What is typically a key characteristic of Type IV anti-icing fluid?

Type IV anti-icing fluid is characterized by its higher viscosity compared to Type I fluid. This increased viscosity allows Type IV fluids to provide a longer-lasting protective layer against ice and snow accumulation on aircraft surfaces. Unlike Type I fluids, which are primarily designed for rapid de-icing and effective at melting snow and ice quickly, Type IV fluids are formulated to remain on the aircraft longer, helping to prevent ice from forming during flight. The higher viscosity is crucial as it helps the fluid adhere better to the aircraft surface, enhancing its effectiveness during prolonged ground operations in adverse weather conditions.

The other options do not accurately reflect the unique characteristics of Type IV fluid; for instance, while it is beneficial for all altitudes, it is not specifically effective only at high altitudes. Additionally, Type IV is not primarily designed for quick de-icing like Type I, and while safety in application is essential, being non-heated is not a defining feature of Type IV fluids.