Cockpit Voice Recorder (CVR)

The CVR is the voice half of the "black box" — it records everything audible in the cockpit for accident investigation. It belongs to the communications chapter because its audio sources are precisely the earlier articles' AMU (radio/interphone/PA) plus the cockpit area microphone. The crew need three layers: what it records, how it records (hot mike / only the last 2 hours), and how to test and erase it (under strict conditions).

1. Architecture

   audio sources                    recording               location
 ┌──────────────┐          ┌──────────────────┐
 │ AMU: radio   │          │  CVR recorder     │       ULB
 │  tx/rx/int/PA │──3 ch──▶│  4 tracks, all     │──▶ underwater locator beacon
 │ (CAPT/F-O/   │  audio    │  simultaneous;     │    (on the recorder)
 │  3rd occ)     │          │  last 120 min only │
 ├──────────────┤          │  crashproof case;  │
 │ cockpit area │──direct─▶│  aft section       │
 │  microphone   │ (ambient └────────┬─────────┘
 │  (hot mike)   │  + warn)          │
 ├──────────────┤          control: CVR control panel + jacks
 │ datalink(ATC)│──msgs──▶  · CVR TEST pb (fail → RECORDER CVR FAULT)
 │ (this config)│           · CVR ERASE pb (ground + parking brake on)
 └──────────────┘           + overhead RCDR GND CTL pb (manual ground start)

2. What it records — five classes plus datalink

In the configuration covered here the recorded content, per FCOM DSC-23-10-40:

The CVR records: Direct conversations between crew members in the cockpit; All aural warnings sounded in the cockpit; Audio communications received and transmitted; Datalink communications received and transmitted; Intercommunications conversations between crew members; Announcements transmitted over the PA system, if PA reception is selected on at least one ACP. Only the last 2 h of recording are retained.

Two points: this configuration also records datalink communications — the AMM adds that the CVR collects and records datalink messages directly from the ATC applications (adapting to the CPDLC era of investigation); and PA is recorded only if at least one ACP has PA reception selected — with nobody listening to PA in the cockpit, the CVR does not capture it.

3. Hot mike — recording you without a PTT

The CVR has a dedicated cockpit area microphone. Per AMM 23-71-00:

The cockpit area microphone picks up and transmits to the CVR direct conversations between crew members, aural warnings in the cockpit and all other ambient noises from the cockpit.

Beyond that, it has a "hot mike" function. Per FCOM DSC-23-10-40:

A 'hot mike' function, which records the crew members voice directly from their microphone, even if the PTT pb is not activated.

[!warning]- The CVR is always "listening" — no PTT needed To transmit you press a PTT; but the CVR's hot mike records your headset microphone whether or not you press it. Add the area microphone capturing ambient sound and warnings — every word spoken and every warning sounded in the cockpit is recorded whenever the CVR is running. That is how investigation reconstructs the final cockpit conversation, and why cockpit discipline under a running CVR matters.

4. Four tracks, last two hours

How it records, per AMM 23-71-00:

The CVR is a four channel system and all channels are recorded simultaneously. When the memory is full, new data are overwritten on the oldest ones to keep the record of the last 120 minutes.

The four tracks correspond roughly to captain, first officer, third occupant (these three audio channels arrive from the AMU, article 3) plus the cockpit area microphone. Only the last 120 minutes (2 h) are retained — a rolling overwrite, a different retention from the flight-data recorder (ATA-31).

5. Automatic recording logic

When it is running, per FCOM DSC-23-10-40:

The CVR is recording automatically: On ground during the first 5 min after the aircraft electrical network is energized; On ground with one engine running; In flight; On ground until 5 min after the last engine shutdown. On ground, when GND CTL pb-sw is pressed, the CVR is recording.

The RCDR GND CTL pushbutton also governs the DFDR and QAR (ATA-31); after engine start its ON light goes out and the recorders run automatically.

6. TEST and ERASE — two conditioned actions

Test, per FCOM DSC-23-10-40:

CVR TEST PB — When pressed: This activates the test, if the CVR is energized. If an acoustic equipment is plugged into the jack (HEADSET or BOOMSET), the flight crew will hear as low frequency signal. If the test is not successful, the ECAM triggers the RECORDER CVR FAULT alert 5 s after the pushbutton is pressed.

Erase — with strict conditions. Per FCOM DSC-23-10-40:

CVR ERASE PB — When pressed for 2 s, the CVR ERASE function erases the CVR full recording, if: The aircraft is on ground, and The parking brake is on.

The AMM adds the fuller condition: on the ground, parking brake on and locked, and electrically powered.

[!warning]- The CVR cannot be erased in flight — by design Worried about erasing the CVR by accident in flight? You cannot: erasure requires "on the ground + parking brake on (and locked) + powered" simultaneously — pressing ERASE in flight or while taxiing does nothing. This is a regulatory requirement (against inadvertent in-flight erasure or destroying evidence). Conversely, maintenance does erase test recordings on the ground per procedure — which is why it is designed to erase only when parked. A failed test raises RECORDER CVR FAULT (article 12).

7. Crashproof recorder and ULB

The recorder's physical design, per FCOM DSC-23-10-40:

A crashproof four-track recorder, equipped with an ULB, in the aft section of the aircraft.

It is in the aft section (aircraft rear sections typically take the least impact, giving the best survival odds). The ULB (Underwater Locator Beacon) activates on immersion and emits an ultrasonic pulse for underwater location — the "black-box signal" searched for after an over-water accident.

Self-test

[!note]- Q1. What five classes of sound does the CVR record, what does this configuration also record, and under what condition is PA recorded? Crew conversations, aural warnings, audio communications tx/rx, intercom, PA. This configuration also records datalink communications. PA is recorded only if at least one ACP has PA reception selected.

[!note]- Q2. What is hot mike, why does it record you without a PTT, and what does it mean for cockpit discipline? The CVR records the headset microphone directly, PTT or not. Everything said in the cockpit is captured whenever the CVR runs — hence discipline under a running CVR.

[!note]- Q3. How many tracks, how long retained, and how does this differ from the flight-data recorder? Four tracks, last 120 minutes (rolling overwrite); the flight-data recorder retains data far longer.

[!note]- Q4. What are the four automatic recording windows, and which button manually starts it on the ground? The first 5 min after the network is energised; on ground with one engine running; in flight; until 5 min after the last engine shutdown. Manual ground start: RCDR GND CTL pb.

[!note]- Q5. What does a failed CVR test raise on the ECAM, and what conditions must be met to erase the recording? Why can it not be erased in flight? RECORDER CVR FAULT. Erase requires on the ground + parking brake on (and locked) + powered. In-flight erasure is prevented by regulation.

Key takeaways

References

• FCOM DSC-23-10-40 — recorded content (incl. datalink), hot mike, 2 h retention, automatic logic, TEST → RECORDER CVR FAULT, ERASE conditions, ULB in the aft section.
• AMM 23-71-00 — four tracks simultaneous, rolling 120-minute overwrite, cockpit area microphone, erase conditions (parking brake on/locked, powered), datalink recording.

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.