ALARMS
The purpose of the warning systems is to alert the crew to a possible failure or to the existence of a potentially dangerous situation.
Although the aircraft and the engine are very often equipped with safety devices, it is important, in the event of faulty operation, that the crew might be immediately informed of the situation so that measures might be taken to preserve the aircraft or the engine.
1. ANALOGUE DIAL INDICATORS:
Some traditional (electromechanical) indicators comprise warning systems:
Dial indicators often have colored sectors, specific to each parameter; this allows the pilot to determine at a glance if the engine functions in a normal and sure range, or in an abnormal and dangerous range.
A green colored sector corresponds to an area of normal engine operation.
A yellow colored sector corresponds to an area where a great prudence and an attentive monitoring are required.
A red colored sector corresponds to a danger zone requiring an immediate action by the pilot to leave this area of operation.
A radial red colored mark indicates a maximum acceptable value (maximum temperature, maximum rotational speed).
2. ELECTRONIC INDICATORS:
These video screens are of “cathode-ray tube” type or of “liquid crystal diodes” type.
They are often used aboard modern aircrafts, by display systems such as the ECAM (Electronic Centralized Aircraft Monitoring) or the EICAS (Engine Indicating and Crew Alerting System).
Warning messages can be displayed on these electronic screens in the margin or below the display of engine parameters.
Note:
Each time a “warning” message is displayed, a sound and visual alarm is set off simultaneously.
These messages have three colors depending on their level of importance:
in white for an “advisory” message: no immediate action by the crew is necessary.
in amber or yellow for a “caution” message: for an immediate awakening by the crew, followed by a later action.
in red for a “warning” message: for immediate measures to be taken by the crew.