What causes abnormal vibrations in a turbine engine?

Abnormal vibrations in a turbine engine are typically indicative of potential mechanical failures. Such vibrations can arise from a variety of issues including imbalances in rotors, misalignments, bearing failures, or even structural defects within the engine components. When the engine is operating outside of its normal parameters due to these mechanical issues, it can result in vibrations that deviate from the expected operational signature.

In contrast, normal operational conditions would not lead to abnormal vibrations, as engines are designed to operate smoothly when functioning correctly. An improper fuel-air mixture can cause performance issues but typically does not lead to mechanical vibrations. Excessive thrust can also affect engine performance characteristics but is less likely to be the direct cause of mechanical vibrations than the underlying issues signified by potential mechanical failures. Thus, identifying the source of abnormal vibrations often points directly to mechanical problems within the engine.