Plain English Meaning

S-LDA is the line on the approach chart that tells you the lowest you can come down on an LDA approach when the approach lines you up well enough with the runway to land straight ahead.

Full Definition

S-LDA is the straight-in landing minimums line published on an LDA (Localizer-Type Directional Aid) instrument approach chart. It gives the lowest altitude (DA or MDA) and visibility a pilot may use when flying the LDA approach to a runway whose final approach course is closely aligned with the LDA course, allowing a normal landing without circling. If the LDA course is not aligned closely enough with the runway, only circling minimums are published instead.