localizer-type directional aid
localizer-type directional aid (LDA)
A NAVAID (navigational aid) used for non-precision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS (instrument landing system) and is not aligned with the runway. The LDA course usually provides a more precise approach course than the similar simplified directional facility (SDF) installation, which may have a course width of 6° or 12°. The LDA is not aligned with the runway. Straight-in minimums may be published where the alignment does not exceed 30° between the course and runway. Where this alignment exceeds 30°, only circling minimums are published.