Final answer:
The hydraulic system accumulators should be pre-charged to a specified pressure during a preflight inspection with no systems powered, as indicated by the accumulator gauge. This ensures that there is immediate hydraulic pressure available for the aircraft's hydraulic-dependent systems upon starting.
Step-by-step explanation:
The question about the readings on hydraulic system accumulators during a preflight inspection refers to the state of the hydraulic system when no systems are powered. While specifics can vary depending on the aircraft, typically, the accumulator gauge should indicate that the accumulator is pre-charged to a certain pressure to ensure readiness and to maintain the system's integrity. The pre-charge pressure is typically specified by the aircraft manufacturer and can be found in the aircraft's maintenance manual. It is essential to check this as part of the preflight inspection because the gauge pressure in the hydraulic system accumulators is critical for the initial function of the hydraulic systems upon system engagement, i.e., when the auxiliary power unit (APU) or engines start and the hydraulic pumps begin to operate. This pre-charge ensures that there is immediate hydraulic pressure availability for the operation of control surfaces and other hydraulic-dependent systems.