What pressurizes the vent surge tank?

The vent surge tank is pressurized primarily by the ram air scoop located under the wing and through the return of fuel to the outboard wing bay. As the aircraft moves forward, the ram air scoop directs incoming airflow into the surge tank. This increase in airflow helps maintain pressure in the tank, preventing vapor lock and ensuring proper fuel delivery to the engines. Additionally, the partitioning of fuel within the system, when fuel is returned from the engines to the outboard wing bay, also aids in maintaining the required pressure conditions within the vent surge tank.

In this context, engine exhaust does not contribute to pressurizing the vent surge tank, as it primarily deals with exhaust gases rather than fuel system pressure. A pumper mechanism, while it can help in various fuel transfer tasks, does not directly pressurize the vent surge tank. Gravity feed from the fuel tanks is responsible for directing fuel toward the engines rather than creating pressure in a surge tank. Thus, the correct answer highlights the crucial roles of both the ram air scoop and the fuel return system in keeping the vent surge tank adequately pressurized during flight operations.