Which of the following can cause fan blade shingling in a turbofan engine?

Fan blade shingling in a turbofan engine refers to the phenomenon where the fan blades become misaligned or deflected due to aerodynamic forces, leading to increased wear and potential failure. One of the primary causes of this condition is the interaction between engine overspeed and large, rapid throttle movements.

When an engine overspeeds, it significantly exceeds its designed rotational speed, causing abnormal forces on various components, including the fan blades. Rapid throttle movements can exacerbate this condition by causing sudden changes in airflow and pressure across the blades, which can lead to increased vibrations and mechanical stress. This dynamic response can cause the blades to flex and misalign, resulting in shingling.

Understanding the mechanical dynamics of the engine and how rapid changes in power settings affect blade integrity is crucial for maintenance and operational procedures. This knowledge helps in diagnosing potential issues before they escalate into serious failures. Hence, the correct answer identifies the specific operating conditions that directly influence the integrity of the fan blades.