Which fluids are preferred for anti-icing during winter operations?

The preferred fluids for anti-icing during winter operations are Type II and IV. These fluids are designed for use in colder temperatures and provide better performance during prolonged ground operations, as they are formulated to adhere to the aircraft's surfaces more effectively.

Type II and Type IV fluids are both glycol-based and have specific properties that enhance their ability to prevent ice formation and improve safety during takeoff. Type IV fluids, in particular, have a thicker viscosity, which allows them to remain on the aircraft longer, ensuring better protection in freezing conditions. They also possess a higher freeze point than Type I fluids, making them ideal for use in scenarios where extended hold-over times are necessary.

In contrast, Type I fluids are primarily designed for de-icing rather than anti-icing, which makes them less effective when it comes to preventing ice accumulation during prolonged ground delays. Type A and B fluids are generic designations that do not specifically refer to known types in the context of anti-icing and de-icing, further supporting the choice of Type II and IV as the optimal options for these operations.