What must be true for the No. 1 engine RPM in order for the hydraulic system to function correctly?

In a hydraulic system, the engine RPM is critical as it often drives the hydraulic pumps that generate the necessary pressure for the system to operate effectively. If the No. 1 engine RPM must drop below a certain limit, this indicates that there is a minimum operational threshold for the engine to maintain sufficient power and pressure to keep the hydraulic system functioning correctly.

When the RPM drops below this specified limit, it can lead to insufficient hydraulic pressure, which can cause a malfunction or failure of the hydraulic system. This threshold is crucial as it ensures that there is enough power delivered to the hydraulic components, which may include actuators, control valves, and other related systems that rely on the consistent performance of hydraulic fluid dynamics.

Maintaining the engine RPM above this minimum threshold helps ensure that the hydraulic fluid is adequately pressurized and can be effectively circulated throughout the system, thereby enabling the desired operation of hydraulic lifting, steering, or braking functions.