When is a pilot allowed to descend below the glide slope during an ILS approach?

A pilot is permitted to descend below the glide slope during an Instrument Landing System (ILS) approach when visual references are established. This means that once the pilot can clearly see the runway environment or specific visual cues that confirm a safe approach to landing, descent below the glide slope is allowable. It is critical for pilots to maintain situational awareness and ensure that they have adequate visual reference to continue safely, as this aligns with the regulations and practices for landing.

Descending before reaching the Decision Height (DH) without visual references could compromise safety because the pilot would be relying only on instrument readings rather than visual confirmations. ATC clearance is necessary for some operational changes, but visual references provide the required safety margin for proceeding with the descent. Therefore, the ability to descend below the glide slope hinges on having clear visual cues confirming it is safe to do so, ensuring a safe landing transition.