fix(fw_latlon_control): compensate TECS min airspeed for load factor

TECS was given the load factor but not the minimum airspeed, derived
from the performance model.

TECS itself does the eas/tas conversion (altitude compensation) but not
load factor or weight compensation, which is the responsibility of the
performance model.

Use set_equivalent_airspeed_min to update the latter, compensated for
load factor, whenever attitude updates. Currently it is only called on
param change, so TECS has a min airspeed based on outdated load factor
and flap setpoint.

src/modules/fw_lateral_longitudinal_control/FwLateralLongitudinalControl.cpp

@@ -608,9 +608,14 @@ void FwLateralLongitudinalControl::updateAttitude() {
 		_long_control_state.pitch_rad = euler_angles.theta();
 		_yaw = euler_angles.psi();
 
-		// load factor due to banking
 		const float load_factor_from_bank_angle = 1.0f / max(cosf(euler_angles.phi()), FLT_EPSILON);
+
+		// Used to compensate for higher induced drag during banking
 		_tecs.set_load_factor(load_factor_from_bank_angle);
+		// Used to give underspeed mitigation the correct minimum airspeed
+		_tecs.set_equivalent_airspeed_min(
+			_performance_model.getMinimumCalibratedAirspeed(load_factor_from_bank_angle, _flaps_setpoint)
+		);
 	}
 }