Final answer:
Frost disrupts the smooth flow of air over an aircraft's wing by causing a rough, uneven surface, which leads to turbulence and a subsequent loss of lift. The air needs to flow faster over the wing than under it to create lift, per Bernoulli's principle, which gets impeded if ice forms on the wing.
Step-by-step explanation:
Frost on an aircraft wing can disrupt the smooth flow of air, which is essential for maintaining the lifting force required for flight. When air flows over a wing, it splits - part of the air goes over the top and part goes beneath. According to Bernoulli's principle, the air moving over the top must move faster than the air below because it has a longer distance to travel. This creates lower pressure on top of the wing, which is a crucial component of the lift that supports the plane's weight. Frost changes the shape of the wing's surface, making it rough or uneven, which disrupts the airflow, can cause air to turbulence rather than smoothly follow the wing's surface, leading to a loss of lift.
In terms of specific speeds for lifting conditions, while the lift depends on speed, air density, and the wing's design, it can be calculated using the Lift formula, which involves the velocity of the air and the air density. For a cruising speed of 245 m/s at an altitude where the air density is one-fourth that of sea level, a precise calculation would require additional information about the wing's characteristics and the aircraft's weight. Therefore, without further data, we can only say that the air must move faster over the wing than below it to create lift, and frost would impede this by disrupting the airflow patterns over the wing.