Which statement best contrasts WAAS and GBAS in terms of ILS performance?

• A. WAAS enables Cat I ILS; GBAS enables Cat II and III ILS
• B. WAAS enables Cat II/III; GBAS enables Cat I
• C. WAAS and GBAS both enable Cat I
• D. GBAS enables Cat II and III; WAAS enables Cat II/III

Answer: (A)

WAAS and GBAS are different augmentation systems that change what kind of precision approach you can fly. WAAS enhances GPS to provide very reliable lateral and vertical guidance, which yields LPV/VNAV-type approaches that are compatible with ILS Cat I minimums. It does not generally provide the tighter minima required for Cat II or Cat III.

GBAS, being a localized ground-based augmentation, can deliver higher-precision guidance tailored to a specific airport and runway. With the appropriate equipment and operations, GBAS can support the tighter minima associated with ILS Cat II and Cat III, offering lower decision heights and better approach integrity in suitable conditions.

So the statement that WAAS corresponds to Cat I and GBAS corresponds to Cat II/III best captures the relative performance capabilities being contrasted. The other options either overstate WAAS’s capability (Cat II/III) or misstate GBAS’s typical role.