What is one of the first indications of icing during engine operation?

One of the first indications of icing during engine operation is compressor surge or stall. Icing can lead to airflow disruptions within the engine's compressor section. When ice accumulates on the compressor blades, it alters the aerodynamic characteristics of the blades, potentially leading to a loss of airflow stability. This instability manifests as compressor stall or surge, which is characterized by irregular airflow that can result in a sudden drop in thrust and engine efficiency.

Understanding this behavior is crucial for monitoring engine performance, as surges or stalls are immediate indicators that something is adversely affecting airflow, including the potential for ice formation. Recognizing these symptoms allows for timely corrective actions to mitigate the risks associated with ice accumulation. This makes monitoring for compressor surge or stall an essential part of operating a gas turbine engine safely in potentially icing conditions.