Annunciator and Warning Systems

While cockpit layout obviously varies tremendously by aircraft, there’s been a trend toward standardization over the years. Each manufacturer has been working to standardize its own cockpit designs (and systems designs, for that matter), in order to reduce pilot training costs across various models.

Airbus Industries, for example, has worked to make all of its fly-by-wire models virtually identical, not only in cockpit layout but also in control response and feel. The twin-engine A-320 and fourengine A-340 are tremendously different in size and capacity but are designed to feel similar in the cockpit.

The same is true with the Boeing 757 and 767, vastly different aircraft that share a common type rating. (Boeing, for years, has had “logic” in the orientation of cockpit toggle switches in all its aircraft. Toggle any switch toward the windshield for “on,” away from the windshield for “off.”)

Annunciator or Advisory Panels

One cockpit system is already well standardized through most of the turbine fleet. Every aircraft, from King Airs through the “big guys,” is equipped with a centrally located pilot advisory panel (or annunciator panel), which depicts everything from system status to emergency warnings (Figure 6.7). Advisory panels are designed to alert pilots to system problems that require further investigation or action. They are normally divided and color coded into three levels of information.

Warning lights (red) alert pilots to emergency or “immediate action required” situations.

L.ENG FIRE

L. GEN

L. ICE VANE APU FIRE

L.DC BUS

R. ICE VANE CABIN DOOR

HYD PRESS

L. BLEED OVRHT CARGO DOOR

CABIN ALT

R. BLEED OVRHT WHL WELL FIRE

R.DC BUS

L. FUEL HEAT R.ENG FIRE

R. GEN

R. FUEL HEAT

Caution lights (yellow or amber) indicate problems that should be addressed as soon as time permits. An emergency could occur if these problems are left unaddressed for an extended period. Status lights (white, green, or blue) indicate status or operation of components that could affect the flight, if not properly selected for conditions.

Annunciators alert or inform pilots of conditions that are important to safety of the flight. This particular panel directs pilots to specific components or problems that require attention.

Fuel Panel

Electrical Overhead Panel Environmental

Hydraulic Pneumatic

Some annunciator panels simply refer pilot attention to caution lights or other indicators activated on specific panels where they may not be immediately seen.

FIGURE 6.7 | Annunciator or advisory panels.

Warning Lights

Warning lights are always red. These are triggered by emergencies that require immediate crew action in order to maintain safe flight. Fire emergencies are the single most important class of emergencies associated with warning lights. Warning indicators are always tied to a master warning light and sometimes also to a “fire bell” or horn. This master warning light is located at eye level directly in front of the pilots, and it illuminates or flashes so it can’t be missed. The idea is for pilots that see it to then check the annunciator panel to determine exactly what the problem is and to follow up with instrumentation, as necessary, to verify the problem. Normally, master warning lights may be pressed, after illumination, to dim or extinguish them after the problem has been addressed (see Figure 6.8).

Caution Lights

Caution lights are always yellow and generally refer attention to serious system malfunctions that require crew action as soon as time permits but do not require immediate emergency action. Caution lights on a turbine aircraft cover nonemergency system malfunctions such as generator and electrical bus failures, overheating of various components, and fuel system anomalies. The key point about caution lights is that, while they reflect a nonemergency situation when first activated, prompt crew action is normally required to prevent development of a more serious situation.

“Master caution lights” are also installed in some aircraft (see Figure 6.8). They illuminate whenever a caution annunciator is activated, thereby directing the pilots to look into the problem. Master caution lights may be extinguished by pressing them after the problem has been addressed.

annunciator panel(s) master warning light

master caution light

FIGURE 6.8 | Cockpit annunciator panel and lights.

Caution and status lights may be found many places in the cockpit. Caution lights normally trigger the master caution light and/or annunciator panel lights.