Slats — Seven per Wing, Blue+Green, Two Actuators Each
The slats share the flaps' architecture — central PCU, two motors, differential gearbox, SFCC control, WTBs — but with slat-specific differences: seven slats per wing on the leading edge, Blue+Green hydraulics, and two actuators per slat. This article focuses on those differences; the shared transmission/POB/half-speed logic is in 26.
Seven single-element slats are installed on each wing... The slats are installed on tracks which are attached to the leading edge of each wing. The operation of the slats is hydro-mechanical. A hydraulic Power Control Unit (PCU) moves the mechanical transmission system which operates the slats. — AMM 27-80-00
1. Seven slats on the leading edge
Per AMM 27-80-00, each wing has seven single-element slats on tracks attached to the leading edge (vs two flaps on the trailing edge). They are driven by the slat PCU through torque shafts and gearboxes to the actuators, monitored and controlled by the same two SFCCs that run the flaps (each SFCC's slat channel), via the shared CSU.
[!note]- Same computers, separate transmissions (integrative synthesis) The slats and flaps share the two SFCCs and the lever/CSU, but each has its own PCU, own torque-shaft transmission, own WTBs and own hydraulics (25). That is why a single SFCC loss slows both to half speed (shared computer), while a hydraulic loss slows only slats or only flaps (separate PCUs) — the article-25 degradation rule in mechanism form.
2. Blue+Green, two actuators per slat
Per AMM 27-84-00, the slat PCU is supplied by the Blue and Green hydraulic systems (vs Yellow+Green for the flaps), with two hydraulic motors, each with a POB and valve block, joined by a differential gearbox — so, exactly as for the flaps, one POB-held motor leaves the other driving at half speed but full torque.
Each slat has two actuators: Type A (levers) and Type B (pinions), installed on the structure. Torque limiters in the transmission and the actuators prevent structural overload, and WTBs protect against asymmetry and runaway (30).
[!note]- The slat/flap hydraulic split is the key memory item (integrative synthesis) Slats = Blue + Green (PCU); flaps = Yellow + Green (PCU). Both share Green, so a Green loss slows both groups, while a Blue loss slows only slats and a Yellow loss slows only flaps (AMM 27-84-00 / 27-54-00). The WTBs use the other pairing (slats blue+green, flaps green+yellow). Knowing which hydraulic feeds which group tells you immediately what a hydraulic failure does to the high-lift system.
3. Indication
Per AMM 27-80-00/85-00, the slat IPPU sends position to the FWC → EIS, shown on the EWD together with the flap position — the single high-lift indication the crew reads.
4. Counterintuitive points
[!warning]- Slats and flaps use different hydraulic pairs — only Green is common Slats Blue+Green, flaps Yellow+Green (AMM 27-84-00 / 27-54-00); a Green loss affects both, a Blue/Yellow loss affects only one group.
[!warning]- Seven slats but two actuators each Each slat is driven by a Type-A (lever) and a Type-B (pinion) actuator off the common transmission (AMM 27-84-00).
Self-test
[!note]- Q1. How many slats per wing, where, and how many actuators each? Seven single-element slats on the leading edge, each with two actuators (Type A lever, Type B pinion).
[!note]- Q2. Which hydraulics power the slat PCU vs the flap PCU? Slats Blue + Green; flaps Yellow + Green (common Green).
[!note]- Q3. What slows only slats vs both vs only flaps? Blue loss → slats only; Green loss → both; Yellow loss → flaps only.
[!note]- Q4. What do the slats share with the flaps, and what is separate? Shared: two SFCCs + lever/CSU; separate: PCU, transmission, WTBs, hydraulics — so one SFCC loss slows both, one hydraulic loss slows one group.
Key takeaways
| Point | Detail |
|---|---|
| Surfaces | 7 single-element slats/wing on the leading edge |
| Actuators | two per slat — Type A (lever) + Type B (pinion) |
| PCU hydraulics | Blue + Green (vs flaps Yellow+Green); two motors + differential gearbox |
| One-motor loss | half speed, full torque (as flaps) |
| Shared / separate | shared 2 SFCCs + CSU/lever; separate PCU/transmission/WTB/hydraulics |
| Protection | torque limiters, APPU, WTB (asymmetry/runaway) |
| Indication | IPPU → FWC → EIS → EWD (with flaps) |
References
- AMM 27-80-00 (Lift Augmenting — Description and Operation) — seven single-element slats per wing on leading-edge tracks, hydro-mechanical; slat PCU + transmission → actuators; two SFCCs (slat channel) + CSU control/monitor; each slat two actuators; torque limiters prevent structural overload; WTBs protect asymmetry/runaway; IPPU → FWC → EIS, position on EWD.
- AMM 27-84-00 (Slats Hydraulic Actuation and Power Transmission) — slat PCU supplied by Blue and Green, two hydraulic motors each with POB + valve block, differential gearbox; POB holds on shutdown/low pressure/failure; one motor held → other drives at half speed/full torque; torque shafts/gearboxes → actuators (Type A levers, Type B pinions, two per slat); torque limiters.
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.