What must be done before conducting fuel system inspections on the APU?

Before conducting fuel system inspections on the APU, it is essential to shut down the APU and allow it to cool. This step is critical for safety reasons. An APU operates at high temperatures during its functioning, and if inspections are performed while the unit is hot, there is a risk of burns and heat-related injuries. Additionally, a cooled APU ensures that there are no residual fuel vapors or pressures that could pose a hazard when inspecting the fuel lines, tanks, or any related components. Taking the time to cool the APU prior to inspection helps ensure that technicians can work in a safer environment and decreases the likelihood of any accidents or injuries occurring during the inspection process.