What is the primary function of the starter motor in the Cessna 172?

The primary function of the starter motor in the Cessna 172 is to crank the engine for starting. When the aircraft's ignition system is activated, the starter motor engages with the engine's flywheel and rotates the engine. This action initiates the engine's cycle of combustion, which is essential for the engine to start running. Once the engine starts, the starter motor disengages and it is no longer needed for operation.

While the cabin temperature control, avionics power supply, and fuel pump operation are all important systems in an aircraft, they do not fall under the primary function of the starter motor. Each of these functions is managed by separate components within the aircraft's systems, highlighting the specific role that the starter motor plays solely in the engine starting process.