diff --git a/conf/messages.xml b/conf/messages.xml
index d958c4e631..83c8e99ea3 100644
--- a/conf/messages.xml
+++ b/conf/messages.xml
@@ -1942,13 +1942,13 @@
   </message>
 
   <message name="AIR_DATA" id="222">
-    <field name="pressure" type="float" unit="Pa"/>
-    <field name="diff_p" type="float" unit="Pa"/>
-    <field name="temp" type="float" unit="deg celcius"/>
-    <field name="qnh" type="float" unit="hPa"/>
-    <field name="amsl_baro" type="float" unit="m"/>
-    <field name="airspeed" type="float" unit="m/s"/>
-    <field name="tas_factor" type="float"/>
+    <field name="pressure" type="float" unit="Pa">static pressure</field>
+    <field name="diff_p" type="float" unit="Pa">differential pressure</field>
+    <field name="temp" type="float" unit="deg celcius">air temperature</field>
+    <field name="qnh" type="float" unit="hPa">barometric pressure adjusted to sea level</field>
+    <field name="amsl_baro" type="float" unit="m">barometric altitude above mean sea level</field>
+    <field name="airspeed" type="float" unit="m/s">Equivalent Air Speed (or Calibrated Air Speed at low speed/altitude)</field>
+    <field name="tas" type="float">True Air Speed (when P, T and P_diff are available)</field>
   </message>
 
   <message name="AMSL" id="223">
diff --git a/sw/airborne/modules/air_data/air_data.c b/sw/airborne/modules/air_data/air_data.c
index c2a6676141..806f86304c 100644
--- a/sw/airborne/modules/air_data/air_data.c
+++ b/sw/airborne/modules/air_data/air_data.c
@@ -126,7 +126,8 @@ static void pressure_diff_cb(uint8_t __attribute__((unused)) sender_id, float pr
 {
   air_data.differential = pressure;
   if (air_data.calc_airspeed) {
-    air_data.airspeed = tas_from_dynamic_pressure(air_data.differential);
+    air_data.airspeed = eas_from_dynamic_pressure(air_data.differential);
+    air_data.tas = tas_from_eas(air_data.airspeed);
 #if USE_AIRSPEED_AIR_DATA
     stateSetAirspeed_f(&air_data.airspeed);
 #endif
@@ -156,7 +157,7 @@ static void send_air_data(struct transport_tx *trans, struct link_device *dev)
                          &air_data.pressure, &air_data.differential,
                          &air_data.temperature, &air_data.qnh,
                          &air_data.amsl_baro, &air_data.airspeed,
-                         &air_data.tas_factor);
+                         &air_data.tas);
 }
 
 static void send_amsl(struct transport_tx *trans, struct link_device *dev)
@@ -187,6 +188,7 @@ void air_data_init(void)
   air_data.pressure = -1.0f;
   air_data.qnh = -1.0f;
   air_data.airspeed = -1.0f;
+  air_data.tas = -1.0f;
   air_data.temperature = -1000.0f;
   air_data.differential = 0.0f;
   air_data.amsl_baro = 0.0f;
diff --git a/sw/airborne/modules/air_data/air_data.h b/sw/airborne/modules/air_data/air_data.h
index 5d7bc90a70..95dcd523c3 100644
--- a/sw/airborne/modules/air_data/air_data.h
+++ b/sw/airborne/modules/air_data/air_data.h
@@ -39,7 +39,8 @@ struct AirData {
   float differential; ///< Differential pressure (total - static pressure) (Pa)
   float temperature;  ///< temperature in degrees Celcius, -1000 if unknown
 
-  float airspeed;     ///< Conventional Air Speed in m/s, -1 if unknown
+  float airspeed;     ///< Equivalent Air Speed (equals to Calibrated Air Speed at low speed/altitude) (in m/s, -1 if unknown
+  float tas;          ///< True Air Speed (TAS) in m/s, -1 if unknown
   float tas_factor;   ///< factor to convert equivalent airspeed (EAS) to true airspeed (TAS)
   float qnh;              ///< Barometric pressure adjusted to sea level in hPa, -1 if unknown
   float amsl_baro;        ///< altitude above sea level in m from pressure and QNH