Which valve allows for fuel to be drained from the airplane?

The jettison valve is designed specifically for the purpose of draining fuel from the airplane. This mechanism is crucial for managing fuel levels, especially in situations where the aircraft needs to reduce weight for departure or in the event of an emergency situation after takeoff. By allowing excess fuel to be released, this valve enables the aircraft to reach a safe landing weight.

Other options, while related to fuel management, serve different roles. The refuel valve is intended for the inflow of fuel into the aircraft's tanks. The separation valve is often involved in managing fuel flow between different sections of the fuel system but does not specifically function to drain the fuel. The firewall shutoff valve is used to prevent the flow of fuel in the event of a fire, blocking fuel access to the engine but not facilitating drainage. Thus, the jettison valve is uniquely positioned within the fuel management system to perform the fuel drainage function.