea for take-off and landing or for any operation close to the surface. This SOP has been included as an option for all Sea Kings.

First Conversion 23rd July 1982 (XV704)



It was some considerable time before the Royal Navy looked to the Sea King as a replacement for its ageing Wessex HU 5. The successful development of the Westland Commando with Egypt and Qatar meant that it could be considered as a developed helicopter, virtually available ‘Off the shelf’ the only additional work necessary would be the inclusion of the RN specific items.

This philosophy indeed paid off, the first RN Sea King Mk4 (ZA290) flew for the first time on 26th September 1979 and by the end of the year 846 squadron received its first aircraft.

The Sea King Mk4 was powered by the Gnome H1400-1. Unlike the basic Commando, it retained the main rotor blade fold. The revised avionic fit included the Decca Doppler 71 and TANS (Tactical Air Navigation System). It gives the ‘Junglies’ a whole new capability being able to carry 27 fully equipped troops and an 8000lb underslung load capability.

First Flight 26th September 1979 (ZA290)



This represented the next major update of the Sea King, dunking sonar, whilst being a very effective detection method it has its short comings and a skilful submarine commander can still gain the advantage. The response to the problem is the combined use of sonobuoys and sonar which allows better area coverage and more precise location.

The Sea King Mk5 included the improved radar, MEL Sea Searcher distinguishable by its large radome and LAPADS sonobuoys equipment, the avionic fit included Doppler71/TANS.

The first Sea King Mk5’s were delivered early in 1981 entering service with 706 and 820 squadrons 824 and 826 quickly followed and the aircraft were well established in time for the Falklands Conflict.

First Conversion 1st August 1980 (XZ916)



Up until the mid 1980’s search and rescue operations were carried out by 771 squadron operating Wessex HU-5 aircraft. The limited range of the Wessex meant that long range SAR was covered by Sea Kings of 706 squadron. With the Wessex being phased out of naval service a decision was taken to look at the conversion of four HAR-5 aircraft to undertake the search and rescue role. At that time rather then bothering the manufacturer (Westlands) with the problem of designing, proving and converting aircraft, which would have been at some considerable cost to the MoD. A system existed whereby modifications of limited applicability and cost could be introduced; these were Naval Service Modifications (NSM’s).

It was the QA department at RNAS Culdrose which were tasked to come up with the required modifications. I do not recall exactly how many NSM’s were required but the conversion consisted of the following: -

The radar was retained but the sonar and Sonics suites were removed along with their system antennae. The Orange Crop (ESM system) control indicator, pulse receiver and antennae were removed although the antennae plinths were retained. A bubble window was fitted at the observer’s window position. A full troop seat fit was adopted through the cabin. A role fit sea tray was fitted. A footstep was introduced at the aft of the cabin door opening with a chine angle protector running forward from the step and being secured at the stbd aft SACRU attachment point. A hoist spot light was attaché to the rescue hoist frame. Finally the aircraft was repainted in the colour scheme as can be seen in the picture above.

Operators of this aircraft have been predominantly 771 squadron which currently operates 7 aircraft, 819 squadron adopted the aircraft when their anti-submarine commitment disappeared. Briefly 820 squadron provided  flights for the carriers whilst the Merlin were being introduced. Currently 771 are the only operator of this aircraft type. During the nineties Westland Helicopters produced a cover Modification to support the type from which day the HAS5 was no more and the HU-5 was officially adopted.

Note: Boscombe Down operate two of this type one is a QinetiQ owned aircraft (XZ575), the other is on long term loan (XV651).

 Sea King HU-5 XZ575


Sea King HU-5 XV651 RFA Argus

 Recent upgrades to the aircraft have involved the removal of the AD120 VHF radio and the introduction of twin AD3400 V/UHF and Elmer SRT651 V/UHF radios, all encompassed in Mod1122. The introduction of an NVG cockpit and the Avionics Upgrade Package 2 (AUP2), which is being rolled out across the Sea King fleet. This involves the fitting of a Smart Zapper transmission detection system and Health and Usage Monitoring System (HUMS). With the Life Extension Programme (LEP) currently underway we may see this venerable aircraft remain in service for at least another ten years which may mean that some airframes will be fifty years old when they finally retire.



Externally the HAS Mk6 is very difficult to distinguish from the Mk5, in fact the only visual clue is the presence of the additional V/UHF antenna on the forward stbd side adjacent to the Doppler Bay.

Internally, the changes are dramatic the introduction of integrated sonar sources processing AQS902G results in a totally different appearance to the aircrewmans crew station and the aircrafts ASW capability is considerably enhanced by the uprated Plessey 2069 with deep water capability.

The later new build Sea Kings were completed as Mk6 but an update programme converted HAS Mk5’s some of which began life as Mk1’s. All the HAS6 aircraft are now in retirement many of them being stored at HMS Sultan in Gosport.

First Conversion 16th April 1987 (XZ581)



A shortage of commando type aircraft lead to a project instigated by the Sea King Integrated Project Team (SKIPT) to look at the many HAS 6 aircraft that were in storage to see if a solution could be found. The result was the HAS 6(CR). Initially a phase 1 aircraft (XZ580) was converted to assess the potential. This conversion involved a number of changes to the airframe to enhance its capability as a troop carrier. The obvious fundamental change was to remove the Sonics suite, sonar and radar from the aircraft and subsequently removal of all aerials relating to these systems. The blanking of the sonar well and the fitting of a full length metal freight floor. The spine radome was removed, the undercarriage was locked down and the undercarriage selector was removed from the cockpit. NVG modifications were carried out and the equipment which could not be removed from the rear cabin was placed in a dwarf console in the position of the old radar optical unit. One further addition was the introduction of a 32amp/hour battery in the nose battery compartment and a second battery on a mounting tray just inside the cabin aft of the cargo door. This was not electrically connected into the aircraft system but an external power lead was stowed with it. The success of this lead to four further conversions to a phase 2 standard, the differences being quite minor. The potential for a further 12 phase2/3 aircraft may be taken up at some time in the near future.

First Conversion 2004 (XZ580) - Phase 1

Second Conversion 2004 (XZ922) – Phase 2



A very significant upgrade to the AEW2 resulted in the ASaC7. This encompasses some fuselage modifications, the removal of the spine radome being the most significant. The Searchwater 2000 system fitted which involved a complete change to the hardware in the cabin although the Scanner and its pallet assembly remain relatively unchanged. Future capability may be enhanced with the introduction of a defensive aids suite similar to that fitted to the HC-4. The 13 Royal Navy airborne early warning AEW.2 helicopters were upgraded to AEW.7 standard with the Thales Defence Searchwater 2000 radar and Cerberus mission system. The helicopters' designation was changed to Airborne Surveillance and Area Control (ASaC Mk 7). The Searchwater 2000 radar processing system incorporates a new pulse Doppler mode and Link 16 JTIDS (Joint Tactical Information Distribution System) datalink. The upgrade programme also includes the installation of an additional HaveQuick II secure radio communications system together with an AN/APX-113(V) interrogator transponder from Hazeltine and a video recorder unit. The first two upgraded Sea Kings were delivered in May 2002 and the programme was completed in 2005. ASaC Mk 7 helicopters were deployed for the first time onboard HMS Ark Royal as part of Operation Iraqi Freedom in March 2003. Two helicopters were lost in a mid-air collision during the conflict and it is expected that two RN Sea King HAS Mk 6 ASW helicopters will be upgraded to ASaC Mk 7 configuration.



The Sea King HAR3 was introduced into service in 1978 as a direct replacement for the Wessex HC-2. The aircraft was built as a dedicated search and rescue aircraft. Fundamentally the aircraft is mechanically no different from any other Sea King in service. Although the cabin fit is tailored specifically towards SAR operations. To such an extent that there is a hot water boiler fitted in the forward cabin area. Along with first aid equipment, troop seats, stretchers and blankets etc. The aircraft now carries a defibrillator. The initial build was fifteen aircraft and these were supplemented by a further four aircraft to lift the HAR3 fleet to 19.

First Flight 6th September 1977 (XZ585)



In the early nineties the Ministry of Defence concluded that the RAF Search and Rescue fleet should be increased to 25 aircraft. This requirement was needed in order to satisfactorily meet the requirement for the aircraft. With the various flights dotted around the country as well as two aircraft based in the Falklands, two to three aircraft required for conversion training and the inevitable 2 to 3 aircraft undergoing majors. The MoD ordered six new build aircraft. It is worth noting that at this time Westlands had finished with Sea King and my understanding was that the jigs and the personnel that knew how to use them had all but been consigned to the scrap heap. So the jigs were dusted off and reinstated and some personnel were brought out of retirement to construct the new aircraft. Although fundamentally the same as the HAR3, the opportunity was taken to upgrade the aircrafts avionics, hence 3A. The biggest change was the introduction of the SN500 autopilot which replaced the Mk31 AFCS as fitted to all other Sea King aircraft. This was a ploy, I think, by Smiths to make obsolete the Mk31 system so that the retrofit of all UK Sea Kings could occur with the new SN500 system. Unfortunately the promise of a better system did not materialise and the Mk3A is still the only aircraft with the SN500. As a footnote the Westland Hack, XZ570 was the test aircraft for the system and it still remains fitted to this day with the aircraft currently stored at HMS Sultan.

As can be seen from the picture above the aircraft has a turret assembly fitted underneath the port sponson stub wing. This is part of the Multi Sensor Suite (MSS). The support assembly for which has utilised the forward weapon station attachment points. It is worth noting that all Sea Kings share a common fuselage in so much as they all have sonar well blanking plates and provision for the fitment for weapon station brackets, whether or not these were ever going to be used.

The MSS upgrade was rolled out across the HAR3 fleet as well this required a significant upgrade to the radar and its display. Externally there is no difference but in the ‘Rad Shack’ the changes are quite obvious. Just recently the decision was taken to replace the ARC115 and 116 radios in the aircraft as the system was virtually obsolete and unsupportable. QinetiQ were tasked to come up with a replacement system, a Rhode and Schwarz Multi Mode Radio was selected and this is currently undergoing trials at Boscombe Down.

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