What is the first step to take in the event of an electrical fire during flight?

In the event of an electrical fire during flight, turning off the master switch is the first crucial step to take. The master switch controls the entire electrical system of the aircraft. When it is turned off, it effectively disconnects all electrical power, which is vital in preventing the fire from potentially spreading or escalating due to active electrical circuits. This step prioritizes safety by removing the source of power and limiting further electrical activity.

Other options may be relevant in the broader context of managing in-flight electrical issues or fires but do not address the immediate need to cut power. For example, the avionics switch could help isolate some components but does not eliminate the risk from other powered systems. Closing cabin air and heat might limit airflow to the fire, but without turning off the master switch, the electrical source remains active. While landing immediately may seem urgent, doing so without first addressing the source of the fire could lead to chaotic and unsafe conditions. Therefore, the most effective and immediate initial response to an electrical fire is to disable the aircraft's electrical system by turning off the master switch.