What is the main purpose of the fuel pump in the APU fuel system?

• A. To increase engine temperature
• B. To supply fuel under all operating conditions
• C. To reduce fuel consumption
• D. To filter unwanted particles

Answer: (B)

The primary function of the fuel pump in the Auxiliary Power Unit (APU) fuel system is to supply fuel under all operating conditions. The fuel pump ensures that an adequate quantity of fuel is delivered to the APU to support its operation, particularly during various phases such as startup, idle, and full-load conditions.

In an APU, consistent fuel supply is crucial for reliability and efficiency, as it directly affects the APU’s ability to generate power, help start jet engines, and provide electrical and pneumatic power when the main engines are not running. The fuel pump must be capable of overcoming various challenges, such as changes in fuel tank levels or variations in altitude and temperature, which can impact fuel flow and pressure.

While factors such as reducing fuel consumption or filtering particles are important within the broader scope of fuel system functionality, they are not the core purpose of the fuel pump itself. The emphasis on supplying fuel reliably under changing conditions accurately reflects the essential role of the pump in maintaining optimal APU performance.