Lateral Normal Law — Bank Angle Protection, Sideslip Target, Turn Coordination

The roll axis in Normal law is roll-rate demand with automatic turn coordination: the stick commands a roll rate (max 15°/s), the system holds bank, coordinates the turn and damps the Dutch roll — the pilot never needs the rudder for a turn. This article covers lateral control, bank-angle protection (33°/67°/45°), the blue beta sideslip target and how it is flown on an engine failure, the low-energy alert, and the crosswind/engine-out handling techniques.

Normal law combines the controls of the ailerons, spoilers (except spoilers 1), and rudder (for turn coordination) in the sidestick. The flight crew does not need to use rudder for turn coordination purpose... the flight control system automatically limits the roll rate and the bank angle, ensures turn coordination and damps the dutch roll. — FCOM DSC-27-20-10-30

1. Lateral control — roll-rate demand

Per FCOM DSC-27-20-10-30, in flight mode the sidestick commands the ailerons, spoilers (except spoiler 1) and rudder (for turn coordination) together. The roll rate is proportional to stick deflection, max 15°/s at full deflection. The system limits roll rate and bank, coordinates the turn, and damps the Dutch roll — so the crew flies roll and heading and never needs rudder for a turn. Flare mode lateral control is the same as flight mode; on ground the surface deflection per stick depends on speed, and the pedals control the rudder directly.

[!note]- The rudder serves takeoff/landing and engine-out — not turns (integrative synthesis) Per FCTM, the rudder and vertical stabiliser exist to provide lateral/directional control in crosswind takeoff/landing within certified limits, and aircraft control on an engine failure with maximum asymmetric thrust above VMCG — the PRIM/SEC give yaw control, yaw damping and rudder-travel limitation. In Normal-law turns the system coordinates yaw automatically, so the rudder is reserved for the cases that genuinely need it (crosswind, engine-out), not for routine turns. Spoiler 1 is excluded from roll (22).

2. Bank-angle protection — 33°, 67°, 45°

Inside the normal flight envelope, the system maintains positive spiral static stability for bank angles above 33°. If the pilot releases the sidestick at a bank angle greater than 33°, the bank angle automatically reduces to 33°. Up to 33°, the system holds the roll attitude constant when the sidestick is at neutral. If the pilot holds full lateral sidestick deflection, the bank angle goes to 67° and no further.

Per FCOM DSC-27-20-10-30:

[!warning]- 33° is the hands-off bank; 67° the maximum; 45° when a pitch protection is active The three numbers: below 33° the bank is held hands-off (no spiral); above it the aircraft rolls back to 33° if you release; full stick gives 67° max. But if AOA, high-speed, or negative-pitch-attitude protection is operative, full stick only reaches 45° (FCOM DSC-27-20-10-30) — the system tightens the roll envelope when it is already protecting another axis. In high-speed protection spiral stability is referenced to 0° bank (returns wings-level), not 33°.

[!warning]- Bank protection disables auto-trim, and the AP quits at 45° Two consequences: when bank-angle protection is active, auto trim is inoperative (FCOM DSC-27-20-10-30) — consistent with the auto-trim freezes. And if bank exceeds 45° the autopilot disconnects and the FD bars vanish, returning only when bank decreases below 40°.

A steep turn (>33°) is conventional: the PF holds lateral pressure to maintain bank and aft pressure to maintain level flight — because beyond 33° the bank is no longer self-holding.

3. Sideslip target — the blue beta on engine failure

In the case of an engine failure at takeoff, or at go-around, the sideslip index on the PFD changes from yellow to blue... the lateral normal law commands some rudder surface deflection to minimize the sideslip... Zero, the beta target value for optimum performance with appropriate rudder application; Accelerate if beta target cannot be zeroed with full rudder.

Per FCOM DSC-27-20-10-30, on an engine failure at takeoff or go-around the PFD sideslip index changes from yellow to blue — the beta target. The lateral normal law already commands some rudder to minimise sideslip, and the modified indication shows the PF the optimum rudder for best climb (ailerons neutral, spoilers retracted). The crew response is instinctive: zero the blue beta with rudder; if it cannot be zeroed with full rudder, accelerate. Computed by the PRIM.

[!warning]- Fly the blue beta to zero, not the slip ball — and apply rudder promptly on a go-around On an engine-out, the conventional "step on the ball" is replaced by zeroing the blue beta target (FCOM DSC-27-20-10-30) — which is offset from zero sideslip to give optimum climb performance, not aerodynamic zero-slip. The FCTM engine-out go-around technique makes the timing explicit: "On the application of TOGA, the flight crew must apply rudder promptly to compensate for the increase in thrust and consequently to keep the beta target centred" (FCTM PR-AEP-ENG). Centring the blue index gives the best second-segment climb; if full rudder won't centre it, the answer is speed, not more rudder.

4. Engine failure — ground yaw assist and roll-out

Per FCOM DSC-27-20-10-30, on an engine failure during takeoff, spoiler 6 and the ailerons deflect on the wing opposite the failed engine to increase yaw efficiency — which reduces VMCG and improves takeoff performance. Conditions: pedal > 2/3 deflection, on ground, pitch < 2.5°, speed > 60 kt, ground spoilers not active.

Per FCTM PR-AEP-ENG, the engine-failure-at-low-speed technique to keep the centreline: all thrust levers to IDLE (reduces asymmetry), select all reversers (irrespective of which engine failed), and use rudder pedal supplemented by differential braking if needed (apply both on the same side). Note below 72 kt the ground spoilers do not deploy and autobrake does not activate.

[!note]- The spoiler-6 yaw assist is a takeoff-performance tool (integrative synthesis) Raising spoiler 6 + ailerons on the side opposite the dead engine adds yawing moment, reducing VMCG (FCOM DSC-27-20-10-30) — so the certified takeoff performance benefits. It only arms on the ground, below 2.5° pitch, above 60 kt, with > 2/3 pedal — i.e. exactly during a takeoff-roll engine failure where directional control is hardest, and it disengages as the aircraft rotates.

5. Crosswind technique

Per FCTM, on a crosswind roll-out the pilot avoids setting stick into the wind — it increases the weathercock effect by creating a differential down-force on the into-wind wheels. The reversers decrease rudder efficiency (destabilising the airflow) and create a side force on any remaining crab; on a contaminated runway with crosswind, if a lateral-control problem occurs the pilot considers setting reversers back to idle.

[!warning]- Don't hold stick into the wind on roll-out — it makes the weathercock worse Counter to instinct, holding lateral stick into the wind during the roll-out increases the weathercock tendency (FCTM) by loading the into-wind wheels. And reverse thrust reduces rudder authority — so on a slippery crosswind runway, idling the reversers can restore directional control. These are the lateral-axis ground-handling subtleties that the in-flight roll-rate-demand law does not address.

6. Adjunct — the low-energy "SPEED SPEED SPEED" alert

Per FCOM DSC-27-20-10-20, the low-energy aural alert "SPEED SPEED SPEED" (every 5 s) warns that energy has fallen below the level from which a positive flight-path angle can be recovered by pitch alone — thrust must be added. Available in CONF 2/3/FULL between 100 and 2000 ft, PRIM-computed from configuration, deceleration rate and flight-path angle, triggering just before alpha floor. Per FCTM, the low-energy recovery is to "increase the thrust or/and adjust the pitch... until the aural alert stops." Inhibited by TOGA, below 100/above 2000 ft, alpha-floor/GPWS active, alternate/direct law, or both RA failed.

[!note]- "SPEED" precedes alpha floor — add thrust yourself (integrative synthesis) The low-energy alert fires before alpha floor during a deceleration (FCOM DSC-27-20-10-20): it tells the PF to add thrust now (and/or adjust pitch), while there is still time to recover before the automatic TOGA. If alpha floor is triggered by stick deflection rather than deceleration, "SPEED" may not precede it.

7. Counterintuitive points

[!warning]- The stick is a roll-rate demand; rudder is never needed for a turn Max 15°/s, auto turn coordination + Dutch-roll damping (FCOM DSC-27-20-10-30); rudder is for crosswind/engine-out.

[!warning]- Full stick gives 67°, but only 45° when a pitch protection is active And bank-angle protection disables auto-trim; AP disconnects above 45° (FCOM DSC-27-20-10-30).

[!warning]- On engine-out, fly the blue beta to zero — and don't hold stick into wind on roll-out Beta target, not the slip ball (FCOM); reversers cut rudder authority in crosswind (FCTM).

8. Self-test

[!note]- Q1. What does the sidestick command in roll, and the max rate? A roll rate proportional to deflection, max 15°/s; the system auto-coordinates the turn (no rudder needed) and damps Dutch roll.

[!note]- Q2. The 33° / 67° / 45° bank numbers? ≤33° held hands-off; >33° returns to 33° on release; 67° max at full stick; 45° max if a pitch protection is active (AP disconnects > 45°).

[!note]- Q3. What is the blue beta target, how is it flown, and the engine-out go-around timing? The engine-out sideslip target (PFD yellow→blue); zero it with rudder for best climb, else accelerate; on a go-around apply rudder promptly with TOGA to keep it centred.

[!note]- Q4. The crosswind roll-out technique? Do not set stick into the wind (increases weathercock); reversers reduce rudder authority — consider idle reversers if lateral control degrades on a contaminated runway.

[!note]- Q5. What does "SPEED SPEED SPEED" mean and what is the recovery? Low-energy alert — add thrust and/or adjust pitch until it stops; fires just before alpha floor, CONF 2/3/FULL, 100–2000 ft.

9. Key takeaways

References

• FCOM DSC-27-20-10-30 (Normal Law — Lateral Control / Bank Angle Protection / Sideslip Target) — sidestick combines ailerons + spoilers (except spoiler 1) + rudder for turn coordination, roll rate ∝ deflection (max 15°/s), auto roll-rate/bank limit + turn coordination + Dutch-roll damping; bank ≤33° held, >33° returns to 33°, full stick 67° max, 45° max if AOA/high-speed/negative-pitch-attitude protection active, high-speed protection spiral from 0°; bank-angle protection makes auto-trim inoperative, AP disconnects >45° (FD returns <40°); engine-out sideslip yellow→blue (beta target, zero with rudder for optimum climb, accelerate if not zeroable), PRIM-computed; takeoff engine failure spoiler 6 + ailerons opposite side to reduce VMCG (pedal >2/3, on ground, pitch <2.5°, speed >60 kt, ground spoilers not active).
• FCOM DSC-27-20-10-20 (Normal Law — Low Energy Aural Alert) — "SPEED SPEED SPEED" every 5 s, CONF 2/3/FULL 100–2000 ft, PRIM-computed (config/deceleration/FPA), before alpha floor; inhibits (TOGA, <100/>2000 ft, alpha floor/GPWS, alternate/direct law, both RA failed).
• FCTM PR-AEP-ENG / PR-NP-SOP (Engine failure; Crosswind; Go-around) — engine-out go-around apply rudder promptly with TOGA to keep beta target centred; low-speed engine failure idle + all reversers + rudder pedal + differential braking (same side), <72 kt no ground spoilers/autobrake; crosswind roll-out avoid stick into wind (weathercock), reversers reduce rudder authority (consider idle on contaminated runway); low-energy recovery increase thrust/adjust pitch until alert stops.

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.