EASA examinations use the Airbus A320 family as an example of fly-by-wire controlled aircraft.

• Normal law is the system mode which is active throughout the flight and is terminated when system failures occur that prevent its use.

• The highest reduced mode of operation in Airbus FBW systems is the Alternate Law, which provides most features of normal law. Some features such as automatic stall protection are lost and replaced by conventional warnings for the pilots to manually correct the condition.
• Should failure conditions prevent operation in Alternate Law, an even more basic Direct Law is available. Autopilot functions are lost, along with flight envelope protection.
• As a last emergency means of operation, Mechanical Backup is provided to maintain level flight only for the limited period of flight control computer reset following a complete loss of power.

As we have stated above, a system degradation results in a loss of protection features, so the required alertness of the crew increases and leads to a higher workload.