OPERATIONAL PHILOSOPHY
FLIGHT CONTROLS
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
ALTERNATE LAW
Applicable to: ALL
In some double failure cases, the integrity and redundancy of the computers and of the peripherals are not sufficient to achieve normal law and associated protections. System degradation is progressive, and will evolve according to the availability of remaining peripherals or computers.
Alternate law characteristics (usually triggered in case of a dual failure): ‐ In pitch: same as in normal law with FLARE in DIRECT
‐ In roll: Roll DIRECT
‐ Most protections are lost, except Load factor protection.
At the flight envelope limit, the aircraft is not protected, i.e.:
‐ In high speed, natural aircraft static stability is restored with an overspeed warning
‐ In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G.
In certain failure cases, such as the loss of VS1G computation or the loss of two ADRs, the longitudinal static stability cannot be restored at low speed. In the case of a loss of three ADRs, it cannot be restored at high speed.
In alternate law, VMO setting is reduced to 320 kt, and α FLOOR is inhibited. (On A318, MMO setting is also reduced to M 0.77.)
OPERATIONAL RECOMMENDATION:
The handling characteristics within the normal flight envelope, are identical in pitch with normal law. Outside the normal flight envelope, the PF must take appropriate preventive actions to avoid losing
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