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SESK: Stuff Everyone Should Know · sesk.info/pilot-magneto-ground-check-at-stop

When stopping the engine, why do pilots briefly switch the magnetos OFF at idle first?

To check the magnetos are properly grounded.

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  1. To cool the cylinders
  2. To check the magnetos are properly grounded ✔
  3. To drain the fuel lines

Why: A faulty magneto switch can read OFF while the magneto is still live, so the engine could start if someone moves the propeller. The AFH engine stop list includes a quick ground check at idle, then mixture to idle cutoff.

Huh, didn't know that: The AFH says a flight is not complete until the engine is stopped and the airplane is secured.

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My magneto failed its ground check. It was just too up in the air.
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References

Answer: To check the magnetos are properly grounded. A faulty magneto switch can read OFF while the magneto is still live, so the engine could start if someone moves the propeller. The AFH engine stop list includes a quick ground check at idle, then mixture to idle cutoff.

  1. Airplane Flying Handbook FAA-H-8083-3C, Chapter 2 www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/airplane_handbook/03_afh_ch2.pdf
    momentarily check for proper grounding in the OFF position at idle rpm.
    Checked 2026-10-09.

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