Airbus Control Laws

There are three main laws on flight controls: the normal law, the alternative law and the direct law. The alternative law is subdivided into alternative law 1 and alternative law 2. Downgrading to either of the alternative legal options depends on the nature of the error. Each of the three laws has different sub-modes, including ground mode, airplane mode, and torch mode. Mechanical Backup is designed to allow pilots to maintain control of the aircraft while restoring flight control computers after a complete power outage. The flight controls of Airbus electric aircraft are all electronically controlled and hydraulically activated. Some surfaces, such as the rudder and tail, can also be mechanically controlled. During normal flight, computers act to avoid excessive forces in pitch and running axes. The following discussion is based on the A330, but much of the information also applies to other types of Airbus. Aircraft equipped with electric flight controls require computer-controlled flight control modes capable of determining the mode of operation of the aircraft (right of calculation). A reduction in electronic flight control can be caused by the failure of a computer device, such as a flight control computer, an information device such as the Air Data Inertial Reference Unit (ADIRU), or the failure of several systems (double hydraulic failure, double engine failure, etc.).

Electronic flight control systems (EFCS) also provide an improvement in normal flight, such as increased protection of the aircraft against overuse or a more comfortable flight for passengers by detecting and correcting turbulence and providing yaw damping. The aircraft is controlled by three main control computers (captain, co-pilot and emergency) and two secondary control computers (captain and co-pilot). In addition, there are two Flight Control Data Computers (FCDC) that read information from sensors, such as aerial data (speed, altitude). This, along with GPS data, is introduced into three redundant processing units called Inertial Air Data Reference Units (ADRUs), which act as both an air data reference and an inertial reference. The ADRUs are part of the inertial reference system of air data connected to the Airbus with eight air data modules: three are connected to Pitot tubes and five to static sources. ADIRU information is fed into one of the many flight control computers (primary and secondary flight controls). Computers also receive information from aircraft control surfaces and aircraft control devices and the pilot`s autopilot. Information from these computers is sent to both the pilot`s main flight screen and control surfaces. [Citation needed] Unlike traditional controls, the sidestick in normal flight mode provides a load factor proportional to the deflection of the stick and independent of the speed of the aircraft. If the sidestick is neutral in manual flight, the system maintains a load factor of 1 g and the aircraft remains in flat flight without the pilot having to change elevators, even when changing gears or configurations. For manual rotations up to 33° bench, no lateral back pressure is required, as the system automatically adjusts the aircraft to maintain a level flight.

The system freezes the auto lining when the angle of attack becomes too large, the load factor exceeds 1.3 g or when the angle of slope exceeds 33 °. If these situations occur as a result of a deliberate maneuver, the pilot must exert back pressure on the side stick to maintain the chosen posture. In any case, load factor protection automatically limits the control inputs so that the aircraft remains within the “g” limits of the AOM, and pitch trim protection limits the in-flight attitude to a maximum of 30° nose up or 15° down. The deterioration of the alt1 law results from certain errors in the horizontal stabilizer, a single elevator error, the loss of a gäh shock absorber actuator, the loss of lamellar position or flap sensors, or a single air data reference error. Depending on the failure, autopilot may not be available. Information from many sources, including pilot sidesticks and rudder pedals, aerial data inertial reference units (ADRUs), landing gear control interface units (LCIU), slatted flap control computers (SFCC), flight management guidance computers (FMGC), and accelerometer are sent to all five flight control computers.

About the author

Newslinkin staff