Are GPS Overlays permissible during LOC(BC) approaches?

During a Localizer Back Course (LOC(BC)) approach, the primary navigation source is the localizer signal. This approach type is specifically designed to be flown with the localizer guidance, and the use of GPS overlays is not permitted due to regulatory and safety reasons. The main concern is the potential for confusion or mismanagement of navigation inputs when a pilot uses GPS in conjunction with the localizer signal, which could lead to deviations and ultimately compromise safety.

Regulations provide a clear structure for instrument approaches to ensure consistency and safety during flight operations. Since the LOC(BC) approach relies exclusively on the localizer, the introduction of a GPS overlay would conflict with the established procedures that are designed for this type of approach. Such overlays can lead to misinterpretation of data, especially when the pilot is transitioning from one navigational method to another.

Thus, the prohibition against GPS overlays during LOC(BC) approaches is firmly rooted in maintaining the integrity of the instrument approach and ensuring pilots adhere strictly to the designated navigation aids. This helps prevent navigational errors that could arise from mixed-use of systems during critical phases of flight.