2 The heartbeat message shows that a system is present and responding. The type of the MAV and Autopilot hardware allow the receiving system to treat further messages from this system appropriate (e.g. by laying out the user interface based on the autopilot). Type of the MAV (quadrotor, helicopter, etc., up to 15 types, defined in MAV_TYPE ENUM) Autopilot type / class. defined in MAV_CLASS ENUM System mode, see MAV_MODE ENUM in mavlink/include/mavlink_types.h Navigation mode, see MAV_NAV_MODE ENUM System status flag, see MAV_STATUS ENUM System safety lock state, see MAV_SAFETY enum. Also indicates HIL operation Bitmask showing which links are ok / enabled. 0 for disabled/non functional, 1: enabled Indices: 0: RC, 1: UART1, 2: UART2, 3: UART3, 4: UART4, 5: UART5, 6: I2C, 7: CAN MAVLink version