FAA Powerplant Written Practice Test

What does a dump valve do in a gas turbine engine?

1. Drains engine manifold lines to prevent fuel boiling

2. Controls the fuel flow rate

3. Regulates the air intake

4. Filters out impurities from the fuel

The correct answer is: Drains engine manifold lines to prevent fuel boiling

A dump valve in a gas turbine engine serves a critical function by draining the engine’s fuel manifold. This action is particularly important for preventing fuel boiling within the fuel system. When fuel is not being used by the engine, or during certain operational conditions, the temperature can rise to a point where the fuel could vaporize, creating vapor locks that inhibit proper fuel flow. The dump valve helps alleviate this risk by allowing the fuel to drain from the fuel manifold, thereby reducing the chances of boiling and ensuring that the fuel system remains efficient and functional. The remaining options pertain to other functions related to the gas turbine engine's operation but do not accurately describe the specific role of a dump valve. For example, controlling fuel flow rate is typically managed by the fuel control unit or a fuel metering system, which adjusts the flow based on operational needs. Regulating air intake is a function of the engine's inlet design and does not involve a dump valve. Lastly, filtering fuel is handled by fuel filters that remove impurities before the fuel reaches the engine components, rather than through a dump valve mechanism.