MEL Dispatch (ATA-23)

Dispatch with a communications item inoperative follows the operator's Minimum Equipment List. The exact categories, installed/required numbers, placards and provisos are operator-specific — this article teaches the logic of ATA-23 dispatch, not any one operator's numbers. Always defer to your current operator MEL for the actual dispatch conditions.

The value here is threefold: which communications items cannot be dispatched inoperative; why the external-voice items (HF/VHF/SATCOM) tie their dispatch to the route; and the recurring pattern that every dispatchable item is allowed only if a substitute means still works.

1. The items that must work (no dispatch relief)

A small set of communications items carry no dispatch relief — the chapter's red lines:

• The CVR — the accident-record floor. (And note the connected clause: if the CVR TEST pushbutton is inoperative, the CVR is considered inoperative, tripping the red line.)
• The CIDS function — the cabin hub. This clause refers to a total CIDS loss (both directors); a single director partial fault shows only on the STATUS page and does not raise COM CIDS 1+2 FAULT (article 12).
• The flight-crew interphone — each operating crew member's system must work; the crew-coordination floor.

[!warning]- Three red lines: CVR, CIDS function, flight-crew interphone These three — the accident record, the cabin hub, and crew coordination — have no dispatch margin. Note especially that a failed CVR TEST pushbutton connects to the CVR red line: it makes the CVR "considered inoperative".

2. External voice — dispatch tied to the route

Dispatch of HF, VHF and SATCOM voice almost always hangs on the operational context — whether ETOPS is planned, whether the route stays within VHF coverage, and the operator's own route/aerodrome provisos. The underlying reason is simply that "how much communication is enough" depends on the route: oceanic sectors need HF/SATCOM, continental sectors are covered by VHF. This is article 4/5's mechanism (HF long, VHF near, SATCOM global) landing on dispatch. Typical logic (generalised — confirm against the operator MEL):

• HF voice: one or both HF may be dispatched inoperative provided the flight stays within VHF coverage and does not perform ETOPS; beyond VHF coverage, a failed HF typically requires SATCOM voice or data to be working; operator route/aerodrome provisos may add requirements.
• VHF voice: with one VHF inoperative (two of three required), a common proviso is to set VHF 3 to VOICE mode and consider the VHF datalink inoperative — you have lost a voice radio, so the data radio is pressed into voice service (article 4/12 discipline).
• SATCOM voice: dispatch is typically constrained for extended ETOPS and by operator-specific aerodrome/route requirements.

3. The datalink bearers

• GND HF DATALINK pushbutton: dispatchable inoperative typically requires HF 1/HF 2 to be set to VOICE mode on the ground and HF not used during refuelling/defuelling/ground fuel transfer (article 4's HF refuelling restriction).
• SATCOM / HF / VHF datalink: dispatchable when the procedure does not require ATC datalink; where it does, another means of ATC communication is required, and beyond VHF coverage ADS-C and CPDLC become unavailable.

4. Audio and frequency management — the "who covers for it" pattern

The core dispatch pattern: a dispatchable item is allowed only if a substitute still works.

• RMP: three installed, two required — RMP 2 or RMP 3 may be inoperative (so RMP 1 must work — the leader and the sole emergency-power survivor, article 2).
• CAPT/F-O ACP: one may be inoperative provided ACP 3 works and AUDIO SWITCHING works — the CAPT/F-O ON 3 fallback of article 3.
• AUDIO SWITCHING / SELCAL / ACP 3: dispatchable inoperative.
• Cockpit loudspeaker: one may be inoperative provided at least one operating crew member wears a boomset throughout.
• Sidestick PTT: may be inoperative in the open (non-transmit) position provided the ACP INT/RAD switches work.

5. Interphone, call and cabin items — the substitute pattern again

• Ground external speaker (horn): dispatchable inoperative typically requires the air-conditioning-pack bay and avionics-bay ventilation to be monitored from the cockpit — because the horn doubles as the battery/ventilation warning (article 6), so a human must cover its warning role.
• CALLS buttons: individually dispatchable; if enough of the FWD/MID/AFT/EXIT set are lost, a common proviso is that the PA be used for cockpit-to-cabin communication.
• Cockpit handset: dispatchable provided the ACP is used for cockpit↔cabin communication.
• CDSS (door surveillance): dispatchable inoperative (with an operational procedure).
• DEU A / DEU B / cabin loudspeakers / handsets / FAP: dispatchable with cabin-safety provisos — e.g. seats that cannot clearly hear the PA are not occupied; a working DEU B and handset remain at each pair of floor-level exits; FAP safety-related information is considered inoperative when the FAP display is dispatched.

6. The three lines of dispatch logic

Line one: the three red lines. CVR / CIDS function / flight-crew interphone — the floors of accident record, cabin hub and crew coordination, no relief. Watch that a failed CVR TEST pushbutton trips the CVR red line.

Line two: external voice binds to the route. HF/VHF/SATCOM voice dispatch hangs on ETOPS / VHF coverage / operator route provisos — because sufficiency of communication depends on the route. Dispatching a VHF voice radio typically forces VHF 3 to VOICE and the datalink to be considered inoperative.

Line three: every dispatchable item has a substitute. A dispatchable communications item almost always requires a working substitute — ACP ↔ AUDIO SWITCHING; external horn ↔ human ventilation monitoring; cockpit handset ↔ ACP; CALLS panel ↔ PA; GND HF DATALINK ↔ HF VOICE + refuelling restriction. In one line: MEL dispatch = "if this fails, who covers for it". Match each item's substitute to the earlier mechanism articles and ATA-23 dispatch becomes the application of the mechanism, not the memorising of clauses.

Self-test

[!note]- Q1. Which three communications items have no dispatch relief, and which CVR sub-item connects to a red line? The CVR, the CIDS function, and the flight-crew interphone. A failed CVR TEST pushbutton makes the CVR considered inoperative.

[!note]- Q2. Of three RMPs, which must work, and why? RMP 1 — the leader and the only emergency-power survivor (RMP 2 or 3 may be inoperative).

[!note]- Q3. Dispatching one CAPT/F-O ACP requires what, and which mechanism backs it up? ACP 3 working and AUDIO SWITCHING working — the CAPT/F-O ON 3 fallback (article 3).

[!note]- Q4. Why does external-voice dispatch tie to ETOPS/VHF coverage, and what does dispatching a VHF voice radio typically force? Because sufficiency of communication depends on the route (oceanic needs HF/SATCOM; continental is covered by VHF). It typically forces VHF 3 to VOICE and the datalink to be considered inoperative.

[!note]- Q5. Why does dispatching the ground external speaker require cockpit ventilation monitoring? The horn doubles as the battery/ventilation warning (article 6), so a human must cover its warning role.

Key takeaways

References

• Operator Minimum Equipment List, ATA-23 — the authoritative dispatch conditions (operator-specific; not reproduced here).
• FCOM DSC-23-10-20 / -30 / -40 / -50 — the mechanisms behind the dispatch logic (RMP leader/emergency survivor, AUDIO SWITCHING, CVR, ground-crew-call horn warning).

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Dispatch is governed by the current operator MEL; always defer to it and to the operator FCOM, FCTM and QRH for operational use.