If you arrive at Riverside Municipal after the tower is closed and ATIS is unavailable, how much should you raise the S-ILS 9 approach Decision Altitude (DA)?

When approaching Riverside Municipal after the tower is closed and ATIS (Automatic Terminal Information Service) is unavailable, pilots must adjust their Decision Altitude (DA) for an ILS (Instrument Landing System) approach based on specific conditions.

In this scenario, raising the S-ILS 9 approach Decision Altitude by 46 feet reflects the necessity to account for the absence of ATIS, which would typically provide updated weather information such as ceiling and visibility. The standard adjustment in such cases is to increase the DA to ensure safety when executing the approach.

This increase ensures that you maintain appropriate obstacle clearance and safely navigate to the runway in conditions where vital information may not be accessible. It is crucial to adjust the DA accordingly to account for potential lower visibility or higher terrain, which may not be fully taken into consideration without the necessary updates from ATIS.