What assists the collector tanks in maintaining a full level of fuel?

The correct answer is the respective scavenge ejector, which is designed to assist collector tanks by ensuring they maintain a full level of fuel. Scavenge ejectors operate by utilizing engine or fuel system pressure to create suction, effectively drawing fuel from the collector tanks. This process helps prevent the fuel from becoming stagnant and ensures there is always a sufficient supply to the engine during operation. By actively maintaining the fuel level, scavenge ejectors play a critical role in overall fuel management, aiding in the consistent delivery of fuel to the pumps.

Other options, while related to fuel systems, do not perform the same function. For instance, fuel transfer pumps are used to move fuel between different tank locations but do not specifically focus on maintaining the level in collector tanks as scavenge ejectors do. A gravity feed system relies on gravitational force to move fuel, which may not provide the necessary control over fuel level in the collector tanks. Pressure relief valves are designed to prevent excessive pressure build-up in the fuel system, which is important for safety but does not relate to maintaining the fuel level within collector tanks. Thus, the unique mechanism of the scavenge ejector makes it the appropriate choice in this context.