Emergency Communication — Evacuation Signal and the ELT

Having covered the internal (interphone/PA) and external (VHF/HF/SATCOM) classes, this article takes the two most critical items of the FCOM's third class — emergency communication:

the evacuation signal (EVAC) — one key puts the whole aircraft into evacuation, cockpit and cabin shouting "evacuate" together;
the ELT (Emergency Locator Transmitter) — after a crash it automatically calls "I am here" to the search-and-rescue system.

One sentence separates them: EVAC shouts "get out" to the inside; the ELT shouts "come find me" to the outside. Both are simple but life-critical, and the crew must know their switch logic to muscle memory.

1. Architecture

Emergency evacuation (EVAC):
   cockpit EVAC panel                        cabin (via CIDS)
   ┌────────────────┐                ┌────────────────────────┐
   │ COMMAND pb(gd) │──trigger──────▶│ all attendant panels    │
   │ HORN SHUT OFF   │                │ EVACUATION ALERT + red  │
   │ CAPT/PURS+CAPT  │◀──cabin origin─│ flash + evacuation tone │
   │ EVAC red flash  │                │ (EVAC/RESET on FAP/AAP) │
   └────────────────┘                └────────────────────────┘

Emergency locator (ELT):
   overhead ELT switch (ARMED / ON / RESET-TEST) ──▶ ELT ──▶ antenna ──▶ SAR
   auto-triggered on impact · external horn if transmitting on ground · light flashes every 5 s

2. The evacuation signal (EVAC)

The evacuation signal lets the cockpit send "evacuate" through the whole aircraft with one key. Per FCOM DSC-23-40-10:

(1) COMMAND pb (guarded) — ON : In the cockpit : EVAC light flashes red. In the cabin : EVAC RESET light flash at all attendant panels; 'EVACUATION ALERT' appears on all attendant indication panels and a red light flashes; Specific evacuation tone sounds. Off : The alert is stopped.

Two companion controls. Per FCOM DSC-23-40-10:

(2) HORN SHUT OFF pb — This button silences the cockpit horn (generated when evacuation is activated from the cabin). (3) CAPT and PURS/CAPT sw — CAPT and PURS : The alert may either be activated from the cockpit or the cabin. CAPT : The alert may only be activated from the cockpit. If one of the cabin EVAC CMD keys is pressed, only the cockpit horn sounds for 3 s.

[!warning]- Why "cockpit only" evacuation authority exists The CAPT/PURS+CAPT switch is about command authority: in many cases the evacuation decision must be issued centrally by the captain (to avoid the cabin initiating a full evacuation on incomplete information). Selecting CAPT means only the cockpit can actually initiate an evacuation; if the cabin presses EVAC, the cockpit gets only a "horn for 3 s" prompt, and the captain decides whether to evacuate. Selecting CAPT+PURS authorises the cabin (purser) to initiate too (e.g. if the cockpit is incapacitated). It is CRM and evacuation-decision authority realised in hardware. The evacuation signal reaches the cabin over the CIDS (article 7).

3. The ELT

The ELT is the last lifeline after a crash — automatically beaconing the search-and-rescue system. The overhead switch has three positions. Per FCOM DSC-23-40-30:

ELT SWITCH — The ELT transmits an emergency signal. The ELT transmits an emergency signal, in the case of impact. If held for 2 s, the ELT stops transmitting. If held for 10 s, the ELT starts an automatic test.

ARMED (normal): on standby; an internal g-sensor triggers transmission on impact;
ON: manual, forced transmission (e.g. actively calling for help after a forced landing);
RESET/TEST: hold 2 s = stop/reset; hold 10 s = self-test.

The inadvertent-trigger handling to remember. Per FCOM DSC-23-40-30:

Note: If the ELT is unduly triggered while in ARMED mode (e.g due to a hard landing), hold the RESET/TEST position for 2 s to reset the ELT and stop the signal.

How you know it is transmitting. Per FCOM DSC-23-40-30:

ON/TEST light — The ELT is transmitting or is in automatic test. If the ELT is transmitting when the aircraft is on ground, the external horn sounds. When the ELT is transmitting, the light flashes every 5 s. After a RESET, the light flashes every second before stopping.

[!warning]- A hard landing can make the ELT "start calling for help by itself" A firm landing can trip the ARMED ELT's g-sensor into reading it as an "impact" and transmitting — the ground external horn sounds and the external-power-panel ELT light comes on. That is not a fault, it is the ELT doing its job; but it ties up the distress frequencies and alarms rescue. Standard handling: hold RESET/TEST for 2 s to reset. After landing, if the external horn sounds inexplicably with the ELT light on, think of this first (do not confuse it with the article-6 battery-warning horn, which is with main power lost; the ELT case has its own ELT light).

Self-test

[!note]- Q1. What happens in the cockpit and the cabin when EVAC COMMAND is pressed, and what does HORN SHUT OFF silence? Cockpit: EVAC light flashes red. Cabin: EVACUATION ALERT on all attendant panels + red flash + evacuation tone. HORN SHUT OFF silences the cockpit horn generated when evacuation is activated from the cabin.

[!note]- Q2. What does the CAPT / CAPT+PURS switch decide? With CAPT selected, what happens if the cabin presses EVAC, and why the limit? Who may initiate evacuation. With CAPT, only the cockpit can; a cabin EVAC gives only a 3 s cockpit horn prompt. It keeps evacuation authority with the captain (CRM).

[!note]- Q3. What are the ELT's three switch positions, and how do you transmit manually / stop / self-test? ARMED (auto on impact), ON (manual transmit), RESET/TEST (hold 2 s to stop, 10 s to self-test).

[!note]- Q4. What is the standard handling after a hard landing trips the ELT, and what two ground signs show it is transmitting? Hold RESET/TEST for 2 s to reset. On the ground the external horn sounds and the ON/TEST light flashes (every 5 s while transmitting).

Key takeaways

Point	Detail
EVAC vs ELT	EVAC shouts "get out" to the inside; the ELT shouts "come find me" to the outside
EVAC authority	CAPT = cockpit only (cabin EVAC gives a 3 s horn prompt); CAPT+PURS authorises the cabin
EVAC path	Reaches the cabin over the CIDS
ELT switch	ARMED (auto on impact) / ON (manual) / RESET-TEST (2 s stop, 10 s test)
Hard-landing trip	Reset by holding RESET/TEST 2 s; ground external horn + light flashing every 5 s

References

FCOM DSC-23-40-10 — EVAC COMMAND / HORN SHUT OFF / CAPT-PURS switch; cockpit and cabin response.
FCOM DSC-23-40-30 — ELT three-position switch, auto-on-impact, 2 s stop / 10 s test, hard-landing reset, ground external horn, light flashing every 5 s.

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.