Pitch Attitude and Load Factor Protection

Normal Law carries four envelope protections. Two of them — angle-of-attack protection and high-speed protection — guard the speed boundaries: how the aircraft saves itself when it is about to stall, or has run away to the high side of the speed scale. The other two, covered here, guard a different family of risk: over-manoeuvring. They do not sit on a speed edge. They sit on an over-g edge and an attitude edge, and they are the first walls a pilot meets when deliberately pulling the sidestick to the stop in an emergency.

That is exactly why they are the two protections you are meant to lean on. The whole design philosophy of the A330 is that the crew can apply a full, instinctive, immediate input and the computers will hold the aircraft inside the structural and energy envelope. Load-factor limitation and pitch-attitude protection are the part of that promise the pilot exercises most directly. Per FCOM DSC-27-20-10-20, the normal flight mode itself is built around this:

The normal law flight mode is a load factor demand law with auto trim and full flight envelope protection.

This article enlarges the two outer walls. The inner two — angle-of-attack and α-floor handling, and high-speed recovery — are taken in AoA Protection, Alpha Floor / TOGA Lock, and High-Speed Protection. The load-factor demand law that both walls are clamped onto is built in Normal Law — Pitch.

[!warning]- The two walls are not the same kind of wall — one clamps, the other reduces your authority.

It is tempting to file both as "limits", but they work by different mechanisms and reading them as identical leads you astray on degradation. Load-factor limitation is a clamp: it is the upper and lower bound of the load-factor demand law, so when you pull fully aft the computers give you the limit g and then simply stop adding — your command is dead-stopped inside the wall. Pitch-attitude protection is an authority-reduction: it does not refuse to fly past the threshold, it progressively reduces your pitch authority once the nose crosses the limit and pulls the attitude back. Per AMM-27-90-00, pitch-attitude protection reduces pilot authority when the aircraft pitch attitude exceeds a defined threshold. Both are honest expressions of the fly-by-wire "full authority plus limiting" philosophy (Flight Control Fundamentals), but they degrade differently — see §5.

1. Where the two walls sit — the four-protection map

After describing the GROUND / FLIGHT / FLARE modes, FCOM opens the protections with a single roster. Per FCOM DSC-27-20-10-20:

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 order matters: load-factor and pitch-attitude come first because they are the protections the pilot commands against, not the ones that quietly catch a developing stall. The reason they exist at all is stated, for pilots, by the FCTM. Per FCTM AOP-10-30-10:

The purpose of the flight control protections is to: ‐ Give full authority to the flight crew, in order to enable them to obtain the best aircraft performance with an instinctive, immediate action on the related control ‐ Minimize the possibility of over-controlling, overstressing, or damaging the aircraft. ... Despite system protections, the PF must not deliberately exceed the normal flight envelope. In addition, these protections are not designed to be structural limit protections (e.g. opposite rudder pedal inputs). Rather, they are designed to assist the PF in emergency and stressful situations, where only instinctive and rapid reactions will be effective.

Keep the second half of that in view throughout. The walls are the confidence to pull all the way in a windshear escape or a TCAS RA — they are explicitly not designed to be structural limit protections, and the PF must not deliberately exceed the normal flight envelope day to day.

1.1 How the walls attach to the demand law

Both protections live inside the load-factor (Nz) demand law, not as separate boxes bolted on. Per AMM-27-90-00, the Nz law is the normal pitch law in which the pilot commands a load factor, and:

In addition, the Nz law enables: ‐ load factor limitation, depending on the flap and slat position, ‐ bank angle compensation, for bank angles lower than 33°, ‐ deflection limitation of the THS in the nose-up direction in the event of activation of the high angle-of-attack protection, excessive load factor and excessive bank angle.

So load-factor limitation is a property of the demand law itself (its ±g bound), and pitch-attitude protection is, per AMM-27-90-00, an integral part of the Nz law that enhances the effectiveness of the angle of attack and high speed protection. The map below shows how the pitch axis routes your stick:

                            ┌────────────────────┐
                            │  HIGH SPEED PROT.  │  art. 08
                            │  (nose-up bias in) │
                            └─────────┬──────────┘
                                      │ pushes down
  ┌───────────┐   normal path   ┌─────▼──────────────┐   surface   ┌──────────┐
  │ SIDESTICK ├────────────────►│  LOAD FACTOR       ├────────────►│ ELEVATOR │──► PITCH
  │  (pitch)  │                 │  DEMAND  (Nz law)  │   command   │  + THS   │
  └─────┬─────┘                 │  ├─ ±g clamp       │             └──────────┘
        │                       │  └─ pitch-att lim  │
        │                       └─────▲──────────────┘
        │                             │ enhances (pulls up)
        │                       ┌─────┴──────────────┐
        │                       │  PITCH ATTITUDE    │  art. 09
        │                       │  PROTECTION        │
        │                       └────────────────────┘
        │  AoA PROT active      ┌────────────────────┐
        └──────────────────────►│  AoA DEMAND        │  art. 06/07
           (switches the law)   │  stick = AoA       │
                                └────────────────────┘

Three readings come off this, and each is a question this article must answer:

1. Normally your pitch stick feeds the load-factor demand law. Pull = ask for more g, release = ask for 1 g. Load-factor limitation is just the ±g bound on that demand; pitch-attitude protection is a correction folded into it from below. Neither changes what the stick means — you are still asking for g.
2. When AoA protection activates, the stick changes meaning — it becomes an angle-of-attack demand (the law itself switches, covered in AoA Protection). The two walls in this article are quantitative limits on the same demand; AoA protection is a different demand altogether. This is the line that separates "limit" from "law change".
3. The protections are not peers. High-speed protection pushes a bias down into the demand, pitch-attitude protection pulls up into it, but only AoA protection has the authority to switch the law — per FCOM it has priority over all other protections (AoA Protection).

2. Load-factor limitation — making "pull to the stop" instinctive

2.1 Why the wall exists

An airline pilot may go a whole career without pulling 2.5 g. There is no continuous g-meter in the cockpit, so crews have no muscle memory for the parameter, and when a sudden avoidance is needed the human reaction is, as FCOM observes, two-stage: hesitant, then aggressive. Those hesitant seconds are precisely the seconds an avoidance manoeuvre cannot spare. Load-factor limitation removes the cost of that hesitation — pull fully aft and the aircraft delivers the limit g at once, with no way to over-stress the wing in the process. FCOM frames the motive in full. Per FCOM DSC-27-20-10-20:

On commercial aircraft, high load factors can be encountered during evasive maneuvers due to potential collisions, or CFIT …

and the operative principle:

Pulling "g" is efficient, if the resulting maneuver is really flown with this "g" number. If the aircraft is not able to fly this trajectory, or to perform this maneuver, pulling "g" will be detrimental.

The numbers themselves are configuration-dependent. Per FCOM DSC-27-20-10-20:

The load factor is automatically limited to : +2.5 g to -1 g, slats retracted +2 g to 0, slats extended

2.2 Why the limit shrinks with slats out

The clean-configuration bounds (+2.5/−1 g) are the classic transport-category structural design load factors; with slats and flaps deployed the upper bound drops to +2 g and the lower bound moves from −1 g up to 0. The reasoning is structural — the deployed high-lift devices are a lower-strength load path, and a negative g would drive reverse aerodynamic load onto the flap underside — so the envelope is narrowed while they are out. (The structural attribution is integrative reasoning; FCOM states the values, not the cause — confirm against the structural limits in ATA-05.)

What is in the manual is how the aircraft picks the right pair: it is automatic, not a pilot selection. Per AMM-27-90-00 the Nz law provides load factor limitation, depending on the flap and slat position. Read against the cockpit, this means that when you extend slats on approach the upper bound slides silently from 2.5 to 2 g with no change in stick feel. The same Nz-law clause also names a second, related limiting action: deflection limitation of the THS in the nose-up direction in the event of ... excessive load factor. That ties straight back to the auto-trim logic — per FCOM DSC-27-20-10-20, when the load factor is higher than 1.3 g ... the THS is limited between the actual setting and 2 ° nose down, so above 1.3 g the system stops trimming further nose-up and cannot drive you closer to the g wall (Normal Law — Pitch, THS).

2.3 The hand-over to AoA protection

The most important mechanism here is what happens after you reach the g limit and keep holding the stick aft. FCOM describes a clean two-stage relay. 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.

and the payoff:

Load factor protection enables immediate PF reaction, without any risk of overstressing the aircraft.

Joining the chain (integrative reasoning, not a verbatim sequence — the timing is confirmed in AoA Protection): full aft stick → load-factor protection first delivers the 2.5 g manoeuvre, extracting the over-g performance → as speed bleeds and AoA rises to αPROT, the law switches to the AoA-demand branch of the §1.1 map → AoA protection takes over and holds the aircraft at αMAX without stalling. One wall manages the over-g boundary, the next manages the stall boundary, and the baton passes seamlessly. That is why "in an avoidance or a windshear escape, pull fully aft and trust the aircraft" is a legitimate, trained action on type. FCOM backs the value with flight data. Per FCOM DSC-27-20-10-20:

Flight experience has also revealed that an immediate 2.5 g reaction provides larger obstacle clearance, than a hesitant and delayed high G Load maneuver (two-second delay).

2.4 Reading the stick-to-g map

The load-factor demand law maps stick position to commanded g, clamped at the configuration bounds:

  Stick position           Commanded load factor          Clamped to
  ──────────────           ─────────────────────          ──────────
  full aft   ──────────►   maximum pull            ────►   +2.5 g  (slats in)
                                                           +2.0 g  (slats out)
  neutral    ──────────►   1 g  (level, no trim)
  full fwd   ──────────►   maximum push            ────►   −1.0 g  (slats in)
                                                            0   g  (slats out)

Two intuitions to lock in. First, stick neutral commands 1 g — per FCOM DSC-27-20-10-20, with the sidestick at neutral and the wings level, the system maintains 1 g in pitch, with no need to trim for speed (the heart of Normal Law — Pitch). Second, the stick commands a load factor, not a surface deflection — which is the fundamental break from a conventional aircraft, and the reason a full pull is safe: you are asking for g, and the g you can ask for is bounded.

[!warning]- 2.5 g is a command ceiling, not a trajectory guarantee.

The common misreading is "the 2.5 g limit means the aircraft can always pull a 2.5 g turn." Predict it yourself: if the aircraft is low and slow, will pulling fully aft actually fly a 2.5 g path? It will not. FCOM is explicit that pulling "g" is efficient, if the resulting maneuver is really flown with this "g" number — 2.5 g is what the computers will command, but whether the aeroplane can fly a tight 2.5 g radius depends on whether it has the speed and lift to produce that load factor right now. Inside the normal envelope, a full pull buys a tight radius that clears the obstacle; already low on energy, the same full pull yields only a shallow arc that does not. The lesson for the pilot: the protection lets you pull with confidence, but the currency of obstacle clearance is energy management — do not run the energy down and then expect 2.5 g to save you. This is the very reason α-floor exists to add thrust automatically (Alpha Floor / TOGA Lock).

3. Pitch-attitude protection — boxing the nose between +30° and −15°

3.1 Why the wall exists

Extreme pitch attitudes threaten energy directly: too high and speed bleeds away, too low and it runs away. And — the key insight — no emergency manoeuvre needs an extreme attitude; avoidance, pull-up, and recovery all complete inside moderate pitch. With no legitimate need to go there, the system simply walls off the region against upsets and mishandling. Per FCOM DSC-27-20-10-20:

Excessive pitch attitudes, caused by upsets or inappropriate maneuvers, lead to hazardous situations: • Too high a nose-up ▸ Very rapid energy loss • Too low a nose-down ▸ Very rapid energy gain Furthermore, there is no emergency situation that requires flying at excessive attitudes. For these reasons, pitch attitude protection limits pitch attitude to plus 30 °/minus 15 °. Pitch attitude protection enhances high speed protection, high load factor protection, and high AOA protection.

3.2 Reading the limits and the mechanism

The +30° / −15° pair is asymmetric. Nose-up is allowed to 30°, nose-down only to 15° — because a nose-down excursion is the more dangerous direction (speed builds fast and drives straight toward the high-speed boundary), so the nose-down wall is set tighter. These are the manual's definitive figures; this article carries +30° / −15° with nothing softened toward "25°" (see §5 trap). (The asymmetry rationale is integrative reasoning; FCOM states the values, not the why.)

The mechanism is authority-reduction inside the Nz law. Per AMM-27-90-00:

9 Pitch attitude protection This FCPC law is engaged during the flight phase. It is an integral part of the Nz law. This law enhances the effectiveness of the angle of attack and high speed protection in extreme conditions and windshear conditions. It reduces pilot authority when the aircraft pitch attitude exceeds a defined threshold.

So pitch-attitude protection does not slam a door; it progressively withdraws pitch authority as the nose crosses the threshold and lets the attitude settle back inside the box.

3.3 The "protection of protections"

Both FCOM and AMM say the same thing about its real role: it enhances the other three protections. It is the outer backstop that keeps the system's own recovery actions from over-shooting in attitude. Worked example: when high-speed protection drives the nose up to recover from an overspeed dive (High-Speed Protection), pitch-attitude protection guarantees the nose is not driven past +30° — chaining the two so the aircraft recovers from the overspeed without ending up in an attitude upset. Equally it caps the nose-up attitude reachable under AoA protection and bounds the attitude side of a high-g manoeuvre. It is, in effect, the wall that guards the other walls.

[!warning]- +30° / −15° (the fly-by-wire wall) is not the 25° / 13° at which the autopilot drops out — two layers, two numbers.

Many pilots conflate "the autopilot disconnects around 25° nose-up" with "pitch-attitude protection is 25°." Predict it: is the attitude at which the AP hands back the same number as the fly-by-wire protection wall? No — they are two different events at two different layers.

• Fly-by-wire pitch-attitude protection (hand-flying): the computers will not let you fly past +30° / −15°, per FCOM DSC-27-20-10-20.
• Autopilot auto-disengagement (AP engaged): per FCOM DSC-22_30-30-30, the APs will disengage when ... Pitch attitude exceeds 25 ° up, or 13 ° down, or bank angle exceeds 45 °.

The autopilot lets go at the inner 25°/13° so that the decision is handed back to the crew before the aircraft reaches the outer fly-by-wire wall at 30°/15°. Two gates, nested — different numbers, do not mix them.

4. The two walls across a flight — six scenes

1. Cruise, sudden TCAS RA "CLIMB" — you instinctively pull fully aft. Load-factor protection delivers 2.5 g at once (clean configuration) and climbs without hesitation; if AoA rises to αPROT during the manoeuvre, AoA protection takes over and holds it. You fly the green band of the RA; the g wall and the stall wall are kept for you.
2. Approach windshear / GPWS escape — full aft stick plus TOGA. 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 2.5 g pull wrings out the performance and AoA protection flies it at maximum usable AoA — but recall §2.4: with too little energy a full pull yields only a shallow arc, so the escape's currency is energy, not stick.
3. Flaps/slats extended on approach — you feel nothing, yet the limit has switched automatically from +2.5/−1 to +2/0 as the Nz law reads slat/flap position. A full pull now reaches only 2 g, protecting the deployed high-lift devices.
4. High-altitude upset pushes the nose up — pitch-attitude protection boxes the nose-up attitude at +30°, working with AoA protection to keep the aircraft off the stall and from bleeding energy.
5. High-speed dive recovery — on the nose-down side, pitch-attitude protection holds the nose at −15° and refuses to let it drop further, while high-speed protection pushes the nose up and trims away nose-down authority (High-Speed Protection). The two walls together pull the aircraft out of the dive.
6. Degradation to Alternate Law — here the fates of the two walls diverge: load-factor (manoeuvre) protection stays, pitch-attitude protection is lost. That is §5.

5. Degradation — which wall survives, which leaves

When the law steps down to Alternate, the two walls part company. Per FCOM DSC-27-20-20-20:

However, alternate law does not maintain any of the protections, except maneuver protection.

and the reconfiguration table lists the other one explicitly:

PITCH ATTITUDE PROTECTION Lost.

So load-factor (manoeuvre) protection is retained — it is the single protection Alternate Law keeps — while pitch-attitude protection is lost. The reasoning is a clean split of priorities (integrative; FCOM states which is kept and which is lost, the full degradation logic is in Alternate Law): load-factor protection guards against structural over-g, the floor that must not be surrendered even in a degraded law, so it survives with the Alternate-Law load-factor demand. Pitch-attitude protection guards energy and attitude — envelope housekeeping — and once the system steps down, that responsibility is handed back to the crew. Per FCOM DSC-27-20-20-20, in Alternate Law the pilot must fly the aircraft more attentively to avoid inadvertently exceeding the normal limits. In one line: when the law degrades, the structural protection stays, the envelope-management protection is handed back to the pilot.

Self-test

[!note]- Q1. Where do +2.5/−1 g (clean) and +2/0 (slats out) come from, and why do both bounds shrink with slats extended?

They are structural. The clean wing's certified design load factors are +2.5/−1 g; with slats and flaps deployed the high-lift devices are a lower-strength load path, so the upper bound drops to +2 g and the lower bound moves from −1 g up to 0 (no negative g, to avoid reverse aerodynamic load on the flap underside). The switch is automatic — per AMM-27-90-00 the Nz law gives load factor limitation, depending on the flap and slat position, so extending slats slides the upper bound from 2.5 to 2 g with no change in stick feel. (The structural why is reasoning; FCOM states the values.)

[!note]- Q2. Why is "pull fully aft" a safe, instinctive emergency action on the A330, and how do the two walls relay?

Because load-factor protection lets the aircraft initially fly a 2.5 g maneuver without losing time and without any risk of overstressing the aircraft; then, if the danger persists and the stick is held aft, the high AOA protection will take over and holds the aircraft near αMAX without stalling. One wall owns the over-g boundary, the next owns the stall boundary, and the baton passes seamlessly. FCOM flight data shows an immediate 2.5 g reaction gives larger obstacle clearance than a hesitant, two-second-delayed pull — which is why "in an avoidance or windshear escape, pull fully aft and trust the aircraft" is trained and recommended.

[!note]- Q3. Pitch-attitude protection limits to +30°/−15°. Which protections does it "enhance", and why does no emergency need a larger attitude?

It enhances high-speed, high load-factor, and high AoA protection — it is their outer backstop (e.g. when high-speed protection drives the nose up, pitch-attitude protection guarantees it is not driven past +30°). No emergency needs a larger attitude because excessive pitch only causes very rapid energy loss (too nose-up) or gain (too nose-down), while avoidance, pull-up, and recovery all complete inside moderate pitch — with no legitimate need, the region is simply walled off against upsets and mishandling. Note the asymmetry: the nose-down wall is tighter (15°) because a nose-down excursion builds speed fast toward the high-speed boundary.

[!note]- Q4. Is "pitch-attitude protection at 25°" correct?

No — that conflates two different layers. The fly-by-wire pitch-attitude protection wall is +30°/−15° (FCOM DSC-27-20-10-20). The 25° up / 13° down (and 45° bank) figure is the autopilot auto-disengagement threshold (FCOM DSC-22_30-30-30): when the AP is engaged, it drops out at the inner 25°/13° so the decision is handed back to the crew before the aircraft reaches the outer fly-by-wire wall. Two nested gates, two numbers.

[!note]- Q5. After degradation to Alternate Law, which of the two walls survives and which is lost — and why?

Load-factor (manoeuvre) protection survives — it is the only protection Alternate Law keeps; pitch-attitude protection is lost (FCOM DSC-27-20-20-20: alternate law does not maintain any of the protections, except maneuver protection ... PITCH ATTITUDE PROTECTION Lost.). The reasoning: load-factor protection guards against structural over-g, the floor that cannot be surrendered, so it stays with the Alternate-Law load-factor demand; pitch-attitude protection is envelope housekeeping, handed back to the crew, who must fly the aircraft more attentively.

[!note]- Q6. "Pulling g is only efficient if the aircraft can really fly that trajectory" — what is the warning?

That 2.5 g is a command ceiling, not a trajectory guarantee. Whether a full aft pull actually flies a tight 2.5 g radius depends on having the speed and lift (energy) to produce that load factor right now. Inside the normal envelope a full pull buys a tight, obstacle-clearing radius; already low on energy, the same pull yields only a shallow arc that does not clear. The protection lets you pull with confidence, but the currency of obstacle clearance is energy management — which is exactly why α-floor exists to add thrust automatically.

Key takeaways

References

Per FCOM DSC-27-20-10-20 (Normal Law — PROTECTIONS: general roster; load-factor limitation full passage incl. CFIT/evasive motive, "pulling g is efficient" principle, +2.5/−1 and +2/0 values, full-aft 2.5 g then AoA take-over, no-overstress payoff, 2.5 g obstacle-clearance flight data; pitch-attitude protection full passage incl. energy-loss/gain rationale, +30°/−15° limits, "enhances" the three protections; GPWS/windshear maximum-lift/thrust/minimum-drag; auto-trim freeze at 1.3 g; stick-neutral 1 g). Per FCOM DSC-27-20-20-20 (Reconfiguration / Alternate Law: only manoeuvre protection retained, "PITCH ATTITUDE PROTECTION Lost", "fly the aircraft more attentively"). Per FCOM DSC-22_30-30-30 (AP auto-disengagement at 25° up / 13° down / 45° bank). Per FCTM AOP-10-30-10 (flight-control-protection design philosophy: full authority, minimise overstress, not structural-limit protections). Per AMM-27-90-00 (Nz law: load-factor limitation depending on flap/slat position, bank-angle compensation, THS nose-up deflection limitation under excessive load factor; pitch-attitude protection as an integral part of the Nz law that enhances AoA/high-speed protection and reduces pilot authority past a threshold; normal-configuration function list). Items flagged as integrative reasoning — the slats-out structural attribution, the seamless load-factor-to-AoA timing chain, the +30°/−15° asymmetry rationale, and the structural-vs-housekeeping degradation split — are synthesis to be confirmed in the structural (ATA-05), AoA Protection, and Alternate 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.