What does positive windshear typically cause?

Positive windshear refers to the change in wind speed or direction, which can affect aircraft performance during takeoff or landing. Specifically, positive windshear occurs when there's an increase in headwind or a decrease in tailwind, generally leading to an updraft in the atmosphere. This updraft can be beneficial, especially during approach and landing, as it may help lift the aircraft.

In scenarios with positive windshear, pilots may experience an increase in lift due to the favorable wind conditions, allowing for a smoother landing or ascent. Understanding how windshear affects flight is critical for pilots, as it can significantly influence the behavior of the aircraft in flight. This is particularly relevant in certain weather conditions, such as near thunderstorms or mountainous terrain, where wind patterns can change rapidly.

In contrast, the other outcomes listed generally relate to adverse effects of windshear. Increased tailwinds or decreased headwinds would create challenges for maintaining controlled flight, while downdrafts can pose serious risks during critical phases of flight. Therefore, the updraft created by positive windshear is the key phenomenon here that aids in lift and overall flight safety.