Monday 5 March 2012

Equipment at 91 Signals Unit – RAF Saxa Vord - Early days

Any radar unit with an operational life of nearly 50 years will see its original radar and communications equipment extensively modified and updated. Indeed, by closure it is hard to think of any equipment still in use at Saxa which had been there since 1957. In the pages which follow I hope to detail what equipment was planned for Saxa and produce evidence for what was actually constructed - when the Unit was declared fully operational in Oct ’57 and, when appropriate, show where it was located. I will also add a few comments on its operational life.
Plans for 91 SU go back to the beginning of the 50’s and, in the light of changing operational requirements and the introduction of new equipment; those plans were frequently updated and altered. With the onset of the Cold War and Soviet nuclear testing from 1949 onwards, major UK wide plans were approved to modernise national defence systems. In the air defence world the biggest programme was called ROTOR. Many radar sites were planned and built under this programme which, due to its size and the availability of resources, had to be implemented in stages. A good article on the ROTOR Plan can be found here:
One of the significant factors of the ROTOR Plan was the decision to use, wherever possible, standardised buildings and equipment. This simplified manufacture and expedited construction. One of the late Stages of ROTOR called for 3 Centimetric Early Warning (CEW) sites, at Aird Uig (on the west side of Lewis in the Outer Hebrides), at Faraid Head (just east of Cape Wrath) and at Saxa Vord on Unst.(Left click on pictures to enlarge).
Within the ROTOR plans each unit was assigned a three letter code:
Aird Uig - WIU
Faraid Head - RAI
Saxa Vord - AXA
I freely admit that when I first saw the Saxa code AXA I thought that it had something to do with the Admiralty Experimental Station – we live & learn!

However, these 3 units were all planned at the same time, all with R10 Ops Buildings and all to be supplied with similar radar. With all things which take time to reach fruition, various elements such as weather, production modifications/delays and changes to operational requirements led to the plans being altered. Whilst it is tempting for me to try and go into the details at each of the 3 sites I am trying to confine this blog to Saxa (& a little bit of Shetland). Besides, there are many people better qualified than I to cover the rest of the Rotor scheme in depth.

The 3 CEW sites were originally scheduled to be opened in 1955/56 but this proved to be over ambitious. The main search radar for the 3 sites was to be the Decca Type 80 (code named “Green Garlic”). This radar was a great leap forward in UK air defence radars and was therefore ordered in large numbers – not only for the UK ROTOR system but for 2ATAF in Germany. The first Type 80 was installed in 1955 at Trimingham. As experience in operating the radar accumulated a number of modifications and upgrades were incorporated and this caused some hold ups in production. Another reason for the CEW operational dates slipping was the fact that the early Type 80’s were not capable of withstanding the high wind speeds experienced in Northern Scotland. The main height finder was to be the Type 13.

The Air Ministry, unlike today’s MOD, believed in a “belt & braces” approach. The ROTOR programme was deemed to be of sufficient importance that in 1952 orders for 2 types of American radar were placed:
12 AN/FPS3 search radars were acquired, in case there was a slippage in the Type 80 programme
12 AN/FPS6 height finders were purchased to augment the Type 13’s.
Early plans for the site on Saxa Vord made provision for the possible siting of an AN/FPS3 and an AN/FPS6, though neither was ever installed.

Very high winds early in 1956 damaged the T80 aerial at Faraid Head revealing basic weakness in the design of the aerial framework and therefore significant strengthening of the centre section of the main frame had to be carried out on the aerials for all 3 CEW sites. Then, I believe towards the end of 1956, gales severely damaged the aerial on the Type 80 at Saxa. Once again the centre section of the main frame had been unable to withstand the wind and the under frame was also damaged.

Late in 1956 the Air Staff decided that the site at Faraid Head would no longer be required and the site was put on care and maintenance, the site permanently closing early in 1958 with all personnel being posted out. The document shown below, also kindly provided by Bob Jenner, shows how the 3 units were being developed to the same plans. Some minor variations are included, in Saxas case mainly involving the Admiralty Buildings. The original plan was dated 1953 but this version must have been considerably later as Amendment List 10 has been incorporated.
Work continued on Aird Uig and on 91 SU but I will leave Aird Uig to someone else to follow up and from here on concentrate on what happened at the top of Saxa Vord.
In seeing what was actually constructed on the Tech Site at 91SU/Saxa we are fortunate that list of Building Numbers and a copy of a plan of the radar site is available, albeit in poor resolution! An extract of the list of Buildings, once again supplied by Bob Jenner, is below. I have inserted an asterisk alongside some of the building numbers which correlate with some on the plan which follows.
I have marked those Building Numbers on the plan of the Tech Site which follows and, for clarity, added the equipment located at those sites.
I should point out that the 3 diagrams on the plan, which I took to be representations of 2 x T13 and 1 x T14 gantries, are in fact marking the pattern of earth electrodes. (Thanks again to Bob Jenner),

To help visualise these sites I have marked them on this over flight photo, taken in 1963.

In a little more detail, starting at the top left:

V. FPS6 Foundations. The foundations were put in place when the site was constructed as it was envisaged that an American FPS6 height finder might be installed in the future. The following picture, from Bob Jenner, is of an FPS6.
 In the event no radar was ever placed there but for many years, starting in the 70’s, anemometer masts were attached to the concrete foundations (I say masts because the wind is believed to have removed a number of them). A photo, taken in the early 80’s is below:

W. FPS3 - Proposed Site. In the early stages of planning 91 SU, provision was made for an AN/FPS3 radar. The W. marks where it would have been placed; however, I have found no evidence of any construction taking place – unlike the AN/FPS6 there appear to be no foundations on the site. Once again Bob Jenner has kindly provided a picture of an FPS3:

Type 14 Radar. The Type 14 was installed and operational when the Unit opened in the autumn of 1957. It was “old technology” and at Saxa it was only ever meant as a standby for the Type 80 (which was also an “S” Band Radar). I believe that the Type 80 was developed from one of the earlier versions of the Type 14. The 2 main periods of use for the Type 14 were in 1961, when the Type 80 was off the air following January gales which removed the reflector; and again in 1963, when the over flight picture above was taken (during the erection of the Type 80 Radome). The Type 14 was removed from the site after it was finally switched off in Sep 1964.

Unfortunately I don’t have a decent picture of the Type 14 on site - if anyone can help out it would be much appreciated –
The picture below is an enlargement of part of a photo  taken in 1968 or early 69, and shows the Type 14 Gantry (top right).
The next photo, taken in 1983 also shows where it had been sited and remains of the gantry legs can be seen. The HF 200 Radome on the left of the picture was constructed long after the Type 14 had been dismantled.

A picture of Saxas original Type 14 being landed at Baltasound in 1955 follows:

Type 13 Plinth and Cables only. Like the FPS 6 foundations – another “phantom radar”. I believe that there was never a radar mounted on this plinth/gantry.  In the past various things have been attached to the gantry, but never a Type 13.  In the early years it definitely had an anemometer attached to it – which I think had to be replaced due to wind damage on a number of occasions. A picture of the site, taken in 2011 is shown below:
Until recently this gantry was reputedly the last surviving Type 13 Gantry. However, having just returned from a visit, I can confirm that it was demolished and removed over the winter 2011/2.

Type 80. The Type 80 was the primary search radar for around 20 years. Twice the massive 75’ x 25’ (22.9m x 7.6m) reflector was so badly damaged by winds it had to be replaced (late ‘56 and early ’61); fortunately the latter occasion was the only time when the Unit was operational. This “operational” event could possibly have been prevented – a third line servicing party from No 3 Ground Radar Servicing Squadron at RAF Norton reported hair-line cracks radiating from many bolt holes on the turntable/main spar of the superstructure, thought to have been caused by wind damage, in the summer of 1960.
A number of stories have been told about the Type 80 which have given the radar a “mythical status”. In 1956, during the construction phase, the reflector was detached from the turntable but it came to rest very close by. In 1961 the reflector was also detached during severe gales (Friday 27 Jan). Once again the 18.5 ton reflector came to rest a few metres away. On neither occasion was the radar “blown over the cliff” – in fact the nearest cliff is about 600m from the Type 80 site. I suspect the legend grew up from a little embellishment/exaggeration – but it was a good story. It’s possible the story started at Saxa – I wouldn’t have gone out on a winters night, when the wind speed was well in excess of 100knots, just to see what had happened.

There is also another story which has circulated in a number of places that the Type 80 was “blown out of it’s radome” in 1965. I arrived at Saxa in 1967 and no one mentioned it during my tour but, more significantly, I have examined the official “Operations Record Book” - F540 - paying particular to the technical entries for 1965. I am confident that this did not happen. An event which may have given rise to this legend happened on 12 Feb 65 when a severe gale blew one of the radome doors off its hinges – the damage was repaired locally. That year the Type 80 serviceability record was reasonable – the only major down time being for periods of preplanned maintenance.

I have already written a couple of sections about the Jan 1961 event:
The earliest picture I have (where the radar is identifiable) was taken by Dave Goodall around 1960 from the area of the most northerly house in UK, at Skaw.
In 1963 a Radome was at last constructed and, if you think I want to be a scaffolder, think again!

Type 13. Like the Type 80 the Type 13 gave valuable service for around 20 years. Whilst it did not have the same range as the main search radar or of later height finders, it stood the test of time. Very early on it the ROTOR plans it was envisaged that there would be up to 3 Type 13’s at Saxa – in the end only this plinth-mounted version was constructed. This Type 13 suffered plenty of wind damage and a complete cabin change was required in 1970 – at least with large numbers manufactured there seemed to be no shortage of spare parts. The earliest photo I have of the Type 13 was taken, once again, by Dave Goodall in typical Saxa winter weather around 1960:
RN CHL/CDU Buildings. These will be the subject of a later section in the blog.

Communications -VHF. The Ward of Norwick (about 600ft) and Sothers (or Sodders) Field (about 700ft) were selected as the sites for the original VHF Transmitters and Receivers as early on as Dec ’52 . The plan was for Saxa to have 10 VHF channels on commissioning, with allowances for the sites to add or convert to UHF as and when the equipment became available. Both Transmitter and Receiver sites were to have their own standby power supply. A VHF triangulation facility – to be controlled by the SOC – was also fitted (I presume this was on 121.5 MHz, the VHF emergency frequency). A Bomber Command VHF forward relay facility was installed in Apr 59 followed by 2 forward relay channels for SOC Buchan the following August. The first UHF Channels became available towards the end of 1959. The earliest pictures I have of Transmitters and Receivers were once again taken By David Goodall in about 1960.
Communications -Telephone links. From 1957 until 1962 all ground links were in the hands of the GPO – though numerous circuits were provided. It was a great advance over the WWII Royal Navy site on the hill – in the beginning they had a single landline which had to be routed though the civilian exchange in the Haroldswick Post Office. The GPO used a fixed multi-channel VHF radio link to carry the telephonic communications. It was constructed on the Ward of Norwick at the Transmitter site. It was not until 1962 that an RAF controlled ACE High Link to the Forward Scatter Site at Mossy Hill was established. A later picture of the ACE High Microwave Tower at Saxa (pointing at Collafirth Hill on the Shetland Mainland) is below. Collafirth Hill then linked to the Forward Scatter Station at Mossy Hill. The ridged building to the right of the tower also belonged to ACE High.
TACAN.  The TACAN (Tactical Air Navigation System) beacon arrived at Saxa somewhat later than I had originally thought. Construction work commenced early in 1960 and, after a few problems, it was successfully tested in December of that year.  It was declared fully operational on 5 Jan 61. Almost immediately a number of problems arose. No 2 GRSS were asked to investigate and a team arrived at Saxa on 20 Jan. Apart from a minor fire having to be dealt with, the antenna shaft had to be replaced and a new klystron fitted.  The equipment was returned serviceable on 25 Jan, just in time for the severe gale on the evening of Friday 27 Jan 61 – the gale which removed the 18.5 ton Type 80 antenna. Once the weather had died down a bit it was thought that the TACAN Tower had developed a slight “list”. Eventually it was found that one of the wedges helping to secure one of the Towers feet had loosened and the problem was easily rectified. The history of the TACAN after that was typical for any item left out to face the elements at that latitude – somewhat chequered.

1. Firstly, an appeal to anyone with pictures and data relating to Saxa Vord to pass the items on, either to me or to an organisation such as the Air Defence Radar Museum at Neatishead. Practically everything covered in this section concerns events which occurred more than 50 years ago. Many service units have disappeared almost without trace and our forbears deserve better treatment.

2. Secondly, I can totally recommend a visit to the Air Defence Radar Museum during its opening season:
There are not many places where you can still see a Type 14 Radar:


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