Automatic Flap Retraction and Load Relief (ARS and FLRS)

The previous high-lift articles built the hardware — the lever, the Slat and Flap Control Computers (SFCC), the Power Control Unit, the torque shafts and the wing-tip brakes (Flap System, Slat System). This article changes the question. It does not ask how the flaps move; it asks when the flaps move themselves. Buried in the flap logic are two speed-driven automatic functions that need no hand on the lever: one wipes off the residual flap angle as the aircraft accelerates after take-off (the Automatic Retraction System, ARS), and one pulls the flaps in by one notch the moment you exceed the flap limit speed (the Flap Load Relief System, FLRS). Both watch airspeed through the SFCC, and both act on the flaps only — never the slats.

Hold the two characters apart from the first line, because the whole article turns on the contrast:

[!warning]- ARS keeps what it took; FLRS gives it back. That single difference is the exam trap.

Both functions retract the flaps automatically, so it is tempting to file them together. They are opposites in one crucial respect. ARS retracts on acceleration and does not re-extend — if the speed later drops back below 200 kt the flaps stay at 0°; getting CONF 1+F back needs a deliberate trip down to low speed (or a prior selection of CONF 2 or more). FLRS retracts on overspeed and does re-extend — once the speed falls back below the limit, the flaps return to the position the lever still selects. ARS is a one-way latch on a one-way phase (you are accelerating away); FLRS is a reversible loan against a reversible event (a transient overspeed). Carry that "keeps versus returns" split into every scenario below.

1. What this article lets you answer

Five questions anchor the piece. If you can answer them from memory at the end, you have it:

1. In what configuration and at what speed does ARS trigger? What configuration does it leave you in, and will the flaps re-extend if the speed drops again?
2. In which configurations is FLRS available? What are the precise trigger and restore speeds, and what notch does each of CONF 2 / 3 / FULL fall back to?
3. Do ARS and FLRS move only the flaps, or the slats too? Who issues the command, and from which sensor's speed?
4. On the E/WD, what colour is F RELIEF versus F LOCKED versus an amber F, and what should you do when you see F RELIEF?
5. At a heavy-weight take-off the FCTM warns that three protections may intervene — which three, and why is a heavy take-off the case that meets them?

The scope is the speed logic only: the configuration framework, ARS, FLRS, the overspeed warning and the E/WD colour code. The flap and slat hardware is in Flap System and Slat System; the slat side's twin protection — the alpha/speed lock that inhibits slat retraction — is in Slat Alpha/Speed Lock and is only named here in passing; the broader configuration and SFCC architecture sits in High-Lift Overview. The trigger sensor for both functions is the air data system (ADIRS, ATA-34), which supplies the computed airspeed.

2. Configuration — one lever, but CONF 1 has two faces

You cannot read ARS without first fixing the configuration framework, or CONF 1 and CONF 1+F blur together. FCOM opens the description with exactly that warning. Per FCOM DSC-27-30-10:

The FLAPS lever has 5 positions: 0, 1, 2, 3 and FULL. Two configurations correspond to the FLAPS lever position 1 : CONF 1 or CONF 1 + F. The selection is done as explained in the following paragraphs.

This is one of the A330's quietly counter-intuitive designs: five physical lever positions, but lever 1 carries two aerodynamic configurations. At the same detent, whether the aircraft gives you "slats only" (CONF 1) or "slats plus flaps" (CONF 1+F) is not chosen by you — it is chosen by speed. That decision is the entry point of the ARS logic. The controls section then leads into the configuration table. Per FCOM DSC-27-30-20:

The FLAPS lever selects simultaneous operation of the slats and flaps. The five lever positions correspond to the following surface positions :

The table below restates the FCOM configuration table for teaching (organised from the six-column FCOM original — lever / slats / flaps / ailerons / ECAM / flight phase — keeping the columns that matter here). Slat and flap angles are the FCOM figures; the precise flap angles in brackets are the control-table/AMM values (the difference is rounding, explained in §3.2). Per FCOM DSC-27-30-20:

FCOM carries two footnotes to that table: the 20°/8° slat/flap pairing is CONF 1*, and the 23°/14° pairing is CONF 2* (per FCOM DSC-27-30-20). Three things to read off the table:

1. The slat angle increases monotonically and then caps. 0 → 16 → 20 → 23, and it stays at 23° from CONF 3 to FULL — everything added between CONF 3 and FULL is flap (22° → 32°). The slats are done extending before the flaps are.
2. CONF 1* and 2* are "small-flap versions" of the same lever position (same slat angle, smaller flap angle). They can be produced only by FLRS — you cannot select them on the lever.
3. The flap angles printed by FCOM are rounded (8 / 14 / 22), while the control table and AMM use 8.5 / 14.5 / 22.5. Same physical deflection, different precision — see §3.2.

The lever also has a mechanical foolproofing that explains why you cannot slam it across its full range in one pull. Per FCOM DSC-27-30-20:

Before selecting any position, the lever must be pulled out of detent. [...] Moreover, balks are provided at Positions 1 and 3 to avoid excessive flap/slat travel demand by a single pilot action.

The balks at positions 1 and 3 give a deliberate "step" you must work through: you cannot collapse the configuration in a single careless movement and demand a large, sudden flap or slat travel — which would mean a large, sudden change in lift and load.

3. The two functions on one state machine

3.1 ARS — the two faces of lever 1, and the auto-command

What decides whether lever 1 gives CONF 1 or CONF 1+F is airspeed and direction of travel, and that decision logic is the heart of ARS. AMM names the whole thing the Flap Auto-Command function. Per AMM 27-51-00:

Two flap configurations, which are dependent on the airspeed, are possible with the slat and flap control lever at the position 1. The configurations are related to the computed airspeeds (CAS) and the lever position (0 or 2) before the lever is set to the position 1.

The CAS thresholds, set out by AMM 27-51-00, separate into a "coming down" branch and a "going up" branch:

And once in the 8.5° configuration, the retraction is automatic and one-directional. Per AMM 27-51-00:

In the 8.5 degree configuration, the flaps retract automatically to 0 deg if the CAS is equal to or more than 200 knots.

That last line is ARS. FCOM states the pilot-facing version of the same fact in one sentence. Per FCOM DSC-27-30-10:

When CONF 1 + F is selected, the auto retraction of flaps to 0 occurs at 200 kt (before VFE, which is 215 kt).

Read the design into it. CONF 1+F (slats 16 / flaps 8.5) is the take-off face of lever 1 — the small flap angle buys lift for the take-off run and initial climb. But the aircraft accelerates the moment it is airborne, and at higher speed those 8.5° of flap are pure penalty (drag and load) with no further need for the lift. Rather than rely on the crew remembering to clean up at exactly the right speed, the SFCC watches CAS and retracts the flaps to 0° as it passes 200 kt, turning CONF 1+F into CONF 1 (slats 16 / flaps 0, slats only). Note the trigger is deliberately set 15 kt below VFE (200 vs 215): ARS is not a last-ditch save before the red line, it is a pre-emptive clean-up well inside the limit. That is the structural difference from FLRS — ARS is preventive housekeeping; FLRS is corrective relief.

3.2 FLRS — shedding one notch on overspeed

If ARS is the routine clean-up on acceleration, FLRS is the emergency relief on overspeed. Its FCOM definition is dense and every clause earns its place. Per FCOM DSC-27-30-10:

Only available in CONF 2, 3, or FULL. When activated, the system retracts the flaps to the deflection corresponding to the next retracted lever position. Auto retraction of the flaps only occurs in case of VFE exceedance (VFE +2.5 kt). If speed is reduced below VFE (VFE -2.5 kt), flaps return to their normal (selected) position.

Clause by clause:

• "Only available in CONF 2, 3, or FULL" — FLRS ignores CONF 1 / 1+F (that is ARS territory). It stands guard only in the large-flap configurations, which carry the most flap and are the most exposed to overspeed load.
• "to the deflection corresponding to the next retracted lever position" — it sheds one notch, not all the flap. CONF FULL relieves to the CONF 3 angle, CONF 3 to the CONF 2 angle (= CONF 2*), CONF 2 to the CONF 1 angle (= CONF 1*). The slat angle is unchanged in all three cases — which for the CONF 3 → 2* and CONF 2 → 1* reliefs is exactly why the result is a "star" configuration (the held-over slat angle no longer matches the new flap notch) rather than a genuine notch change. CONF FULL → CONF 3 is the exception: CONF FULL and CONF 3 already share the same slat angle (23), so the relief lands on a genuine CONF 3, not a star.
• "VFE +2.5 / VFE -2.5" — trigger and restore are separated by a 5 kt hysteresis band. The function fires at VFE +2.5 and releases only at VFE -2.5; the gap stops the flaps cycling in and out when the speed sits and trembles right on VFE.
• "flaps return to their normal (selected) position" — the load-bearing difference from ARS. FLRS gives the flap back once the overspeed clears, because it serves a reversible event (a transient overspeed), not a one-way acceleration.

FCOM then nails the exact results and the headline fact about the star configurations. Per FCOM DSC-27-30-10:

In CONF 2, auto retraction results in CONF 1 (20 ° slats/8 ° flaps). In CONF 3, auto retraction results in CONF 2* (23 ° slats/14 ° flaps). These configurations can be obtained only by FLRS activation.*

"Can be obtained only by FLRS activation" is the operational tell: if you see 1* or 2* on the E/WD, FLRS is — or was just — acting. There is no lever position that produces them.

The maintenance source describes the same function as a generic relief and confirms the sensor and direction logic. Per AMM 27-51-00:

The flight control system has a relief function. This stops damage to the flaps due to aerodynamic loads caused by airspeeds which are too high. [...] The SFCCs use Computed Airspeed (CAS) data from the Air Data/Inertial Reference System (ADIRS): - to retract the flaps from the extended position to the next lower lever position, if the CAS increases to more than that for the flap configuration limited speed, - to extend the flaps to the related position, if the CAS decreases below the retract speed for the selected lever position.

Two structural points fall out of the AMM. First, ARS and FLRS share one drive logic — AMM groups them under a single heading, "Flap Auto-Command or Flap Load Relief Function", and both drive the flaps the same way the lever does. Per AMM 27-51-00:

When the SFCCs receive a command from the ADIRS the SFCCs energize the extend (retract) solenoids and the POB solenoids at both PCU valve blocks. The PCU drives the flap transmission system with a certain speed.

The only difference between the two and a manual selection is where the command comes from: a normal selection comes from the CSU (the lever), while ARS and FLRS commands come from the ADIRS (the speed). The valve-block / PCU / transmission / flap chain downstream is identical. Second, neither function is a separate box — there is no "ARS unit" or "FLRS unit." They are two pieces of software running inside the same SFCCs that already drive the slats and flaps, comparing CAS against a threshold and deciding which way to move.

3.3 The state machine and the speed thresholds

The configuration logic is easiest to hold as a small state machine. ARS governs the two faces of lever 1; FLRS governs the one-notch relief with hysteresis. Both are drawn below.

 ── ARS: the two faces of lever 1 ───────────────────────────────────────
                                                  ┌─ CAS ≥ 200 ─► CONF 1   (16 / 0)
   lever 0 ─► 1 ────────────────────────────┬────┤
   (from clean)                             │    └─ CAS ≤ 100 ─► CONF 1+F (16 / 8.5)
                                            │
   lever FULL/3/2 ─► 1 ──────────────┬──────┤    ┌─ CAS ≥ 200 ─► CONF 1   (16 / 0)
   (from a larger configuration)     │      └────┤
                                     │           └─ CAS < 200 ─► CONF 1+F (16 / 8.5)
                                     │
        once in CONF 1+F: ───────────┴── CAS ≥ 200 ──► ARS retracts flaps 8.5°►0°
        and NO return to 1+F until CAS ≤ 100  (or CONF 2+ previously selected)

 ── FLRS: one notch of relief, with a 5 kt hysteresis band ──────────────
                       trigger (VFE +2.5)            restore (VFE -2.5)
   ┌──────────┐  CAS > 198.5  ┌──────────┐   CAS < 193.5   back to
   │  CONF 2  │ ────────────► │  CONF 1* │ ──────────────► CONF 2
   └──────────┘               └──────────┘
   ┌──────────┐  CAS > 188.5  ┌──────────┐   CAS < 183.5   back to
   │  CONF 3  │ ────────────► │  CONF 2* │ ──────────────► CONF 3
   └──────────┘               └──────────┘
   ┌──────────┐  CAS > 182.5  ┌──────────┐   CAS < 177.5   back to
   │ CONF FULL│ ────────────► │  CONF 3  │ ──────────────► CONF FULL
   └──────────┘               └──────────┘
   (slats unchanged throughout — only the flap angle moves by one notch)

The numeric thresholds, pulled together:

Two notes on these numbers and their provenance:

• The FLRS trigger and restore speeds are VFE +2.5 and VFE -2.5 applied to each configuration's VFE — that rule is FCOM verbatim text. The concrete figures (198.5 / 193.5, 188.5 / 183.5, 182.5 / 177.5) and the per-configuration VFE behind them (CONF 2 = 196, CONF 3 = 186, FULL = 180) are read off the FCOM Retraction/Extension Schematic (DSC-27-30-10) and the AMM Flap – Auto Functions figure (27-51-00-23850-00-B); the body text gives the rule, the figures give the values. The two text-stated VFE anchors are 215 kt for CONF 1+F ("before VFE, which is 215 kt") and the VFE next of 205 kt for CONF 1* (Note below).
• The 8° / 14° versus 8.5° / 14.5° flap angles are not two measurement layers — they are the same deflection written to different precision. FCOM's FLRS-result text rounds CONF 1*/2* to 8°/14°; the control table and AMM use 8.5°/14.5°.

3.4 What the PFD shows — VFE and VFE NEXT

FLRS reaches into the PFD speed scale, and FCOM spends three notes on exactly how. These are the source of the 205 kt "VFE next" that appears in the state machine. Per FCOM DSC-27-30-10:

Note: 1. When FLAPS 1 is selected, VFE of CONF 1 or CONF 1 + F is displayed, depending on the actual configuration. In approach, VFE next is 205 kt (VFE of CONF 1). 2. When FLAPS 2 is selected in approach, VFE of CONF 2 or CONF 1* is displayed, depending on the FLRS activation. 3. When FLAPS 3 is selected, only VFE of CONF 3 is displayed on PFD independently of FLRS activation.*

For the pilot:

1. At lever 1, the displayed VFE tracks the actual configuration (CONF 1 or 1+F); in approach the VFE next preview is 205 kt — the VFE of CONF 1*, which is why the state machine prints 205 against that cell.
2. At lever 2 in approach, if FLRS has already relieved to CONF 1*, the displayed VFE switches from CONF 2's value to CONF 1*'s; if not relieved, it stays at CONF 2's.
3. Lever 3 is the exception — the PFD shows only CONF 3's VFE whether or not FLRS has acted. It is the one selection where the displayed VFE does not follow FLRS. Memorise that to avoid mis-reading the scale.

There is a second, easily-confused display rule from the FCTM that applies to the take-off case (the approach behaviour is the FCOM notes above). In CONF 2 at take-off, FCTM states the displayed VFE stays put — covered with its quote in §4.

4. The overspeed warning and the E/WD colour code

4.1 FLRS is the first line; OVERSPEED is the second

FLRS sheds one notch to protect the flap; if the speed keeps climbing after that, a second, louder defence triggers. Per FCOM DSC-27-30-10:

In case of FLRS activation, the ECAM upper display shows a flashing F RELIEF message. If the speed is increased by 4 kt above the VFE, corresponding to the actual flap/slat configuration, an OVERSPEED warning appears on the ECAM.

The layering is the point. FLRS acts on the aircraft — it automatically relieves load by retracting one notch. OVERSPEED acts on the crew — if, after the relief, the speed still exceeds the new configuration's VFE by 4 kt, the red ECAM warning tells the pilot that the automatic defence has already been spent and active deceleration is now required. FLRS saves the flap; OVERSPEED calls the pilot. One is the automatic hand, the other is the demand to take over.

4.2 Reading the F and S symbols — colour before text

The single most useful skill here is decoding the E/WD flap/slat indication at a glance, and FCOM lays out the full colour meaning of the F and S symbols. Per FCOM DSC-27-30-20:

The F symbol is : ‐ replaced by the amber "F LOCKED" message, when wing tip brake is applied to flaps. ‐ replaced by the green pulsing "F RELIEF" message when the flap load relief system is activated. ‐ displayed in amber at flap system failure or at yellow and green hydraulic system low pressure. The S symbol is : ‐ replaced by the amber "S LOCKED" message when wing tip brake is applied to slats. ‐ replaced by the green pulsing "A LOCK" message when the alpha/speed lock function is activated. ‐ displayed in amber at slat system failure or at blue and green hydraulic system low pressure.

F RELIEF is green and pulsing, not amber. In Airbus colour grammar, green means a system working normally and protecting you — so F RELIEF is telling you "you exceeded VFE, I have already taken one notch of flap off to carry it, now bring the speed back below VFE -2.5 and I will hand the flap back." That is a different world from amber F LOCKED (a wing-tip brake has latched the flap transmission — a genuine fault, flap frozen). The colour is the divider: green = automatic protection running, amber = something has failed.

4.3 The green box pulses too — a dual cue from independent sensors

F RELIEF is not the only visual cue. The flap/slat indication is built from two overlaid element sets: the F/S letter symbols (above) and the green position boxes that track the actual surface position. FCOM pins down the box behaviour. Per FCOM DSC-27-30-20:

The green boxes move independently, when flaps/slats are retracted or extended. When fully retracted, boxes are side by side with wing fixed part. The signal is acquired by separate sensors, not used by the SFCC. Symbols become amber when S (F) LOCKED. The slat box pulses in green, when the alpha/speed lock function is active. The flap box pulses in green, when the flap load relief system is active.

Two pilot takeaways:

1. FLRS gives a dual cue. When it acts, the F symbol is replaced by green-pulsing F RELIEF and the flap position box pulses green at the same time. (The slat side mirrors it: alpha/speed lock gives green-pulsing A LOCK plus a green-pulsing slat box.) Two independently-driven elements flashing together make the automatic action hard to miss.
2. The box runs on its own sensors — "not used by the SFCC". The position box reflects the real physical surface position through a separate sensor chain, independent of the SFCC control loop. So the F/S symbol (SFCC-sourced) and the green box (independent-sensor-sourced) are deliberately drawn from different signal sources, giving a built-in cross-check: if the SFCC channel ever disagreed with the true surface position, the box is the uncontaminated reference.

The E/WD decode, condensed:

Read colour before text: green is a protection doing its job, amber is a failure.

5. The heavy-weight take-off — three protections in a queue

The one flight phase that can meet ARS, FLRS and the slat alpha lock in quick succession is a heavy take-off, and the FCTM addresses it directly. Per FCTM PR-NP-SOP-120:

If takeoff is carried out at heavy weight, the maneuvring speed F may be close to VFE Conf 2 and S speed is above VFE Conf1+F. In this case, three protections may intervene: ‐ The Flap Load Relief System (FLRS) ‐ The Automatic Retraction System (ARS) ‐ The alpha Lock function

Why heavy weight specifically: at high gross weight the manoeuvring speeds (F and S) rise until they sit hard against the configuration VFEs, so an ordinary acceleration can brush each limit in turn — F speed near VFE CONF 2 invites FLRS, passing 200 kt in CONF 1+F invites ARS, and selecting flaps 0 at high angle of attack invites the slat alpha lock. The FCTM's ARS detail makes the "no re-extend" behaviour explicit. Per FCTM PR-NP-SOP-120:

While in Conf 1+F and IAS reaches 200 kt [...], the ARS is activated. The ARS automatically retracts flaps to 0°. The VFE displayed on the PFD change from VFE CONF1+F to VFE CONF1. As the aircraft accelerates above S speed, the flap lever can be selected to 0. If IAS decreases below 200 kt [...], the flaps will not extend back to 1+F.

And the FLRS detail, with a display behaviour FCOM does not spell out for the take-off case. Per FCTM PR-NP-SOP-120:

When IAS reaches VFE, the FLRS is activated. It retracts automatically the flaps to the next further retracted lever position. Typically, this may occur in CONF 2, when F speed is close to VFE CONF2. In this case, VFE is unchanged on PFD speed scale. (Displayed VFE remains VFE CONF 2 in accordance with the flap lever position). "RELIEF" is displayed on the E/WD Flap/Slat indication. As the aircraft accelerates above F speed, the flap lever can be selected to 1. If IAS decreases below VFE, the flaps will re-extend.

Note the two FCTM additions over FCOM: (1) CONF 2 is the typical FLRS case at heavy weight, because F speed sits so close to VFE CONF 2; and (2) when FLRS relieves CONF 2 to CONF 1* at take-off, the displayed VFE on the PFD does not jump to the CONF 1* value of 205 — it stays at the lever-position (CONF 2) value, "in accordance with the flap lever position." This is a different display rule from the FCOM approach notes in §3.4, where a CONF 2 selection does switch the shown VFE on relief. The two coexist: take-off CONF 2 holds the VFE display; approach CONF 2 switches it. The technique is unchanged either way — keep accelerating on schedule and let the protections clear themselves; do not fight them by hand. (The alpha lock is developed in Slat Alpha/Speed Lock.)

6. Flying ARS and FLRS — a few scenes

1. Normal take-off, CONF 1+F, accelerating. Rotate, gear up, accelerate. Passing 200 kt the ARS retracts the flaps 8.5° → 0°; the PFD VFE steps up from 215 (CONF 1+F) toward CONF 1, and the E/WD flap angle disappears (now CONF 1, slats only). You touched nothing. Past S speed, lever to 0 to bring the slats in. Catch: if a gust then drops the speed back to 195 kt, the flaps do not return to 1+F — ARS does not re-extend.
2. Heavy take-off, F speed close to VFE CONF 2. The FCTM's textbook case — three protections may queue: FLRS first (still in CONF 2 with F speed past 198.5), then ARS (in CONF 1+F passing 200), then the slat alpha lock (selecting 0 at high AoA). Technique: keep accelerating on the schedule and let each clear in turn; do not retract or re-extend by hand.
3. Approach in CONF FULL, a downdraught spikes the speed. IAS jumps from 175 to 184 kt (> 182.5). FLRS retracts the flaps 32° → 22.5° (to the CONF 3 angle) and the E/WD shows green-pulsing F RELIEF with the flap box pulsing alongside. Green is not a fault — it is the system shedding flap load. Ease the speed back; below 177.5 kt the flaps re-extend to 32° on their own and F RELIEF clears.
4. FLRS relieved but the speed keeps rising. Continue the previous scene without arresting the speed: it climbs past the relieved configuration's (CONF 3) VFE by 4 kt and ECAM throws a red OVERSPEED. The second line is now calling you — the automatic relief is spent, decelerate.
5. Approach, FLAPS 1 gives 1+F, not 1. Because you have already passed through CONF 2/3 on the way down, "CONF 2 or more previously selected" is latched, and with speed above 100 kt a selection of FLAPS 1 yields CONF 1+F (16/8.5), not bare CONF 1 — the mirror of the clean acceleration case where lever 1 above 100 kt gives CONF 1. Same lever position, different history, different result.
6. A glance at the E/WD to read the state. Scan the flap/slat block: green-pulsing F RELIEF = FLRS acting (you are over VFE); green-pulsing A LOCK = slat lock acting (high AoA / low speed); amber F LOCKED / S LOCKED = a wing-tip brake latched (a real jam); an amber F or S = system failure or dual-hydraulic low pressure. Colour first, text second.

Self-test

[!note]- Q1. In what configuration and at what speed does ARS trigger, what does it leave you in, and will the flaps re-extend if the speed drops back to 195 kt?

ARS triggers in CONF 1+F (slats 16 / flaps 8.5) when CAS reaches 200 kt, retracting the flaps 8.5° → 0° to give CONF 1 (slats 16 / flaps 0); the PFD VFE steps from 215 toward CONF 1's value (per FCOM DSC-27-30-10). It will not re-extend — the FCTM states that if IAS drops below 200 kt the flaps will not extend back to 1+F. To get CONF 1+F back, the speed must fall to 100 kt or less, or CONF 2 or more must have been previously selected. The design reasons that ARS serves a one-way acceleration phase, so it is built as a one-way latch rather than cycling the flaps in and out.

[!note]- Q2. In which configurations is FLRS available, and what are the trigger/restore speeds and result for each?

FLRS is available only in CONF 2, 3 and FULL (per FCOM DSC-27-30-10). Results: CONF 2 (flaps 14.5°) → CONF 1* (8.5°), trigger > 198.5 kt, restore < **193.5 kt**; CONF 3 (22.5°) → **CONF 2*** (14.5°), trigger > 188.5, restore < **183.5**; CONF FULL (32°) → CONF 3 angle (22.5°), trigger > 182.5, restore < 177.5. The rule is trigger = VFE +2.5, restore = VFE -2.5, a 5 kt hysteresis band that prevents cycling. Only the flap angle moves — the slat angle is unchanged — which is why the results are "star" configurations.

[!note]- Q3. What are the two most fundamental differences between ARS and FLRS?

First, reversibility: FLRS re-extends the flaps to the selected position once the speed falls below VFE -2.5; ARS does not re-extend (until the 100 kt / CONF 2 conditions). Second, timing and purpose: ARS triggers before VFE (200 vs 215) as preventive clean-up of residual flap on acceleration, while FLRS triggers after VFE is exceeded (VFE +2.5) as corrective relief of one notch. They share three things: both move only the flaps (never the slats), both are driven by the SFCC reading CAS from the ADIRS, and neither is a separate box — both are software functions inside the SFCCs (per AMM 27-51-00).

[!note]- Q4. On the E/WD, what colour is F RELIEF versus F LOCKED, and what do you do when you see F RELIEF?

F RELIEF is green and pulsing — FLRS is acting, the flap is relieved by one notch, and the flap position box pulses green alongside it (a dual cue from independent sensors). F LOCKED is amber — a wing-tip brake has latched the transmission, a genuine fault that freezes the flap. An amber F symbol means a flap-system failure or yellow+green hydraulic low pressure (per FCOM DSC-27-30-20). On F RELIEF, you have exceeded VFE and the system has shed load for you — ease the speed back below VFE -2.5 and the flap re-extends and the message clears; do not mistake the green message for a failure. The rule: green = protection running, amber = fault.

[!note]- Q5. The FCTM says three protections may intervene at a heavy take-off — which three, and why heavy weight?

FLRS, ARS and the slat alpha lock (per FCTM PR-NP-SOP-120). At heavy weight the manoeuvring speeds F and S rise until they sit against the configuration VFEs — F speed near VFE CONF 2, S speed above VFE CONF 1+F — so a normal acceleration brushes each limit in turn: FLRS (CONF 2 past 198.5), ARS (CONF 1+F past 200) and the alpha lock (flaps 0 at high AoA). The technique is to keep accelerating on schedule and let each protection clear itself rather than retracting or re-extending by hand. The alpha lock is covered in the slat alpha/speed lock article.

[!note]- Q6. You see 1* on the E/WD. What does it tell you, and which lever position are you on?

1* (CONF 1*, slats 20 / flaps 8.5) can be produced only by FLRS — there is no lever detent for it. So seeing 1* tells you the lever is at 2 and FLRS has relieved the flap by one notch because you exceeded VFE CONF 2. The same logic applies to 2*: lever at 3, FLRS relieving CONF 3. The star is the system's signal that the flap load relief is — or has just been — active.

Key takeaways

The whole article reduces to a single mental model: at lever 1 the flap angle is not a fixed mapping but a value the SFCC computes from speed, and in the large configurations the SFCC will quietly shed a notch to protect the flap and hand it straight back when it is safe. Watch the speed, read the green-versus-amber on the E/WD, and let the automatics run.

References

Per FCOM DSC-27-30-10 (Flaps and slats — description: five lever positions and the two faces of CONF 1; ARS — auto retraction at 200 kt below VFE 215; FLRS — availability in CONF 2/3/FULL, one-notch relief, VFE +2.5 / -2.5 hysteresis, CONF 1*/2* obtainable only by FLRS, the three PFD VFE/VFE-next notes incl. 205 kt, flashing F RELIEF and the +4 kt OVERSPEED). Per FCOM DSC-27-30-20 (Controls and indicators — configuration table of slat/flap/aileron angles and CONF 1*/2* footnotes; lever detent and balks at positions 1 and 3; TAKEOFF / GO-AROUND / 0→1 configuration-selection rules and CONF 1+F re-availability below 100 kt; full E/WD F and S symbol colour code incl. green-pulsing F RELIEF / A LOCK and amber F LOCKED / S LOCKED; independent green position boxes "not used by the SFCC" pulsing with FLRS / alpha-lock). Per FCTM PR-NP-SOP-120 (Slats/flaps retraction at heavy weight — three protections FLRS/ARS/alpha lock; ARS "will not extend back to 1+F"; FLRS typical in CONF 2 with VFE unchanged on the PFD at take-off). Per AMM 27-51-00 (Flaps electrical control and monitoring — Flap Auto-Command or Flap Load Relief Function: CAS thresholds for the two faces of lever 1, automatic retraction to 0° at CAS ≥ 200, the relief function and its CAS-driven retract/extend logic, the SFCC→ADIRS command driving the PCU valve blocks). Trigger sensor (computed airspeed) per ADIRS, ATA-34. Figure-sourced values — the per-configuration VFE of CONF 2/3/FULL (196/186/180) and the resulting FLRS trigger/restore speeds (198.5/193.5, 188.5/183.5, 182.5/177.5) — are read from the FCOM Retraction/Extension Schematic (DSC-27-30-10) and the AMM Flap – Auto Functions figure (27-51-00-23850-00-B); the VFE +2.5 / -2.5 rule and the 215 kt / 205 kt anchors are FCOM body text. Items flagged as reasoning — ARS as a one-way latch on a one-way phase, the 5 kt hysteresis as anti-cycling, and the FLRS-then-OVERSPEED two-line framing — are integrative synthesis from the cited passages, 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.