Angle-of-Attack Protection

Normal Law carries four envelope protections. Three of them — load-factor, pitch-attitude, high-speed — keep the aircraft from flying badly. The fourth, high angle-of-attack (AOA) protection, is the one that keeps the aircraft from stalling, and that is why the manual gives it priority over all the others. This article enlarges that single protection: what αPROT and αMAX are, how the sidestick changes meaning when AOA protection engages, why full back stick is the correct input in a GPWS or windshear escape, how the THS is half-frozen on the way in, why releasing the stick does not exit the protection, and how the same protection behaves up at the buffet boundary at high Mach.

It builds directly on Normal Law (Pitch): the everyday law is a load-factor demand law — stick deflection orders g, independent of speed. AOA protection is what happens at the low-speed end of that law when the aircraft can no longer be left to fly purely on g.

[!warning]- At αPROT the sidestick stops meaning "g" and starts meaning "angle of attack". This is a change of law, not an added limiter.

In ordinary Normal Law the stick is a load-factor demand — pull half-back, get a steady g. The single most important fact in this chapter is that the moment the current AOA exceeds αPROT, the demand law is switched: the same stick now commands an angle of attack. Per FCOM, the normal law demand is modified and the side stick input is an angle-of-attack demand, instead of a load factor demand. This is why the protection sits "above" the others — it does not clip the load-factor demand at the edge, it replaces the whole control path at the very last stage. Carry the "it's just a limiter" model into this chapter and the exit logic, the auto-trim freeze, and the full-back-stick behaviour will all read wrong.

1. Where it sits — the four protections, and why this one has priority

Per FCOM DSC-27-20-10-20, Normal Law's protection set is stated plainly:

The normal law provides complete flight envelope protection as follow: Load factor limitation, Pitch attitude protection, High angle of attack (AOA) protection, High speed protection.

The four are not equal in consequence. Lose load-factor, pitch-attitude (09) or high-speed (08) containment and the aircraft only flies untidily; lose AOA containment and it stalls. (The lateral side of Normal Law — bank-angle protection — is its own subject in Lateral Law and Bank Angle Protection.) The manual makes the ranking explicit. Per FCOM DSC-27-20-10-20:

This High AOA protection has priority over all other protections.

The other protections are written to feed this one rather than compete with it. Load-factor limitation lets the crew pull instinctively to the stop, and then hands the aircraft over. Per FCOM DSC-27-20-10-20:

With load factor protection, the PF may immediately and instinctively pull the sidestick full aft: The aircraft will initially fly a 2.5 g maneuver without losing time. Then, if the PF still needs to maintain the sidestick full aft stick, because the danger still exists, then the high AOA protection will take over. Load factor protection enhances this high AOA protection.

So the sequence the crew actually flies in an escape is 2.5 g first, then AOA hold: the load-factor protection delivers the immediate snatch, and as speed bleeds and the angle climbs, the AOA protection takes the baton and holds the aircraft just short of the stall. Pitch-attitude protection (09) is described the same way — as enhancing high AOA protection — which is why this article is the hinge of the whole protection group.

2. The switch — load-factor demand becomes angle-of-attack demand

The mechanism is one passage, and it is the spine of the article. Per FCOM DSC-27-20-10-20:

In normal law, the aircraft is protected against stall, in dynamic maneuvers or gusts. When the current angle-of-attack becomes greater than αPROT, the high angle-of-attack (AOA) protection activates. Without the flight crew input, the F/CTL computers will maintain the angle-of-attack equal to αPROT. The AOA can be further increased by the flight crew input, up to a maximum value equals to αMAX. When the High AOA protection is activated, the normal law demand is modified and the side stick input is an angle-of-attack demand, instead of a load factor demand. The PF must not deliberately fly the aircraft in the High AOA, except for brief periods, when the maximum maneuvering speed is required.

Read it as three facts a pilot must hold:

αPROT is the trigger and the resting point. Cross it, and with the stick at neutral the computers maintain the angle-of-attack equal to αPROT — the aircraft sits there and does not climb on towards the stall.
αMAX is the ceiling. The crew can ask for more by pulling further, but only up to a maximum value equals to αMAX. The stick cannot drive the aircraft past it.
The stick's units change. Below αPROT the stick is g; above αPROT it is angle of attack. That re-definition is what the diagram below shows.

                sidestick electrical signal
                          │
              ┌───────────┴───────────┐
              ▼                        ▼
     ┌─────────────────┐     ┌─────────────────┐
     │ LOAD FACTOR     │     │ ANGLE-OF-ATTACK │
     │ DEMAND   (g)    │     │ DEMAND   (α)    │
     └────────┬────────┘     └────────┬────────┘
              └──────────┬────────────┘
                         ▼
                ┌─────────────────┐
                │   CHANGEOVER    │   α < αPROT → g-demand path
                │   set by the    │   α > αPROT → α-demand path
                │   current AOA   │
                └────────┬────────┘
                         ▼
                ┌─────────────────┐
                │ ELEVATOR + THS  │
                └─────────────────┘

The two demand paths feed the same surfaces (elevators and THS); only the algorithm upstream of the changeover is swapped. That is the structural reason for the priority claim in §1: AOA protection wins because it seizes the control path at the changeover, downstream of everything else.

[!warning]- "Normal Law has no speed stability" is true — and AOA protection is exactly why it does not need any at the bottom end.

A conventional aircraft is speed-stable: let the speed decay and the nose drops, pushing you back towards trim speed. Normal Law deliberately has none of that — it is a load-factor demand law, so with the stick at neutral the aircraft holds 1 g regardless of speed and there is no nose-drop cue as you slow down. What stops the speed running away is not stability but this hard AOA floor: the aircraft will sit at αPROT and refuse to go slower. The IAS-referenced low speed stability — a genuine nose-down demand built from airspeed — only appears one rung down, in Alternate Law, where AOA protection is lost (per FCOM DSC-27-20-20-20, at low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack). See Alternate Law. Do not confuse the two: in Normal Law the low-speed safety net is angle-of-attack-based; in Alternate Law it is speed-based and weaker.

The angles themselves are not fixed numbers — they move with the aircraft's state, and the computation belongs to the PRIM. Per FCOM DSC-27-20-10-20:

Vα PROT, Vα MAX, and αfloor condition are mainly computed based on the AOA, and therefore they vary with configuration, weight and load factor. The Vα PROT and Vα MAX, displayed on the PFD, are computed by the PRIM. The αfloor activation logic is provided by the PRIM.

The angle is built from the air data. Per FCTM PR-AEP-NAV, the PRIM use a computed single AOA value, that is a combination of the three AOA measured values, both to drive the protection and to compute the speeds shown on the PFD. The three AOA probes are an ADIRS-fed input (ATA-34); the protection's whole sense of "how close to the stall am I" rides on that single synthesised value — a point that matters when a probe goes wrong (§6). The same angle-of-attack sense is put to a separate use elsewhere in the chapter — locking the slats extended near the stall (Slat Alpha/Speed Lock).

3. Reading it on the PFD — αPROT, αMAX and the strips

The crew never sees an angle of attack directly; the PRIM translates each AOA threshold into a speed on the PFD speed scale. The trap is that the two scales run in opposite directions: lower speed means higher AOA.

   C_L (lift coefficient)               PFD SPEED SCALE
   rises with AOA                       (read DOWNWARD = AOA rising)

   C_L ▲           ●  1 g stall          high  │  VLS     ← lowest selectable
       │         ╱  ╲                     spd  │
       │       ╱     ╲  stall             ▲    │  Vα PROT ← top of the amber
       │     ╱  │  │  █                    │   │  ▓▓▓▓▓▓     and black strip
       │   ╱  αPROT │ █ αMAX               │   │  Vα MAX  ← top of the red
       │  ╱     │ αfloor                   │   │  ██████
       │ ╱      │  │  │                    ▼   │
       │╱       │  │  │                   low  │
       └────────┴──┴──┴───► α            spd   │

   AOA  small → large :  αPROT  <  αfloor  <  αMAX  <  (≈ 1 g stall)
   Speed high → low   :  VLS  >  Vα PROT  >  Vα MAX
   ⇒ αPROT sits BELOW αMAX, but Vα PROT sits ABOVE Vα MAX — the scales oppose.

Two markings carry the protection. Per FCOM DSC-27-20-10-20, the aircraft enters the protection at the amber and black strip (αPROT) — the top of that black-and-amber strip is Vα PROT. Per FCOM DSC-31-40, Alpha Protection Speed is the top of a black and amber strip along the speed scale, and Alpha Max Speed — Vα MAX, the speed at αMAX — is the top of a red strip along the speed scale; VLS, the minimum selectable speed, sits above both as the top of an amber strip. The αfloor threshold lies between αPROT and αMAX (§5).

[!warning]- αPROT is below αMAX in angle, but Vα PROT is above Vα MAX in speed. Most pilots get the ordering backwards.

Because a lower speed corresponds to a higher AOA, the speed scale is a mirror of the AOA axis. αPROT (the smaller angle, where protection begins) maps to Vα PROT, the higher speed; αMAX (the larger angle, the ceiling) maps to Vα MAX, the lower speed. On the PFD the amber-and-black strip (Vα PROT) therefore sits above the red strip (Vα MAX). If you reason "αPROT comes first so its speed must be lower", you have it inverted — first in angle is last in speed.

4. Holding full back stick — what the aircraft does, and the THS

This is the paragraph the escape manoeuvre depends on. Per FCOM DSC-27-20-10-20:

The angle-of-attack will not exceed αMAX, even if the flight crew gently pulls the sidestick all way back. The flight crew can hold full back stick, if it is needed, and the aircraft stabilizes at an angle-of-attack close to but less of the 1 g stall. When flying at the αMAX, the PF can make gentle turns, if necessary. If the flight crew releases the sidestick, the angle-of-attack returns to the αPROT and stays there. As the aircraft enters the protection at the amber and black strip (αPROT), the system inhibits further nose-up trim beyond the point already reached. The nose-down trim remains available, if the flight crew pushes the stick forward.

Three things to take operationally:

Full back stick parks the aircraft at αMAX, close to but less of the 1 g stall. That is the design intent: it wrings out the maximum usable lift (the AOA just short of the C_L peak) while still keeping a sliver of margin. Pulling all the way back is not reckless here — it is the manoeuvre the system was built to fly. (With both pilots on the sticks at once, the inputs combine under the dual-input rules of Sidestick Priority Logic.)
You can still turn. At αMAX the PF can make gentle turns, if necessary — useful when an escape also needs a heading change.
Release returns you to αPROT, not to normal flight. Let the stick go and the angle drops back to αPROT and stays there. The aircraft remains inside the protection; relaxing the stick is not the way out (see §7).

One special case sits inside the same FCOM passage. Per FCOM DSC-27-20-10-20, Note: At takeoff, the αPROT is equal to the αMAX for 8 s. — for those eight seconds at takeoff the two angles coincide, rather than αPROT sitting below αMAX as it does everywhere else (§3).

The THS is half-frozen on entry

Auto-trim does not keep winding nose-up into the protection. The trigger and the limits come from the FLIGHT MODE rules. Per FCOM DSC-27-20-10-20:

When the angle of attack protection is active, the THS is limited between setting at entry in protection and 2 ° nose down (i.e. further nose up trim cannot be applied).

So on entering the protection the stabiliser is pinned between the value it held at entry and 2° nose-down. Nose-up trim is locked; nose-down trim stays live, matching the cabin-facing line above (the nose-down trim remains available, if the flight crew pushes the stick forward).

[!warning]- Freezing nose-up trim is what keeps the recovery from fighting you.

If the THS were allowed to keep trimming nose-up while you sat at high AOA, then the instant you pushed to recover, the stabiliser's stored nose-up bias would resist the push and tend to drag the nose back up into the protection. By capping trim at the entry setting and leaving only the 2°-nose-down range available, the system pre-loads an escape route: there is always a nose-down path out, and never a nose-up trim state working against the recovery. The freeze is not a side-effect — it is half of how the protection stays safe to leave.

5. The energy handover — αfloor between αPROT and αMAX

Holding the angle does not hold the energy: pin the AOA at αMAX with the thrust at idle and the aircraft still sinks. That is where α floor takes over, automatically commanding go-around thrust. Per FCOM DSC-27-20-10-20:

Between αPROT and αMAX, the αfloor protection may automatically set go-around thrust. The αfloor will usually be triggered just after entering the αPROT, and go-around thrust will automatically be applied. Therefore, if the sidestick is held aft, either inadvertently or deliberately, the aircraft will start to climb at a relatively constant low airspeed. To recover a normal flight condition, the αPROT should be exited by easing forward on the sidestick, as described above, and the αfloor should be cancelled by using the disconnect pushbutton on either thrust lever as soon as a safe speed is regained. Refer to DSC-22_30-50-50 ALPHA FLOOR for more information.

The clean way to remember the division of labour: αPROT holds the angle (PRIM, on the surfaces); α floor restores the energy (auto-thrust, go-around thrust) — and α floor fires almost the instant you enter αPROT, so in practice the two arrive together. The result is the climb at a relatively constant low airspeed the manual describes. The full α floor logic — its trigger band, the TOGA LK latch, and its inhibitions — is its own article: Alpha Floor / TOGA Lock. Here, only the handshake matters.

6. The other end — high altitude, the buffet boundary, and an abnormal V Alpha Prot

The same protection works up high, but against a different limit. At altitude the threat is not a low-speed stall but the buffet boundary, and the protective angle shrinks with Mach. Per FCOM DSC-27-20-10-20:

The aircraft can also enter αPROT at a high level, where it protects the aircraft from the buffet boundary. As at the low speed or low level, if the sidestick is merely released to neutral, the aircraft maintains the alpha for αPROT. This value of alpha is not the same as the value used at the low speed. The alpha for αPROT is reduced as a function of Mach, therefore, the aircraft may climb with the sidestick free, when leaving a turn after entering αPROT.

[!warning]- At high altitude the aircraft can climb on its own with the stick released — and that is the protection working, not a malfunction.

Pull into a steep high-altitude turn and you may brush αPROT (a bank needs more AOA to hold level). Roll out, and the AOA needed for level flight drops — but the protection still wants to hold the αPROT angle, and because αPROT is reduced as a function of Mach, that angle now corresponds to a climbing attitude. So as you leave the turn with the stick free, the nose rises and the aircraft climbs by itself. A crew that does not know the mechanism may read this as a runaway; it is the buffet-boundary protection holding its angle. Ease the stick forward if you do not want the climb.

When the displayed Vα PROT is wrong

Because the protection rides on the single synthesised AOA value, a faulty probe corrupts it. Per FCTM PR-AEP-NAV:

the high AOA protection and the display of the V Alpha Prot may be affected by inaccurate AOA measured values in some exceptional conditions: One or several AOA probes blocked, or Damage to the probe that causes a small offset in the measurement of the AOA value.

and:

In this situation, the V Alpha Prot may reach the current airspeed and the high AOA protection may initially trigger based on the erroneous computed AOA value.

The tell-tale is an abnormal rise of Vα PROT (the top of the black-and-amber strip) as Mach increases. The QRH procedure applies only under stabilised conditions — a steady flight path and heading, with Vα PROT above Green Dot speed. Per QRH ABN-NAV (Abnormal V Alpha Prot):

If V Alpha Prot (top of the black and amber strip) exceeds Green Dot speed during stabilized flight path (level flight or stabilized climb) with steady heading. V ALPHA PROT ... MONITOR. ... During stabilized flight path with steady heading, if margin between V Alpha Prot and current airspeed decreases below 15kt: ALTITUDE ... DO NOT INCREASE; MACH ... DO NOT INCREASE.

The "why" behind the limits is in the FCTM: as Mach rises the protection triggers at a lower computed AOA, so the margin between current airspeed and Vα PROT shrinks — do not climb or accelerate further, or that margin keeps closing and the protection may trip spuriously. The fuller unreliable-AOA handling belongs with the ADIRS chapter (ATA-34); here it is the interface that matters.

7. Leaving the protection — three keys, and the technique

Releasing the stick does not exit the protection — it only returns you to αPROT (§4). Getting out takes a deliberate push, and the threshold depends on how high the angle still is. Per FCOM DSC-27-20-10-20:

The aircraft leaves angle-of-attack protection when the: Sidestick is pushed more than 8 ° forward, or Sidestick is pushed more than 0 ° forward for at least 1 s, when α < αMAX, or The sidestick is at neutral or pushed forward, for at least 0.5 s, when α < αPROT.

The design logic is a graded hysteresis: the lower the angle, the easier the exit.

Current AOA	What it takes to exit
High (near αMAX)	a decisive push — sidestick more than 8° forward
Below αMAX	any forward push (> 0°) held at least 1 s
Below αPROT	sidestick neutral or forward, held at least 0.5 s

The hysteresis exists so a momentary stick wobble cannot bounce you out of a stall protection. In a life-critical regime the system would rather hold on a fraction too long than let go a fraction too early.

The recommended technique combines the push with thrust. Per FCOM DSC-27-20-10-20:

If the flight crew flies into αPROT, the flight crew should leave it as soon as other considerations allow, by easing forward on the sidestick to reduce alpha below the value of αPROT, while simultaneously adding power (if the αfloor has not yet been activated, or has been cancelled).

— ease forward to drop the angle, add power at the same time, and if α floor has already fired, cancel it with the thrust-lever disconnect once a safe speed is back.

8. Why it is worth having — the GPWS / windshear payoff

The protection earns its keep in the escape. Per FCOM DSC-27-20-10-20:

In the case of application of GPWS or windshear procedures, the aircraft protections provide maximum lift / maximum thrust / minimum drag. Therefore, CFIT escape maneuvers will be much more efficient.

The three together come from the pieces already covered: maximum lift because high AOA protection holds the aircraft at an angle close to but less of the 1 g stall, at the C_L peak (§4); maximum thrust because α floor commands go-around thrust (§5); minimum drag because the angle is held just short of, not into, the stall, avoiding the drag of a stalled wing.

The manual quantifies the gain against an unprotected aircraft. Per FCOM DSC-27-20-10-20:

The graph demonstrates the efficiency of the protection, to ensure a duck-under that is 50 % lower, a bucket-distance that is 50 % shorter, a safety margin that more than doubles (due to a quicker reaction time), and a significant altitude gain (± 250 ft). These characteristics are common to all protected aircraft, because the escape procedure is easy to achieve, and enables the PF to fly the aircraft at a constant AOA, close to the max AOA. It is much more difficult to fly the stick shaker AOA on an aircraft that is not protected.

   ALT
     │                                  ╱── protected A/C
     │                              ╱──╱    (climbs out early, ±250 ft gain)
   0 ┼──●─────────────────────────╱──────── initial altitude
     │   ╲                     ╱
     │    ╲   protected       ╱
     │     ╲___duck-under____╱     50% shallower, 50% shorter
     │      ╲               ╱
     │       ╲  non-       ╱── non-protected A/C
     │        ╲ protected ╱
     │         ╲_________╱        deeper duck-under, longer bucket
     └───┬──────────────────────────────► distance
      "GPWS PULL UP"

The teaching point sits in the last sentence: on an unprotected aircraft the pilot must hand-fly the angle right at the stick-shaker edge — pull too little and the performance is left on the table, too much and it stalls. The A330 hands that job to the computer: pull fully back, and the aircraft parks itself at αMAX. The duck-under halves and the climb-out comes early because the escape is easy to achieve — which is the entire reason the protection exists.

[!warning]- The protection is the licence to pull all the way in an escape — not an invitation to fly against the stall in normal operations.

Per FCOM, the PF must not deliberately fly the aircraft in the High AOA, except for brief periods, when the maximum maneuvering speed is required. The value of high AOA protection is that in a GPWS pull-up or a windshear escape you can apply full instinctive aft stick and extract every bit of performance without stalling. It is not a wall to lean on day-to-day. This is the chapter-wide protection philosophy — full authority for instinctive emergency action, while still flying inside the envelope yourself — set out in Flight Control Fundamentals and FCTM AOP-10-30-10.

Self-test

[!note]- Q1. When AOA protection activates, what changes about the sidestick? Where does the aircraft stop with full back stick, and where does it go when you let go?

The demand law switches: in ordinary Normal Law the stick is a load-factor (g) demand; once the current AOA exceeds αPROT, the stick becomes an angle-of-attack demand. This is a change of law, not an added limiter, which is why AOA protection has priority over all other protections — it seizes the control path at the final changeover. With full, gentle back stick the angle will not exceed αMAX; the aircraft stabilises close to but less of the 1 g stall, wringing out maximum lift. Release the stick and the angle returns to αPROT and stays there — you are still inside the protection.

[!note]- Q2. On entering the protection, how is the THS auto-trim limited, and why is that arranged this way?

The THS is limited between setting at entry in protection and 2 ° nose down — further nose-up trim is locked, but nose-down trim stays available if the pilot pushes. The reason is recovery: if nose-up trim could keep winding while you sat at high AOA, it would fight the push when you tried to recover and drag the nose back up. Capping trim at the entry value and leaving only the nose-down range pre-loads a clean escape path — there is always a way out and never a nose-up trim state resisting it.

[!note]- Q3. A pilot says "to get out of AOA protection, just let the stick go." Correct?

No. Releasing the stick only returns the aircraft to αPROT; it does not exit the protection. Leaving requires a forward input, with a threshold that eases as the angle drops: sidestick more than 8° forward; or any forward push (> 0°) held at least 1 s when α < αMAX; or neutral/forward held at least 0.5 s when α < αPROT. The graded hysteresis stops a momentary stick wobble from bouncing the aircraft out of a stall protection. The technique is to ease forward to drop the angle while simultaneously adding power.

[!note]- Q4. At high altitude you leave a turn and the aircraft climbs with the stick released. Is something broken?

No — it is the protection working. Up high, αPROT guards the buffet boundary, and the protective angle is reduced as a function of Mach, so it differs from the low-speed value. Having entered αPROT in the turn, the system holds that angle; when you roll out, the AOA needed for level flight falls, but the held αPROT angle now corresponds to a climb, so the aircraft climbs with the stick free. Ease forward if you do not want it.

[!note]- Q5. In a GPWS or windshear escape, what does the protection deliver, and how much better is it than an unprotected aircraft?

It provides maximum lift / maximum thrust / minimum drag — maximum lift from holding the AOA at the C_L peak just short of the stall, maximum thrust from α floor going to go-around thrust, minimum drag from staying short of (not into) the stall. Against an unprotected aircraft: a duck-under 50% lower, a bucket-distance 50% shorter, a safety margin that more than doubles, and an altitude gain of about ±250 ft — because the pilot only has to pull fully back while the computer parks the aircraft at αMAX, instead of hand-flying the stick-shaker edge.

[!note]- Q6. Vα PROT (the top of the amber-and-black strip) creeps up towards your airspeed in the cruise. What is happening and what do you do?

A blocked or slightly offset AOA probe can corrupt the single computed AOA value the PRIM uses, so the displayed Vα PROT rises abnormally as Mach increases and may approach current airspeed — possibly tripping the protection on the erroneous value. If the flight path and heading are stabilised and Vα PROT exceeds Green Dot speed, apply the QRH Abnormal V Alpha Prot procedure: MONITOR Vα PROT, and if the margin to current airspeed falls below 15 kt, do not increase altitude and do not increase Mach — both would shrink the margin further. Fuller unreliable-AOA handling is an ADIRS (ATA-34) matter.

Key takeaways

#	Point
1	High AOA protection has priority over all other protections — it switches the whole demand law, it does not merely clip the load-factor demand.
2	Above αPROT the sidestick becomes an angle-of-attack demand; with no input the aircraft holds αPROT; full back stick holds αMAX, close to but less of the 1 g stall; releasing the stick returns to αPROT (not out of the protection).
3	On entry the THS auto-trim is locked nose-up (limited between the entry setting and 2° nose-down); nose-down trim stays available — pre-loading a clean recovery path.
4	Vα PROT = top of the amber-and-black strip; Vα MAX = top of the red strip; both computed by the PRIM. αPROT < αMAX in angle, but Vα PROT > Vα MAX in speed (scales oppose).
5	At high altitude αPROT guards the buffet boundary and reduces with Mach, so the aircraft can climb with the stick free on leaving a turn. A faulty AOA probe can drive Vα PROT abnormally high (QRH: monitor; margin < 15 kt → do not increase altitude/Mach).
6	Exit needs a forward push: > 8° forward; or > 0° for ≥ 1 s when α < αMAX; or neutral/forward for ≥ 0.5 s when α < αPROT. Technique: ease forward and add power; cancel α floor with the thrust-lever disconnect once safe.
7	Escape payoff — maximum lift / maximum thrust / minimum drag; against an unprotected aircraft, duck-under 50% lower, bucket-distance 50% shorter, margin more than doubled, ±250 ft altitude gain.

References

Per FCOM DSC-27-20-10-20 (Flight Control System – Normal Law: the four-protection overview; high AOA protection trigger at αPROT and the load-factor-demand → angle-of-attack-demand switch; hold to αMAX, close to but less of the 1 g stall, gentle turns, release returns to αPROT; THS limited between entry setting and 2° nose-down in the FLIGHT MODE auto-trim freeze; takeoff αPROT = αMAX for 8 s; priority over all other protections; load-factor protection handover to high AOA protection; buffet-boundary entry and reduction with Mach, climb with stick free; three exit conditions and the ease-forward-with-power technique; α floor between αPROT and αMAX; Vα PROT/Vα MAX/αfloor computed by the PRIM; GPWS/windshear maximum lift / maximum thrust / minimum drag; protected-vs-unprotected trajectory — duck-under 50% lower, bucket-distance 50% shorter, margin more than doubled, ±250 ft gain). Per FCOM DSC-31-40 (PFD indications — Alpha Protection Speed as the top of a black-and-amber strip, Alpha Max Speed as the top of a red strip, Minimum Selectable Speed VLS as the top of an amber strip). Per FCOM DSC-27-20-20-20 (Alternate Law low speed stability — IAS-referenced nose-down demand — cited only to mark the Normal-vs-Alternate boundary). Per FCTM PR-AEP-NAV (single computed AOA value from three probes; abnormal V Alpha Prot from blocked/offset AOA probes; when-to-apply conditions and the Mach/altitude rationale). Per QRH ABN-NAV (Abnormal V Alpha Prot — monitor; margin < 15 kt → do not increase altitude/Mach). Per FCTM AOP-10-30-10 (protection design philosophy, referenced via Flight Control Fundamentals).

The ASCII figures (demand-changeover schematic, C_L/AOA-to-speed-scale cascade, and protected-vs-unprotected trajectory) are redrawings of the corresponding FCOM "Airbus AOA Protection" and "Protected A/C Versus Non-protected A/C Go-around Trajectory" figures, reconstructed from the figure logic; exact graphical layout follows the source. The attribution of the maximum lift / maximum thrust / minimum drag triplet to high AOA protection, α floor, and the just-short-of-stall angle respectively is integrative synthesis of the cited FCOM statements, not a single verbatim passage.

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.