Which statement about Localizer-type directional aids (LDAs) is true?

• A. It is not a part of a complete ILS and is not aligned with the runway; Some LDAs are equipped with a glideslope.
• B. It must be aligned with the runway centerline for precision alignment.
• C. It provides vertical guidance only for approach.
• D. Some LDAs are identical to Localizers in all respects.

Answer: (D)

Localizer-Type Directional Aids provide lateral guidance like a localizer, but they are not part of a complete ILS and they can be offset from the runway centerline. That offset is often driven by terrain or obstacles that prevent a perfectly straight path over the runway. Some LDAs do include a glide slope to provide vertical guidance, but even with that, the facility is not an ILS; it’s still an LDA-based approach. So the true statement is that an LDA is not part of a complete ILS and is not aligned with the runway, and some LDAs are equipped with a glideslope. The other ideas don’t fit: LDAs don’t have to be aligned with the runway, they primarily give lateral guidance (vertical guidance only comes if a glide slope is present, which is not always the case), and LDAs are not identical to Localizers in all respects because they may be offset and are not part of a full ILS.