Overview
The primary caution and warning system is designed to warn the
crew of conditions that may adversely affect orbiter operations.
The system consists of hardware and electronics that provide the
crew with both visual and aural cues when a system exceeds predefined
operating limits. The primary system's visual cues consist of
four master alarm lights, a 40-light array on panel F7 and a 120-light
array on panel R13. The aural cue is sent to the communications
system for distribution to flight crew headsets or speaker boxes.
The C/W system interfaces with the auxiliary power units, data
processing system, environmental control and life support system,
electrical power system, flight control system, guidance and navigation,
hydraulics, main propulsion system, reaction control system, orbital
maneuvering system and payloads. The audio alarms are classified
as emergency (class 1), C/W (class 2) and alert (class 3).
The emergency alarms consist of a siren (activated by the smoke
detection system) and a klaxon (activated by the delta pressure/delta
time sensor that recognizes a rapid loss of cabin pressure), and
they are annunciated by hardware. The siren's frequency varies
from 666 to 1,470 hertz and returns at a five-second-per-cycle
rate. The klaxon is a 2,500-hertz signal with an on/off cycle
of 2.1 milliseconds on and 1.6 milliseconds off, mixed with a
270-hertz signal with a cycle of 215 milliseconds on and 70 milliseconds
off.
The class 2 alarm is activated by the primary (hardware) system,
the backup (software) system or both. The C/W tone is an alternating
375 hertz and 1,000 hertz at 2.5 hertz. The alternating C/W alarm
tone is generated when the hardware system detects an out-of-limit
condition on any of the 120 parameters it monitors or when the
software (backup) system detects a parameter that is out of limits.
Both guidance, navigation and control and systems management
software sense out-of-limit conditions. These software systems
also serve some less critical parameters and annunciate the systems
management alert tone. The SM alert tone is a steady tone of 512
hertz of predefined duration generated in the C/W electronics
when activated by inputs from the onboard computers.
Visual cues for the flight crew consist of four red master alarm
push button light indicators on panels F2, F4, A7 and M052J; the
40-light (red or yellow) C/W light array on panel F7; the 120
parameter status lights on panel R13; the blue SM alert light
on panel F7; the red backup C/W light on panel F7; fault messages
on cathode ray tubes; and status characters on CRTs.
Inputs enter the C/W logic circuitry from the onboard computers
through multiplexers/demultiplexers to activate alarm tones and
the backup C/W alarm. Some of these are used to turn the backup
C/W light on panel F7 on and off. One additional signal resets
the master alarm lights and tones.
The primary C/W system has three modes of operation: ascent,
normal and acknowledge. These modes are controlled by the caution/warning
asc , norm, ack switch on panel C3. The normal mode is discussed
first.
One hundred twenty inputs are received by the primary C/W system
directly from transducers through signal conditioners or from
the flight forward MDMs and are fed into a multiplexing system.
Of these 120 inputs, 95 come directly from transducers, five are
from input/output processors, 18 are provided through MDM software
and two are spares. These inputs can be either analog or bilevel.
The analog signals are zero to 5 volts dc; the discretes are either
zero, 5, or 28 volts dc. All of these inputs are designed to provide
upper or lower limit detection. If the parameter has exceeded
its limits, it will turn on the C/W tone, light the appropriate
C/W light on panel F7, illuminate the four red master alarm push
button light indicators and store the parameter in memory. The
C/W tone can be silenced and the master alarm red light extinguished
by depressing any one of the master alarm push button light indicators;
however, the C/W light on panel F7 will remain illuminated until
the out-of-tolerance condition is corrected. Any one of the master
alarm push button light indicators will reset all tones, including
the systems management tone.
The C/W ascent mode is the same as the normal mode, except that
the commander's red master alarm push button light indicator will
not be illuminated.
The C/W acknowledge mode is also the same as the normal mode,
except that the 40 annunciator lights on panel F7 will not be
illuminated unless one of the red master alarm push button light
indicators on panel F2 for the commander or panel F4 for the pilot
is depressed.
Each of the 120 status C/W red parameter lights on panel R13
receives an input from a specific parameter. A primary C/W parameter
matrix cue card identifies the 120 input channels and correlates
them to the panel F7 C/W annunciator light matrix. If an out-of-limit
condition exists on a specific parameter that is set on panel
R13, it illuminates the corresponding light on panel F7. If the
caution/warning param status switch on panel R13 is held in the
tripped position when an out-of-limit parameter light on panel
F7 is illuminated, the corresponding light on panel R13 will also
be illuminated.
The three caution/warning parameter select thumbwheels on panel
R13 provide signals to the C/W electronics unit and define the
specific parameter for enabling and inhibiting the parameter and
setting and reading the parameter's limits.
The caution/warning limit set switch grouping on panel R13 is
used to change limits or to read a parameter's limits. The three
value thumbwheels provide the signals to the C/W unit, defining
the voltage value setting of a parameter's upper or lower limit,
X.XX.
The caution/warning limit set limit upper switch on panel R13
provides a signal to the C/W electronics unit, which modes the
electronics to set or read the upper limit of a parameter specified
by the settings on the value thumbwheels for that parameter; and
the caution/warning limit func switch is cycled to set or read
the upper limit of that parameter. The caution/warning limit lower
switch on panel R13 functions in the same manner as the limit
upper switch, except for the lower limit for a parameter.
The caution/warning limit set func set switch position on panel
R13 provides a signal to the C/W electronics unit, which sets
the value specified by the limit set value thumbwheels into the
parameter as specified by the parameter select thumbwheels and
limit set limit switch. The limit set func read switch position
on panel R13 provides a signal to the C/W electronics unit, which
illuminates the lights under the status limit volts X.XX columns
on panel R13, that correspond to the voltage parameter limit specified
by the parameter select thumbwheels and the limit set limit switch.
The value read corresponds to the parameter's full-scale range
on a scale of zero to 5 volts dc. The limit sec func switch center
position disables the set and read functions.
The caution/warning param enable switch position on panel R13
provides a signal to the C/W electronics unit to enable the parameter
indicated on the parameter select thumbwheels, which allows the
parameter to trigger the primary C/W alarm when out of limits.
The inhibited position operates the same as enable , except it
inhibits the parameter from triggering the primary C/W alarm.
The center position of the switch disables the enable and inhibit
functions.
The caution/warning param status tripped switch position on panel
R13 provides a signal to the C/W electronics unit, which illuminates
the C/W status lights on panel R13 that correspond to the parameters
that are presently out of limits, including those that are inhibited.
The inhibited position illuminates those C/W lights on panel R13
that have been inhibited. The center position disables the tripped
and inhibited functions.
The caution/warning memory read switch position on panel R13
provides a signal to the C/W electronics unit, which illuminates
the C/W status lights on panel R13 that correspond to the parameters
that have been out of limits since the last positioning of this
switch or the caution/warning memory switch on panel C3 to clear
. The clear position on panel R13 or panel C3 provides a signal
to the C/W electronics unit that clears from the memory any parameters
that are presently within limits, but any parameters that are
out of limits during this action remain in memory. The center
position of the switch on panel R13 or panel C3 disables the clear
and read functions.
The caution/warning tone volume A switch on panel R13, when adjusted
clockwise, increases the system A siren, klaxon, C/W, and SM tone
generator output signals to the audio central control unit. The
B switch functions the same as the A switch for system B tone
generators.
The caution/warning lamp test switch on panel R13, when positioned
to left, provides a signal to the C/W electronics unit, which
illuminates the left five columns of the C/W status matrix lights
on panel R13. The right position functions the same as the left
, except for the right five columns of lights.
The backup C/W system is part of the systems management fault
detection and annunciation, GN&C and backup flight system
software programs. All backup C/W alarms are class 2. Only the
69 backup C/W alarms that are produced by FDA have limits that
can be changed and displayed in engineering units accessed through
the SM table maintenance specialist function display (SPEC 60).
The remaining backup C/W alarms that are produced by the guidance
and navigation program are accessed through general-purpose computer
read/write procedures. A backup C/W out-of-tolerance condition
will trigger a master alarm light, illuminate the red backup C/W
alarm light on panel F7, and display a message on the fault message
line and fault summary page on the SM CRT.
The SM alert program is another portion of the SM program and
operates like the backup C/W system. It is designed to inform
the flight crew of a situation leading up to a C/W or one that
may require additional procedures. When an SM alert parameter
exceeds its limits, the blue SM alert light on panel F7 is illuminated,
a discrete is sent to the primary C/W system to turn on the SM
tone, and the software displays a fault message on the fault message
line and fault summary page on the SM CRT.
Annunciator lights provide visual indications of the status of
the vehicle and payload systems. The annunciator lights are classified
as emergency, warning, caution and advisory. Emergency and warning
annunciators are red; cautions are yellow; and advisory may be
white (status), green (normal configuration), yellow (alternate
configuration) or blue (special applications).
Annunciator lighting is provided by incandescent lamps that illuminate
the lens area of the annunciators. Most annunciators are driven
by an annunciator control assembly that controls the illumination
of the lights during a normal or test input and the brightness
level. The C/W status lights and GPC status lights have separate
electronic units for lighting control.
There are three different lens configurations for push button
indicator and indicator lights. One configuration has illuminated
nomenclature in the appropriate color on an opaque black background,
and the nomenclature cannot be seen until it is illuminated. Another
configuration has non-illuminated white nomenclature on an opaque
black background and a bar that illuminates in the appropriate
color; this nomenclature is always visible. The third configuration
has a bar that is illuminated on an opaque black background and
no nomenclature on the lens, but the nomenclature is available
as part of the panel.
The forward flight deck annunciator bus select ACA 1 and ACA
2/3 switches on panel O6 provide electrical power to enable the
corresponding ACAs. ACA 1 is enabled by positioning bus select
ACA 1 to either the MN A or MN B position, and thus the annunciator
lights associated with ACA 1. Bus select ACA 1 also provides electrical
power to the annunciator light intensity bright , var switch on
panel O6 and the low, med rotary switch on panel O6, controlling
the intensity of the annunciator light associated with ACA 1.
ACAs 2 and 3 are enabled by positioning the bus select ACA 2/3
switch to either the MN B or MN C position, and thus the annunciator
lights associated with ACAs 2 and 3. Bus select ACA 2/3 also provides
electrical power to the annunciator light intensity bright , var
switch on panel O6 and the low, med rotary control on panel O6,
thus controlling the intensity of the annunciator light associated
with ACAs 2 and 3. The off position of the bus select ACA 1 switch
removes power from ACA 1, disabling the annunciator lights associated
with it. The off position of the bus select ACA 2/3 switch removes
power from ACAs 2 and 3, disabling the annunciator lights associated
with them.
The annunciator intensity switch on panel O6 positioned to bright
bypasses the intensity low , med rotary control on panel O6. The
annunciator intensity switch positioned to var permits the intensity
low, med rotary control to control annunciator light intensity.
The annunciator lamp test switches on panel O6 or panel O8 positioned
to left apply power to the ACA 1, 2 and 3 annunciator lamp test
circuits, illuminating annunciator lights on panels F2, F6, L1,
O1 and M029J; the 20 C/W lights on panel F7; and the SM alert
on panel F7. Positioning the lamp test switches to right applies
power to the ACA 1, 2 and 3 annunciator lamp test circuits, illuminating
the annunciator lights on panels C3, F4, F8 and M052J; the 20
C/W lights on panel F7; and the main engine lights.
The aft flight deck annunciator bus select switch on panel A6
provides electrical power to enable ACAs 4 and 5. ACAs 4 and 5
are enabled by positioning bus select to either the MN B or MN
C position, and thus the annunciator lights associated with ACAs
4 and 5. The bus select switch also provides electrical power
to the annunciator light intensity bright, var switch on panel
A6 and the low , med rotary control on panel A6, thus controlling
annunciator light intensity associated with ACAs 4 and 5. The
off position of the bus select switch removes power from ACAs
4 and 5, disabling the annunciator lights associated with them.
The annunciator intensity switch on panel A6, when positioned
to bright, bypasses the intensity low, med rotary control on panel
A6. Positioned to var, it permits the intensity low , med rotary
control to vary annunciator light intensity.
The annunciator lamp test switch on panel A6, when positioned
to left, applies power to the ACA 4 and 5 annunciator lamp test
circuits, illuminating the annunciator lights on panels A2 and
A6 and columns 0 through 4 on panel R13. Positioning the switch
to right applies power to the ACA 4 and 5 annunciator lamp test
circuits, illuminating the annunciator lights on panel A7 and
columns 5 through 9 on panel R13.