rounds. Turret stabilization is an important capability because it enables firing on the move and prevents crew fatigue. Engine Modern AFVs have primarily used either petrol (gasoline) or diesel piston engines. More recently, gas turbines have been used. Most early AFVs used petrol engines, as they offer a good power-to-weight ratio. However, they fell out of favour during World War II due to the flammability of the fuel. Most current AFVs are powered by a diesel engine; modern technology, including the use of turbo-charging, helps to overcome the lower power-to-weight ratio of diesel engines compared to petrol. Gas turbine (turboshaft) engines offer a very high power-to-weight ratio and were starting to find favour in the late 20th century – however, they offer very poor fuel consumption and as such some armies are switching from gas turbines back to diesel engines (i.e. the Russian T-80 used a gas turbine engine, whereas the later T-90 does not). The US M1 Abrams is a notable example of a gas turbine powered tank. Modern classification by type and role Notable armoured fighting vehicles extending from post-World War I to today. Tank The tank is an all terrain AFV incorporating artillery which is designed to fill almost all battlefield roles and to engage enemy forces by the use of direct fire in the frontal assault role. Though several configurations have been tried, particularly in the early experimental "golden days" of tank development, a standard, mature design configuration has since emerged to a generally accepted pattern. This features a main tank gun or artillery gun, mounted in a fully rotating turret atop a tracked automotive hull, with various additional secondary weapon systems throughout. Philosophically, the tank is, by its very nature, an offensive weapon. Being a protective encasement with at least one gun position, it is essentially a pillbox or small fortress (though these are static fortifications of a purely defensive nature) that can move toward the enemy – hence its offensive utility. Psychologically, the tank is a force multiplier that has a positive morale effect on the infantry it accompanies. It also instills fear in the opposing force who can often hear and even feel their arrival. Tank classifications Tanks were classified either by size or by role. Classification by relative size was common, as this also tended to influence the tanks' role. Light tanks are smaller tanks with thinner armour and lower-powered guns, allowing