diff --git a/src/main/decode.test.ts b/src/main/decode.test.ts
index a3ab53b..11f5064 100644
--- a/src/main/decode.test.ts
+++ b/src/main/decode.test.ts
@@ -41,6 +41,6 @@ describe('Decoder aircraft tracking', () => {
 describe('Decoder telemetry', () => {
   it('exposes the five readouts', () => {
     const ids = new Decoder().telemetrySnapshot().map((r) => r.id)
-    expect(ids).toEqual(['RPM', 'D_IAS_DEG', 'D_FLAPS_IND', 'D_ALT_NEEDLE', 'D_FUEL'])
+    expect(ids).toEqual(['RPM', 'D_IAS_DEG', 'D_FLAPS_IND', 'ALT_FT', 'D_FUEL'])
   })
 })
diff --git a/src/main/decode.ts b/src/main/decode.ts
index 9f928ca..df86063 100644
--- a/src/main/decode.ts
+++ b/src/main/decode.ts
@@ -11,13 +11,46 @@ interface TelemetrySpec {
   unit: string
 }
 
-// DCS-BIOS gauge outputs are 0..max needle positions, not engineering units, so
-// readouts are reported as percent of full scale (honest, no fake knots/feet).
+// Three altimeter drum addresses encode digit positions 0–9.999 as 0–65535.
+// ALT_FT is a virtual telemetry id computed from them; it has no DCS-BIOS address.
+const ALT_DRUM_IDS = new Set(['D_ALT_10K', 'D_ALT_1K', 'D_ALT_100S'])
+const ALT_FT_MAX = 50_000
+
+// Piecewise-linear IAS calibration: [raw, knots] pairs derived from A-4E gauge face.
+// The pitot-static scale is nonlinear (angle ∝ v²); raw=0 is init/parked (0 kt).
+// Tunable — fly at known speeds and update the table as needed.
+const IAS_KT_LUT: [number, number][] = [
+  [0, 0],
+  [5461, 80],
+  [10923, 120],
+  [16384, 150],
+  [24576, 200],
+  [32768, 300],
+  [40960, 400],
+  [46432, 500],
+  [49152, 600]
+]
+const IAS_MAX_KT = 600
+
+function iasRawToKnots(raw: number): number {
+  const lut = IAS_KT_LUT
+  if (raw <= lut[0][0]) return lut[0][1]
+  if (raw >= lut[lut.length - 1][0]) return lut[lut.length - 1][1]
+  for (let i = 1; i < lut.length; i++) {
+    if (raw <= lut[i][0]) {
+      const [r0, k0] = lut[i - 1]
+      const [r1, k1] = lut[i]
+      return k0 + ((raw - r0) / (r1 - r0)) * (k1 - k0)
+    }
+  }
+  return NaN
+}
+
 const TELEMETRY: TelemetrySpec[] = [
   { id: 'RPM', label: 'RPM', unit: '% RPM' },
-  { id: 'D_IAS_DEG', label: 'IAS', unit: '% FS' },
+  { id: 'D_IAS_DEG', label: 'IAS', unit: 'kt' },
   { id: 'D_FLAPS_IND', label: 'Flap', unit: '% DN' },
-  { id: 'D_ALT_NEEDLE', label: 'Press Alt', unit: '% FS' },
+  { id: 'ALT_FT', label: 'Press Alt', unit: 'ft' },
   { id: 'D_FUEL', label: 'Fuel', unit: '% QTY' }
 ]
 
@@ -35,12 +68,15 @@ export class Decoder {
   private readonly name = new StringRegion(ACFT_NAME_ADDRESS, ACFT_NAME_MAX)
   private readonly telemetry = new Map<string, number>() // id -> latest value
   private readonly telemetryMax = new Map<string, number>()
+  private readonly altDrums = new Map<string, number>() // D_ALT_10K/1K/100S raw values
   private lastName = ''
   private sawA4ecAddress = false
   private aircraftDirty = true
 
   constructor() {
-    for (const t of TELEMETRY) this.telemetry.set(t.id, NaN)
+    for (const t of TELEMETRY) {
+      if (t.id !== 'ALT_FT') this.telemetry.set(t.id, NaN)
+    }
   }
 
   /** Apply one write; returns the decoded log rows it produced (may be empty). */
@@ -70,6 +106,9 @@ export class Decoder {
         this.telemetry.set(o.id, value)
         this.telemetryMax.set(o.id, o.max > 0 ? o.max : 0xffff)
       }
+      if (ALT_DRUM_IDS.has(o.id)) {
+        this.altDrums.set(o.id, value)
+      }
     }
     return rows
   }
@@ -89,10 +128,28 @@ export class Decoder {
 
   telemetrySnapshot(): TelemetryReadout[] {
     return TELEMETRY.map((t) => {
+      if (t.id === 'D_IAS_DEG') {
+        const raw = this.telemetry.get('D_IAS_DEG') ?? NaN
+        const kt = Number.isNaN(raw) ? NaN : iasRawToKnots(raw)
+        const pct = Number.isNaN(kt) ? 0 : Math.max(0, Math.min(1, kt / IAS_MAX_KT))
+        return { id: 'D_IAS_DEG', label: t.label, value: kt, pct, unit: t.unit }
+      }
+      if (t.id === 'ALT_FT') {
+        const d10k = this.altDrums.get('D_ALT_10K')
+        const d1k = this.altDrums.get('D_ALT_1K')
+        const d100s = this.altDrums.get('D_ALT_100S')
+        const alt =
+          d10k !== undefined && d1k !== undefined && d100s !== undefined
+            ? Math.floor((d10k / 65535) * 10) * 10000 +
+              Math.floor((d1k / 65535) * 10) * 1000 +
+              Math.floor((d100s / 65535) * 10) * 100
+            : NaN
+        const pct = Number.isNaN(alt) ? 0 : Math.max(0, Math.min(1, alt / ALT_FT_MAX))
+        return { id: 'ALT_FT', label: t.label, value: alt, pct, unit: t.unit }
+      }
       const raw = this.telemetry.get(t.id) ?? NaN
       const max = this.telemetryMax.get(t.id) ?? 0xffff
       const pct = Number.isNaN(raw) ? 0 : Math.max(0, Math.min(1, raw / max))
-      // value = percent of full scale; NaN => "—" in the UI (not exported yet)
       const value = Number.isNaN(raw) ? NaN : Math.round(pct * 100)
       return { id: t.id, label: t.label, value, pct, unit: t.unit }
     })
diff --git a/src/renderer/src/tabs/Connection.tsx b/src/renderer/src/tabs/Connection.tsx
index d0b0b85..2b67917 100644
--- a/src/renderer/src/tabs/Connection.tsx
+++ b/src/renderer/src/tabs/Connection.tsx
@@ -1,5 +1,19 @@
 import { fmtUptime, useStore, type SourceMode, type Transport } from '../store'
 
+const REC_DOT = (
+  <span
+    style={{
+      display: 'inline-block',
+      width: 8,
+      height: 8,
+      borderRadius: '50%',
+      background: 'var(--red)',
+      marginRight: 6,
+      verticalAlign: 'middle'
+    }}
+  />
+)
+
 function NodesCard() {
   const nodes = useStore((x) => x.nodes)
   const sourceMode = useStore((x) => x.sourceMode)
@@ -67,6 +81,7 @@ export function Connection() {
   const setConfigField = useStore((x) => x.setConfigField)
   const toggleRelay = useStore((x) => x.toggleRelay)
   const openReplay = useStore((x) => x.openReplay)
+  const toggleCapture = useStore((x) => x.toggleCapture)
 
   // The device details are live: populated once a SimGateway is actually found.
   // Before that, only the match target (VID/PID) is shown — not real device data.
@@ -272,6 +287,30 @@ export function Connection() {
           </div>
         </div>
 
+        {s.sourceMode !== 'replay' && (
+          <div className="card field">
+            <div className="card-h" style={{ marginBottom: 12 }}>
+              Record
+            </div>
+            <button className="browse" onClick={() => toggleCapture()} disabled={!s.relaying}>
+              {s.recording ? (
+                <>
+                  {REC_DOT}Stop recording · {s.recordEvents ?? 0} events
+                </>
+              ) : (
+                'Start recording…'
+              )}
+            </button>
+            <div className="hint">
+              {s.recording
+                ? 'Recording live DCS-BIOS stream. Stop to save — replay the file on any machine with no DCS.'
+                : s.relaying
+                  ? 'Capture a live session to replay later with no DCS running.'
+                  : 'Start the relay first to enable recording.'}
+            </div>
+          </div>
+        )}
+
         <button
           className={`bigbtn${s.relaying ? ' bigbtn--stop' : ''}`}
           onClick={() => toggleRelay()}
diff --git a/src/renderer/src/tabs/Overview.tsx b/src/renderer/src/tabs/Overview.tsx
index 21ef67f..baba43d 100644
--- a/src/renderer/src/tabs/Overview.tsx
+++ b/src/renderer/src/tabs/Overview.tsx
@@ -80,7 +80,7 @@ export function Overview() {
 
   const gaugeColor = (id: string, pct: number): string => {
     if (id === 'D_FUEL') return pct < 0.25 ? 'var(--red)' : 'var(--gold)'
-    return id === 'D_FLAPS_IND' || id === 'D_ALT_NEEDLE' ? 'var(--blue-2)' : 'var(--blue)'
+    return id === 'D_FLAPS_IND' || id === 'ALT_FT' ? 'var(--blue-2)' : 'var(--blue)'
   }
   const gauges = s.telemetry.map((r) => ({
     label: r.label,