AA Batteries Categorisation
From our site visits to the surviving heavy anti-aircraft (HAA) battery locations, it has become clear that several designs were used. The general layout remains consistent, with four emplacements laid out in an arc, usually around a command post, but the placement of the other buildings can vary, and may have been dependent upon site topography and geology. The design of the emplacements and buildings has also been noted to vary, together with the materials used in their construction.
There appear to be no official publications reporting or detailing these differences, therefore we feel it important to record our observations while the battery sites are still available. In the absence of any official categorisation or typing of these differences, the following types have been created so they may be referred to consistently throughout this web site.
- A military installation consisting of a prepared position for siting a weapon.
- The position within an emplacement where a weapon is fixed or mounted.
- command post
- A building which houses the battery commander, and where fire control instructions are issued from.
Emplacements can range from basic installation made from little more than a few sandbags, through the enclosures we see around HAA batteries which contain ammunition racks and shelters, all the way to massive concrete bunkers which protected the giant guns of coastal batteries.
The emplacements generally lie on an arc centred on the command post, and within our reports will usually be numbered clockwise, beginning at number 1, as seen from the command post, where the arc is usually centred.
Holdfasts within such emplacements (if we restrict our consideration to those found with HAA batteries) can be deceptively simple in appearance, appearing to be little more than rings of bolts or studs extending about the surface of the ground, especially if overgrown. In reality, they are similar to icebergs, with the majority of their structure buried below ground level, extending both downward and outward from the visible fixings. The bolts are the surface evidence of a reinforced concrete structure set into the ground, and are attached to an underlying metal cage set into the concrete, and provide a secure mounting for the gun. To assist with their installation, both 3.7-inch and 4.5-inch guns were fitted with two locating dowels, which dropped into the holes in the holdfast and aligned all the mounting bolts.
Since there were insufficient numbers of guns available to arm all the anti-aircraft batteries at the same time, guns were moved about periodically, and some batteries were never armed.
Command posts may also incorporate observation posts where range and height finding equipment were mounted, allowing the observers to pass their readings directly to the commander. Later, more advanced batteries used predictors which could accept signals directly from the observers' equipment, process the variables and transmit the required setting directly to the guns. Later still, radar was used to locate and track the targets, and directly control the guns.
The main difference between the HAA batteries we have been able to examine relates to the design and construction of the emplacements, with lesser differences occurring in the command posts.
World War II emplacements
The emplacements are octagonal with the four shelters forming four of the sides. One side is open and forms the entrance. Interestingly on this type the perimeter wall is attached to the inner edge of the four shelters and not the outside. This gives the initial impression that they are much smaller than the other types. Each emplacement has a shelter attached to one side which is probably a magazine since it has a ventilator and each has a connecting hole to the holdfast area knocked through the wall.
The walls are built of red brick with reinforced concrete roofs.
The emplacements are octagonal with all sides being the same length. There are four ready use shelters, presently (2008) open at both ends but pictures of an English site show that they all had steel doors fitted. Closer examination of the Larkfield Battery revealed that there are retainers on the walls allowing doors to be hooked in the open position. On some sites the outer ends of some are bricked up. There are two shelters that differ, and are open at both ends but are slightly deeper to allow a short wall with brick sized ventilators on all four corners. It has been suggested that they were used for pre-primed shells or for the fuses. On some sites there are holes in the walls for ammunition racking. Only every second emplacement has the brick-built magazine attached although the same internet source suggests that they are actually air raid shelters for the crew. They have one door on the end facing the entrance to the emplacement.
Construction of the emplacements is reinforced concrete except for the attached magazines or air raid shelters which are brick. The shelters in the emplacements are lined with brick to allow supports for ammunition storage.
The emplacements are an irregular dodecahedron with three sides missing to create the entrance. Construction is entirely of red brick with reinforced concrete roofing. This model has seven ready use shelters and two integral magazines per emplacement. The magazines have only one entrance - into the holdfast area. No further magazine provision has been found on these sites.
GL radar ramp
These ramps were used to locate the trailers which housed the GL Radar hardware over the mat (a large metal mesh rolled out onto the surrounding ground) which formed an electrical ground plane for the antenna and increased the efficiency of the radar system. The ramps were provided with small extensions on to which outriggers fitted to the trailers could rest, and be used to level the trailers. Larger extensions on either side of the ramps helped personnel access the trailer.
The ramps probably also helped stopped the trailers sinking into soft or boggy ground.
World War II AA battery under construction
This picture, found in the Imperial War Museums collection, is described as "5.25-inch anti-aircraft battery under construction, 21 August 1944."
Cold War emplacements
These massive emplacements were constructed throughout from reinforced concrete. The engine room and computer/radar room were sited away from the guns, together with separate buildings for technical service and support. The large 5.5-inch guns were fully radar and computer controlled, all the crews had to do was feed in the shells. These installations were built about 1950-51, and were out of service by 1956. All were constructed on the surface except Rosneath, which was found to have its emplacements almost buried to ground level. Five batteries of this type were built as part of the Clyde Postwar AA Defences.
Type H (World War II conversion)
The emplacements are octagonal with the longer sides being twice the length of the shorter sides. Each emplacement has three ammunition shelters, double ended, with a partition dividing one end, possibly allowing for the storage of three types of shell. All shelters are fitted with wooden racks machined to fit the shells. The fourth shelter at some sites doubles as an entrance to the attached engine house which is linked to the holdfast by a cable or pipe duct. On other sites the entrance is at the opposite end. There are three holes in the wall, two plain and one lined with a ceramic pipe, thought to be a cable duct. This was initially assumed to have been a late type of battery using automated guns aimed by hydraulics, but recent information from England and research into aerial and land photography at Bellsmyre suggest that these are actually of postwar construction and were designed for 3.7-inch guns.
Construction of the gun site is entirely of reinforced concrete.
Each site has a small store fitted with a heavy door, possibly a fuel store for the engine driven hydraulic pump although it has been suggested elsewhere that they are crew shelters this seems questionable since the headroom is only 5 feet.
Following upon research into their own aerial photographs, RCAHMS have now (2008) accepted that these sites are indeed post war and were built to handle automatic 3.7 or 4.5-inch guns. These are now identified within the category of Postwar AA Battery Conversion.
Battery command posts
These are thought to be the earliest design of HAA battery command post and are of a complex design. They are constructed in brick with cement render and have a reinforced concrete roof. The placement of the three pits varies occasionally from site to site, possibly because of geological factors. The purpose of the third pit is not known.
Recent examination of a 1946 aerial photograph of the battery at Bellsmyre has shown that the Type A command post extant in 2007 was not there in 1946, hence it must have been built after the war and the Type A is therefore not exclusively an early design.
These posts are constructed in brick, and usually not rendered. There are variations, and a few have been found with earth banking, other have been provided with a double doorway in the rear wall. Another,Mugdock, was provided with a low wall fitted with pointed concrete capping running along the back of the main room, which was initially thought to have set aside a corridor space. However, a site visit showed that it was almost certainly a later addition by a farmer and was a shallow trough probably for treating the feet of sheep.
Instruments were mounted on a raised platform at the front of the building, and could be accessed from either end by a set of steps leading up through a window leading to a small room. The Predictor stood at the end where the cable ducts are, and the Height Finder at the other end. In the centre was a Range Finder which was used to identify a target aeroplane.
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