What is the correct preflight sequence for starting and arming avionics?

• A. Avionics first, then battery power.
• B. Start with external power and ignore nav data validity.
• C. Power down all avionics before start.
• D. Battery power, avionics master switch, check for power, verify nav data validity.

Answer: (D)

Powering avionics in the correct order ensures a safe, reliable startup and reliable navigation guidance. Start by applying battery power so the aircraft’s essential electrical system has a stable, primary source. Then switch on the avionics master to energize the avionics buses, allowing all displays, radios, and navigation systems to come alive. After that, verify that power is actually present to the avionics—you should see active displays and normal system indicators. Finally, check the nav data validity to confirm the navigation database is current and usable; relying on outdated data can lead to incorrect routing or navigation decisions.

Starting with avionics before the battery could leave the systems unpowered or powered from an improper source. Using external power while ignoring nav data validity risks the same issue of unreliable data guidance. Powering down avionics before start defeats the purpose of arming and using them. The sequence in this order aligns power availability with equipment readiness and data accuracy, which is essential for safe operation.