diff --git a/src/blackgui/editors/interpolationsetupform.cpp b/src/blackgui/editors/interpolationsetupform.cpp
index 67bb59e7c..4c32efc85 100644
--- a/src/blackgui/editors/interpolationsetupform.cpp
+++ b/src/blackgui/editors/interpolationsetupform.cpp
@@ -29,7 +29,8 @@ namespace BlackGui
                 connect(cb, &QCheckBox::stateChanged, this, &CInterpolationSetupForm::onCheckboxChanged);
             }
 
-            connect(ui->co_InterpolatorMode, &QComboBox::currentTextChanged, this, &CInterpolationSetupForm::onInterpolatorModeChanged);
+            // one conect is enough, otherwise 2 change signals
+            connect(ui->rb_Linear, &QRadioButton::toggled, this, &CInterpolationSetupForm::onInterpolatorModeChanged);
         }
 
         CInterpolationSetupForm::~CInterpolationSetupForm()
@@ -43,10 +44,7 @@ namespace BlackGui
             ui->cb_ForceVtolInterpolation->setChecked(setup.isForcingVtolInterpolation());
             ui->cb_SendGndFlagToSim->setChecked(setup.isSendingGndFlagToSimulator());
             ui->cb_FixSceneryOffset->setChecked(setup.isFixingSceneryOffset());
-
-            const QString im = setup.getInterpolatorModeAsString();
-            if (im.contains("linear", Qt::CaseInsensitive)) { ui->co_InterpolatorMode->setCurrentIndex(1); }
-            else { ui->co_InterpolatorMode->setCurrentIndex(0); }
+            this->setInterpolatorMode(setup.getInterpolatorMode());
         }
 
         CInterpolationAndRenderingSetupPerCallsign CInterpolationSetupForm::getValue() const
@@ -58,7 +56,7 @@ namespace BlackGui
             setup.setSendingGndFlagToSimulator(ui->cb_SendGndFlagToSim->isChecked());
             setup.setSimulatorDebuggingMessages(ui->cb_DebugDriver->isChecked());
             setup.setFixingSceneryOffset(ui->cb_FixSceneryOffset->isChecked());
-            setup.setInterpolatorMode(ui->co_InterpolatorMode->currentText());
+            setup.setInterpolatorMode(this->getInterpolatorMode());
             return setup;
         }
 
@@ -70,7 +68,8 @@ namespace BlackGui
             CGuiUtility::checkBoxReadOnly(ui->cb_ForceVtolInterpolation, readonly);
             CGuiUtility::checkBoxReadOnly(ui->cb_SendGndFlagToSim, readonly);
             CGuiUtility::checkBoxReadOnly(ui->cb_FixSceneryOffset, readonly);
-            ui->co_InterpolatorMode->setEnabled(!readonly);
+            ui->rb_Linear->setEnabled(!readonly);
+            ui->rb_Spline->setEnabled(!readonly);
         }
 
         CStatusMessageList CInterpolationSetupForm::validate(bool nested) const
@@ -85,9 +84,27 @@ namespace BlackGui
             emit this->valueChanged();
         }
 
-        void CInterpolationSetupForm::onInterpolatorModeChanged(const QString &mode)
+        CInterpolationAndRenderingSetupBase::InterpolatorMode CInterpolationSetupForm::getInterpolatorMode() const
         {
-            Q_UNUSED(mode);
+            if (ui->rb_Linear->isChecked()) { return CInterpolationAndRenderingSetupBase::Linear; }
+            return CInterpolationAndRenderingSetupBase::Spline;
+        }
+
+        void CInterpolationSetupForm::setInterpolatorMode(CInterpolationAndRenderingSetupBase::InterpolatorMode mode)
+        {
+            switch (mode)
+            {
+            case CInterpolationAndRenderingSetupBase::Linear : ui->rb_Linear->setChecked(true); break;
+            case CInterpolationAndRenderingSetupBase::Spline:
+            default:
+                ui->rb_Spline->setChecked(true);
+                break;
+            }
+        }
+
+        void CInterpolationSetupForm::onInterpolatorModeChanged(bool checked)
+        {
+            Q_UNUSED(checked);
             emit this->valueChanged();
         }
     } // ns
diff --git a/src/blackgui/editors/interpolationsetupform.h b/src/blackgui/editors/interpolationsetupform.h
index ba6436f69..ed9c6d21f 100644
--- a/src/blackgui/editors/interpolationsetupform.h
+++ b/src/blackgui/editors/interpolationsetupform.h
@@ -60,7 +60,13 @@ namespace BlackGui
             void onCheckboxChanged(int state);
 
             //! Interpolator mode
-            void onInterpolatorModeChanged(const QString &mode);
+            void onInterpolatorModeChanged(bool checked);
+
+            //! Mode from UI
+            BlackMisc::Simulation::CInterpolationAndRenderingSetupBase::InterpolatorMode getInterpolatorMode() const;
+
+            //! Set mode
+            void setInterpolatorMode(BlackMisc::Simulation::CInterpolationAndRenderingSetupBase::InterpolatorMode mode);
         };
     } // ns
 } // ns
diff --git a/src/blackgui/editors/interpolationsetupform.ui b/src/blackgui/editors/interpolationsetupform.ui
index 25291ee09..defbf190b 100644
--- a/src/blackgui/editors/interpolationsetupform.ui
+++ b/src/blackgui/editors/interpolationsetupform.ui
@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>231</width>
-    <height>96</height>
+    <width>223</width>
+    <height>91</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -40,24 +40,10 @@
      </property>
     </widget>
    </item>
-   <item row="0" column="0">
-    <widget class="QComboBox" name="co_InterpolatorMode">
-     <item>
-      <property name="text">
-       <string>Spline interpolator</string>
-      </property>
-     </item>
-     <item>
-      <property name="text">
-       <string>Linear interpolator</string>
-      </property>
-     </item>
-    </widget>
-   </item>
-   <item row="1" column="1">
-    <widget class="QCheckBox" name="cb_SendGndFlagToSim">
+   <item row="1" column="0">
+    <widget class="QCheckBox" name="cb_EnableParts">
      <property name="text">
-      <string>send gnd.to simulator</string>
+      <string>enable parts</string>
      </property>
      <property name="checked">
       <bool>true</bool>
@@ -81,18 +67,75 @@
      </property>
     </widget>
    </item>
-   <item row="1" column="0">
-    <widget class="QCheckBox" name="cb_EnableParts">
+   <item row="1" column="1">
+    <widget class="QCheckBox" name="cb_SendGndFlagToSim">
      <property name="text">
-      <string>enable parts</string>
+      <string>send gnd.to simulator</string>
      </property>
      <property name="checked">
       <bool>true</bool>
      </property>
     </widget>
    </item>
+   <item row="0" column="0">
+    <widget class="QWidget" name="wi_InterpolatorType" native="true">
+     <layout class="QHBoxLayout" name="hl_InterpolatorType">
+      <property name="leftMargin">
+       <number>0</number>
+      </property>
+      <property name="topMargin">
+       <number>0</number>
+      </property>
+      <property name="rightMargin">
+       <number>0</number>
+      </property>
+      <property name="bottomMargin">
+       <number>0</number>
+      </property>
+      <item>
+       <widget class="QRadioButton" name="rb_Spline">
+        <property name="text">
+         <string>spline</string>
+        </property>
+        <property name="checked">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QRadioButton" name="rb_Linear">
+        <property name="text">
+         <string>linear</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <spacer name="hs_InterpolatorType">
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+        <property name="sizeHint" stdset="0">
+         <size>
+          <width>40</width>
+          <height>20</height>
+         </size>
+        </property>
+       </spacer>
+      </item>
+     </layout>
+    </widget>
+   </item>
   </layout>
  </widget>
+ <tabstops>
+  <tabstop>rb_Spline</tabstop>
+  <tabstop>cb_EnableParts</tabstop>
+  <tabstop>cb_SendGndFlagToSim</tabstop>
+  <tabstop>cb_FixSceneryOffset</tabstop>
+  <tabstop>cb_ForceVtolInterpolation</tabstop>
+  <tabstop>cb_DebugDriver</tabstop>
+  <tabstop>cb_LogInterpolation</tabstop>
+ </tabstops>
  <resources/>
  <connections/>
 </ui>