What is one safety precaution to take before servicing the APU?

Ensuring the APU is turned off and secured prior to servicing is a fundamental safety precaution. This action minimizes the risk of accidental activation while maintenance is being performed. The APU, which provides power and pneumatic support for various aircraft systems, can pose a significant hazard if it is operational during servicing activities. By confirming that it is off and secured, personnel can work more safely, preventing unintended movement, noise, or pressurized output that could lead to injuries or equipment damage.

Other options, while also important in the context of safety, do not address the immediate risk associated with servicing. Checking fuel levels before starting is crucial for operational efficiency but does not directly relate to safety during the servicing process. Verifying that personnel are wearing safety gear is important for overall workplace safety, but it does not mitigate specific hazards related to the APU itself. Lastly, while ensuring the APU is in maintenance mode may be a step taken during servicing, it assumes the APU is off beforehand, making it complementary rather than primary in the safety hierarchy.