What should be checked when the AUX BAT Switch is turned ON, apart from the standby instruments?

• A. Primary Flight Display
• B. Backup UHF Control Head
• C. Both Fire Warning System and AEDD
• D. None of the above

Answer: (C)

When the AUX BAT Switch is turned ON, it's crucial to check both the Fire Warning System and the AEDD (Aircraft Engine Data Display). This action is part of the pre-flight and operational checks to ensure that critical systems are functioning properly.

The Fire Warning System is essential for alerting the crew to potential fire hazards, and ensuring it operates correctly provides safety reassurance. The AEDD also gives crucial data regarding engine performance and system status, which is vital for the safe operation of the aircraft. Checking these two systems ensures that the aircraft is ready for operation and that any potential issues are identified before takeoff.

While the Primary Flight Display and Backup UHF Control Head are important components within the aircraft, they are not specifically noted to be checked in the context of activating the AUX BAT Switch in this scenario. Therefore, option C is the correct choice as it encompasses critical safety measures necessary when the AUX BAT Switch is engaged.