Datalink Abnormals and Degradation

Datalink abnormals share a clear character: almost all are Level 1/2 "crew awareness", and the handling is almost always the same — revert to voice. Because datalink is an aid (article 1), its failure does not imperil the aircraft; it only removes the convenience of "typing to ATC/company", and reverting to voice suffices. This article covers the three PRO-ABN-DATALINK ECAM alerts and ties datalink degradation to the ATA-23 media faults.

1. The ECAM datalink alert family (PRO-ABN-DATALINK)

All three are crew-awareness level.

2. DATALINK ATC — revert to voice with ATC

The commonest one, the ATC datalink is down. Per FCOM PRO-ABN-DATALINK:

This alert triggers when: The ATC datalink communications are failed, or The ATC datalink application is lost.

The STATUS tells you the action: ATC COM VOICE ONLY + INOP DATALINK ATC — "use voice with the controller", reverting to HF/VHF voice (article 1). CPDLC/ADS-C/DCL/OCL are unavailable; ATIS may still be usable (media-dependent).

3. DATALINK ATSU FAULT — ATC and company datalink lost together

The ATSU is the datalink hub (article 1); an initialisation failure loses the whole datalink. Per FCOM PRO-ABN-DATALINK:

This alert triggers when there is a failure in ATSU initialization associated with ATSU INIT FAULT ECAM message.

STATUS: ATC COM VOICE ONLY + COMPANY COM VOICE ONLY; INOP: ATSU, DATALINK ATC, DATA COMPANY — ATC and company datalink lost together, all revert to voice.

[!warning]- The ATSU is the "router" — it falls and the whole thing drops DATALINK ATC loses only ATC; ATSU INIT FAULT loses everything (ATC + company) — because the ATSU is the router that hosts all datalink applications and manages all media (article 1); its initialisation failure is "the router did not boot". Common root cause: no VHF scan mask (article 1 — the scan mask is mandatory, and its absence gives ATSU INIT FAULT). See ATSU INIT FAULT, think scan mask / ATSU initialisation, revert everything to voice.

4. DATALINK COMPANY FAULT — only company datalink lost

Only AOC (company) datalink is down; ATC datalink is intact. Per FCOM PRO-ABN-DATALINK:

This alert triggers when the AOC datalink communications are failed.

STATUS: INOP DATA COMPANY — use voice/other means with the company, but CPDLC/ADS-C with the controller are unaffected. The smallest of the three.

5. Tie-in with ATA-23 media faults

Datalink is the application layer; its failure may be the application layer itself (ATSU/DATALINK), or the medium carrying it — and media faults are in ATA-23.

[!note]- Two layers of datalink degradation: application (46) vs media (23) On a datalink loss, split into two layers: (1) application/ATSU layer (this chapter, 46) — DATALINK ATC / ATSU FAULT / COMPANY FAULT, revert to voice; (2) media layer (ATA-23) — COM VHF 3 DATA FAULT (VHF 3 data failed, the datalink tries to switch to SATCOM), COM HF DATA FAULT, COM SATCOM DATA FAULT (see ATA-23-12). If a medium fails the ATSU auto-switches to the next (VHF→SATCOM→HF); only when all media fail is the datalink fully down. The DATALINK STATUS page (article 9) is the diagnostic handle — a glance at each medium's DLK AVAIL/VOICE/INOP. Whichever layer, the endpoint is the same — revert to voice.

Self-test

[!note]- Q1. What are the three datalink ECAM alerts, their triggers, and their STATUS messages? DATALINK ATC (ATC datalink failed → ATC COM VOICE ONLY); DATALINK ATSU FAULT (ATSU init failure → ATC + COMPANY VOICE ONLY); DATALINK COMPANY FAULT (AOC failed → DATA COMPANY inop).

[!note]- Q2. Why does ATSU INIT FAULT lose both ATC and company datalink, and what is the common root cause? The ATSU is the router hosting all applications; its init failure drops everything. Common cause: no VHF scan mask.

[!note]- Q3. What does ATC COM VOICE ONLY require you to do? Use voice with the controller.

[!note]- Q4. How do you split the two layers of datalink degradation, and what page do you diagnose with? Application/ATSU (46) vs media (23). Diagnose on the DATALINK STATUS page; the endpoint is revert to voice.

Key takeaways

References

• FCOM PRO-ABN-DATALINK — DATALINK ATC / ATSU FAULT / COMPANY FAULT; ATC COM VOICE ONLY / COMPANY COM VOICE ONLY.
• FCOM DSC-46-10-10 / -50 / -100 — ATSU INIT FAULT (scan mask), temporary-loss handling, ATC MSG RECORD NOT RELIABLE.
• FCOM DSC-23 — media-layer COM VHF3/HF/SATCOM DATA FAULT (ATA-23-12).

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.