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Consult the appropriate Manufacturers Maintenance Publication

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Warning

In the above figure, all switches and relays are in the normal "OFF" position. These diagrams illustrate the electrical operations of the magneto circuits . 

They are not to be used for installation purposes.

 

Typical Ignition System with Starting Vibrator

 

With the combination ignition and starter switch in its "START" position, the right magneto is grounded. Starter soleniod L1 is energized, closing its relay contact R1. Battery current flows through the vibrator points V1, coil L2, (and L3 in 24 volt models), through the switch and the main and retard breakers of the left magneto to ground. A magnetic field built up around coil L2 causes vibrator points V1 to open. Current ceases in the circuit , causing the magnetic field to collapse and vibrator points to re-close. Current flow resumes and re-energizes coil L2. Vibrator points V1 open again.

 

When the engine reaches its normal advance firing position, the main contact assembly opens. However, the vibrator current is still carried to ground through the retard contact assembly which does not open until the starting retard position of the engine is reached. On all systems, when the retard contact assembly opens (main contact assembly is still open), the vibrator current flows through the primary of transformer T1, producing a magnetic field around the coil. As the vibrator points V1 open, current flow through the primary of transformer T1 ceases. This causes a high voltage to be introduced in the secondary which fires the spark plug. A shower of sparks is produced at the spark plug due to this opening and closing of the vibrator points V1 while the main and retard contact assemblies are open.

 

When the engine fires and begins to increase speed, the ignition and starter switch is realesed and automatically returns to the "BOTH" position. This opens the vibrator and the starter circuits, rendering them inoperative. The right magneto is no longer grounded and both magnetos are firing simultaneously in full advance.

Test, Repair, Inspect and Overhaul Bendix and Slick aircraft magnetos