Approach Capability — CAT II and CAT III

Article 11 put the aircraft on the beam; this article is about the small print in FMA column 4 — CAT1 / CAT2 / CAT3 SINGLE / CAT3 DUAL — the qualification system: where it is computed, which minima each grade unlocks, and which limitations each grade carries. In one line: the modes answer which rails the aircraft is on; the capability answers how low those rails are certified to take you.

1. A qualification computed, not chosen

Per FCOM DSC-22_30-70:

The approach and landing capability provides the flight crew with the aircraft capability to perform an approach, and land the aircraft. The FMA displays this capability. The approach and landing capability depends on: ‐ The availability of aircraft systems, ‐ The type of approach selected on the ARRIVAL page.

Who computes it: each FMGEC, for itself, from its own side's sensors (per AMM 22-13-00). With both APs engaged the total capability is the lower of the two computations, and FAIL OP (DUAL) requires both FMGECs healthy — the mechanical sequel to article 06's point that on a dual-AP approach the two FMAs are independent judgements to be cross-checked.

Monitoring splits in two layers — the two braces on the QRH equipment table: FMGES-monitored items (AP, A/THR, PRIMs, hydraulics, radio altimeters, ILS receivers… — fail one and the FMA downgrades by itself) and NOT-FMGS-monitored items (DH indication, the mechanical parts of anti-skid and nose-wheel steering… — fail one and the FMA does not move; only the table and the MEL catch it). So CAT3 DUAL on the FMA does not mean everything required is serviceable — the FMA vouches only for the half it watches.

The official capability-to-minima map:

And one exclusion:

Note: No approach and landing capability is displayed when an RNAV (RNP) approach is selected in the FMS.

FM-type approaches (article 11's FINAL APP) simply do not play in this ILS qualification league — column 4 stays blank.

2. Fail-operational and fail-passive — the DUAL/SINGLE watershed

Per FCOM DSC-22_30-70:

An automatic landing system is fail-operational if, in the event of a failure below alert height, the remaining part of the automatic landing system allows the aircraft to complete the approach, flare, and landing. The CAT3 DUAL approach and landing capability is fail-operational automatic landing system. Note: In the event of a failure, the automatic landing system operates as a fail-passive system.

An automatic landing system is fail-passive if, in the event of a failure, there is no significant out-of-trim condition, or deviation of flight path or attitude, but the landing is not completed automatically. The following approach and landing capabilities are fail-passive automatic landing system. ‐ CAT3 SINGLE ‐ CAT2 ‐ CAT1

Read fail-passive's promise carefully: it is not "the landing gets done" — it is "the failure moment does not hurt you". No out-of-trim lurch, no path or attitude excursion; the aircraft hands control back quietly, and the completion is yours. That is why CAT3 SINGLE carries a DH of 50 ft (you must see something before letting it continue), while CAT3 DUAL flies to an alert height of 200 ft — and an AH is not a decision height. Above 200 ft a failure means go around; below it the fail-operational system carries the failure itself, and no visual reference is required at the AH. DH asks "have you seen it?"; AH asks "how many lives does the system have left?"

3. Display and computation — five gates and a lock

Per FCOM DSC-22_30-70:

The approach and landing capability is displayed in the 'Approach and Landing Capability' column of the FMA and of the HUD , when: ‐ An LS approach is manually or automatically selected on the ARRIVAL page ‐ The flight crew presses one of the following pushbutton on the FCU: • The LS pb, or • The LOC pb, or • The APPR pb.

The computation of the CAT 1, CAT 2, CAT 3 SINGLE or CAT 3 DUAL approach and landing capability depends on the AP engagement. Therefore, when the flight crew presses the APPR pb to arm or engage the final approach mode, and one or both AP(s) is engaged then CAT 1, CAT 2, CAT 3 SINGLE or CAT 3 DUAL approach and landing capability can be displayed (both APs are necessary for CAT 3 DUAL). However, if the North reference is TRUE, the CAT 1 is the only available capability.

Capability hangs off AP engagement (dual AP for DUAL — article 05's approach-only dual-AP rule cashing in), and a TRUE north reference caps everything at CAT1 — the hidden price of polar operations. Then the two height gates:

L2 CAT 1, CAT 2, CAT 3 SINGLE or CAT 3 DUAL approach and landing capability is computed only if the aircraft is above 400 ft RA when the flight crew arms the approach modes. Below 200 ft RA, CAT 3 SINGLE, or CAT 3 DUAL is memorized and remains displayed as long as: ‐ At least one AP is engaged, and ‐ LAND, FLARE, or ROLL OUT is engaged.

Arm above 400 ft or no computation; and below 200 ft the CAT 3 capability is latched — the AMM states it as "no downgrading below 200 ft": beneath the alert height the system stops re-grading itself, and failures are handed to the AUTOLAND warning system instead (article 13). Practical reading: column 4 is a negotiation tool above 200 ft; in the last 200 ft, stop watching it — watch the AUTOLAND light and the deviations. The floor case:

L2 If the FMGEC is not able to compute the approach and landing capability, CAT 1 capability is displayed on the FMA, regardless of the FMS flight phase.

Cannot compute → CAT1 as the safe floor (the same reason a high-altitude G/S capture shows CAT1 until the radio altimeters wake up — article 11). Typography, for the callout: CAT1/CAT2 occupy one line of column 4; CAT 3 stacks over DUAL/SINGLE in two lines — read the block whole: "CAT THREE DUAL".

4. The LIM catalogue

ILS CAT II. Per FCOM LIM-AFS:

Minimum decision height ...............................................................................................................100 ft At least one autopilot must be engaged in APPR mode, and CAT 2 or CAT 3 SINGLE or CAT 3 DUAL must be displayed on the FMA. For manual landing, AP should be disconnected no later than 80 ft AGL.

SA CAT II and OTS CAT II (same clause set; note the last sentence — on an airframe without HUD it is the rule):

With HUD , the flight crew must use the HUD to monitor the approach and perform an automatic landing or a manual landing. If the flight crew performs an automatic approach without automatic landing, the autopilot must be disengaged no later than at 80 ft AGL. Without HUD, the flight crew must perform an automatic landing.

The baseline airframe of this series has no HUD (article 01) — so SA/OTS CAT II means autoland, full stop.

ILS CAT III fail-passive (SINGLE):

A/THR must be used in selected or managed speed. One autopilot must be engaged in APPR mode, and CAT 3 SINGLE or CAT 3 DUAL must be displayed on the FMA. Minimum decision height .................................................................................................................50 ft

(A/THR mandatory — either speed reference; article 17 collects this clause.)

ILS CAT III fail-operational (DUAL):

Alert height.................................................................................................................................... 200 ft A/THR must be used in selected or managed speed. Both autopilots must be engaged in APPR mode, and CAT 3 DUAL must be displayed on the FMA. CAT III without DH: Minimum Runway Visual Range ..............................................................................................75 m

Engine-out:

CAT II and CAT III autoland are only approved in Configuration 3, and if engine-out procedures are completed before reaching 1 000 ft in approach.

Single-engine CAT II/III autoland: CONF 3 only, and the engine-out procedures finished before 1000 ft on the approach — what happens when the engine fails later is section 6's QRH note. (The library also carries GLS CAT I clauses — DH 200 ft, autoland wording — awareness only: GLS is not installed on the baseline airframe.)

5. Wind limits — and whose wind counts

Per FCOM LIM-AFS:

Headwind: 35 kt Tailwind : 10 kt Crosswind: 20 kt

Note: Wind limitation is based on the surface wind reported by the tower. If the wind displayed on the ND exceeds the above-noted autoland limitations, but the tower reports surface wind within the limitations, then the autopilot can remain engaged. If the tower reports surface wind beyond the limitations, only a CAT I automatic approach without autoland can be performed.

The ND wind is the air-mass wind up where you are (IRS/FM computed); the certification envelope was flown against surface wind. So "the ND shows 40 kt of headwind" is not a reason to disconnect — the tower's number is the legal input, and a tower report beyond limits reduces you to a CAT I automatic approach without autoland.

6. The QRH equipment table — when to open it, what to read

One representative airframe's aircraft-specific QRH landing-capability table (spine rows; columns CAT2 / CAT3 SINGLE / CAT3 DUAL):

AP 1 AP ENGAGED 1 AP ENGAGED 2 AP ENGAGED AUTO THRUST 0 1 1 FMA 1 2 2 ELECTRICALLY POWER SUPPLY SPLIT 0 0 1

Two rows repay memorising. AUTO THRUST 0/1/1 — CAT2 can legally fly without A/THR; only CAT III mandates it (dovetailing with the LIM wording above). ELECTRICALLY POWER SUPPLY SPLIT 0/0/1 — required only for DUAL:

‐ Electrical power supply split: This ensures that each FMGEC is powered by an independent electrical source (AC and DC).

Fail-operational's "second life" must not share even a power source — article 01's AP ELEC PWR SPLIT relay cashing in operationally. Other key rows (table paraphrase): hydraulics 2/2/3 (DUAL wants all three systems); PRIMs 1/1/(1+2 or 1+3); SECs 1/1/2; radio altimeters 1 (displayed both sides)/2/2; ADR and IR 2/2 rising to 3/3 for DUAL; excess-deviation monitoring 1 (PM side)/2/2; the AUTOLAND light required at every grade; and the BSCU/anti-skid/nose-wheel-steering footnote — needed (1) only if automatic rollout is intended, 0 for an autoland without it.

Three usage notes, verbatim:

Note: ‐ Flight crews are not expected to check the equipment list before approach. When an ECAM or local caution occurs, the crew should use the list to confirm the landing capability. ‐ On ground, the equipment list determines which approach category the aircraft will be able to perform at the next landing.

‐ The DH will be displayed on the FMA, and the 'Hundred Above' and 'Minimum ' auto callouts will be announced, provided that the DH value has been entered on the MCDU. ‐ In the case of an engine failure during a CAT III approach, revert to CAT 3 SINGLE minima.

The table is a downgrade lookup card, not pre-approach homework; the DH-driven callout chain is only as good as the PERF APPR entry; and an engine failing mid-CAT III drops you to SINGLE minima — a downgrade, not an abandonment. Two more counter-intuitive rows: the mechanical parts of anti-skid and nose-wheel steering are NOT-monitored — the capability column will never tell you they broke; and the CHECK APPR SELECTION scratchpad message (article 11) opens its display window from 100 NM before T/D in cruise. Every capability downgrade (say CAT3 DUAL → CAT2) announces itself with a triple click and obliges a fresh minima decision — the AMM lists capability downgrade among the triple-click sources (article 13 assembles the full warning set).

7. Flying the capability line

A CAT III DUAL approach as a capability timeline (synthesis — each node quoted above): on the ground, the equipment table sets the grade for the next landing → ILS selected, APPR pressed, both APs in (article 05) → FMA shows CAT3 DUAL (armed above 400 ft) → an ECAM en route (one hydraulic, one SEC…) → triple click + open the table to confirm the new grade → above the 200 ft AH a downgrade means re-decide against the new minima; below it the display is latched and the AUTOLAND warning system owns failures (article 13) → land, or apply "engine failure during CAT III → SINGLE minima".

Dispatch alignment (article 32): a failed APPR pushbutton caps at CAT 1 (article 02); one FMGEC out caps at CAT3 SINGLE; A/THR out keeps CAT2 (its column reads 0) but kills CAT III — the MEL's dispatch grades and the QRH columns are the same structure used twice. And a technique note: the CAT II 80 ft AGL disconnect is a legal floor, not a recommendation — the stabilised-approach philosophy wants a longer manual segment when conditions allow (article 30).

[!warning]- Four misconceptions this article corrects (1) CAT3 DUAL on the FMA does not certify the whole aircraft — the FMA vouches only for FMGES-monitored items; DH indication and the mechanical anti-skid/steering parts are outside its sight. (2) An alert height is not a decision height — no visual reference is required at 200 ft on a DUAL approach; AH counts the system's remaining lives, DH counts your visual contact. (3) The ND wind does not invalidate an autoland — the certification wind is the tower-reported surface wind; ND 40 kt with tower-in-limits keeps the AP engaged. (4) Below 200 ft RA the capability display is deliberately frozen — a blank refusal to downgrade is not a stuck display; failures there speak through the AUTOLAND warning instead.

Self-test

[!note]- Q1. Define fail-operational and fail-passive in one sentence each — and after one failure, in what regime does a CAT3 DUAL system continue?

Fail-operational: after a failure below alert height, the remaining system still completes approach, flare and landing. Fail-passive: a failure causes no significant out-of-trim condition or path/attitude deviation, but the automatic landing is not completed. After one failure, the DUAL system continues as fail-passive.

[!note]- Q2. The essential difference between AH 200 ft and DH 50 ft — which requires visual reference?

The DH requires a decision on visual reference (see it or go around). The AH requires none — above it a failure means go-around; below it the fail-operational system absorbs the failure. AH counts system lives, not runway lights.

[!note]- Q3. You press APPR and only CAT1 shows — name three possible reasons.

Any three of: no AP engaged (capability computation hangs on AP engagement); radio altimeters not yet in range (cannot compute → CAT1 floor); TRUE north reference selected; approach modes armed below 400 ft RA; the FMGEC otherwise unable to compute.

[!note]- Q4. Below 200 ft, what two conditions keep the latched CAT 3 capability displayed?

At least one AP engaged, and LAND, FLARE or ROLL OUT engaged.

[!note]- Q5. Latest AP disconnect for a CAT II manual landing — and the landing method for SA/OTS CAT II without HUD?

80 ft AGL. Without HUD, SA/OTS CAT II must be an automatic landing (the baseline airframe has no HUD, so that is the operative rule).

[!note]- Q6. The three elements of engine-out CAT II/III?

Approved only in CONF 3; engine-out procedures completed before 1000 ft in approach; and if the engine fails during a CAT III approach, revert to CAT 3 SINGLE minima.

[!note]- Q7. The three autoland wind numbers — and does an over-limit ND wind with an in-limits tower report force a disconnect?

Headwind 35 kt, tailwind 10 kt, crosswind 20 kt. No — the limitation is based on tower-reported surface wind; the AP may remain engaged. Tower wind beyond limits: CAT I automatic approach, no autoland.

[!note]- Q8. What does the "electrical power supply split" row verify, and for which grade is it required?

That each FMGEC is powered by an independent electrical source, both AC and DC. Required only for CAT3 DUAL (0/0/1) — fail-operational cannot share power sources.

[!note]- Q9. When is the QRH equipment table meant to be opened?

Not before approach as routine — when an ECAM or local caution occurs, to confirm the remaining landing capability; and on the ground, to determine the achievable category for the next landing.

Key takeaways

References

Capability definition, mapping, fail-operational/fail-passive definitions, display conditions, AP dependency, TRUE-north cap, 400/200 ft gates and the cannot-compute floor per FCOM DSC-22_30-70; FMA typography and the CHECK APPR SELECTION window per FCOM DSC-22_30-80-20. CAT II, SA/OTS CAT II, CAT III fail-passive/fail-operational, engine-out and wind-limit clauses per FCOM LIM-AFS (article 33 carries the complete limitation set). Equipment-table rows and usage notes per one representative operator's aircraft-specific QRH landing-capability table (contents vary by airframe — use your own). Per-FMGEC computation, lower-of-two rule, no-downgrading latch and triple-click sources per AMM 22-13-00. The capability timeline is an integrative synthesis. GLS clauses are awareness-only on the baseline airframe (function not installed).

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.