The most significant effect of snow or ice on the wing surface is its influence on the smooth flow of air over the surface contour. Both the maximum lift which can be developed and the angle of attack at which it will be developed will be reduced significantly. Stall buffet and stall will be encountered at higher than normal airspeeds. Lift and Drag Effects of Wing Contamination Ice contamination of an aircraft wing also has a significant detrimental effect on the aircraft's total drag, that is, the force which resists the aircraft's forward motion through the air. The total drag has two components, parasite drag and induced drag.
Induced drag is that drag which is produced by the generation of lift.
Induced drag increases as the angle of attack increases. Therefore, since a contaminated wing must fly at a higher angle of attack at a given airspeed to produce the required lift, the induced drag generated at that airspeed will be higher than the induced drag of an uncontaminated wing. Furthermore, since ice contamination causes the airflow to separate earlier from the upper surface of the wing, it results in a higher induced drag value at any angle of attack. The increase in parasite drag as a result of ice contamination is small in comparison to the increase in induced drag. On a wing contaminated by surface roughness, the normal stall progression of a swept wing is altered.