The first is the fuel-pump system. Most of these pumps are engine-driven pumps. The second fuel system is called the gravity-feed system. This is because fuel flows from the wings to the engine due to a difference in pressure caused by gravity. These systems are normally found in high-wing aircraft, since the vertical distance from the wing to the engine is usually sufficient enough to provide enough pressure for the engine to operate.
All aircraft have fuel gauges for each fuel tank to indicate the quantity of fuel.
Aircraft with fuel pumps usually have a fuel pressure gauge as well. This fuel is colored blue to help identify it among the various other aviation fuels. The electrical system is also a complex system. Its primary component is the alternator. It functions exactly the same way as a car alternator does.