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In which of these cloud types can icing be virtually ruled out?
  • A
  • B
  • C
  • D
We know that one of the requirements for the ice to form on aircraft structure is the presence of water in liquid state. Cirriform clouds such as Cirrus (CI) or Cirro-Stratus (CS) are high-level clouds with bases between 16 500 ft - 45 000 ft => well above the freezing levels and therefore they only contain ice crystals => no water in liquid state is present => no icing possibility.

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