What common error might occur during the engine starting sequence?

Advancing the Power Control Lever (PCL) past the start ready position during the engine starting sequence can lead to an improper or unsafe start. The start ready position is specifically designed to ensure that the engine start sequence initiates correctly and safely. If the PCL is advanced too far before the engine is adequately prepared for start, it may cause adverse effects like flooding the engine with too much fuel or even potentially damaging engine components.

While the other options may also pose risks, they typically involve safety or procedural oversights rather than directly influencing the engine's start sequence. For example, not checking fuel levels could lead to insufficient fuel for flight, but it does not interfere with the starting process itself. Forgetting to install safety pins can create a hazardous situation on the ground, and leaving the canopy open might impair visibility or allow unwanted airflow during taxi or takeoff, but these do not directly impact how the engine is started. Therefore, advancing the PCL improperly during start is a critical error in the context of engine starting.