Instrument Flying Handbook Practice Test

The key idea is that ILS readings can be corrupted by ground-based signal interactions, leading to real-world confusion on the approach path. Reflections from surface vehicles or other aircraft near the approach area can scatter the ILS signals, creating multipath reception that distorts the localizer or glideslope indications. A second common issue is a false glide-slope reading, where the glide-slope system itself produces an apparently higher glidepath due to reflections or coupling within the glide-slope antenna setup. This can mislead you about how steeply you’re descending. Weather or altimeter/heading indicator problems aren’t typical ILS-reading errors and wouldn’t be described as common ILS errors, though adverse conditions can degrade signal quality. In practice, always cross-check ILS indications with other instruments and be prepared to discontinue the approach if readings don’t align with the expected path.