After refueling an aircraft and the lead pump deenergizes, at what PSI does the 58AF-9-1 defuel/flush valve close?

The correct answer is derived from the specific operational parameters set for the 58AF-9-1 defuel/flush valve in aircraft refueling systems. This valve is designed to close at a pressure of 80 PSI after the lead pump deenergizes.

Understanding the context of this operational pressure is crucial as it helps maintain system integrity and ensures safe fuel handling during both refueling and defueling processes. The valve's closing pressure is specifically engineered to prevent over-pressurization and potential fuel leaks, which could pose safety hazards or environmental risks.

The other pressure options do not align with the specifications for the 58AF-9-1 valve. Each of those alternative PSI settings—70, 75, and 85—would not provide the correct operational threshold for shutting the valve, potentially leading to malfunction or failure in the system’s ability to safely manage fuel flow. Recognizing the precise operational limits of equipment like the defuel/flush valve is essential for personnel involved in aircraft maintenance and refueling operations to ensure safety and reliability.