What is the role of the nitrogen charged accumulator in the APU starting system?

• A. To store fuel
• B. To provide hydraulic pressure
• C. To regulate engine temperature
• D. To filter impurities

Answer: (B)

The role of the nitrogen charged accumulator in the APU (Auxiliary Power Unit) starting system is to provide hydraulic pressure. This accumulator acts as a storage vessel for hydraulic fluid under pressure, typically using nitrogen gas to maintain the pressure when the system requires it. During the starting process of the APU, the accumulator releases this hydraulic pressure to assist in various operations, such as engaging starter motors or actuating valves, which are essential for starting the engine efficiently.

In the context of aircraft systems, hydraulic systems are critical for various functions, including starting engines, and the accumulator helps ensure that there is a reliable and immediate source of hydraulic pressure available when needed. This makes the starting process more efficient and responsive, contributing to the overall functionality of the APU.

Other answer choices pertain to functions that do not align with the primary role of the accumulator. For example, storing fuel is handled by the fuel system, regulating engine temperature involves cooling components, and filtering impurities is managed by dedicated filtration systems. Each of these functions is essential to aircraft operations but does not pertain to the specific role the nitrogen charged accumulator plays in providing hydraulic pressure in the APU starting system.