Aircraft Critical Surface Contamination
Aircraft critical surface contamination refers to the presence of frost, ice, or snow on any critical aerodynamic surface of an aircraft that could adversely affect its performance during takeoff or flight. Critical surfaces include the wings, control surfaces, stabilizers, propeller blades, and engine inlets.
The Clean Aircraft Concept
Transport Canada and ICAO require adherence to the “clean aircraft concept” — no aircraft may take off when frost, ice, or snow is adhering to its wings, control surfaces, propellers, engine inlets, or other critical surfaces. Even a thin layer of frost on a wing can reduce lift by up to 30% and significantly increase stall speed.
Ground De-icing and Anti-icing
- De-icing: Removal of existing contamination using heated fluid (Type I or II)
- Anti-icing: Application of fluid (Type II, III, or IV) that prevents re-attachment for a defined holdover time
- Holdover time: Estimated duration anti-icing fluid remains effective under specific weather conditions — must not be exceeded before takeoff
On the TC Written Exam
The clean aircraft concept is a regulatory requirement, not just good practice. Know: frost on wings must be removed; even thin contamination can cause loss of control; holdover times are a planning tool, not a guarantee.