If RVR is not acceptable due to a difference of more than 400 feet, which statement is true?

• A. The RVR data is not acceptable
• B. The RVR data is critical for planning
• C. ATC can still rely on RVR data
• D. Pilots must ignore RVR

Answer: (A)

When the RVR readings differ by more than 400 feet, the data are considered unreliable for use in planning and operations. That means the RVR data is not acceptable and should not be used to determine approach or landing decisions. In this situation, ATC should not rely on the RVR readings for instructions tied to visibility, and pilots should reference other sources of visibility information (such as prevailing visibility from METARs, cloud ceilings, and pilot reports) for判断. The choice that claims the RVR data is not acceptable best captures the idea that reliability has been breached; the others imply the data remains valid or that pilots should ignore it, which isn’t correct when a reliability threshold has been exceeded.