Which instrument approach provides lateral and vertical guidance with integrity limits similar to BARO VNAV?

• A. Global Landing System
• B. BARO VNAV
• C. Global Positioning System (GPS)
• D. Ground Proximity Warning System (GPWS)

Answer: (A)

The concept being tested is getting both lateral and vertical guidance on an instrument approach with integrity similar to BARO VNAV. Global Landing System fits this because it uses ground-based augmentation (GBAS) to provide precise corrections to GPS, giving a localizer-like path for horizontal guidance and a glideslope-like path for vertical guidance. The system is designed to meet high integrity requirements, so pilots can rely on both axes during the approach much like BARO VNAV does with barometric vertical guidance.

GPS by itself can provide lateral guidance and, with augmentation, some vertical guidance, but without the specific integrity standards of GLS it doesn’t match the precision-approach integrity described. GPWS is a warning system for terrain and does not provide instrument-path guidance. BARO VNAV provides vertical guidance based on altitude and does not supply the lateral guidance needed for a full precision-like approach.