How long must AC power be applied to the aircraft to provide cooling for the EFIS tubes?

To provide adequate cooling for the Electronic Flight Instrument System (EFIS) tubes, AC power must be applied for a duration of five minutes. This time frame allows the internal components of the EFIS to reach optimal operating temperatures, ensuring reliable performance during flight. Proper cooling is crucial because excessive heat can affect the accuracy and functionality of the displays, which play a vital role in navigating and controlling the aircraft.

In contrast, durations such as three minutes, seven minutes, or ten minutes may not align with the specific cooling requirements of the EFIS system, making them insufficient or excessive for ensuring the proper operational stability of the instrumentation. The five-minute duration strikes the right balance, ensuring that the system is adequately prepared for use without unnecessary delays or risks to its operational integrity.