diff --git a/viewer/index.html b/viewer/index.html
index db41fe7..2242c3b 100644
--- a/viewer/index.html
+++ b/viewer/index.html
@@ -1228,9 +1228,9 @@ async function loadSortieData(sortieId) {
     const usvResp = await fetch(`${API2}/sorties/${encodeURIComponent(sortieId)}/usv`);
     if (usvResp.ok) {
       const usvData = await usvResp.json();
-      renderUSV(usvData.signals);
+      switchTab('usv');  // BUG1d FIX: switch BEFORE renderUSV so Plotly renders on visible divs
       showNoDataOverlay(false);  // BUG2 FIX: hide overlay when data loaded
-      switchTab('usv');  // BUG1c FIX: auto-switch to USV tab where charts are rendered
+      renderUSV(usvData.signals);
     }
     prog.textContent = 'Chargement AUV…';
     await loadAuvTabs(sortieId);