How many degrees of coverage extends valid localizer signal on a backcourse at 13NM from the transmitter?

In the context of Instrument Approach Procedures, the localizer serves as a guiding signal for aircraft during an ILS (Instrument Landing System) approach. When considering the backcourse coverage of a localizer at a distance of 13 nautical miles (NM) from the transmitter, it is important to understand the signal's characteristics.

The valid localizer signal on a backcourse typically extends to approximately 10 degrees from the centerline. This 10-degree coverage allows for sufficient lateral guidance for aircraft that are using the localizer in the backcourse mode, distinguishing it from the regular front course operation.

The reason for this 10-degree coverage is that it provides adequate precision for navigation while minimizing the risk of interference and ensuring that the aircraft remains aligned with the desired backcourse approach path. This information is critical for pilots to effectively utilize the localizer signal, especially during approaches and landings under instrument flight rules (IFR).

In this case, opting for 10 degrees accurately reflects the operational standards established for localizer backcourse coverage, making it the valid choice.