What does the starter/generator do until the engine starts?

The starter/generator in the T‑6B plays a crucial role during the engine start sequence, primarily by turning the compressor until the engine reaches self-sustaining speeds. This is vital because the compressor is responsible for drawing in air and compressing it, which is essential for the combustion process to occur.

When the engine is not yet running, the starter/generator engages with the aircraft's electrical system and mechanically operates the compressor. This action ensures that sufficient airflow is provided to facilitate fuel atomization and ignition once the fuel is introduced into the combustion chamber.

While the starter/generator may also be involved in powering other systems after the engine starts, its primary initial function is to ensure the compressor is spinning. This incorporation of airflow is necessary for the successful initiation of the combustion process, leading to engine start and ongoing operation.