One Operational Navigation Facility requires adding which increment to MDA or DA?

• A. Add 1/2 Statute Mile
• B. Add 400 ft to MDA or DA
• C. Add 200 ft to MDA or DA
• D. Add 1 Statute Mile

Answer: (B)

When an instrument approach uses only one operational navigation facility to define the final segment, a safety buffer is required to compensate for the reduced assurance of position and altitude information. The standard buffer is 400 feet added to the published MDA or DA. This extra altitude helps ensure obstacle clearance if that sole facility becomes unreliable or if cross-checks from a second facility aren’t available. So the correct practice is to add 400 feet to MDA or DA. The other options describe distances or a smaller altitude margin that aren’t the established safeguard in this scenario.