Communication Operations

The first ten articles covered how the communications system is built and works; this one lands it on how the crew use it well — tuning technique, transmit/receive technique, the VHF 3 datalink discipline, interference avoidance, and SELCAL and oceanic listening watch. These points are scattered as operating notes through the earlier articles; here they are gathered into one strand, anchored on the FCOM how-to section, DSC-23-50 (VHF, HF Utilization).

[!note]- Naming note: the FCOM's "SOP-23" is not the communications SOP Avoid a trap: in the FCOM, PRO-NOR-SOP-23 is "SECURING THE AIRCRAFT", numbered 23 by SOP sequence — unrelated to ATA-23 communications (its content is PARK BRK / ADIRS / BAT / APU shutdown). The communications operating technique lives in DSC-23-50, not SOP-23.

1. Communication set-up flow (from DSC-23-50)

Pre-departure / approach set-up (each tuning)
  ① RMP ON/OFF ......................... CHECK ON
  ② press the onside RMP's VHF/HF key .. green light on; ACTIVE/STBY show active/preset
  ③ rotate the knob (outer = whole, inner = decimals) → change STBY preset (136 MHz: decimals ≤ 975)
  ④ press transfer ..................... STBY↔ACTIVE swap; the transceiver tunes to the new active frequency
  ⑤ (HF if required) press AM .......... green light on
  ⑥ select the radio back on the onside RMP → SEL lights out (clears the cross-tune reminder)
  ⑦ ACP: press the reception key (white light) + rotate for volume; transmit with the transmit key + PTT

2. Tuning discipline — the onside RMP and managing SEL

DSC-23-50 opens by setting "use the onside RMP". Per FCOM DSC-23-50:

The flight crew should normally use his/her onside RMP, to tune any one of the VHF or HF radios. If a frequency is tuned on the RMP not dedicated to its associated VHF (e.g. VHF 1 tuned on RMP 2), the SEL lights come on (on the 3 RMPs) to remind the flight crew that at least one radio system is not selected on its associated RMP. After each tuning, in order to be able to read VHF 1 and VHF 2 frequencies, the flight crew should select the radio system associated with his/her RMP. This will extinguish the SEL lights.

This is the operating face of the SEL light from article 2: after tuning, select the radio back on your onside RMP — clearing SEL and ensuring your onside PFD can read the onside frequency.

3. Transmit and receive technique

The tuning sequence (DSC-23-50): radio key PRESS (green) → knob TURN to change STBY (outer whole, inner decimals) → transfer PRESS (activate) → AM PRESS if HF requires. One decimal limit. Per FCOM DSC-23-50:

Note: To tune a VHF frequency of 136 MHz, the flight crew should set the decimals to a value lower or equal to 975.

For receive/transmit: press the ACP reception key (white light, rotate for volume) and the transmit key (green bars, microphone and PTT to that station). Transmission is exclusive, reception parallel (article 3).

4. The VHF 3 datalink discipline

The single most important day-to-day discipline (the operating face of article 4). Per FCOM DSC-23-50:

Do not use VHF 3 for voice communications, unless VHF 1 and VHF 2 are inoperative. The datalink connection with the ATC is temporarily lost when VHF 3 is set to voice mode. The flight crew may encounter sudden disconnections from the ATC if they switch VHF 3 to voice mode too frequently.

One rule: VHF 3 is the data radio, leave it for the datalink; want a third voice radio? Confirm 1 and 2 are truly inoperative first.

5. Interference avoidance

DSC-23-50 and DSC-23-30-10 give concrete interference/noise avoidance. Per FCOM DSC-23-50:

If two frequencies are closer than 2 MHz (between VHF 1 and 2, or between VHF 3 and 2), or closer than 6 MHz (between VHF 1 and 3), some interference may occur. Reception of 130.275, 130.280 and 130.285 may be noisy (squelch open) on VHF 1 and/or VHF 3. In such cases, use VHF 2.

There is also an entertainment-system note (article 4, DSC-23-30-10): some IFE installations can produce audible noise on 121.500, 135.000, 135.005 — and 121.500 is the emergency frequency, so a hiss while guarding it may be equipment noise.

[!note]- Interference crib sheet Three rules: (1) keep two VHF frequencies apart (VHF 1&2 or 3&2 closer than 2 MHz, VHF 1&3 closer than 6 MHz, can interfere); (2) noise on 130.275/280/285 → use VHF 2; (3) noise on 121.5/135.0/135.005 may be the IFE. With these three in mind, on an unexplained hiss suspect equipment first before doubting the real signal.

6. SELCAL check and oceanic listening watch

Before entering HF/SELCAL over the ocean, the standard action is a SELCAL check (request the ground station transmit the aircraft code, confirm the buzzer and legend). Thereafter the crew need not guard the headset continuously — SELCAL will page them (article 4). Remember the SELCAL aural signal is inhibited on take-off/landing — so run the SELCAL check once established in the cruise, not in the busy take-off/landing phase.

7. SATCOM and HF — oceanic/polar division of labour

• Oceanic (non-polar): datalink rides SATCOM (VHF 3 automatically switches out of line-of-sight, article 5); before entry check the MCDU SATCOM STATUS page for LOGGED-ON + signal HIGH; voice on SATCOM or HF;
• Polar (high latitude): the SATCOM high-gain antenna loses lock at low satellite elevation, so HF is the primary polar voice (article 4), with SELCAL watch.

(This section synthesises the main-library mechanisms across the earlier articles; the specific procedures follow the operator's oceanic/polar manuals.)

8. RMP failure handling

When a single RMP goes black (article 2). Per FCOM DSC-23-50:

When an RMP fails: The affected RMP no longer controls the selected receiver. The frequency displays disappear, and the green VHF or HF lights go out. Affected RMP ... SWITCH OFF. One RMP can control all receivers.

Switching OFF lets the upstream RMP take over transparently (article 2's leader priority). The fuller communications degradation (audio channels, stuck PTT, the emergency-electrical inventory) is in article 12.

Self-test

[!note]- Q1. Why tune on the onside RMP, and why select the radio back to it afterward? What is the operating meaning of the SEL light? To keep your onside PFD able to read the onside frequency. Selecting back onside clears SEL, which otherwise reminds you a radio is tuned on a non-associated panel.

[!note]- Q2. What is the standard tuning sequence, and what decimal limit applies at 136 MHz? Radio key → knob to change STBY (outer whole, inner decimals) → transfer to activate → AM if HF requires. At 136 MHz the decimals must be ≤ 975.

[!note]- Q3. When may VHF 3 be used for voice, and what is the consequence? Only when VHF 1 and VHF 2 are both inoperative; the ATC datalink connection is temporarily lost.

[!note]- Q4. Give the three interference rules. Where might a hiss on 121.5 come from? Keep VHF frequencies apart (1&2 or 3&2 <2 MHz, 1&3 <6 MHz); noise on 130.275/280/285 → use VHF 2; noise on 121.5/135.0/135.005 may be the IFE.

[!note]- Q5. When is the SELCAL check made and why not on take-off/landing? Why is HF the primary polar voice? Once established in the cruise, because the SELCAL aural is inhibited on take-off/landing. In the polar region the SATCOM antenna loses lock at low elevation, so HF carries the voice.

Key takeaways

References

• FCOM DSC-23-50 — tuning (onside RMP/SEL/136 MHz decimals), transmit/receive, VHF 3 discipline, interference notes, RMP failure handling.
• FCOM DSC-23-30-10 — SELCAL aural inhibit on take-off/landing; IFE interference frequencies.
• FCOM DSC-23-30-20 — SATCOM STATUS (LOGGED-ON / signal) for the oceanic check.

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; §7 oceanic/polar division of labour synthesises the main-library mechanisms and follows operator manuals for specific procedures.