What is the purpose of the two-step deicing procedure?

The two-step deicing procedure is specifically designed to ensure that an aircraft is both deiced and treated with anti-icing fluid before takeoff. The initial step of the procedure typically involves the removal of any existing ice, snow, or frost from the aircraft surfaces, which is crucial for maintaining aerodynamic performance. Following this, the application of anti-icing fluid serves to prevent the formation of ice or snow accumulation during the aircraft's operation in cold weather conditions.

This comprehensive approach is essential for flight safety, as it addresses not only the removal of hazardous materials but also the prevention of their reformation during flight. Applying only deicing fluid would not provide ongoing protection from ice accumulation, which is why it is vital to combine the two processes effectively.