enabling angle of attack logging in tecs_status message

msg/TecsStatus.msg

@@ -15,6 +15,7 @@ float32 true_airspeed_derivative_raw	# True airspeed derivative raw [m/s^2]
 
 float32 total_energy_rate_sp		# Total energy rate setpoint [m^2/s^3]
 float32 total_energy_rate		# Total energy rate estimate [m^2/s^3]
+float32 alpha			# Angle of attack in radians
 
 float32 total_energy_balance_rate_sp	# Energy balance rate setpoint [m^2/s^3]
 float32 total_energy_balance_rate	# Energy balance rate estimate [m^2/s^3]

src/modules/fw_pos_control/FixedwingPositionControl.cpp

@@ -438,6 +438,7 @@ FixedwingPositionControl::tecs_status_publish(float alt_sp, float equivalent_air
 	tecs_status.pitch_sp_rad = _tecs.get_pitch_setpoint();
 	tecs_status.throttle_trim = throttle_trim;
 	tecs_status.underspeed_ratio = _tecs.get_underspeed_ratio();
+	tecs_status.alpha = _aoa;
 
 	tecs_status.timestamp = hrt_absolute_time();
 
@@ -1056,6 +1057,14 @@ FixedwingPositionControl::control_auto_position(const float control_interval, co
 	// waypoint is a plain navigation waypoint
 	float position_sp_alt = pos_sp_curr.alt;
 
+	if (_airspeed_valid)
+	{
+		const Vector2f airspeed_2d{_airspeed_eas*cosf(_yaw), _airspeed_eas*sinf(_yaw)};
+
+		const float air_gnd_angle = acosf((airspeed_2d*ground_speed)/(airspeed_2d.length()*ground_speed.length()));
+	        _aoa = air_gnd_angle;
+	}
+
 	// Altitude first order hold (FOH)
 	if (_position_setpoint_previous_valid &&
 	    ((pos_sp_prev.type == position_setpoint_s::SETPOINT_TYPE_POSITION) ||

src/modules/fw_pos_control/FixedwingPositionControl.hpp

@@ -265,6 +265,7 @@ class FixedwingPositionControl final : public ModuleBase<FixedwingPositionContro
 	double _current_latitude{0};
 	double _current_longitude{0};
 	float _current_altitude{0.f};
+	float _aoa{0};
 
 	float _roll{0.f};
 	float _pitch{0.0f};