Earth radical on the left - when something 塌s, it is earth or earthwork that gives way: a wall caving in, a roof falling, ground sinking. The radical anchors 塌 in the soil/structure family alongside 坍 (collapse), 堵 (block), 坑 (pit), 城 (city wall).
Top of the right side - 日 sits above 羽, together forming a phonetic compound (tà). Here 日 is just the upper graphic of that compound; it does not contribute meaning on its own. Walking the nested IDS exposes both pieces so each can be looked up.
Bottom of the right side. Together with 日 above it forms the phonetic compound that gave 塌 its tā reading (via Old Chinese tap-final). Visually two compressed feather shapes. Pure phonetic role; 'feathers' contributes nothing semantic to 'collapse.'
