AF447 Thread No. 3

[A33Zab]

Law reconfiguration.

@Chris:

Think if one will try to flowchart all possible reconfiguration you will end up in spaghetti,
but let’s give it a try and a start, if you need some specific data (sure not knowing them all!) to assist you just PM me.

** When you call any activation of a protection a new ‘law’ then you will find out there are dozens of ‘laws’ more.
** A (like B) documentation isn’t very consistent in making difference between a protection or a ‘law’

In (autoflight or manual flight) and A/C response = commanded --> Normal Law
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If (autoflight or manual flight) and certain A/C protections can’t be fulfilled -->Alternate Law
Possible causes:
High speed and high angle of attack protections enters Alternative law.

ALT1 - If there are faults in the horizontal stabilizer; an elevator; yaw-damper actuation; slat or flap sensor or a single ADR or IR fault.

ALT2 - Dual hydraulic failure(low press), faults in 2 IR or ADR references, with A/P lost except with an ADR DISAGREE; In all spoilers fault; certain ailerons fault or pedal transducers fault.

Indicated by ECAM MSG
F/CTL ALTN LAW
MAX SPEED 305/.82

if auto pitch trim not available à Amber USE MAN PITCH TRIM (first 6 sec flashing) below FMA.

On the PFD specific symbols (=) and formatting of low speed information on the speed scale indicates which protections are available.
When protections are lost, amber crosses (XXX) appear, instead of the green protection symbols (=).
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In manual flight only and if alternate Nz law can’t be kept --> Direct Law

E.g. If all 3 ADR or IR, 3 PRIM failure; 2 Elevator fault.

Indicated by ECAM MSG
F/CTL DIRECT LAW
MAX SPEED 305/.80
MAN PITCH TRIM USE

Amber “USE MAN PITCH TRIM” (first 6 sec flashing) below FMA
-------------------------------------------------------------------------------------------
In case of all electric FCPC/FCSC failure à Mechanical Only

“MAN PITCH TRIM ONLY” below FMA

Pitch: Elevators are hydraulic centered and becomes ‘fixed part’ of THS.
Yaw: à Rudder pedals (supported with yaw damper if available)

************************************************************ *********************
Alternate Law:

. In pitch: Same as in normal law
. In roll: Same as in normal law (ALTN1), or Roll Direct (ALTN2)
. In yaw: Same as in normal law (ALTN1), or degraded (ALTN2)

. Most protections are lost, except :
-- Load factor protection
-- Bank angle protection, if normal roll is still available (ALTN1 only).

At the flight envelope limit, the aircraft is not protected:
. In high speed, natural aircraft static stability is restored with an overspeed warning
. In low speed, the auto pitch trim stops at Vc prot (below VLS), 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.

VMO/MMO settings are reduced and A FLOOR is inhibited.


If certain values are exceeded abnormal attitude law is triggered.

. Pitch (50 degrees up, 30 degrees down)
. Bank (125 degrees)
. AOA (>30 degrees, < -10 degrees)
. Speed (>440 kt, < 60 kt)
. Mach (0.96, 0.1).

Abnormal attitude law:
. Pitch alternate (adapted Nz Law) with load factor protection (without autotrim)
. Lateral direct law with yaw alternate

After A/C recovery and until landing:
. Pitch Nz Law (with autotrim)
. Lateral direct law with yaw alternate