What is the acceptable range indicated by the FREQ meter on the AC SYS CONTROL PANEL?

The FREQ meter on the AC SYS CONTROL PANEL indicates the frequency of the electrical generation system, which is critical for ensuring that the aircraft's electrical systems operate efficiently without causing damage. The acceptable range of 394 to 406 Hz aligns with the operational requirements for the C-5’s APU, as it ensures the power supplied is stable and within design parameters to avoid fluctuations that could disrupt the aircraft's systems.

Operating outside this range could lead to inefficiencies, malfunctions, or potential damage to sensitive equipment. Understanding this frequency range is essential for operators and maintenance personnel to ensure optimal performance of the APU and associated electrical systems, thereby ensuring aircraft safety and reliability.