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Impulse coupling and Magneto during engine start

Asked by: 6703 views Aircraft Systems, Commercial Pilot, General Aviation, Private Pilot, Student Pilot

Impulse coupling is usually located on the left magneto and its job is to produce intense sparks during start of the engine.

So my question is, impulse coupling being on the left side of magneto, is the spark coming out from the left magneto and only one spark plug at each cylinder is getting fired or right magneto is also being rotated by crankshaft and producing sparks as well, thus firing two spark plugs at each cylinder?

 

Steve.

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1 Answers

  1. Best Answer


    Craig Johnston on Jul 27, 2016

    Most airplanes have an impulse coupling on the left mag only. During engine start, the ignition key grounds out the right mag, so only the left mag provides spark. The timing of the spark from the left mag is retarded (later than usual) during engine start so the engine will start easier. Once the ignition key is released from the start position, the timing of the spark is restored to normal, and the right mag starts firing.

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