SESK: Stuff Everyone Should Know · sesk.info/pilot-alternator-failure-radio-power
Why can an alternator failure eventually silence the aircraft radios?
The radios then depend on limited battery power.
- Magnetos stop instantly
- The vacuum pump powers them
- Battery backup is limited ✔
Why: Aircraft radios normally use the electrical system. After an alternator or generator failure, the battery provides only a limited supply, so conserve it according to the POH.
Huh, didn't know that: Turn off nonessential electrical equipment to conserve battery power.
Why did the battery ask for a break? It was drained.
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References
Answer: Battery backup is limited. Aircraft radios normally use the electrical system. After an alternator or generator failure, the battery provides only a limited supply, so conserve it according to the POH.
- FAA Pilot's Handbook of Aeronautical Knowledge, Chapter 7 www.faa.gov/sites/faa.gov/files/09_phak_ch7.pdf
a limited supply of electrical power for use in the event the alternator or generator fails
Checked 2026-10-09.
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