Top cover -- air defence turrets: the low-flying strike aircraft and assault helicopter constitute the mechanised land forces' main enemies. Both present potentially lethal, fast-moving and fleeting targets that are difficult to engage other than by dedicated air defence vehicles with rapid response weapons. (Air Defence).

Until recently, coping with such unpredictable targets meant that specialised, complex and bulky systems with powered turrets, requiring large vehicle chassis to carry them, had to be made available to mechanised formations. These days that task can be assumed by smaller, lighter and handier systems based around turrets mounting both guns and missile launchers.

Guns

Automatic guns still predominate for low-level air defence. The fast and fleeting nature of aircraft targets means that putting more projectiles into the air in the brief time available makes the possibility of a hit more certain. In addition, many low-flying aircraft and attack helicopters now have considerable armoured protection for the crews and vital components so the more armour-penetrating projectile strikes that can be made the better the chances of inflicting a kill. For such requirements the fast-firing gun still scores over the guided missile. There is also the topic of cost. Missiles, even small ones, can be expensive and once launched they cannot be reused. Missiles also typically have a shelf life of between ten and fifteen years. By contrast, guns remain always ready for action.

It goes without saying that modern gun turret systems rely on electronic computers for their fire control and subsequent turret drive controls, to the point of target selection, tracking and firing at the optimum instant.

Air defence turret guns vary in calibre from 76.2 mm down to 20 mm, but we will plumb the bottom end at 23 mm. Under that calibre air defence guns are close range and nearly all visual engagement-only types.

Big Guns

The sole example of 76.2 mm is the Otomatic from Otobreda of Italy. The formidable gun used in this single-gun system has a cyclic fire rate of 120 rds/min, the gun and associated surveillance and tracking radars being carried in a turret on a Leopard 1 tank chassis. In common with just about every other turret system mentioned in this summary, the Otomatic turret can be transferred to many other similar chassis with a minimum of modification.

The hydraulically loaded gun is a derivative of the widely used Otobreda 76/62 naval gun. It can tackle aircraft targets up to 6000 metres distant, although the usual surveillance radar has an operational range of about 15,000 metres. A single five-round burst is stated to be sufficient to bring down any aerial target. The turret interior is relatively spacious for the crew of just two, and there is stowage for 64 rounds, some of which can be a specially developed armour-piercing APFSDS for engaging land targets.

Despite having been around since the late 1980s, the potent Otomatic has yet to attract any orders.

Further down the calibre chain come a few 57 mm air defence gun turret systems. The passing from fashion of the relatively slow-firing 57 mm guns is largely due to most extant examples dating from a previous generation that relied on visual target engagements in daylight only. They were without benefit of …