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SESK: Stuff Everyone Should Know · sesk.info/pilot-battery-alternator-jobs

In a typical small airplane, what normally powers the electrical system once the engine is running?

The engine-driven alternator or generator.

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  1. The magnetos
  2. The alternator or generator ✔
  3. The pitot tube

Why: The battery provides power for engine starting and limited backup power. Once the engine runs, the alternator or generator supplies the electrical system and recharges the battery.

Huh, didn't know that: An alternator can usually produce useful current at lower engine speeds than a generator.

The dad joke
The alternator worked hard because it wanted to stay current.
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References

Answer: The alternator or generator. The battery provides power for engine starting and limited backup power. Once the engine runs, the alternator or generator supplies the electrical system and recharges the battery.

  1. FAA Pilot's Handbook of Aeronautical Knowledge, Chapter 7 www.faa.gov/sites/faa.gov/files/09_phak_ch7.pdf
    Engine-driven alternators or generators supply electric current to the electrical system.
    Checked 2026-10-09.

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