What is an indication of excessive turbine temperature?

Visual smoke indications are a direct sign that could point to excessive turbine temperature. When the turbine operates at temperatures beyond its design limits, it can lead to incomplete combustion of fuel or physical damage within the engine. This incomplete combustion can result in the production of smoke, which can be observed visually. Such indications serve as a critical warning for pilots to take immediate action to prevent further damage to the engine.

In the context of the other options, low oil pressure typically signifies issues with lubrication, which could potentially lead to engine problems, but it does not directly indicate turbine temperature. High fuel flow may not correlate directly with turbine temperature either, as increased fuel flow could result from various operational conditions and is not a reliable sign of overheating. Sudden engine noise might suggest mechanical failure or other issues but doesn't specifically point to excessive turbine temperature. Thus, visual smoke indications are the most indicative of potential further complications related to turbine temperature.