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Are magnetos on the same electrical system as the battery?

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Aircraft Systems

Do mags ground to the same source as the battery and other electric consumers?  If my battery explodes or I take a lightning strike that fries my electrical system, would my magnetos be affected?  If the positive terminal on the battery somehow contacts the airframe (ground), could it fry my mags as well since everything is connected via ground?

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1 Answers



  1. John D Collins on Sep 09, 2015

    The magneto’s and the ignition system for your engine are not connected to the battery. They are independent. Most aircraft have dual magnetos and each cylinder has two spark plugs, one attached to each magneto for redundancy. The magnetos derive the spark energy from permanent magnets that induce a current in the magneto coil windings. The voltage is stepped up in the magneto to a sufficiently high voltage to generate the spark and a distributor switches the high voltage to the spark plug wires.

    For metal aircraft, the current from a lightning remains on the surface metal skin of the aircraft and often won’t affect the electrical system directly. It may burn a hole where the aircraft is struck and where the bolt exits the aircraft. An exploding battery would be a bad problem as it would be a fire hazard. In either of these scenarios, the engine is likely to remain running, but you may have bigger issues with the airframe integrity. If you were hit by lightning, you are probably in or near a thunderstorm, which is no place to be in the first place.

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