A320 FLIGHT CONTROL LAWS

The Electrical Flight Control System (EFCS) computers convert pilot inputs into aircraft control objectives. The computers calculate the control laws that are used to compute the surface deflections. The system has a high degree of redundancy and it will reconfigure itself when failures occur.

NORMAL LAW

• In normal conditions, the normal law is used to compute the surface deflection orders.

• Normal laws provide full flight phase envelope protection. This means that the aircraft will be protected from excessive maneuvers during all flight phases.

ALTERNATE LAW

• The alternate law is automatically introduced as soon as the normal law is lost due to system failures.

• The alternate law gives reduced protection.

DIRECT LAW

• The direct law is automatically introduced when further failures occur.

• In direct law, all protections are lost. There is a direct relationship between the side stick orders and the surface.

• The direct law is automatically activated on the ground.

MECHANICAL BACK-UP

• The mechanical backup lets the aircraft be controlled during a temporary complete loss of electrical power or flight control computers.

• Longitudinal control is achieved using the trim wheels to control the THS, as the elevators are kept at zero deflection.

• Lateral control is achieved from the rudder pedals.

• Hydraulic power is still needed to operate the surfaces of the THS and the Rudder.