Which of the following is NOT a desirable property of ALRE hydraulic fluids?

• A. Rapid degradation with seals
• B. Fire resistance
• C. Appropriate viscosity
• D. Good lubricity

Answer: (D)

Fluid compatibility and stability with seals and system performance. ALRE hydraulic fluids must stay chemically stable and be compatible with the seals and materials in the system. If the fluid rapidly degrades whenever it contacts seals, it can alter viscosity, produce corrosive or acids, and cause seals to swell, crack, or lose elasticity. That leads to leaks, reduced reliability, and potential actuator failure—clearly undesirable in launch and recovery operations.

Fire resistance is desirable because it minimizes ignition risk in environments with heat, friction, and electrical components near aircraft. Appropriate viscosity is essential to ensure the fluid can be pumped properly, provides adequate film strength, and operates effectively across the temperature range. Good lubricity helps reduce wear on pumps and actuators, extending component life and reliability. So the property that is not desirable is rapid degradation with seals, while fire resistance, proper viscosity, and good lubricity are desirable.