In large passenger aircraft, fuel management is automated, but in small trainer aircraft, pilots must manually configure the fuel selector valve (FSV). Forgetting to open the FSV during pre-flight checks is a critical human-factor risk that can lead to engine failure after takeoff. Currently, small training aircraft lack a dedicated warning system for this specific oversight. This study presents a novel, non-invasive warning system to mitigate this hazard. The system uses a cockpit-mounted camera and an embedded NVIDIA Jetson Nano to run a YOLOv5-based computer vision model that detects the FSV’s position in real-time. If a hazardous state (CLOSED or FAULTY) is identified, the pilot receives simultaneous audible and vibrotactile alerts. When tested on Cessna 172 and Viper SD4 aircraft, the system demonstrated high operational reliability. A frame-by-frame analysis of real-time demonstrations showed an overall accuracy of 90.9%. Most importantly, for the safety–critical CLOSED position, the system achieved perfect precision (100%) and a recall of 96.9%. This study provides a practical and cost-effective solution to a persistent safety gap in general aviation.