Stillbrew armour

Stillbrew armour,or more correctly, theStillbrew Crew Protection Package (SCPP)was an add-on passivecomposite armourapplied to theFV4201 Chieftainmain battle tankused by the British Army'sRoyal Armoured Corpsin the mid-1980s and early-1990s so as to provide increased protection fromanti-tank warfareweapons.It was named after the two men that invented it, Colonel Still and John Brewer,from the Military Vehicles and Engineering Establishment inSurrey.The tanks to which it was fitted were colloquially referred to asStillbrew Chieftains.

Background

During the1973 Arab-Israeli War,theIsraeli Defence Forces(IDF) lost many tanks, mainly to hollow orshaped chargeprojectiles. Among the losses were British-suppliedCenturions.TheRoyal Armoured Corps(RAC), through organisations such as theMilitary Vehicles and Engineering Establishment(MVEE) and theRoyal Armament Research and Development Establishment(RARDE), began conducting research into how to improve the effectiveness of the armour used in itsarmoured fighting vehicles(AFVs).

With the outbreak of theIran-Iraq Warin 1980, research accelerated after many Iranian Chieftains were destroyed or severely disabled by IraqiT-62s,and forensic examination of captured Iranian Chieftains supplied by Iraq was undertaken.The British assessment of these vehicles concluded that the front of Chieftain'shullandturret,originally designed to provide protection against all types of ammunition from the Soviet 100mm main gun fitted to the older SovietT-54/T-55tanks, protected inadequately againstarmour-piercing fin-stabilized discarding sabot(APFSDS) andhigh-explosive anti-tank(HEAT) ammunition from the newer T-62's larger 115mm main gun, nor other similar current or near-future tank ammunition. Consequently, a program to up-armour the Chieftain commenced at the MVEE, which resulted in theStillbrewarmour package.

Design

Chieftain Mark 11C atThe Tank Museum,Bovington. Stillbrew armour is visible on the turret front.

Stillbrew armour was a passive (i.e., non-explosive, non-reactive)appliqué armourdesigned to provide added protection against HEAT ammunition and hollow andshaped chargeweapons such asRPG-7rocketsandAT-3Saggeranti-tank guided missiles,by deflecting the explosive jet, and increased protection against ballistic and kinetic projectiles such as APFSDS ammunition by increased armour thickness.

The armour was designed as modular blocks consisting of six layers of steel plate spaced with thick rubber, which were added to the front of the turret and on the hull around the driver's position,which served to increase protection to the turret ring. The blocks were fastened to the vehicle by stainless steel bolts, and a final layer of sheet steel was welded over the block covering the bolt heads and providing a flush surface; this also provided protection from water andchemical, biological, radiological, and nuclear(CBRN) agents from getting under the blocks and causing corrosion and contamination of the vehicle's surfaces.

When struck by a shaped charge, one or more layers of the block would shift or shear away, effectively providing a new surface the explosive jet had to penetrate, thus further deflecting or depleting the jet with every successive layer it encountered. The layers and the spacing was also found to be effective in counteringhigh-explosive squash head(HESH) ammunition.When struck by a kinetic projectile, the armour blocks effectively increased the vehicle's armour path by a minimum of 50% (this figure was more than just the added thickness of the armour block; when struck by a ballistic penetrator, the kinetic energy would cause the layers, particularly the rubber layers, to expand), minimising or removing the chances of penetration of the vehicle's hull or turret.Also, it was discovered that armour blocks were of sufficient strength to render medium-calibre projectile (up to 25mm conventional or 20mmtungstenarmour-piercing ammunition(AP) 100% ineffective and did not damage the blocks.

While Stillbrew armour was later found to also be effective against HEAT rounds from the 125mm main gun of aT-72,it was insufficient to stop tungsten anddepleted uraniumAPFSDS rounds from this weapon, and an added minimum increase of 30% effectiveness of the original design would be required. However, further development was cancelled due to the emergence of the superiorChobham armour.

Operational history

Testing of the prototype armour began in 1984, with firing and mobility trials being conducted until 1985. The design was deemed successful with no changes needed. Production of the armour began in 1985 at the Royal Ordnance Factory Leeds (ROF Leeds) and fitting began in 1986. Vehicles located in the UK were fitted with the armour package by theRoyal Electrical and Mechanical Engineers(REME) in base workshops across the country, while those vehicles deployed toWest Germanywere fitted at 23 REME Base Workshop inWetterin theRuhr.

The armour was first fitted to the Mark 10 Chieftain in 1986, and was also later fitted to the Marks 11 and 12. It was also due to be fitted to the Mark 13, which was to be the final model Chieftain, but this variant was cancelled with the introduction of theChallenger 1.

Stillbrew armour was rendered obsolete by the introduction of the more effectiveChobham armour,first fitted to the experimental Chieftain 800 and 900 (and which features on the Challenger 1).

No other armoured fighting vehicles nor Chieftains sold to foreign armies (including exports of the Mark 10A), were fitted with Stillbrew armour.

External links

• World Register of Surviving Historic Armoured Vehicles - FV4201 Chieftain Tank