When can you descend below the glideslope when landing on a runway served by a VASI?

The correct answer indicates that you can descend below the glideslope when a lower altitude is necessary for a safe landing. This is consistent with the principles of flying and landing safely. In situations where the aircraft may be too high on the approach, it is essential for pilots to exercise discretion to ensure a safe landing. If you find yourself in a position where descending below the prescribed glideslope is necessary to achieve a safe touchdown on the runway, then that action becomes justified.

In practical operations, pilots must evaluate individual circumstances on approach, including the aircraft's altitude, speed, and the prevailing conditions at the time of landing. The goal is always to ensure the aircraft can land safely and effectively, which may sometimes necessitate a descent below nominal guidance.

The other options do not align with standard safety practices. Descending below minimums compromises safety, as does the idea of only starting the descent once the runway is visible. The final choice, suggesting you can descend at all times during landing, undermines the structured flight paths and safety protocols designed to maintain order and safety in aviation. Understanding when and how to adjust your approach is critical for any pilot's training and operational effectiveness.