Can GPS Overlays be utilized during an ILS approach?

The use of GPS overlays during an ILS (Instrument Landing System) approach is restricted due to specific design criteria established to ensure safety. When an ILS approach is being conducted, it relies on precise ground-based navigation signals. GPS overlays, while they provide beneficial navigation capabilities, are not intended to serve as a primary navigation source for the precision required during an ILS approach.

The ILS system has specific integrity and accuracy requirements that ground-based navigation aids fulfill during critical phases of landing. If a GPS overlay were to be used, it could potentially introduce inconsistencies in the approach path and decision-making process, particularly because GPS signals are susceptible to various factors such as satellite geometry and possible signal disruption.

This is why an ILS approach has stringent criteria, and the use of GPS overlays is not deemed appropriate in this context. Alternative navigational aids must be relied upon to maintain the highest levels of safety during the approach where precise landing guidance is necessary.