When starting a MEP 12, what happens when the engine toggle switch is released to the run position?

When the engine toggle switch is released to the run position on a MEP 12, the engine accelerates to rated speed and the voltage regulator indicates field charging. This is the expected operation because releasing the toggle switch allows the engine to transition from the start mode to the operational mode. During this transition, the engine management system takes over, enabling the engine to reach optimal running speed.

At rated speed, the electrical output stabilizes, and the voltage regulator ensures that the output voltage is correctly maintained by managing the field current. This process is essential for the generator to function effectively, supplying power while preventing issues like overvoltage or under-voltage.

In contrast, the other options do not accurately reflect the expected behavior of the MEP 12 when the switch is set to run. For instance, if the engine were to shut down immediately, it would indicate a malfunction or a procedural error, which is not how the system is designed to operate under normal conditions. Similarly, the engine does not just accelerate to idle speed; it must reach rated speed to fulfill its purpose. Lastly, while a warning light might indicate issues in various scenarios, it is not a standard response upon simply releasing the toggle to the run position.