Why is ethylene glycol deicing fluid diluted with water in non-precipitation conditions?

Diluting ethylene glycol deicing fluid with water serves to decrease the freeze point of the mixture. This is crucial in non-precipitation conditions because, without precipitation, ice or frost can still form on surfaces, particularly at lower temperatures. By diluting the fluid, the effective freezing point is lowered, allowing the deicing fluid to remain in a liquid state at temperatures that would otherwise cause it to solidify.

This property is particularly useful for maintaining effective deicing operations, as it helps to ensure that the fluid can flow easily over surfaces, breaking down any ice or frost that may have formed. In practical terms, a lower freeze point enhances safety and operational efficiency, as the aircraft can be deiced more effectively even during cold, dry conditions.