FV5571 ‘Castellan’ Main Battle Tank
Development of the Castellan series of main battle tanks began in 1956 with the aim of producing a vehicle that could replace both the 68 tonne Cataphract heavy tank and the 50 tonne Cougar medium tanks.
While it was initially hoped to produce a 45 tonne vehicle using modern armour concepts and metallurgy, the requirement for a heavy 120mm gun and sufficient armour to defend against peer threats rendered this impossible, with the final vehicle coming in at just under 51 tonnes. Consequently the mobility of the vehicle suffered with the RHE-816 530kw V8 multi-fuel diesel being unable drive vehicle at the desired 60km/h road speed.
Achieving the desired armoured protection in light of the increasing effectiveness of hollow charge ammunition required some outside the box thinking in the form of siliceous-cored armour which was applied in a limited fashion to the lower glacis and turret mantlet to reduce the weight of these sections while maintaining effectiveness against chemical energy weapons. Protection on other sections of the forward arc was provided by extreme armour angling far in excess of that found on the Cougar, this required the driver to be positioned in an extreme supine position.
Armament was the new L551 120mm rifled gun which was though provide a reasonable compromise between the 84mm gun of the Cougar and the 138mm monster fitted to the Cataphract. Ammunition was initially HESH and a range of APDS rounds based on the ammunition developed for the lighter 84mm Model 1948. however later a special HEAT round with a decoupled liner was developed for use with the rifled gun allowing it to successfully engage armoured targets at far greater ranges.
This was coupled with a coaxial 7.5mm L22E4 Tank machinegun and on the production E1 version a 13.2mm L18E3 ranging machinegun.
The vehicle commander was provided with a powered cupola fitted with a filtered searchlight capable of emitting both white and infrared light and a 7.5mm L22E4 Tank machinegun. This cupola replicated the Hunter Killer capability of the Cataphract heavy tank but lacked it’s independent rangefinder, requiring the gunner to determine distance either with the optical coincidence rangefinder or the RMG after the commander designated a target.
Night fighting capability was limited to active image intensification enabled by either the TC’s cupola searchlight or a large dismountable 1.5 million candle power xenon searchlight on the mantlet.
The production E1 version of the Castellan had a number of minor improvements over the initial run of pre-production vehicles ranging from sheet metal dust skirts and external fuel tank brackets, to a larger 13.2mm coax for use as an RMG and a horseshoe shaped feed box from the TC’s cupola MG that wrapped around his hatch.
These vehicles entered service in 1966 and were primarily used in training roles as units slowly converted over to the new vehicle and learned how to use a Main Battle Tank.
In 1972 the E2 upgrade was rolled out to the fleet and principally concentrated on improving the fire control systems.
This consisted of removing the existing range finding equipment and replacing it with a Perspicacia Instruments LRS-2 Laser Ranging Sight mounted in the right hand rangefinder blister, the 13.2mm RMG was replaced with a standard 7.5mm MG to improve ammunition stowage and reduce logistical burden. A muzzle reference system was also fitted to tie the weapon into the new ballistic drive to best take advantage of the longer range the LRS provided.
Dual salvo 10 round smoke grenade dischargers were also fitted to either side of the turret to provide a more instantaneous smoke screen then could be provided by the exhaust smoke system.
A range of support vehicles were developed based on the Castellan’s hull including a scissor type armoured bridge layer, armoured recovery vehicle with a 20 ton capacity crane, and a combat engineering vehicle fitted with a 165mm demolition gun, A-frame jib crane and a dozer blade.
The XFV5570/4 trials vehicle was part of a program to develop a next generation fighting vehicle using the very latest in shaped charge and guided weapons technology and consisted of a modified turret fitted with IR and Laser emitters for guiding the supersonic missile fired from the XL71E2 165mm gun launcher.
As the program developed it became clear that the resulting vehicle would be extremely expensive compared to a standard ‘gun’ Castellan and so it was scaled back to one squadron of missile Castellans per armoured battalion. To many within the Armoured Corps this seemed suspiciously like a return to the days of the Cataphract and the Heavy Troop and all the logistical problems that entailed and in light of the ever increasing technical problems enthusiasm for the project evaporated by the early 70s.
The Castellan Powertrain Improvement Programme vehicle was built as part of UAWs next generation MBT project, and consisted of a modified Castellan forward hull mated to a newly designed rear hull segment with a gently sloped engine deck and rear hull plate, that provided enough room for the VTW 761-41 Series I V-10 710Kw turbo-charged diesel engine and RHE HTT-650/A Gearbox which substantially improved the Castellan’s mobility both on and off road.
While this was not intended as a realistic upgrade for the legacy Castellan fleet it did lead to the development of the Castellan II.
The Castellan II was developed by UAW in the late 70s as a private venture to provide a next generation MBT for the export market as well as entice the Armoured Corps into replacing the Castellan I in front line units. To this end they set out to fully capitalise on advancements in armoured vehicle technology, and included full passive night fighting capability enabled by improved image intensifying sights and a Low light level TV camera mounted on the right hand side of the turret mantlet. Protection wise the vehicle made extensive use of space composite armour in both the turret and hull. Mobility was provided by the Powerpack developed fin the Castellan PIP coupled with new independent Hydrogas suspension.
While the Castellan II ultimately proved far too expensive for the Laritaian Government at the time it did see reasonable export success around the world in a variety of configurations as the Castellan IIE, such as this Asturian example which has a 105mm gun, rubber skirts and a periscopic commanders sight instead of the low profile weapon station of the developmental vehicle.
The E3 upgrade programme began in 1981 and sought to make general improvements to the Castellan’s combat capabilities, especially in the realms of night fighting, this was achieved primarily by the adoption of advanced passive image intensification system, a new digital ballistic computer and the installation of the NOGS LLLTV camera on the gun mantlet. The ability to mount the searchlight was retained, but once crews became acquainted with capabilities of the Night Observation and Gunnery System this was only done infrequently.
Also upgraded was the powertrain which was beginning to struggle with the increased weight of the vehicle, and the ammunition for the 120mm gun, which saw the adoption of a Wolfram heavy alloy LRP round
A separate program that took place concurrently with the E4 upgrade lead to the installation of ‘Lamellar’ Reactive armour on both the turret and hull of the non Hybrid tanks to try and increase protection against the increasing threat of ATGMS.
The E4 programme was essentially an attempt by the Armoured Corps to get a new tank past the money conscious Conservative government of the time, by mating new Castellan II welded turrets to older Castellan I cast hulls, resulting what were termed by their crews as the ‘Hybrids’ and featured significantly improved digital fire control and the return of the venerable 13.2mm L18 Heavy machine gun to Armoured Corps vehicles this time in a low profile commanders weapon station. however even this proved to be more expensive then the treasury was willing to bare and only 225 vehicles were produced.
Delays in the Future Battle tank 90 programme lead to the ‘Stallion’ programme which fitted technologies developed under FBT90 to the existing fleet of Castellan MBTs resulting in the E5 and E6 variants, which featured advanced thermal imaging and fully integrated fire control systems allowing them to fire accurately on the move, as well as depleted uranium LRP ammunition to enable them to go toe to toe with increasingly well protected opponents.
In the early 2000s FV6531 ‘Contender’ began to arrive in sufficient numbers to supplant the Castellan as the Armoured Corps premier main battle tank, however it was as ever judged that sufficient funds would not in the medium term be available to replace every vehicle in service and as such the Castellan would continue to solider on in the reserve yeomanry units. To that end the E7 was developed to reduce the logistical cost of the reactive armour equipped Castellans by replacing it with NERA modules on the turret and hull.
While this program was under way it was decided to further reduce the Armoured Corps logistical burden by phasing out the legacy rifled 120mm gun and therefore liquidate it’s stock of spare parts and ammunition onto the export market, this resulted in the final variants of the Castellan main battle tank to see service in the Laritaian Armoured Corps, the E8 and E9 which featured a modified version of the same 120mm L691 ‘Super Velocity’ smoothbore gun as the Contender.
Two separate weapon carriers were developed based upon the Castellan hull for use by the Artillery. The first of which was the FV5576 SPAAG which featured a massive 30mm gatling gun and all weather optical and radar targeting capability, this was later augmented with a three round rack of Hail infrared guided missiles in 80s as part of the E1 upgrade.
The second weapons carrier was the FV5574 ATGM Tank Destroyer which was developed as a way of defeating numerically superior armoured assaults with having to rely on air support.
The ‘Giraffe’ as it became knows would position itself behind a tree line or other such terrain feature and elevate it’s mast mounted turret till the commanders periscope sight was exposed, from this position it could covertly observe the enemy and launch devastating salvoes of missiles.
However the advance of missile technology and the development of heavy attack helicopters by the Army Air Corps rendered the ‘Giraffe’ obsolescent and it was withdrawn from service in the early 90s.