What is activated whenever the avionics master is turned on?

When the avionics master is turned on, it activates specific systems that are essential for the operation of avionics equipment in the aircraft. One of the primary systems that is activated at this time is the evaporator blowers. These blowers are crucial for maintaining proper temperature and airflow within the avionics compartment, which helps in preventing overheating and ensuring the reliability of the electronic systems onboard.

While the other options mentioned involve important aircraft systems, they typically do not get powered on merely by switching on the avionics master. For instance, landing gear indicators indicate the status of landing gear and are generally driven by different inputs, not the avionics master switch. Fuel pumps are also primarily controlled by other systems or switches specifically designed for fuel management. Emergency lighting, although essential for safety, is usually activated by a separate switch to ensure that it is only engaged when needed, such as during an emergency scenario.

This distinction clarifies why turning on the avionics master specifically engages the evaporator blowers to support the operational integrity of the avionics systems.