ALTERNATE LAW 1
PITCH CONTROL
Ground mode
Identical to normal law ground mode.
Flight mode
Flight law is a load factor demand law, similar to normal law, with limited pitch rate feedback and gains, depending on speed and configuration.
Note : When the yaw dampers actuators are not available (hydraulic G + Y failure for example), the yaw damping function is made through the ailerons and the BYDU.
Flare mode
Flare law is identical to normal flare law.
LATERAL CONTROL
Lateral control is similar to normal law, except that alterations of positive spiral static stability will not occur due to the loss of high AOA and high speed protection.
PROTECTIONS
Low speed stability
At low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack, and alternate law changes to direct law.
It is available, whatever the slats/flaps configuration, and it is active from about 5 knots up to about 10 knots above the stall warning speed, depending on the aircraft's weight and slats/flaps configuration.
A gentle progressive nose down signal is introduced, which tends to keep the speed from falling below these values. The pilot can override this demand.
Bank angle compensation is provided.
In addition, audio stall warning (crickets + “STALL” synthetic voice message) is activated at an appropriate margin from the stall condition.
The PFD speed scale is modified to show a black/red barber pole below the stall warning.
Vα prot and Vα max are replaced by Vsw (stall warning speed).
The α floor protection is inoperative.
ALTERNATE LAW 2
PITCH CONTROL
Identical to ALT 1 law.
LATERAL CONTROL
Roll direct law
Provides a direct stick-to-surface position relationship. The gains are automatically set according to the slats/flaps configuration.
The maximum roll rate is approximately 20 to 25° / second, depending on the speed and
configuration.
Spoilers 2, 3 and 6 are inhibited, except in case of some additional failures affecting the lateral control.
Yaw alternate law
The dutch roll damping function is available, and damper authority is limited to ± 4° rudder (CONF 0) and ± 15° (other configuration).
Turn coordination is also provided, except in CONF 0.
PROTECTIONS
Identical to protections in ALT 1, except that :
1. There is no bank angle protection in ALT 2 law.
2. In case of failure of 2 ADRs, there is no low speed stability.
3. In case of failure of 3 ADRs, there is no high speed stability.