Datalink Operations

The first nine articles covered how datalink is built and how each application works; this one lands it on how the crew use it well — the operating workflow, VHF/media assignment, FANS route requirements and performance (RCP/RSP), and the revert-to-voice discipline that runs through the chapter. The authority is the FCOM how-to (DSC-46-10-50), with cockpit preparation (PRO-NOR-SOP-06) and Airbus's Getting to grips with FANS (GTG-FANS) for operational background.

1. VHF assignment and media priority

The VHF assignment at cockpit preparation. Per FCOM PRO-NOR-SOP-06:

Use VHF 1 for ATC (only VHF 1 is available in emergency electrical configuration), VHF 2 for ATIS and company frequencies. VHF 3 is normally devoted to ACARS.

This matches ATA-23-04's "VHF 3 is the data radio, do not use for voice". The ATSU auto-selects the best datalink medium in a fixed order. Per GTG-FANS:

the ATSU that manages all the communications and automatically chooses the best available medium (e.g. VHF, SATCOM and HF, in that order).

[!note]- Media priority: VHF first, SATCOM second, HF last Over land / near range, VHF 3 (cheap, fast); beyond VHF coverage (oceanic) it switches automatically to SATCOM; where SATCOM fails too (polar loss of lock), it falls back to HFDL (HF datalink). This is the same coverage difference as the ATA-23 voice media (VHF near, SATCOM global-less-poles, HF polar). The crew rarely intervene (the ATSU is automatic), but should read the DATALINK STATUS page (article 9) to see which medium is in use and which is left.

2. FANS route requirements and performance

Which routes require FANS — GTG-FANS names them. Per GTG-FANS:

FANS routes over China: Aircraft that intents to fly Y1, Y2, Y3 or L888 routes must be fitted with FANS 1/A.

Datalink performance is measured by RCP/RSP (the datalink counterpart of RNP). Per GTG-FANS:

RCP 240 defines a maximum time of 240 seconds for an ATC controller to initiate a transaction and receive the response from the flight crew [...] RSP 180 defines a maximum time of 180 seconds to send a position report from the aircraft to the ground.

[!note]- RCP/RSP: the datalink RNP As RNP specifies navigation performance, RCP (Required Communication Performance) / RSP (Required Surveillance Performance) specify communication/surveillance timing performance. Reduced-separation operations (e.g. 30/30 oceanic) require the normal medium (SATCOM) to meet RCP 240/RSP 180 and the alternate (HFDL) to meet RCP 400/RSP 400. This is why the message timers (article 4) are so strict — to meet RCP/RSP. Advanced datalink operations include DARP (dynamic airborne re-route, article 7), Tailored Arrival, and In-Trail Procedure.

3. The datalink operating workflow

A typical datalink run (synthesised from articles 2–9, all sourced):

1. Preflight initialisation — flight number identical to the ICAO plan (article 2); do not set the clock manually (GPS ±1 s, article 1);
2. Notification — 15–45 min before the area, via the MCDU NOTIFICATION page (article 2);
3. Connection — established by the controller; the active centre on the DCDU/CONNECTION STATUS (article 2);
4. Communication — build requests on the MCDU (LAT/VERT/OTHER REQ), read/answer on the DCDU (select WILCO/UNABLE then SEND), position report manual/automatic (articles 3/4/8);
5. Close/record — CLOSE archives to the MSG RECORD, RECALL within 5 min (articles 8/9).

4. Revert to voice — the floor running through the chapter

On temporary loss or doubt, revert to voice is the master handling (article 1's four conditions, and article 11): emergency, doubt about a message, timer timeout (NO ATC REPLY / SEND FAILED), a response not correctly transmitted — any of these, revert to voice to clarify. Temporary loss of datalink (DSC-46-10-50 How to Manage Temporary Loss) is likewise: revert to voice, resume when available.

[!warning]- One operating rule: datalink is the aid, voice is the primary means However advanced FANS is, voice is always the primary means (article 1). Datalink is non-instantaneous, delayed, and can time out — so critical instructions, doubtful messages, and timed-out dialogues all revert to voice. Do not assume ATC received a CPDLC just because you sent it; if no reply in seven and a half minutes (article 4), make the call. This threads articles 1/4/8/11 into one line.

Self-test

[!note]- Q1. Which radio is assigned to ATC, ATIS/company, and data? In what fixed order does the ATSU select media? VHF 1 for ATC, VHF 2 for ATIS/company, VHF 3 for data. The ATSU selects VHF → SATCOM → HF.

[!note]- Q2. Which China routes require FANS 1/A, and what are RCP 240 / RSP 180? Y1, Y2, Y3, L888. RCP 240: a 240 s maximum for a controller transaction/response; RSP 180: a 180 s maximum for a position report to the ground.

[!note]- Q3. What are the five steps of the datalink workflow, and the two preflight disciplines? Preflight init → notify → connect → communicate → close/record. Disciplines: flight number = ICAO plan; do not set the clock manually.

[!note]- Q4. What are the four revert-to-voice conditions, and what do you do on temporary loss? Emergency, doubt, timer timeout, failed response. On temporary loss: revert to voice, resume when available.

Key takeaways

References

• FCOM PRO-NOR-SOP-06 — VHF 1 ATC / VHF 2 ATIS-company / VHF 3 ACARS.
• FCOM DSC-46-10-50 — how-to: initialise/notify/connect/request/answer/position report/DCL/D-ATIS/EMER/temporary loss.
• GTG-FANS — media priority VHF→SATCOM→HF, China FANS routes Y1/Y2/Y3/L888, RCP 240/RSP 180, DARP/TA/ITP.

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.