General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

What is the purpose of demand pumps in a hydraulic system?

1. To maintain a constant pressure

2. To provide supplementary hydraulic power during high demand

3. To cool the hydraulic fluid

4. To replace hydraulic fluid lost in leaks

The correct answer is: To provide supplementary hydraulic power during high demand

Demand pumps play a critical role in hydraulic systems by ensuring that there is sufficient hydraulic power available during periods of high demand. Unlike other types of pumps that may operate continuously or maintain a constant pressure, demand pumps are designed to activate in response to increased hydraulic requirements. This feature allows the system to efficiently manage varying loads by supplying additional fluid to meet the immediate demands of machinery or equipment. The option related to maintaining constant pressure is more characteristic of other pump types, such as pressure-compensating or constant-pressure pumps, which are designed explicitly to manage and stabilize pressure in the system. Cooling the hydraulic fluid is typically managed through cooling systems rather than the function of demand pumps. Similarly, addressing leaks in hydraulic fluid typically involves maintenance measures rather than the operation of demand pumps, which do not replace lost fluid but rather bolster the system's capacity when needed. Thus, the primary function of demand pumps is to provide supplementary hydraulic power during high-demand scenarios, ensuring optimal performance of the hydraulic system.