LVFR Airbus A330 NEO — Advanced: FMS / CDU Deep Dive

How the classic MCDU's flight-planning tools actually work

01Architecture: Classic MCDU, Not a Glass FMS

The LVFR Airbus A330 NEO deliberately keeps the real A330-900's classic, physical-key MCDU presentation (Delta FCOM Vol. 2, 34.6) rather than a newer glass-cockpit-style flight computer. Two full crew MCDUs share the same route and FMS state; a third, independent center MCDU is display/navigation reference only — it is not a spare flight computer.

Every page hangs off one router, reached by dedicated hardware keys (INIT, F-PLN, DIR TO, PROG, PERF, DATA, FUEL PRED, SEC F-PLN, MCDU MENU) or by line-select key (LSK) links from within a page — the same LSK-driven navigation convention used throughout, so once you understand it on one page, it transfers to the rest.

02DIR TO — Direct-To Routing

Direct-To is more than "draw a line to a waypoint." A few details make it behave correctly rather than just look correct:

The DIR TO page was rebuilt to the FCOM 34.6.6.11 spec — if you learned it before that rework, the layout and options are worth a second look.

An off-route direct-to target is inserted at the active-leg position, not appended to the end of the plan — appending it would wipe or hide every downstream waypoint by sequencing straight past them.
Typing an identifier that matches more than one navaid or waypoint in the database opens a DUPLICATE NAMES disambiguation page, sorted nearest-first — the same generic pattern used for any manually-typed ident, not just Direct-To.
Activating a direct-to auto-engages NAV (managed lateral) mode, even from a selected HDG/TRACK mode — matching FCOM behavior rather than leaving you selected after committing a direct-to.

03HOLD — Holding Patterns

The underlying LNAV computer already natively flies standard holding-pattern leg types (racetrack entries) with auto-suspend at the hold fix — the CDU's job is mostly to expose the crew-facing controls cleanly:

Insert a hold at any waypoint in the active flight plan; entry geometry is computed automatically.
IMMEDIATE EXIT and RESUME are wired to the same suspend-sequencing mechanism the LNAV computer already exposes — pressing IMM EXIT commands an exit on the next crossing of the hold fix, and RESUME re-arms normal sequencing.
Because holding is a native LNAV capability rather than a bespoke geometry engine, hold behavior is consistent with the rest of lateral guidance — the same steering law, the same intercept behavior.

04SEC F-PLN — Secondary Flight Plan

SEC F-PLN lets you build and hold a second, alternate flight plan without touching the one you're actually flying, then swap it in if you need it — for example, preparing a diversion routing well before you'd ever want to fly it.

Scope: one secondary plan, not three. The real Delta FCOM depiction for this classic MCDU shows a single secondary flight plan slot (unlike some other Airbus-family MCDUs, which offer SEC 1/2/3). SEC INDEX offers COPY ACTIVE, INIT, SEC F-PLN (the FROM/TO/leg editor), DELETE SEC, and ACTIVATE SEC — a three-way swap between active and secondary.

Procedures and airways are now supported on the secondary plan — you can insert a SID/STAR/approach or an airway on SEC F-PLN the same way you would on the active plan, and ACTIVATE SEC runs real FCOM gating rather than a simplified always-available prompt.

SEC PERF (secondary performance predictions) is the one piece still not implemented — a disclosed scope cut, not a bug.

05FIX INFO — Four Independent Slots

FIX INFO lets you mark a reference fix and project radials, a radius ring, and an abeam point off it — independent of your flight plan, purely for situational awareness or diversion planning.

Per the FCOM, this is four separate pages, not four radials on one page. Each of the four independent slots holds one reference fix, up to two radials, one radius ring, and one abeam point — for a possible total across all four of 8 radials, 4 radius rings, and 4 abeam fixes at once. All four fixes you've set draw on the Navigation Display simultaneously; paging through FIX INFO on the CDU only changes which one you're currently editing.

Each slot has its own intercept prediction, computed independently.
A TMPY INSERT step holds your entry as a temporary/proposed change before it commits — the same insert-then-confirm idiom used elsewhere on this CDU.
A duplicate-name reference fix (same ident as another database entry) routes through the same DUPLICATE NAMES picker used by Direct-To.

06RTA and CMS — Time and Mach Management

Both pages are reached from VERT REV and manage a specific cruise/arrival constraint:

RTA — Required Time of Arrival

Set a target time at a waypoint; the page computes a time-error tolerance and works out what speed adjustment is needed to hit it.

The AT / AT-OR-BEFORE / AT-OR-AFTER qualifier isn't a separate radio-button control — it's encoded directly in the time entry via a leading + or − sign, matching the FCOM's own literal description of the entry format (e.g. a leading “−” means “at or before”). This is arguably more authentic than a picker with radio options.

CMS — Constant Mach Segment

Hold a specific Mach number across a defined stretch of the cruise, between a start and end waypoint.

Start/end waypoints are typed idents, consistent with every other waypoint field on this CDU, validated as down-path waypoints where the end comes after the start.
CMS is always offered from VERT REV rather than being phase-gated to cruise only in the menu — the underlying Mach-segment manager itself is a no-op outside cruise, so offering the page early is harmless and avoids a confusing disappearing menu item.

07WIND Pages — Forecast Wind Entry

Separate WIND pages exist for climb, cruise, and descent, feeding the FMS's forecast wind model — more accurate predictions for T/C, T/D, fuel, and ETA than assuming zero wind.

Wind entry uses an all-digit format rather than a DDD/SSS-with-separator format — the CDU keypad has no slash or colon key, so any multi-part field on this MCDU (wind direction/speed, or a time field) is entered as a straight digit string.

08Fuel Planning — INIT B and FUEL PRED

Fuel planning runs on one shared prediction model behind both INIT B and FUEL PRED, so the two pages can never quietly disagree with each other — a common failure mode on simplified FMS implementations, where a flat planning estimate and a livelier in-flight predictor drift apart over a flight.

TRIP fuel is predictor-backed: a full climb→cruise→descent profile with VNAV top-of-climb/top-of-descent, your selected cost index or LRC Mach, forecast winds (from the WIND pages), and ODM fuel-flow anchors — not a flat distance-times-burn-rate estimate.
ALTN (destination-to-alternate) fuel is estimated per FCOM 34.6.4.3 using FL100/FL220/FL310 bands by distance, with the FL310 cruise flow anchored to a real ODM data point (M.80, 400,000 lb gross weight, ~12,230 lb/hr) — the lower bands are labelled estimates rather than presented as equally precise.
FUEL PLANNING / BLOCK CONFIRM (FCOM 34.6.3.4.11/.12) walks you from a proposed minimum block figure to a confirmed one: once ZFW and ZFW CG are entered, a prompt appears; selecting it computes for a moment, then shows the minimum block (TAXI + TRIP + Route Reserve + MIN DEST FOB) for you to confirm. Predictions stay dashed until you confirm — the figure is only proposed until then.
TRIP WIND is suppressed automatically once the individual CLB/CRZ/DES WIND pages have entries, since the profile-based winds supersede a single flat trip-wind guess.
CHECK MIN FUEL AT DEST and DEST EFOB BELOW MIN cautions read live from this same model, so they can actually fire — rather than watching a value nothing else in the aircraft ever writes to.

09ATC COMM / ATSU — Datalink Suite

The full ATC COMM suite lives under MCDU MENU: CONNECT, REQUEST, REPORT, MSG RECORD, D-ATIS, and EMER, plus the ATSU/AOC menu for company communications — consolidated onto the classic CDU's page-and-LSK idiom rather than a tabbed interface.

REQUEST and REPORT are each a single page class with an internal state field for their sub-category (position report type, request category) rather than separate routes — switching sub-view is a local state change, not a navigation event.
MSG RECORD shows one compact line per message (time, direction, response chip). Responding to an open uplink is the same "type the token, press the row" idiom used elsewhere on this CDU — type WILCO/UNABLE/STANDBY/ROGER/AFFIRM/NEGATIVE into the scratchpad, then press that message's own LSK.
PDC and Oceanic Clearance requests auto-fill from your active flight plan via Hoppie ACARS, so in the common case you only need to review and send.
D-ATIS synthesizes a real ATIS broadcast from live METAR data for the departure/arrival airport.

This is a simulated datalink layer (MSFS has no real-world CPDLC/ADS-C network) — Hoppie ACARS provides the real message transport; the request/report content itself is generated locally against your flight plan.

10DATA and Reference Pages

The DATA index and related pages cover reference lookups that don't belong to the active route itself:

CLOSEST AIRPORTS (with EFOB shown for each) — nearest diversion candidates and what fuel you'd land with.
PILOTS WAYPOINTS / PILOTS ROUTES — save and reuse your own custom waypoints and routes across flights.
POSITION MONITOR — cross-check of the aircraft's computed position sources.
ROPS LANDING DISTANCE — a runway-overrun-protection distance estimate independent of the PERF APPR page.
ROUTE SUMMARY and EQUI-TIME POINT — route-level distance/time summaries and the balanced point between two diversion airports.

11Known Scope and Limitations

In the interest of not overselling: a few FCOM-depicted details are deliberately simplified given the classic-keypad paradigm used everywhere else on this MCDU, and are disclosed here rather than left to be discovered.

SEC F-PLN: SEC PERF (secondary performance predictions) isn't built — procedures and airways are now supported, so this is the one remaining gap.
RTA: the AT/AT-OR-BEFORE/AT-OR-AFTER qualifier is sign-encoded in the time entry rather than a separate radio control (arguably closer to the FCOM's own description, not a compromise).
CMS: start/end waypoints are typed idents rather than a scrollable picker list of flight-plan waypoints.
ATC COMM REPORT/REQUEST/EMER pages trim some lower-priority freetext fields present in the FCOM's full page depiction.
D-ATIS reflects live METAR only — there is no real-world D-ATIS data network to connect to.