SITL: fill in wind from flightaxis

libraries/SITL/SIM_Aircraft.cpp

@@ -408,6 +408,8 @@ void Aircraft::fill_fdm(struct sitl_fdm &fdm)
     fdm.wind_vane_apparent.direction = wind_vane_apparent.direction;
     fdm.wind_vane_apparent.speed = wind_vane_apparent.speed;
 
+    fdm.wind_ef = wind_ef;
+
     if (is_smoothed) {
         fdm.xAccel = smoothing.accel_body.x;
         fdm.yAccel = smoothing.accel_body.y;

libraries/SITL/SIM_FlightAxis.cpp

@@ -489,8 +489,8 @@ void FlightAxis::update(const struct sitl_input &input)
        can't get that from m_airspeed_MPS, so instead we calculate it
        from wind vector and ground speed
      */
-    Vector3f m_wind_ef(-state.m_windY_MPS,-state.m_windX_MPS,-state.m_windZ_MPS);
+    wind_ef = Vector3f(state.m_windY_MPS,state.m_windX_MPS,state.m_windZ_MPS);
-    Vector3f airspeed_3d_ef = m_wind_ef + velocity_ef;
+    Vector3f airspeed_3d_ef = velocity_ef - wind_ef;
     Vector3f airspeed3d = dcm.mul_transpose(airspeed_3d_ef);
 
     if (last_imu_rotation != ROTATION_NONE) {

libraries/SITL/SITL.h

@@ -87,6 +87,9 @@ struct sitl_fdm {
     } wind_vane_apparent;
 
     bool is_lock_step_scheduled;
+
+    // earthframe wind, from backends that know it
+    Vector3f wind_ef;
 };
 
 // number of rc output channels