Which part initiates the engine start process?

The initiation of the engine start process involves the Bendix gear, which is crucial in connecting the starter motor to the aircraft's engine. When the pilot engages the starter switch, the Bendix gear extends and engages with the flywheel or ring gear on the engine's crankshaft. This connection allows the starter motor to turn the engine, effectively cranking it and starting the combustion process.

The Bendix gear's role is to ensure that the starter motor can transfer its rotational power effectively to the engine, while also allowing for the disconnection once the engine is running. This prevents damage to the starter once the engine is operational. Performance factors related to fuel valves, crankshaft, or camshaft are essential in other phases of engine operation but do not initiate the engine start process itself. Thus, the Bendix gear is the correct answer as it is specifically responsible for kicking off the starting sequence of the engine.