Which operation would be described as preventative maintenance?

• A. Replenishing Hydraulic Fluid
• B. Replacing Engine
• C. Repainting Exterior
• D. Upgrading Avionics Software

Answer: (A)

Preventive maintenance means doing routine, scheduled tasks to keep systems operating reliably and to prevent problems before they occur. Replenishing hydraulic fluid is a classic example because it’s a regular, planned check that ensures the hydraulic system has the proper fluid level and cleanliness. Keeping the fluid at the right level prevents loss of hydraulic pressure, reduces wear, and helps avoid leaks or air in the system, all of which support safe, predictable control of the aircraft.

Replacing the engine is a major, infrequent operation tied to life limits or failure risk, not a routine preventive task. Repainting the exterior is cosmetic and doesn’t address the reliability or safety of flight systems. Upgrading avionics software is an improvement task rather than a standard preventive maintenance item, though software updates can be important for performance and safety, they aren’t the typical example of preventative maintenance.