Spoilers (1) — Roll Assist and Speedbrake, the Summed Surfaces

Each wing has six spoilers (1–6) that serve three overlapping jobs by summing demands on the same surfaces: roll assist, speedbrake, and MLA. This article covers the two in-flight functions — roll (spoilers 2–6) and speedbrake (spoilers 1–6) — plus the fail-safe behaviour. The ground-spoiler function and the full allocation matrix are in article 23.

Six spoilers (1 thru 6) are installed on the rear upper surface of each wing. They are used in different configurations for: roll control (spoilers 2 thru 6 and ailerons), speed brake and ground spoiler function (spoilers 1 thru 6), maneuver load alleviation (spoilers 4 thru 6 and ailerons). — AMM 27-60-00

1. Six spoilers, three functions

Per AMM 27-60-00, each wing carries six spoilers on the rear upper surface, with a maximum deflection of 35°, each positioned by one servojack powered from green, yellow or blue and controlled by a PRIM or SEC. The function allocation:

[!note]- One surface, several demands summed (integrative synthesis) A spoiler can be doing roll + speedbrake + MLA at once — the computer adds the demands on each surface. Speedbrake is symmetric (both wings up together), roll is differential (the down-going wing's spoilers rise), and MLA is symmetric on 4–6. Note spoiler 1 is excluded from roll (10), and in direct law spoilers 2, 3 and 6 are inhibited (13).

2. Roll assist

Per AMM 27-60-00, spoilers 2–6 assist the ailerons in roll: on the wing being rolled down, the spoilers rise to dump lift on that side, augmenting the aileron roll moment. They move differentially about whatever symmetric speedbrake/MLA deflection is already commanded, so roll and speedbrake coexist on the same surfaces.

3. Speedbrake

Per AMM 27-60-00, for the speedbrake the control lever sends electrical signals to the FCPC, which extends them to the FCSC, which drives the spoiler servocontrols — spoilers 1–6 extend symmetrically for in-flight deceleration. (The detailed lever logic and operational inhibitions are in the FCOM limitations/procedures, not the DSC-27 description.)

[!warning]- Speedbrake and roll share the surfaces — roll keeps priority margin Because speedbrake (symmetric) and roll (differential) use the same spoilers, the system must keep roll authority while the speedbrakes are out: it commands a symmetric base deflection for speedbrake and adds the differential roll on top (AMM 27-60-00). This is why full speedbrake with a large roll input can leave the down-going-wing spoilers near their limit while the other wing's retract — roll is preserved by giving back symmetric deflection.

4. Fail-safe behaviour

Per FCOM DSC-27-10-20:

• the system automatically retracts a spoiler to zero on a fault or loss of electrical control;
• on hydraulic pressure loss, the spoiler retains its deflection — or less if aerodynamic forces push it down;
• when a spoiler fails on one wing, the symmetric one on the other wing is inhibited — except spoilers 4 and 6.

[!warning]- A faulted spoiler retracts — a stuck-up spoiler is the danger to avoid The fail-safe is retract to zero (FCOM DSC-27-10-20): an extended spoiler that can't be controlled would spoil lift asymmetrically, so the system parks it down. The symmetric-inhibit rule keeps roll symmetric after a single-spoiler failure (drop the mirror surface too) — but 4 and 6 are exempt because they are needed for MLA/speedbrake. On a pure hydraulic loss the surface simply holds or blows down, which is benign.

5. Counterintuitive points

[!warning]- Spoiler 1 does not do roll Roll uses spoilers 2–6 + ailerons; spoiler 1 is speedbrake/ground-spoiler only (AMM 27-60-00).

[!warning]- A failed spoiler's mirror is inhibited — except 4 and 6 Single-spoiler failure inhibits the symmetric surface for roll symmetry, but spoilers 4 and 6 are exempt (FCOM DSC-27-10-20).

Self-test

[!note]- Q1. How many spoilers per wing, max deflection, and the three function groups? Six (1–6), 35° max; roll 2–6, speedbrake/ground spoiler 1–6, MLA 4–6.

[!note]- Q2. How do roll and speedbrake coexist on the same spoilers? Speedbrake is a symmetric base deflection; roll is added differentially on top — the demands are summed.

[!note]- Q3. What does a spoiler do on a fault vs a hydraulic loss? Fault / loss of electrical control → retract to zero; hydraulic loss → holds its deflection or less (aero blows it down).

[!note]- Q4. The symmetric-inhibit rule and its exception? A spoiler failing on one wing inhibits the mirror spoiler — except spoilers 4 and 6.

Key takeaways

References

• AMM 27-60-00 (Spoiler — Description and Operation) — six spoilers (1–6) on rear upper surface of each wing; roll control (spoilers 2–6 + ailerons), speedbrake + ground spoiler (spoilers 1–6), MLA (spoilers 4–6 + ailerons); speedbrake lever → FCPC → FCSC → spoiler servocontrols; one FCPC or FCSC controls each servocontrol; position on lower ECAM via FCDC.
• FCOM DSC-27-10-20 (Architecture — Spoilers) — one servojack per spoiler (green/yellow/blue, PRIM or SEC), 35° max; auto-retract to zero on fault or loss of electrical control; hydraulic loss → retains deflection or less (aero pushes down); failed spoiler on one wing inhibits symmetric one except spoilers 4 and 6; spoilers 2/3/6 inhibited in direct law.

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.