Ailerons — Inboard/Outboard, High-Speed Lockout and Droop

Each wing has two ailerons (inboard and outboard), driven by two electrohydraulic servo-controls each. Beyond roll, they do MLA and droop with the flaps, and the outboard pair is locked out at high speed to protect the wing. There is no aileron trim.

Two inboard and outboard ailerons are provided on each wing; two electrohydraulic servocontrols actuate each aileron... At high speed (Vc higher than 190 kts in CLEAN CONF), the outboard ailerons are servoed to zero. — AMM 27-10-00

1. Layout and functions

Per AMM 27-10-00, each wing carries an inboard and an outboard aileron (four total), each actuated by two electrohydraulic servo-controls (actuation modes), with a maximum deflection of 25°. Together with the spoilers they provide three functions:

• roll control (inboard/outboard ailerons + spoilers 2–6; with the rudder for roll/yaw coordination and Dutch-roll damping);
• MLA (ailerons + spoilers 4–6);
• aileron droop (inboard/outboard ailerons).

There is no aileron trim control; surface position is shown on the SD via the FCDC.

[!note]- The ailerons droop with the flaps to add lift (integrative synthesis) "Aileron droop" means the ailerons deflect down when the flaps are extended (AMM 27-10-00 / DSC-27-10-20) — effectively extending the flapped trailing edge outboard, adding lift in the landing/takeoff configurations. They still move differentially for roll about that drooped position, so droop and roll coexist.

2. The high-speed outboard lockout

At high speed (Vc higher than 190 kts in CLEAN CONF), the outboard ailerons are servoed to zero. In AP mode and in certain failure cases, the outboard ailerons are used up to 300 kts. When the RAT is extended, the outboard ailerons are not used, associated servo controls being switched to the damping mode in order to minimize the hydraulic consumption.

Per AMM 27-10-00:

• at Vc > 190 kt in CLEAN CONF, the outboard ailerons are servoed to zero — roll then comes from the inboard ailerons and spoilers;
• in AP mode and certain failure cases, the outboard ailerons are used up to 300 kt;
• with the RAT extended, the outboard ailerons are not used — their servos go to damping to minimise hydraulic consumption.

[!warning]- The outboard ailerons are parked at high speed to protect the wing Above 190 kt clean the outboard ailerons go to zero (AMM 27-10-00): using the outboard surface at high speed imposes large twisting loads on the outer wing, so the system rolls with the inboard ailerons + spoilers instead. The exception (AP / certain failures up to 300 kt) and the RAT case (outboard to damping for hydraulic economy) are the two situations worth remembering — both about managing wing loads and hydraulic power at the wingtip.

3. Actuation and reconfiguration

Per AMM 27-10-00 / 27-14-00, each aileron's two servo-controls run one active, one damping (article 03); the inboard aileron jack connects to one FCPC + one FCSC, the outboard to one FCPC or FCSC. The servos switch automatically to damping on dual hydraulic low pressure (green+yellow or blue+green) or a computer failure. On the ground with hydraulics unpressurised, the ailerons may or may not droop to the servo-control stop depending on bearing/seal friction — a normal, non-fault condition.

[!note]- Damping is the safe fallback here too (integrative synthesis) Just as in the generic actuation logic, a dual-hydraulic or computer failure drops the aileron servos to damping (AMM 27-10-00) — the surface follows the airflow and is flutter-damped rather than locked. The inboard/outboard computer split means a single computer or hydraulic loss never disables both ailerons on a wing.

4. Counterintuitive points

[!warning]- Outboard ailerons are servoed to zero above 190 kt clean Roll at high speed uses inboard ailerons + spoilers; outboard return at AP/failure up to 300 kt; RAT → outboard to damping (AMM 27-10-00).

[!warning]- There is no aileron trim, and ground droop is normal No aileron trim control; unpressurised ground droop varies with friction and is not a fault (AMM 27-10-00).

Self-test

[!note]- Q1. How many ailerons per wing, how actuated, and max deflection? Inboard + outboard (two per wing), each by two electrohydraulic servo-controls; 25° max.

[!note]- Q2. What happens to the outboard ailerons above 190 kt clean, and with the RAT out? Servoed to zero above 190 kt CLEAN (up to 300 kt with AP/certain failures); with RAT extended they go to damping (hydraulic economy).

[!note]- Q3. What is aileron droop? Ailerons deflect down with the flaps to add lift, still moving differentially for roll.

[!note]- Q4. Which computers drive the inboard vs outboard aileron jacks? Inboard: one FCPC + one FCSC; outboard: one FCPC or FCSC; auto-damping on dual hydraulic low pressure or computer fault.

Key takeaways

References

• AMM 27-10-00 (Aileron — Description and Operation) — two ailerons (inboard/outboard) per wing, two electrohydraulic servo-controls each; functions roll control (with spoilers 2–6, rudder roll/yaw coordination + Dutch-roll damping), MLA (with spoilers 4–6), aileron droop; manual roll from sidesticks → FCPC + FCSC per control laws; outboard ailerons servoed to zero above Vc 190 kt CLEAN, used to 300 kt in AP/certain failures, switched to damping when RAT extended (hydraulic economy); ground unpressurised droop varies with friction; no aileron trim; position on SD via FCDC.
• FCOM DSC-27-10-20 / AMM 27-14-00 — two ailerons + five spoilers per wing, 25° max aileron deflection, droop with flaps; servojack active/damping, auto-damping on dual hydraulic low pressure or computer fault; inboard jack one FCPC + one FCSC, outboard one FCPC or FCSC.

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.