In a backup system, what does "no-leak" condition refer to?

The "no-leak" condition in a backup system refers specifically to the hydraulic system pressure. In hydraulic systems, maintaining pressure without any leaks is crucial for ensuring that the hydraulic fluid can perform its function effectively. This pressure is essential for operating various components within the aircraft, including landing gear, brakes, and flight control surfaces.

A "no-leak" condition indicates that the hydraulic system is sealed properly and that all components are functioning as intended without any loss of fluid or pressure. If there were to be a leak, it could lead to a loss of hydraulic pressure, which would affect the system’s capability to function safely and reliably. This term is particularly important in aviation maintenance and operations to ensure the flight safety and performance of the aircraft.

Other options like integrity of fuel lines, electrical circuitry, or air pressure control have their own significance in operation, but they do not pertain directly to the concept of a "no-leak" condition as it relates to hydraulic systems.