If one standby pump is inoperative, what is the operational condition for the aircraft?

The operational condition for the aircraft with one standby pump inoperative is that operations are prohibited. This is due to the critical function that standby pumps serve in the King Air 350’s hydraulic system. The aircraft relies on redundancy in its hydraulic systems to ensure safety and control, especially during critical phases of flight such as takeoff, landing, and in the event of an engine failure.

If one standby pump is inoperative, the redundancy necessary for safe operation is compromised, leading to potential control issues and increased operational risk. Therefore, the manufacturer and regulatory authorities do not allow operations under such conditions until the inoperative component is repaired or replaced.

This principle prioritizes safety, ensuring that pilots have all necessary systems fully operational before conducting flights. Other options such as allowing operations under certain altitude limitations or under emergency conditions do not apply, as the absence of a standby pump fundamentally alters the aircraft's ability to handle hydraulic system failures safely.