If ground speed decreases, what must happen to the rate of descent to stay on the ILS glide slope?

When an aircraft's ground speed decreases while on an ILS glide slope, a corresponding adjustment to the rate of descent is necessary to maintain the correct path toward the runway. The glide slope provides a visual cue that indicates the proper angle of descent for landing.

As ground speed is defined as the rate at which the aircraft moves over the ground, a decrease in this speed means the aircraft takes longer to reach the runway. To compensate for this slower approach, the rate of descent needs to be decreased. By reducing the rate of descent, the aircraft can stay on the glide slope while aligning properly with the runway. This adjustment ensures that the aircraft does not descend too quickly, which could result in a missed glide slope and lead to a potentially dangerous situation.

Just like maintaining speed during a descent to ensure a safe landing, adjusting the rate of descent with respect to ground speed is crucial for accurately following the ILS glide slope.