What are the two primary sources of power for most flight instruments and electrical systems on modern airplanes, and what happens if one fails?

What are the two primary sources of power for most flight instruments and electrical systems on modern airplanes, and what happens if one fails?

• A. The airplane's battery and alternator/generator; if the alternator fails, the system runs on the battery for a limited time.
• B. The airplane's hydraulic system and battery; if hydraulic fails, instruments fail.
• C. Solar panels and generator; if solar fails, instruments fail.
• D. The airplane's generator alone; if it fails, instruments fail immediately.

Answer: (A)

Power for most flight instruments and electrical systems comes from two sources: the engine-driven generator (alternator) and the aircraft battery. The generator supplies continuous power in flight, while the battery provides starting power and serves as a backup when the generator isn’t delivering power. If the generator fails, the electrical system can run on the battery for a finite period, depending on how much load is kept on the system. During that time, pilots are expected to conserve power by turning off nonessential equipment and rely on the essential instruments until a safe landing can be made.

Power for most flight instruments and electrical systems comes from two sources: the engine-driven generator (alternator) and the aircraft battery. The generator supplies continuous power in flight, while the battery provides starting power and serves as a backup when the generator isn’t delivering power. If the generator fails, the electrical system can run on the battery for a finite period, depending on how much load is kept on the system. During that time, pilots are expected to conserve power by turning off nonessential equipment and rely on the essential instruments until a safe landing can be made.