1. General
A. The warning system provides the flight crew with visual and aural warnings. Warnings are provided for abnormal airplane system conditions. They are also provided for airplane out of configuration conditions for various operating modes.
B. The warning system consists of a warning electronics unit, aural warning loudspeakers, aural cancel switch, and test switches. It also includes the master WARNING switch-lights, SPEEDBRAKES light, and discrete warning light.
C. Input signals are received from airplane sensors, other airplane systems, or generated by the pilots. Signals are processed within the warning electronics unit (WEU).
D. The visual displays are level A warning messages on the display unit and red WARNING lights. The aural signals are bell, siren, owl, and ground proximity warning system voice messages.
2. Component Details
A. Warning Electronics Unit (WEU)
(1) The warning electronics unit (WEU) P51 is located in the forward electrical/electronic equipment area.
(2) The WEU contains two power supply modules with fault indicators and reset switch, and plug-in modules which generate warning signals. The WEU provides output signals to the warning loudspeakers, master warning lights, and discrete warning lights. The unit weighs 33 lbs and is cooled by externally blown air.
(3) The modules located in the WEU and their functions are as follows:
A. Warning Electronics Unit (WEU)
(1) The warning electronics unit (WEU) P51 is located in the forward electrical/electronic equipment area.
(2) The WEU contains two power supply modules with fault indicators and reset switch, and plug-in modules which generate warning signals. The WEU provides output signals to the warning loudspeakers, master warning lights, and discrete warning lights. The unit weighs 33 lbs and is cooled by externally blown air.
(3) The modules located in the WEU and their functions are as follows:
(a) Power Supply Modules
1) The two redundant power supplies receive 115 volts ac power and develop the +5 volts and ±12 volts dc power required for all warning modules. There are two ball type fault indicators, one for each module. Each ball latches to black when the corresponding power supply is operating properly and latches to yellow when a fault occurs. The RESET switch is provided to set the fault balls back to the operational mode.
2) The two power supply fault indicators and a reset switch are located on the WEU BITE module inside P51.
(b) EMI Filter Module
1) There are two EMI filter modules in the WEU. Each filter module is paired with a power supply module. The EMI filter module connects to the power line and filters the AC line noise.
(c) Stall Warning Module
1) There are two stall warning modules. The left module provides the captain's warning signal and the right module, the first officer's warning signal. The modules are each microprocessor controlled.
(d) WEU BITE Module
1) The WEU BITE module provides fault indications for the two power supplies and the two stall warning computers.
(e) Altitude Alert Module
1) The altitude alert module is microprocessor controlled. It provides altitude acquisition advisory and deviation cautions.
(f) Takeoff Configuration Warning Module
1) The takeoff configuration warning module provides warning signals for improper airplane configuration during takeoff.
(g) Landing Configuration Warning Module
1) The landing configuration warning module is microprocessor controlled. It provides warning signals for improper airplane configuration during landing and speed brake caution signals.
(h) Master Warning Module
1) The master warning module is microprocessor controlled and provides the warning signals to turn on the master warning lights.
(i) Bell/Chime Aural Warning Module
1) The bell/chime aural warning module provides fire bell warning and crew call chime signals to the audio amplifiers in the siren/owl aural warning modules.
(j) Siren/Owl Aural Warning Module
1) The left and right siren/owl aural warning modules supply level A warning and level B caution signals.
2) The siren warning is activated by overspeed, cabin altitude exceedance, T/O configuration warnings, and Landing configuration warnings.
3) The siren warning is also activated by autopilot disconnect.
4) The owl warning is activated by level B EICAS messages and altitude alert.
5) The siren/owl modules also supply amplification of the bell/chime warnings and ground proximity voice.
6) The siren/owl modules also amplify voice messages received from the TCAS.
(k) Clacker/Wailer Aural Warning Module
1) The clacker/wailer aural warning modules provide autopilot warning signals to the siren/owl aural modules. The clacker is not used.
(l) EICAS Signal Consolidation Card (SCC)
(f) Takeoff Configuration Warning Module
1) The takeoff configuration warning module provides warning signals for improper airplane configuration during takeoff.
(g) Landing Configuration Warning Module
1) The landing configuration warning module is microprocessor controlled. It provides warning signals for improper airplane configuration during landing and speed brake caution signals.
(h) Master Warning Module
1) The master warning module is microprocessor controlled and provides the warning signals to turn on the master warning lights.
(i) Bell/Chime Aural Warning Module
1) The bell/chime aural warning module provides fire bell warning and crew call chime signals to the audio amplifiers in the siren/owl aural warning modules.
(j) Siren/Owl Aural Warning Module
1) The left and right siren/owl aural warning modules supply level A warning and level B caution signals.
2) The siren warning is activated by overspeed, cabin altitude exceedance, T/O configuration warnings, and Landing configuration warnings.
3) The siren warning is also activated by autopilot disconnect.
4) The owl warning is activated by level B EICAS messages and altitude alert.
5) The siren/owl modules also supply amplification of the bell/chime warnings and ground proximity voice.
6) The siren/owl modules also amplify voice messages received from the TCAS.
(k) Clacker/Wailer Aural Warning Module
1) The clacker/wailer aural warning modules provide autopilot warning signals to the siren/owl aural modules. The clacker is not used.
(l) EICAS Signal Consolidation Card (SCC)
1) The EICAS SCC converts analog signals to digital signals which are then sent to the EICAS function.
B. Configuration Warning Test Switch
(1) The configuration warning test switch is located on the miscellaneous test panel on the right side panel. It is a two-position, spring loaded switch. The T/O position is for testing the takeoff configuration warning circuits. The LDG position is for testing the landing configuration warning circuits.
C. Gnd Prox/Config Gear Ovrd Switch
(1) The Gnd Prox/Conf Gear Ovrd Switch is located on the first officer's instrument panel. It is an alternate action light switch. The switch cancels the landing configuration aural warning and displays the amber OVRD message when pressed.
D. Master Warning Lights
(1) The red master WARNING lights are located on both ends of the pilots' glareshield P7. The lights come on when the master warning module in the warning electronics unit generates a warning signal. Pressing the indicator light cap will turn off the light and silence the fire bell warnings, Landing configuration warning, or the cabin altitude warning.
E. Discrete Warning Light
(1) The red CONFIG discrete warning light is located on the center instrument panel. The light comes on when the configuration warning module in the warning electronics unit generates a warning signal. The light is powered by the master dim and test circuit.
F. Loudspeakers
(1) The configuration warning test switch is located on the miscellaneous test panel on the right side panel. It is a two-position, spring loaded switch. The T/O position is for testing the takeoff configuration warning circuits. The LDG position is for testing the landing configuration warning circuits.
C. Gnd Prox/Config Gear Ovrd Switch
(1) The Gnd Prox/Conf Gear Ovrd Switch is located on the first officer's instrument panel. It is an alternate action light switch. The switch cancels the landing configuration aural warning and displays the amber OVRD message when pressed.
D. Master Warning Lights
(1) The red master WARNING lights are located on both ends of the pilots' glareshield P7. The lights come on when the master warning module in the warning electronics unit generates a warning signal. Pressing the indicator light cap will turn off the light and silence the fire bell warnings, Landing configuration warning, or the cabin altitude warning.
E. Discrete Warning Light
(1) The red CONFIG discrete warning light is located on the center instrument panel. The light comes on when the configuration warning module in the warning electronics unit generates a warning signal. The light is powered by the master dim and test circuit.
F. Loudspeakers
(1) The warning loudspeakers are located above the captain's and first officer's seats. Each loudspeaker is a permanent magnet speaker driven by an internal single stage amplifier. The two speakers provide aural tones and messages when turned on by either the left or right siren/owl aural warning module.
G. Speed Brake Handle Position Switch
(1) The speed brake handle position switch is located on the control stand. The switch is a thru-contact microswitch with a roller control arm. If the switch is set at the down detent position, a ground is applied to the takeoff configuration warning module. A warning is given when the switch is not in the down detent.
(1) The speed brake handle position switch is located on the control stand. The switch is a thru-contact microswitch with a roller control arm. If the switch is set at the down detent position, a ground is applied to the takeoff configuration warning module. A warning is given when the switch is not in the down detent.
In the following video a power up test and an aural test using a loudspeaker from cockpit.
