Failsafe landing without position control fixed

src/modules/commander/commander.cpp

@@ -1747,8 +1747,11 @@ set_control_mode()
 		control_mode.flag_control_auto_enabled = true;
 		control_mode.flag_control_rates_enabled = true;
 		control_mode.flag_control_attitude_enabled = true;
-		control_mode.flag_control_position_enabled = true;
-		control_mode.flag_control_velocity_enabled = true;
+
+		/* in failsafe LAND mode position may be not available */
+		control_mode.flag_control_position_enabled = status.condition_local_position_valid;
+		control_mode.flag_control_velocity_enabled = status.condition_local_position_valid;
+
 		control_mode.flag_control_altitude_enabled = true;
 		control_mode.flag_control_climb_rate_enabled = true;
 	}

src/modules/mc_pos_control/mc_pos_control_main.cpp

@@ -1001,6 +1001,18 @@ MulticopterPositionControl::task_main()
 						_att_sp.roll_body = euler(0);
 						_att_sp.pitch_body = euler(1);
 						/* yaw already used to construct rot matrix, but actual rotation matrix can have different yaw near singularity */
+
+					} else if (!_control_mode.flag_control_manual_enabled) {
+						/* autonomous altitude control without position control (failsafe landing),
+						 * force level attitude, don't change yaw */
+						R.from_euler(0.0f, 0.0f, _att_sp.yaw_body);
+
+						/* copy rotation matrix to attitude setpoint topic */
+						memcpy(&_att_sp.R_body[0][0], R.data, sizeof(_att_sp.R_body));
+						_att_sp.R_valid = true;
+
+						_att_sp.roll_body = 0.0f;
+						_att_sp.pitch_body = 0.0f;
 					}
 
 					_att_sp.thrust = thrust_abs;