Annunciator panel

In the aircraft industry, annunciator panels are groupings of annunciator lights. They 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.

On this aircraft overhead panel [ [http://www.airliners.net/open.file/0150219/L/ Photos: British Aerospace BAe-146-200A Aircraft Pictures | Airliners.net ] ] , the pilot is pressing the test switch. You can also see how the lights are grouped together with their associated systems into various panels of lights.

The following colours are normally utilised with the following meanings [ [http://www.b737.org.uk/warningsystems.htm Warning Systems ] ] :
*Red - Warning, this systems condition is critical and requires immediate attention (such as an engine fire, hydraulic pump failure)
*Orange/Yellow - Caution, this system requires timely attention or may do so in the future (ice detected, fuel imbalance)
*Green - Advisory/Indication, a system is in use or ready for operation (such as landing gear down and locked, APU operating)
*White/blue - Advisory/Indication, a system is in use (seatbelt signs on, anti-ice system in-use, landing lights on)

On occasion, the annunciator panel will 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.

In this aircraft cockpit, [ [http://www.airliners.net/open.file/0574133/L/ Photos: British Aerospace BAe-146-300 Aircraft Pictures | Airliners.net ] ] the annunciator panel is clearly visible in the centre of the panel (just to the left and below the big red handle/lever), displaying a variety of warnings of differing severity. Directly below the windscreen area, on both the left and right side of the picture, is a large red light with a large yellow one below it. These are the master warning and master caution lights/switches.

References

The Visual Annunciator Systems are utilized to display plant or process status by lighting individual windows, identifying specific process function. The inputs are derived from dry or live contacts to indicate the process condition or status. Single point or multipoint alarm logic modules operate the window lights based on a preselected ISA 18.1 or custom sequence.