Standby power for essential flight instruments is typically supplied by what combination?

• A. Standby battery or dedicated generator
• B. Standby battery only
• C. Dedicated generator only
• D. External power unit

Answer: (C)

Standby power for essential flight instruments is provided by a dedicated generator that feeds a separate standby electrical bus. This setup keeps the critical instruments powered independently of the main electrical system, so even if the main generators and buses fail, the instruments like attitude, altitude, and airspeed remain operable. A dedicated standby generator is designed to start automatically and supply the correct voltage and frequency for the standby bus, ensuring reliability over flight durations. Using a standby battery alone would rely on its limited capacity and duration, which may not meet the required flight-time endurance for all scenarios. An external power unit is intended for ground operations, not for in-flight standby power.