Final answer:
Fuel is supplied to engine-driven pumps usually by boost pumps to ensure proper pressure and flow. Gravity feed is less common and generally only used in small aircraft. Electric pumps can act as backups, and engine-driven fuel pumps provide the final necessary pressure.
Step-by-step explanation:
Fuel from the collector tanks is typically supplied to engine-driven pumps using boost pumps. The role of the boost pumps in an aircraft fuel system is to ensure that fuel is delivered to the engine-driven fuel pumps at the correct pressure, particularly under conditions where gravity feed may be insufficient due to the aircraft's attitude or during high-demand situations.
Electric fuel pumps might also be used in some situations, but primarily as backup systems. The gravity feed system is sometimes used in small, light aircraft where the fuel tank is placed above the engine to let gravity move the fuel. However, for larger aircraft and under many flying conditions, relying on gravity alone is not feasible. Lastly, the engine-driven fuel pumps are typically high-pressure pumps that are actually driven by the engine to supply the final pressure and flow of fuel necessary for the engine's operation, but these do not usually draw fuel from the collector tanks directly.
Understanding the fuel supply mechanism is crucial in fields like aeronautical engineering and maintenance because it ties into the overall safety and functionality of the airplane.