Type II fluids form a film that remains on the aircraft until speeds of how many knots are reached?

Type II fluids form a film that remains on the aircraft until speeds of how many knots are reached?

• A. 150 knots
• B. 50 knots
• C. 200 knots
• D. 100 knots

Answer: (D)

Type II de-icing fluid forms a thick, viscous film on aircraft surfaces to protect during taxi and the initial takeoff roll. That film is designed to stay in place until the airflow over the surfaces becomes strong enough to shear it off. In practice, the film remains until about 100 knots indicated airspeed; once you reach roughly that speed, aerodynamic shear removes most of the film, minimizing its effect on takeoff performance. The other speeds don’t match how Type II fluids behave—too slow, and the film would still be present; much faster, and the film would shear off earlier than expected.

Type II de-icing fluid forms a thick, viscous film on aircraft surfaces to protect during taxi and the initial takeoff roll. That film is designed to stay in place until the airflow over the surfaces becomes strong enough to shear it off. In practice, the film remains until about 100 knots indicated airspeed; once you reach roughly that speed, aerodynamic shear removes most of the film, minimizing its effect on takeoff performance. The other speeds don’t match how Type II fluids behave—too slow, and the film would still be present; much faster, and the film would shear off earlier than expected.