What is a likely cause of a gradual decrease in power during flight?

A gradual decrease in power during flight is often attributed to carburetor ice build-up. Carburetor icing can occur under certain atmospheric conditions, typically when there is high humidity and temperatures are low or near freezing. As the engine draws in air, the reduction in temperature caused by the vaporization of fuel and the expansion of air can lead to ice formation on the carburetor. This ice restricts airflow to the engine, resulting in a loss of power over time.

It is important to monitor engine performance and recognize the signs of carburetor icing, as it can affect engine efficiency and safety in flight. While fuel starvation can lead to power loss, it usually results in a more abrupt performance drop rather than a gradual decrease. Electrical failure typically causes other critical issues before affecting engine power output, and excessive weight might lead to different performance characteristics, such as reduced climb rate, rather than a gradual decrease in power itself.