What could cause a pilot to have to actively manage glide path during an ILS approach?

During an ILS (Instrument Landing System) approach, a pilot may need to actively manage the glide path when there are variable or changing wind conditions that could affect the aircraft's descent profile. In the case of the correct answer, a parallel wind that increases in speed at altitude can cause variations in the aircraft's vertical speed.

When there is an increase in parallel wind speed, it can exert additional lift or drag on the aircraft, which can alter its descent path. If the wind is pushing the aircraft along its glide slope in a way that causes it to gain altitude or descent rate incorrectly, the pilot must actively manage the glide path by adjusting the aircraft's configuration or power settings to maintain the correct approach profile. This management ensures that the aircraft stays on the glide slope, leading to a safe landing.

Other options indicate different wind conditions, such as a steady headwind or a constant tailwind, which typically do not require active glide path management since they produce predictable influences on the aircraft's vertical descent. An increasing crosswind from the right would primarily affect the lateral control rather than the vertical glide path, allowing the pilot to adjust for lateral drift rather than descent rate.