What characterizes a hydraulic system referred to as a 'power pack' system?

A hydraulic system referred to as a 'power pack' system is characterized by having all hydraulic power components located in one unit. This configuration means that the hydraulic pump, reservoir, and often filters and accumulators are housed within a single assembly. This centralization simplifies maintenance and reduces the complexity of installation within the aircraft since technicians can access all related components in one location, increasing efficiency and reliability.

In contrast, systems that have components distributed across different locations may introduce more complexity and potential points of failure, which is not optimal for a power pack system designed for streamlined operation. A system that relies on an external power source would not be considered a true hydraulic power pack since it typically works independently and should be self-contained. Lastly, while pneumatic systems can be used in various aircraft systems, a power pack system specifically refers to hydraulic components and does not engage pneumatic systems for its operation.