Annunciator

An annunciator panel, also known in some aircraft as the Centralized Warning Panel (CWP), is a group of lights used as a central indicator of status of equipment or systems in an aircraft, industrial process, building or other installation. Usually, the annunciator panel includes a main warning lamp or audible signal to draw the attention of operating personnel to the annunciator panel for abnormal events or conditions.

In the aircraft industry, annunciator panels are groupings of annunciator lights that indicate status of the aircraft's subsystems. The lights are usually accompanied with a test switch, which when pressed illuminates all the lights to confirm they are in working order. More advanced modern aircraft replaces these with the integrated electronic Engine Indicating and Crew Alerting System or Electronic Centralised Aircraft Monitor.

An aviation annunciator panel will have a test switch to check for burned out lamps. Indicator lights are grouped together by their associated systems into various panels of lights.

Lamp colours are normally given the following meanings:

The annunciator panel may display warnings or cautions that are not necessarily indicative of a problem; for example, a Cessna 172 on its after-landing roll will often flicker the "Volts" warning simply due to the idle throttle position and therefore the lower voltage output of the alternator to the aircraft's electrical system.

More complicated aircraft will feature "Master Warning" and "Master Caution" lights/switches. In the event of any red or yellow annunciator being activated, the yellow or red master light, usually located elsewhere in the pilots line of sight will illuminate, in most installations they flash and an audible alert will accompany them. These "masters" will not stop flashing until they have been acknowledged, usually by pressing the light itself and in some cases the audible alert will also continue until this acknowledgement. On some aircraft (most Boeing airliners, for example) the 'masters' will also flash briefly and the audible alert will sound whenever the autopilot is disconnected as an additional reminder to the pilots that manual control is now required.

In industrial process control, an annunciator panel is a system to alert operators of alarm conditions in the plant. Multiple back-lit windows are provided, each engraved with the name of a process alarm. Lamps in each window are controlled by hard-wired switches in the plant, arranged to operate when a process condition enters an abnormal state (such as high temperature, low pressure, loss of cooling water flow, or many others). Single point or multipoint alarm logic modules operate the window lights based on a preselected ISA 18.1 or custom sequence.

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