Which lights illuminate when the pilots start up the APU?

When the pilots start up the Auxiliary Power Unit (APU) in the MH-60S, the anti-collision lights are designed to illuminate as a safety feature. The purpose of the anti-collision lights is to alert personnel on the ground to the presence of the aircraft, especially when it is in operation and potentially in an area where people are working around it. This increase in visibility helps prevent accidents, as the APU is a crucial part of the aircraft's power system during ground operations.

The activation of anti-collision lights during APU startup is in line with aviation safety protocols to ensure that the aircraft is seen at all times, especially when it is preparing to become operational. In contrast, navigation lights, landing lights, and taxi lights serve different purposes and are not specifically designed to indicate the status of the APU.