When should the winterization kit be installed on the aircraft?

The winterization kit should be installed on the aircraft when temperatures are below 7 degrees Celsius. This is because colder temperatures can lead to engine performance issues, fuel system problems, and other operational challenges that can arise in winter conditions. Installing the winterization kit helps minimize the risk of icing in the fuel system and ensures that the aircraft operates effectively, maintaining the necessary combustion efficiency and preventing potential engine hazards.

The other options suggest scenarios that would not warrant the installation of the winterization kit. Installing it during summer months or when temperatures are above 10 degrees Celsius does not align with the requirement for enhanced precautions against winter-specific issues. Similarly, limiting the installation to only long flights disregards the fact that temperature concerns may arise during shorter flights as well in cold conditions. Therefore, the guideline of installing the kit below 7 degrees Celsius stands to ensure safe operation during winter.