Law Degradation and Reconfiguration

This is the capstone of the control-law block. Articles 05–11 built Normal Law and its protections; articles 12–16 opened up Alternate, Direct, Abnormal Attitude, Mechanical Back-Up and the sidestick priority logic one box at a time. This article threads them into a single degradation ladder: which failure combinations push the aircraft down a step, what each step costs you in protection, how the step shows on the PFD and ECAM, and what the FCTM tells you to change in your hands. After reading it you should carry a "control-law state machine" in your head — so that the instant any F/CTL message appears you can place yourself: which step am I on, what is left, and what must I no longer do.

Two reframings up front, because they decide how the rest reads:

[!warning]- "Alternate Law roll is direct" is the chapter's number-one trap. It is true only for ALT 2.

Alternate Law splits into ALT 1 and ALT 2, and the split lives in the roll axis. In ALT 1 the roll is roll normal and the bank-angle limitation is still effective; only in ALT 2 does roll degrade to roll direct with bank protection lost. FCOM states it in a footnote in black and white: Bank angle limitation remains effective in ALT 1, which uses roll normal. The general "Roll control is direct" sentence in the Alternate section describes the ALT 2 feel; reading it across the whole of Alternate is exactly how pilots mis-file ALT 1.

[!warning]- At the bottom of the ladder, yaw is not on a cable. Clear the classic mechanical-rudder picture.

When the aircraft reaches the mechanical back-up, pitch survives on the THS manual trim wheel and yaw survives on the BCM — a back-up computer giving direct pedal-to-rudder command, powered by its own generator off the Blue or Yellow hydraulic. There is no cable run to the rudder in this aircraft; the rudder is rudder-by-wire to the end (see Flight Control Fundamentals).

1. What "control law" means — and why a downgrade is not a small thing

The FCTM defines the term that the whole block turns on. Per FCTM AOP-10-30-10:

The relationship between the pilot input on the sidestick, and the aircraft response, is called the control law. The control law determines the handling characteristics of the aircraft.

Degradation is, at root, this input-to-response relationship being swapped out. Push the same centimetre of sidestick and Normal Law reads it as "give me this load factor", while Direct Law reads it as "deflect the elevator this many degrees" — the aircraft's reaction is not the same. So a law downgrade is not "the aircraft is slightly broken"; it is a different set of handling qualities, and the crew must change technique to match. That is why this article spends as much effort on recognising the step (§7) and flying it (§8) as on listing what each step contains.

The architecture is built so that downgrades are rare and graceful: redundant computers and multi-system hydraulic actuation keep the aircraft in the most-protected law for essentially the whole fleet life, and a single failure usually changes nothing about the law (see EFCS Computer Architecture). The ladder below is what catches the aircraft when failures do stack.

2. The three reconfiguration levels and the trigger matrix

FCOM opens the subject by counting the landing points. Per FCOM DSC-27-20-20-10:

Depending on the type of failures affecting the flight control system, or its peripherals, there are 3 possible reconfiguration levels: ‐ Alternate law (ALT 1 or ALT 2) ‐ Direct law, or ‐ Mechanical.

Normal is not one of "the 3" because Normal is the healthy state — reconfiguration is counted down from it. Since Alternate itself splits into ALT 1 and ALT 2, the real set of landing points is five: Normal / ALT 1 / ALT 2 / Direct / Mechanical, plus one temporary side-branch (Abnormal Attitude, §6).

What turns "I am in Alternate" into "I have lost this specific protection" is a set of footnotes FCOM attaches to its reconfiguration table — the soul of the trigger matrix. Per FCOM DSC-27-20-20-10:

(*) Only in case the AOA, of the remaining ADRs, disagrees with the AOA (as computed by the PRIM's). (1) Protection is totally lost, in case of VS 1g computation failure (loss of weight, or slat/flap position). (2) Protection is lost, in case of a dual ADR failure (or ADR DISAGREE). (3) Protection is lost, in case of a triple ADR failure (or ADR DISAGREE). ... (4) Bank angle limitation remains effective in ALT 1, which uses roll normal. However, since ALT 1 is generally an unprotected law, all protection marks on the PFD are in amber for simplicity. (5) When both elevators have failed, only pitch mechanical backup is available, by using the manual pitch trim (THS). "MAN PITCH TRIM ONLY" is displayed in red on the PFDs.

Unpacked for the pilot:

• Footnote (1) is the harshest. Lose weight, or slat/flap position, and the VS 1g (1-g stall reference speed) computation fails — and because VS 1g is the basis on which every low-speed protection is built, all protection is then lost. This is why a seemingly "small" sensor loss can drop you a long way down the ladder.
• Footnotes (2) and (3) tie air-data quantity to protection: a dual ADR failure removes low speed stability; a triple ADR failure removes high speed stability as well. The less speed information survives, the further you fall.
• Footnote (4) is the headline counter-intuitive point (callout up front, and §4): ALT 1 roll is roll normal and the bank-angle limit is still active — the PFD just paints every protection mark amber "for simplicity", so you cannot tell from the display that bank is still protected.
• Footnote (5) is the step from Direct into the mechanical back-up: both elevators failed leaves only the THS trim wheel, shown as red MAN PITCH TRIM ONLY.

[!warning]- An amber protection cross on the PFD does not prove that protection is gone.

Footnote (4) says that in ALT 1 all protection marks on the PFD are in amber for simplicity, even though the bank-angle limitation is genuinely still working. So an amber X means "the system no longer guarantees this protection set is intact" — it is not a per-item statement that each protection has actually been lost. The true picture comes from the law you are in plus the specific ECAM messages, not from the colour of one symbol.

3. The ladder at a glance

Tie §2 together and the EFCS has a health spectrum: the more that fails, the further the law steps down, the fewer the protections, and the closer the handling gets to a bare aircraft.

┌────────────────────────────────────────────────────┐
│ NORMAL LAW                        (healthy)        │
│ pitch: load-factor demand + autotrim               │
│ roll : roll normal + bank limit 67°                │
│ ALL protections active                             │
└────────────────────────────────────────────────────┘
                            │
                            ▼   more computer / hydraulic / sensor failures
┌────────────────────────────────────────────────────┐
│ ALTERNATE LAW              (ALT 1 / ALT 2)         │
│ pitch ~ normal (+autotrim, flare at 100 ft)        │
│ only MANEUVER protection retained                  │
│ ALT 1 roll = roll normal  (bank limit ON)          │
│ ALT 2 roll = roll direct  (bank limit OFF)         │
└────────────────────────────────────────────────────┘
                            │
                            ▼   further failures
┌────────────────────────────────────────────────────┐
│ DIRECT LAW                                         │
│ pitch: stick -> elevator, NO autotrim              │
│ roll : roll direct, no protection                  │
│ amber  USE MAN PITCH TRIM                          │
└────────────────────────────────────────────────────┘
                            │
                            ▼   both elevators fail
┌────────────────────────────────────────────────────┐
│ MECHANICAL BACK-UP                                 │
│ pitch = THS manual trim wheel                      │
│ yaw   = BCM (direct pedal -> rudder)               │
│ red  MAN PITCH TRIM ONLY                           │
└────────────────────────────────────────────────────┘

  and, off to one side — engageable from any law:
┌──────────────────────────────────────────────────┐
│ ABNORMAL ATTITUDE LAW            (temporary)     │
│ Engages from ANY law when the aircraft is        │
│ thrown far outside the envelope:                 │
│   pitch alternate · roll direct · yaw mechanical │
│   (no autotrim, USE MAN PITCH TRIM)              │
│ On recovery -> pitch alt(+autotrim)/roll direct/ │
│   yaw alt, F/CTL ALTN LAW for rest of flight     │
└──────────────────────────────────────────────────┘

Three things to read off it:

1. The trunk is "the more breaks, the lower you go" — Normal → Alternate → Direct → Mechanical. Abnormal Attitude is a temporary side-branch, not a rung: it is forced on when the aircraft is thrown outside the envelope, and on recovery it does not climb back to Normal — it settles into Alternate (§6).
2. What you lose at a level is set by the specific failure, not by the level wholesale. The same ALTN LAW annunciation hides different protection losses depending on whether two or three ADRs failed (§2 footnotes). "I am in Alternate" is therefore not the same as "I have lost everything".
3. The roll axis is the divider between ALT 1 and ALT 2. ALT 1 keeps roll normal and the bank limit; ALT 2 drops to roll direct. Almost every mis-statement about Alternate Law comes from blurring those two.

A note on what holds the ladder up. Law degradation is a software event, but it can degrade gracefully only because every surface sits on an actuation chain with a defined fall-back order — the AMM's flight-control arrangement figure labels the arrows on that chain ARROWS INDICATE THE ACTUATION RECONFIGURATION PRIORITIES. Each step down the law ladder corresponds to one of those hardware priorities being spent: a failed computer moves the master, a lost hydraulic system drops servos, and at the floor only the mechanical THS run and the self-powered BCM are left. The master-logic detail is in EFCS Computer Architecture.

Quick-reference: the landing points

4. Alternate Law — and the ALT 1 / ALT 2 split

Alternate is the first stop down, and the place most A330 failures finally settle (even an all-engine flameout stays here, §7). FCOM gives its character. Per FCOM DSC-27-20-20-20:

Alternate law in pitch is almost the same for the pilot, as normal control law. However, alternate law does not maintain any of the protections, except maneuver protection. As a result, the pilot must fly the aircraft more attentively to avoid inadvertently exceeding the normal limits.

Two stakes go in here: pitch feel is almost unchanged (still a load-factor demand law, so you barely notice it), but protection is almost all gone — only the maneuver (load-factor) protection survives as the one soft wall against pulling the aircraft apart. FCOM adds that Alternate Law also reduces MMO to 0.82 — the speed limit you will then see on the ECAM (§8). Feels like Normal, protects almost nothing: that is exactly where Alternate bites — it is easy to fly, but nobody is catching you any more.

The low-speed side is where the change does show. Per FCOM DSC-27-20-20-20:

At low speed, the change in the speed scale is very noticeable. VLS remains, but Vα PROT and Vα MAX disappear, replaced by a single black and red strip, the top of which is stall warning speed. Unlike VLS, which is stable, VSW is g sensitive so as to give additional margin in turns.

The green protection band of Normal Law gives way to the VSW black-and-red barber pole, whose top is the stall warning speed — the visual cue that the floor is now a warning, not a hard protection.

The roll split. The Alternate section first describes the general feel — and it is the sentence most easily over-read. Per FCOM DSC-27-20-20-20:

Roll control is direct. The roll rate is generally higher than with normal law and, at first, the aircraft appears to be very sensitive.

Bank stability and limits are no longer active, and the flight crew should be careful to remain within normal limits.

That description matches ALT 2. The true ALT 1 roll behaviour is stated separately. Per FCOM DSC-27-20-20-20, ALT 1 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.

Only in ALT 2 does roll actually become direct. Per FCOM DSC-27-20-20-20, ALT 2 lateral control:

ROLL DIRECT LAW Provides a direct stick-to-surface position relationship. ... The maximum roll rate is approximately 20 to 25 °/s, 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.

And the protection difference between the two is explicit. Per FCOM DSC-27-20-20-20, ALT 2 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.

So the iron rule, consistent with the architecture and with Alternate Law: ALT 1 roll ≈ normal, bank limit retained; ALT 2 roll = direct, bank protection gone. Alternate's low-speed protection, "low speed stability", reverts to direct law near the stall with α floor inoperative — the full feel and thresholds are deepened in Alternate Law.

[!warning]- Alternate "handles like Normal" is the trap, not the comfort.

FCOM says pitch in Alternate is almost the same for the pilot, as normal control law — and that very familiarity is the danger. The protections that would normally stop an inadvertent overspeed or approach to the stall are not maintained ... except maneuver protection. Good handling is not the same as having a safety net: in Alternate you must watch the stall and overspeed boundaries yourself.

5. Direct Law

One step further down is Direct — the most "bare-aircraft" law that is still a flying law. Per FCOM DSC-27-20-20-30:

Pitch direct law is a direct stick to elevator relationship (elevator deflection is proportional to stick deflection). In all configurations, the maximum elevator deflection varies as a function of the CG. ... As there is no automatic trim, the pilot has to use manual trim. The "USE MAN PITCH TRIM" amber message is displayed on the PFD. All protections are inoperative. The α floor function is inoperative. As per alternate law, overspeed and stall warnings are available.

Two watersheds separate Direct from Alternate: autotrim disappears (which is precisely why USE MAN PITCH TRIM comes up — you must wind the trim wheel yourself), and protection goes from "almost none" to "none" — even the maneuver soft wall is gone, leaving only the overspeed and stall warnings, which alert but do not intervene. The PFD therefore replaces the protection symbols with amber crosses and the Vα band with VSW. Per FCOM DSC-27-20-20-30, the PFD display notes:

USE MAN PITCH TRIM (amber) displayed in direct law, or in flare law without RA.

MAN PITCH TRIM ONLY (red) displayed, if a L + R elevator fault is detected.

That second note is the hinge into the mechanical back-up (§7): amber USE MAN PITCH TRIM means you still have electrical pitch control but must trim by hand; red MAN PITCH TRIM ONLY means both elevators are gone and the trim wheel is all the pitch you have. The colour is the level. Full treatment in Direct Law.

6. Abnormal Attitude Law — the temporary side-branch

Abnormal Attitude Law is not on the main trunk. It is forced on when the aircraft is thrown well outside the normal envelope, to hand the PF the most effective recovery law. The trigger set is worth a feel for. Per FCOM DSC-27-20-20-40:

The abnormal attitude law engages when one of the following values is reached: ‐ If at least 2 ADCs are valid and consistent: Pitch attitude above 50 ° nose up or below 30 ° nose down. If not: Pitch attitude above 40 ° nose up or below 20 ° nose down ‐ Bank angle is above 125 ° ‐ Angle of attack is above 40 ° ‐ Speed is above 440 kt or below 60 kt ‐ Mach is above 0.96 or below 0.1.

What it gives you while engaged, and crucially what it leaves you with after recovery, is fixed. Per FCOM DSC-27-20-20-40:

When the abnormal attitude law engages: ‐ The pitch alternate law is active ‐ The roll direct law is active ‐ The yaw mechanical law is active ‐ Autotrim is not available. ... When the aircraft returns within the normal flight envelope, the abnormal attitude law disengages and the following conditions remains for the remainder of the flight: ‐ The pitch alternate law is active with autotrim ‐ The roll direct law is active ‐ The yaw alternate law is active ‐ F/CTL ALTN LAW is displayed on the ECAM.

[!warning]- Recover from an extreme attitude and the aircraft does not return to Normal Law.

After an upset recovery the aircraft settles into Alternate (pitch alternate with autotrim, roll direct, yaw alternate) and keeps F/CTL ALTN LAW for the remainder of the flight. It will not climb back to Normal on its own. The price of one loss-of-control recovery is flying the rest of the leg in a degraded law. Detail in Abnormal Attitude Law.

7. Mechanical Back-Up — the floor

The bottom of the ladder. FCOM first states its purpose and its near-irrelevance in practice. Per FCOM DSC-27-20-20-50:

The purpose of the backup is to achieve all safety objectives in MMEL dispatch condition: To manage a temporary and total electrical loss, the temporary loss of five fly-by-wire computers, the loss of both elevators, or the total loss of ailerons and spoilers. It must be noted that it is very unlikely that the backup will be used, due to the fly-by-wire architecture. For example, in case of electrical emergency configuration, or an all-engine flameout, alternate law remains available.

And the two surviving means of control. Per FCOM DSC-27-20-20-50:

Pitch mechanical control is achieved through the THS, using manual trim control. «MAN PITCH TRIM ONLY» is displayed in red on the PFDs.

The Backup Control Module (BCM) computer provides yaw damping and direct rudder command with pedals. This computer includes its own electrical generator, supplied by the B or Y hydraulic system.

So in the mechanical back-up you have the THS trim wheel for pitch and the BCM (pedals to rudder) for yaw — and no dedicated electrical roll control, which is flown indirectly through the roll that sideslip induces. The aim is not precision but holding the attitude steady while systems are restored (§8). Deepened in Mechanical Back-up and BCM and Electrical Back-up BCM/BPS.

[!warning]- The mechanical back-up is a "last fraction of a percent" fallback — even all-engines-out stays in Alternate.

FCOM is explicit that the back-up is very unlikely to be used: an electrical emergency configuration or an all-engine flameout still leaves Alternate Law available. Reaching the true mechanical back-up needs the far more extreme stack — a temporary total electrical loss, the temporary loss of all five fly-by-wire computers, both elevators failed, or ailerons-and-spoilers all gone. Know it cold, but do not picture it as a routine degradation.

8. Reading the degradation off the screens

You learn which step you are on from two instruments. First the ECAM. Per FCOM DSC-27-20-20-10, the messages and their speed limits (A330 values):

Hold two numbers: Alternate pulls MMO back to 0.82 (matching the reduces MMO to 0.82 of §4) and Direct tightens it to M 0.80, with both indicated airspeeds capped at 330 kt. A downgrade means slow down — §9 says why.

Then the PFD, which is the crew's first-glance status instrument. Per FCOM DSC-27-20-20-10:

When protections are lost, amber crosses (X) appear, instead of the green protection symbols (=). When automatic pitch trim is no longer available, the PFD indicates this with an amber "USE MAN PITCH TRIM" message below the FMA.

FCOM states the design value of that single instrument. Per FCOM DSC-27-20-20-10:

Therefore, by simply looking at this main instrument (PFD), the flight crew is immediately aware of the status of flight controls, and the operational consequences.

The low-speed end of the speed scale changes with the law too: Normal Law's green Vα PROT / Vα MAX give way to the VSW black-and-red strip once protections are lost (§4). PFD display detail is in Controls and Indications.

Two easily-missed notes round out the picture. Per FCOM DSC-27-20-20-10:

Note: 1. In case of dual RA failure, flare law is introduced when the landing gear is extended and both autopilots are disengaged. The specific normal law pitch down effect at 50 ft no longer applies. 2. A jerk may be felt, in the case of flight control computers reconfiguration (due to hydraulic failure, computer failure, electrical transient...).

Note 2 is the practical one: the instant the law reconfigures the aircraft may "jerk" once — that is the computers handing over, not a fault, and not a reason to make a large input.

9. Operating in reconfiguration laws — warnings, technique, dispatch

9.1 F/CTL message → law level → where to read more

Each F/CTL line on the ECAM points to a definite place on the ladder. This is the crew's translator:

One-line use: see ALTN/DIRECT and do three things first — slow to the limit, confirm whether autotrim is still there (do I trim by hand?), and switch to the technique for that law.

9.2 How to fly it (FCTM)

FCOM tells you what the system became; the FCTM tells you what your hands must change. Per FCTM AOP-10-30-20:

When the aircraft is in reconfiguration law, the flight crew should consider the following: ‐ At high altitude, descend to a lower altitude to increase the margin to buffet and keep satisfying handling qualities. ... ‐ At high speed, maneuver with care and use small control inputs. Depending on the re-configuration law, the pitch control law can have different modes, but the roll control law will always be in direct law.

[!warning]- FCTM "roll will always be in direct law" vs FCOM "ALT 1 uses roll normal" — both are right, at different layers.

The FCTM tells you to treat roll as direct because that is the conservative, prepare-for-the-worst handling assumption. FCOM footnote (4) tells you the system truth that ALT 1 still runs roll normal with the bank limit. These do not conflict: one is an operating instruction (fly it as if it were direct), the other is the underlying logic (ALT 1 still protects bank). Plan your hands by the FCTM; understand the system by FCOM.

The per-law techniques. Per FCTM AOP-10-30-20:

ALTERNATE LAW 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 control, and/or avoid high speed excursions. ... DIRECT LAW The PF must avoid performing large thrust changes, or sudden speedbrake movements, particularly if the center of gravity is aft. If the speedbrakes are out, and the aircraft has been re-trimmed, the PF must gently retract the speedbrakes to give the aircraft time to re-trim, and thereby avoid a large nose down trim change.

And the back-up. Per FCTM AOP-10-30-20:

In such cases, the objective is not to fly the aircraft accurately, but to maintain the aircraft attitude safe and stabilized, in order to allow the restoration of lost systems. The pitch trim wheel is used to control pitch. Any action on the pitch trim wheel should be applied smoothly, because the THS effect is significant due to its large size. The rudder provides lateral control, and induces a significant roll with a slight delay.

Three techniques to carry: in Alternate, stay inside the envelope yourself (normal feel, no net); in Direct, fly gently — beware aft CG and the speedbrakes (no autotrim means a coarse input can drive a large trim change); in the back-up, only stabilise — wind the THS smoothly and lead the roll when steering on rudder.

9.3 Dispatch: Alternate may go, Direct may not

Degradation has a clean line at the dispatch level. Under a typical operator MEL (item ME-27), F/CTL ALTN LAW arising from certain failures — for example an aileron servocontrol — is dispatchable under MEL conditions (the MEL points to the relevant aileron-servocontrol items), whereas F/CTL DIRECT LAW carries NO DISPATCH. The logic tracks the laws themselves: Alternate still flies like Normal in pitch and keeps the maneuver protection, while Direct has lost autotrim and every protection (warnings only), a clear step up in risk.

Note: dispatch relief is defined by each operator's approved MEL and may differ between operators; the ALTN-dispatchable / DIRECT-no-dispatch split reflects MMEL-derived practice and should be confirmed against the applicable MEL.

9.4 The ladder, flown once through

1. Cruise, one PRIM trips (F/CTL PRIM 1 FAULT) — master shifts to P2, the others cover the failed computer's tasks (spoilers excepted), and the law is usually still Normal. An ECAM note, unchanged feel — the ladder has not started.
2. Cruise, a hydraulic system plus a computer lost — you may step into ALT 1: F/CTL ALTN LAW, amber crosses on the PFD, but roll still like normal with the bank limit retained (footnote 4). Slow to the limit, watch the envelope.
3. High altitude, dual ADR failure (ADR DISAGREE) — ALT 2: roll goes direct, bank protection lost, and no low speed stability (footnote 2); the speed scale becomes the VSW strip. Descend for buffet margin, fly small inputs.
4. Further failures to Direct — F/CTL DIRECT LAW + MAN PITCH TRIM USE: autotrim gone, so trim by hand; retract speedbrakes gently, mind aft CG. Remember: this state is no-dispatch.
5. Upset — thrown outside the envelope — pitch beyond 50° nose-up engages Abnormal Attitude Law (pitch alt / roll direct / yaw mechanical) to recover; after recovery the aircraft stays in Alternate for the rest of the flight, ALTN LAW latched.
6. The floor — both elevators failed / temporary total electrical — red MAN PITCH TRIM ONLY: the mechanical back-up, THS wheel for pitch and BCM pedals for yaw. Wind the wheel smoothly, lead the rudder. This step is extremely unlikely — even all-engines-out stays in Alternate.

Self-test

[!note]- Q1. Counting down from Normal, what are the landing points, and where does Abnormal Attitude Law sit on the chain?

The trunk landing points are Normal → Alternate (ALT 1 / ALT 2) → Direct → Mechanical Back-Up. FCOM frames the possible reconfiguration as "3 levels: Alternate (ALT 1 or ALT 2), Direct, Mechanical" (Normal is the healthy state, not a reconfiguration). Abnormal Attitude Law is not on the trunk — it is a temporary side-branch: forced on when the aircraft is thrown outside the envelope (pitch alternate, roll direct, yaw mechanical) to aid recovery, and on return to the envelope it settles into Alternate (roll direct) for the rest of the flight rather than climbing back to Normal.

[!note]- Q2. How do ALT 1 and ALT 2 differ in roll, and why is "Alternate roll is direct" a trap?

ALT 1 roll is roll normal — FCOM footnote (4) states Bank angle limitation remains effective in ALT 1, which uses roll normal, and ALT 1 lateral control is similar to normal law. ALT 2 roll is ROLL DIRECT LAW — a direct stick-to-surface relationship, ~20–25 °/s maximum roll rate, spoilers 2/3/6 inhibited, and There is no bank angle protection in ALT 2. The trap: the Alternate overview sentence "Roll control is direct" describes the general (ALT 2) feel; applied to the whole of Alternate it wrongly strips the bank protection from ALT 1. Truth: ALT 1 keeps bank, ALT 2 loses bank.

[!note]- Q3. Dual ADR failure, triple ADR failure, and loss of slat/flap position — what does each remove?

Per the FCOM DSC-27-20-20-10 footnotes: (2) a dual ADR failure (or ADR DISAGREE) removes low speed stability; (3) a triple ADR failure removes high speed stability as well; (1) a VS 1g computation failure (loss of weight, or slat/flap position) removes protection totally, because VS 1g is the reference on which all low-speed protection is computed — lose the reference and the whole set collapses. So "I am in Alternate" still depends on which sensors went: the less air data survives, the deeper you fall.

[!note]- Q4. Amber USE MAN PITCH TRIM versus red MAN PITCH TRIM ONLY — what does each mean, and which level?

Amber USE MAN PITCH TRIM = autotrim is no longer available, so trim by hand; it appears in Direct law, Abnormal Attitude Law, or flare law without RA. Electrical pitch control still exists — only the trimming is manual. Red MAN PITCH TRIM ONLY = both elevators have failed and the THS mechanical trim wheel is the only pitch channel left (footnote 5), i.e. the mechanical back-up. The colour is the level: amber = still electrically controlled but trim manually; red = mechanical only.

[!note]- Q5. What is the essential dispatch difference between F/CTL ALTN LAW and F/CTL DIRECT LAW?

F/CTL ALTN LAW from certain failures (e.g. an aileron servocontrol) is dispatchable under MEL conditions, while F/CTL DIRECT LAW is NO DISPATCH. The reason is the laws themselves: Alternate still handles like Normal in pitch and retains the maneuver (load-factor) protection — "good handling, fewer nets" — whereas Direct has lost autotrim and every protection (warnings only), a clear jump in risk, so the operator MEL draws the line at Direct.

[!note]- Q6. Why does FCOM say the mechanical back-up is "very unlikely to be used", and what one-time jolt is normal during a downgrade?

Because the fly-by-wire redundancy is deep enough that an electrical emergency configuration or even an all-engine flameout still leaves Alternate Law available; reaching the back-up needs an extreme stack (temporary total electrical loss, temporary loss of all five computers, both elevators failed, or ailerons-and-spoilers all gone). As for the jolt: FCOM notes that a jerk may be felt when the flight control computers reconfigure (hydraulic failure, computer failure, electrical transient) — it is the hand-over, not a fault, and not a cue for a large input.

Key takeaways

References

Per FCOM DSC-27-20-20-10 (General — the three reconfiguration levels; the (*)/(1)–(5) trigger footnotes; ECAM FLT CTL ALTN/DIRECT LAW (PROT LOST) with A330 speed limits; PFD amber X / USE MAN PITCH TRIM; PFD status-awareness statement; dual-RA flare and reconfiguration-jerk notes); FCOM DSC-27-20-20-20 (Alternate Law — pitch almost as normal, only maneuver protection; low-speed VSW barber pole; ALT 1 lateral "similar to normal law"; ALT 2 ROLL DIRECT LAW / YAW ALTERNATE LAW and the ALT 2 protection deltas); FCOM DSC-27-20-20-30 (Direct Law — stick-to-elevator, no autotrim, all protections inoperative, α floor inoperative, overspeed/stall warnings only; PFD display notes (4) and (5)); FCOM DSC-27-20-20-40 (Abnormal Attitude Law — engage thresholds and the engaged / post-recovery law sets); FCOM DSC-27-20-20-50 (Mechanical Back-Up — purpose and MMEL objectives, "very unlikely", THS MAN PITCH TRIM ONLY, BCM yaw with its own B/Y-supplied generator). Per FCTM AOP-10-30-10 (definition of the control law) and FCTM AOP-10-30-20 (flying in reconfiguration laws; Alternate / Direct / Backup techniques; "roll control law will always be in direct law"). Dispatch split per the operator MEL (item ME-27): F/CTL ALTN LAW dispatchable under conditions, F/CTL DIRECT LAW no dispatch. The actuation substrate referenced in §3 is the AMM flight-control arrangement figure (ARROWS INDICATE THE ACTUATION RECONFIGURATION PRIORITIES); the "each law step spends one hardware reconfiguration priority" framing, the state-machine topology, and the VS 1g rationale are integrative synthesis to be confirmed against EFCS Computer Architecture and the per-law articles, not verbatim manual statements.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.