In a turbine engine with a starter-generator, placing the start switch in START position causes which of the following actions?

• A. Current flows into the starter relay which closes and actuates the ignition exciter.
• B. The generator immediately supplies power to the aircraft bus.
• C. The ignition system is automatically shut down.
• D. The starter motor disengages from the engine.

Answer: (A)

When you set the start switch to START, current is sent to the starter relay. Energizing the relay coil pulls in the contacts, which closes the high-current path to the starter motor so it begins turning the engine. At the same time, the ignition exciter is energized, preparing the ignition system to produce sparks when the engine reaches light-off speed. In this setup, the starter-generator acts as a motor to start the engine, and the ignition system is enabled for ignition during start. The other options don’t fit because the generator isn’t supplying the aircraft bus during start, ignition isn’t shut down, and the starter isn’t disengaged at this moment.