The FMA and the Mode System

The first commandment of Airbus automation is not "know the buttons" — it is "read the FMA". The stick does not move and the levers do not move (article 01), so the flight mode annunciator is the guidance system's only complete voice. This article sets up the mode taxonomy and the FMA grammar that articles 07–11 build on. Per FCTM AS-FG:

The FMA indicates the status of the AP, FD and A/THR and their corresponding operating modes. The PF must monitor the FMA and announce any FMA change.

‐ WHAT IS THE AIRCRAFT EXPECTED TO FLY NOW? ‐ WHAT IS THE AIRCRAFT EXPECTED TO FLY NEXT?

Two standing questions. "Now" is answered in green (active); "next" in cyan or magenta (armed). The FMA's colour system exists precisely to answer them.

1. The FMA map

Per FCOM DSC-22_30-80-20:

The FMA is located on the upper part of the PFD, and displays the following information, associated to flight guidance: ‐ A/THR messages and modes ‐ AP/FD modes (Vertical, Lateral, Common) ‐ Approach and landing capability ‐ AP, FD, and A/THR engagement status ‐ Special Messages ‐ Autobrake modes.

The layout, as a map (synthesis):

Where the words come from: the FMA is not a placard. Each DMC receives one bus from each FMGEC (FD orders, engagement status, modes, landing capability) and selects a source by logic — the same family as the FD source-switching in article 05; who is displayed under single and dual AP is section 6.

2. Mode taxonomy — cruise versus common

Per AMM 22-10-00:

The AP/FD has two types of modes: - Cruise modes - Common modes.

Cruise modes are the single-axis building blocks (V/S–FPA, the ALT family, CLB/DES families, HDG–TRK, NAV). Common modes are the phase scripts that couple both axes (TAKEOFF, GO-AROUND, LOC, APPROACH). And their state machines differ. Per FCOM DSC-22_30-40-10:

An AP/FD lateral or vertical mode can be armed, engaged, or disengaged. An AP/FD common mode can either be engaged or disengaged. When all APs and FDs disengage, all AP/FD modes disengage.

Why arming exists at all: an armed mode is a conditional trigger — ALT ACQ is armed almost permanently waiting for the capture condition; LOC arms and waits for the beam. A common mode, by contrast, is a whole script whose scenes advance internally (G/S* → G/S → LAND → FLARE), so externally it only reports "running or not". And the last sentence explains a familiar surprise: switch both FDs off and on again, and every mode starts from scratch (the FDs return in V/S + HDG — article 05).

One engine out, the taxonomy holds — with the bank reined in. Per FCOM DSC-22_20-10-50:

‐ All selected modes remain available (the “HDG/TRK”, “V/S”, and “OPEN” modes, for example)

‐ The system limits Autopilot (AP) and Flight Director (FD) bank angles during the takeoff and approach phases, as follows: • 15 ° when the aircraft speed is below maneuvering speeds (F, S, or Green Dot speed), - 10 kt • Then linear increase to 25 ° up to maneuvering speeds (F, S, or Green Dot speed) - 3 kt • 25 ° above maneuvering speeds (F, S, or Green dot speed) - 3 kt.

The same section fixes the engine-out SRS speed references (takeoff: the higher of V2 and current speed, capped at V2+15; go-around: VAPP or the higher current speed, capped at VLS+15 — article 07, article 14). Note the family resemblance to article 05's roll-limit schedule: the AP's boldness follows the energy available.

3. Five ways to select a mode

Per AMM 22-10-00:

Modes can be selected in several ways: - Automatically, e.g. the altitude acquisition mode is always armed except in some cases (approach) - By action on a pushbutton switch located on the FCU - By push or pull action on one of the reference selection knobs (speed/Mach, heading/track, altitude, vertical speed/flight path angle) on the FCU - By cancelling an engaged mode - By means of the throttle control levers (selection of takeoff and go-around modes).

Two of the five deserve a second look. Number five: the thrust levers are a mode selector — TOGA is not merely "full thrust", it is the engagement switch for SRS and GA TRK, the root of the go-around traps in article 14. And number four: cancelling is selecting — deselect APPR and the system must choose a successor mode; that necessity is why the reversion system (article 10) exists. (The ground test case from article 05 also lives here: engines stopped, modes can engage on the ground for testing — and everything drops at engine start.)

4. Managed and selected — the register

Article 02 gave the gestures (pull = selected, push = managed). Here is the register of which mode belongs to whom (AMM 22-10-00, rearranged):

Per AMM 22-10-00:

Automatic approach, landing, takeoff and go-around are considered as managed modes because no targets are entered through the FCU.

Look at the approach row: the selected column is empty. There is no "selected edition" of a precision approach — either the managed script, or a retreat to cruise modes flown by hand (V/S plus HDG on raw data). That is exactly why, when the APPR pushbutton fails, the MEL's replacement menu reads NAV/FPA, TRK/FPA, LOC/FPA, raw data (article 02) — cruise-mode bricks.

Two clauses guarantee speed is never orphaned (article 16 has the pairing table):

The AFS is designed in such a way that the aircraft speed is always controlled by the AP/FD function and by the A/THR function when A/THR is engaged.

If neither the AP nor the FD is engaged, the A/THR will be active in SPD/MACH mode only.

And a subtlety about the ALT pushbutton that examiners love. Per AMM 22-10-00:

On the ALT pushbutton switch, the three green bars come on when the ALT mode is engaged whatever the cause of the ALT mode engagement i.e. through the altitude selector knob on the FCU, or due to an FM altitude constraint, or through a level-off commanded by an action on the ALT pushbutton switch. Pushing on the illuminated ALT pushbutton switch has no effect.

- In both cases, the ALT control law is used. - In the first case (ALT pushbutton switch pushed), ALT is shown on the FMA. - In the second case (V/S/FPA selector knob pushed), V/S + 0000 (or FPA + 0.0) is shown on the FMA.

Two gestures, one control law, two different FMA announcements. The lesson generalises: the FMA reports intent semantics, not control laws. "ALT" says I am holding an altitude; "V/S +0000" says I am holding zero vertical speed. Keep that distinction — it is the reading key when an FCU altitude change during ALT* reverts you to V/S (article 10).

5. Reading the FMA — colours, the white box, column 5, special messages

The five colours, officially. Per AMM 22-00-00:

Green for the active modes - Cyan for the armed modes - Magenta for the modes armed or engaged because of a constraint - White for the engagement status of AP, FD and A/THR - Amber for indications which require special attention.

Magenta is the FM speaking: this target is not yours — a constraint put it there (a magenta ALT means an FM altitude constraint will level you — article 07; it is the same magenta as the MCDU's constraint colour, article 03).

The white box is the news marker. Per FCOM DSC-22_30-80-20:

A white box appears for 10 s around the annunciation of: ‐ An A/THR mode engagement ‐ An AP/FD mode engagement ‐ The approach and landing capability (or the change of the approach and landing capability) ‐ An AP, FD, or A/THR engagement status change.

Whatever just happened gets boxed for ten seconds — the visual trigger for a callout (reversions add a triple click and flashing FD bar — article 05, article 10).

Column 5's compact code. Per AMM 22-10-00:

AP engagement: white AP1, AP2 or AP1+2 message (2 APs engaged) on the 1st line - FD engagement: white 1FD2 message on the 2nd line with both FDs engaged, or 1FD1, 2FD2, -FD1, -FD2, 1FD-, 2FD- messages according to FD availability or engagement.

Read the FD line as [captain's source][FD][first officer's source]: a digit names which FMGEC feeds that side's FD, a dash means that side's FD is not engaged. 2FD2 = both sides on FMGEC 2's FD; 1FD- = FD2 not engaged. Line 3 is the answer to article 02's ambiguous green light: blue A/THR = armed but not active; white A/THR = active (the FCOM's display condition for the blue form is literally the A/THR is armed and not active).

Special messages have a pecking order. Per FCOM DSC-22_30-80-20:

Special Messages displays three types of messages by the following priority: ‐ First priority is given to F/CTL messages ‐ Then vertical FMS messages ‐ Then EFIS reconfiguration messages.

(MAN PITCH TRIM ONLY will always displace DECELERATE.) Two messages to know from this article:

This message is displayed when the AP/FD remains engaged at: ‐ 150 ft RA during a non-precision approach.

— DISCONNECT AP FOR LDG: still coupled at 150 ft RA on a non-precision approach, time to take over (the full trigger list, including a CAT 1 case, is in the source table). And:

FMA Display FCU ALT ABOVE A/C (Remains 10 s then disappears) ... The vertical mode of guidance is V/S or FPA with a descent profile, and the altitude set on the FCU is above the current aircraft altitude.

— you are descending in V/S–FPA while the FCU target sits above you (the BELOW variant mirrors it in a climb): flying away from your own target.

The autobrake column extends the same grammar to the ground. Per FCOM DSC-32-30-10: The armed AUTO BRK mode is displayed in blue on the Flight Mode Annunciator (FMA). — armed blue, active green, one colour system. (Gear-down flight procedures add a check in this column: confirm BRK MAX does not appear.)

6. Whose words are on the FMA

Behind the display, the two FMGECs are forced into agreement. Per AMM 22-10-00:

To ensure a consistent operation of the AFS, both FMGECs must have the same modes active and armed.

In cruise phase and on condition there is at least one AP/FD engaged, the FMGEC which has priority imposes the cruise modes active and armed to the FMGEC which has no priority.

(The priority ladder is article 05's: AP1 → FMGEC 1, only AP2 → FMGEC 2, …, none engaged → FMGEC 1.) So whose words do you read? Single AP — both sides read the same computer:

Each DMC uses the FMGEC bus which corresponds to this AP. Each PFD displays: - AP1 or AP2 message depending on the AP engaged - the modes corresponding to this AP - the landing capabilities computed by the FMGEC corresponding to the AP engaged.

Dual AP — each side reads its own:

Therefore CAPT (F/O) PFD (PFD1 (2)) displays: - AP1+2 message - the modes corresponding to AP1 (2) - the landing capabilities computed by the FMGEC1 (2).

Sit with that for a moment: on a CAT III dual-AP approach, the left and right landing-capability annunciations are two computers' independent judgements. They can briefly disagree — one side CAT 3 DUAL, the other degraded — and that is precisely why capability changes are cross-checked across both FMAs (the PM's capability watch in article 13, and the QRH equipment table counting "FMA 1/2/2" in article 12).

7. Callouts and checks

The callout convention, verbatim. Per FCOM PRO-NOR-SCO:

The PF should call out any FMA change, unless specified differently (e.g. CAT II & III task sharing). Therefore, the PF should announce : ‐ All armed modes with their associated color (e.g. blue, magenta): "G/S blue", "LOC blue" ‐ All active modes without their associated color (e.g. green, white): "NAV", "ALT". The PM should check and respond, "CHECKED" to all FMA changes called out by the PF.

Why do armed modes carry their colour and active modes not? An active mode owns the "now" slot — no ambiguity to resolve. An armed mode could be cyan or magenta, and the one word names the target's source: "blue" = I set it; "magenta" = a constraint set it. What the PM cross-checks differs accordingly (blue → the FCU; magenta → the F-PLN constraint).

Before takeoff, the FMA is part of the FCU setup check. Per FCOM standard procedures:

CHECK that the FMA CLB (or ALT) mode is armed on column 2.

Note: ALT (in blue or magenta) may be displayed instead of CLB if the FCU altitude or a constraint is set at or below the acceleration altitude.

That note defuses a classic false alarm: with a low initial clearance, ALT blue (or magenta) instead of CLB blue is correct arming, not a setup error.

When the aircraft does not fly as expected, the FCTM ladder is two rungs, no agonising. Per FCTM AS-FG:

If the aircraft does not fly as expected: ‐ If in managed mode, select the desired target ‐ Or, disengage the autopilot, and fly the aircraft manually.

And dispatch closes the loop on how central the FMA is (article 32, some operators' MEL practice): one side's FMA AP/FD indication inoperative bars RNP AR; both sides inoperative means the AP and FD are not used at all, with ETOPS, RNP AR and CAT 2/3 barred and capability capped at CAT 1. If you cannot see the FMA, you do not get the automation — official confirmation that the FMA is the automation's only mouth.

[!warning]- Five misconceptions this article corrects (1) TOGA is not just thrust — the levers are the fifth mode selector, engaging the takeoff/go-around scripts. (2) There is no selected version of a precision approach — the approach row's selected column is empty; the fallback is cruise-mode bricks on raw data. (3) Pressing the lit ALT button does nothing, and "ALT" vs "V/S +0000" can be the same control law — the FMA reports intent, not law. (4) On a dual-AP approach the two FMAs are not copies — each PFD shows its own FMGEC's modes and capability, and they can legitimately differ for a moment. (5) ALT blue instead of CLB blue before takeoff is not a mis-set FCU when the cleared altitude is at or below the acceleration altitude — read the note before "correcting" it.

Self-test

[!note]- Q1. Give three cruise modes and three common modes — and why do common modes have no armed state?

Cruise: V/S–FPA, ALT family, CLB/DES, HDG–TRK, NAV (any three). Common: TAKEOFF, GO-AROUND, LOC, APPROACH. A common mode is a two-axis phase script whose scenes sequence internally — externally it is simply engaged or not. (The ARM you see for LOC/APPR belongs to their lateral/vertical component modes.)

[!note]- Q2. The five ways a mode gets selected — and is deselecting APPR one of them?

Automatic arming; FCU pushbutton; FCU knob push/pull; cancelling an engaged mode; thrust levers (TOGA). Yes — cancellation forces the system to select a successor, which is the doorway to the reversion rules.

[!note]- Q3. Recite the approach row of the managed/selected register. Why is the selected side empty?

Managed: RNAV, APPR, LAND/LOC/GLIDE/FLARE/ALIGN/ROLLOUT/RETARD. Selected: nothing. Approach/landing/takeoff/go-around are managed by definition — their targets never come through the FCU (V2 from the MCDU, LOC/G-S from the beam), so no selected edition exists.

[!note]- Q4. ALT magenta versus ALT cyan — where does each target come from, and how does the callout distinguish them?

Cyan: the crew's FCU selection. Magenta: an FM constraint. Armed modes are called with the colour — "ALT blue" vs "ALT magenta" — telling the PM whether to verify the FCU window or the F-PLN constraint.

[!note]- Q5. What states do "2FD2" and "1FD-" describe in column 5?

2FD2: both sides' FD bars are driven by FMGEC 2 (FMGEC 1's FD unavailable). 1FD-: captain's side on FMGEC 1's FD, and FD2 not engaged — the dash marks the disengaged side.

[!note]- Q6. On a dual-AP approach, whose landing capability does each PFD show — and what does a momentary disagreement mean?

PFD1 shows FMGEC 1's computation, PFD2 shows FMGEC 2's. A disagreement means the two computers currently judge capability differently (one degraded) — exactly why capability calls are cross-checked on both FMAs before continuing.

[!note]- Q7. Column 2 shows ALT blue rather than CLB blue before takeoff — necessarily a setup error?

No. If the FCU altitude or a constraint is at or below the acceleration altitude, ALT (blue or magenta) armed instead of CLB is the correct display.

[!note]- Q8. After an engine failure, do selected modes survive? And what bank does the AP allow at low speed?

All selected modes remain available. In takeoff and approach phases the AP/FD bank is limited to 15° below manoeuvring speed −10 kt, opening linearly to 25° by manoeuvring speed −3 kt — authority follows energy.

Key takeaways

References

FMA layout, white box, special messages and their priority, DISCONNECT AP FOR LDG and FCU ALT ABOVE A/C per FCOM DSC-22_30-80-20 (the full 32-page FMA table remains the lookup source for complete trigger conditions); mode families and state machine per FCOM DSC-22_30-40-10 and AMM 22-10-00; engine-out mode provisions and bank-limit schedule per FCOM DSC-22_20-10-50; five selection paths, managed/selected register, ALT-pushbutton behaviour, FMGEC mode synchronisation and FMA source selection per AMM 22-10-00; colour definitions per AMM 22-00-00. Callout convention per FCOM PRO-NOR-SCO; takeoff FMA check and its ALT note per FCOM standard procedures; monitoring philosophy and the two-rung ladder per FCTM AS-FG. Autobrake FMA colour per FCOM DSC-32-30-10. Dispatch consequences reflect some operators' MEL practice. The five-column map and the "news channel" framing are integrative syntheses. Individual FMA messages not quoted here should be verified against the FCOM table before teaching them as triggers.

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.