12 / 20

In a piston engine, if the ground wire between one of the magnetos and the ignition switch becomes disconnected, the most noticeable result will be that the engine…

  • A
    cannot be started with the switch in the ON position.
  • B
    will run but maximum power will be unobtainable.
  • C
    cannot be shut down by turning the switch to the OFF position.
  • D
    will run but the faulty magneto will be earthed out.

A magneto is a self-contained, engine-driven electrical generator designed to supply a high voltage to the sparking plugs. This is achieved in a timely sequence for a precise compression stroke.

Each magneto is controlled by its own ignition switch. The switch isolates the magneto’s ignition circuit by connecting the circuit to Earth. In order to completely switch off the ignition system, the primary circuit needs to be grounded. In this condition, it is said to be ‘grounded’. However, if the grounding wire is broken, the magneto will keep working normally and the engine will continue running. Another situation where the engine can keep running is when excessive carbon deposit has formed in the cylinder head. Because the deposit is still hot enough when you arrive at your parking position after the flight in order to ignite the charge without the spark from the plugs. The effects will be a hardly rumbling engine that is still running.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • United Kingdom