The power of an engine can be increased by adding cylinders producing multi-cylinder engines. This is a more efficient way of increasing power than making a single cylinder larger, and also has the benefit of making the engine run smoother. There are various types of engine design with regard to cylinder arrangement.
The cylinder arrangement selected for a particular engine will depend on the type of cooling of the engine, the power required, and role of the aircraft. Early aircraft used In-line engines.
These have their cylinders arranged in a straight line, one after the other, they can be liquid or air-cooled. The air-cooled variants are limited to around six cylinders. Many in-line engines are inverted, so that the crankshaft is at the top and pistons below. The propeller is driven from the crankshaft and this arrangement gave greater ground clearance for the propeller.
The V Engine arrangement was used for larger more powerful engines of eight to twelve cylinders. These engines powered the fighter aircraft of World War 2. Liquid-cooled, the V arrangement of cylinders could easily be streamlined into the fuselage so reducing drag. The liquid cooling system however increased weight and complexity of the engine. Like the in-line engine they could also be inverted.
The Radial Engine gave a large frontal area to the aircraft, but was short in length. The pistons are arranged radially around a single-throw crank. Although drag was increased the engines were light, rigid and produced high power.
Radial engines always have an odd number of cylinders. By placing further rows of cylinders behind the first produced Double and Triple Bank radials. These engines, although very powerful, had the disadvantages of being heavy and presenting a large frontal area as they were air-cooled.
Most modern light aircraft use four or six cylinder engines arranged in the Flat/Horizontally Opposed configuration. This arrangement makes for a short rigid engine, which is easily streamlined.