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NORM ALTN NORM ALTN
TRIPLE IRS / TRIPLE FMS INSTALLATION
TRIPLE IRS INSTALLATION
DUAL IRS INSTALLATION
P604_17_003
PFD EICAS
NORM
L MFD
1 2
NORM
ADC
1 2
NORM
DCP
EICAS PFD
NORM
R MFD
ED
1
ED
NORM
EICAS
D EIC
2
AS PF
1 2
NORM
IRS
NAVIGATION SYSTEMS
17-8 For Training Purposes Only
Jan 04
P I LOT T R A I N I N G GU I D E
IRS Normal Alignment
Normal alignment is achieved for IRS alignments between ±73° of latitude. When the
mode selector switches are in OFF, power is removed from the IRUs. When NAV is
selected, power is applied to the IRUs, and the IRUs automatically progress through a
self-test mode, followed by an alignment period before navigation (NAV) mode
becomes available. The IRU will automatically sequence to NAV mode 7 minutes
after the MSU selector switch is turned to NAV if all of the following conditions are
met:
• aircraft is on the ground with no excessive motion detected
• the gyro temperature is above 0°C
• the latitude and position tests have passed
• valid IRS initialization data has been received
IRS Initialization
In order to initialize the IRS, the present latitude and longitude coordinates must be
entered from either FMS CDU via the POS INIT page. The IRUs remain in the
alignment mode with NAV selected on the MSU if the present position is not entered.
The initialization data can be changed during the alignment, but both latitude and
longitude coordinates must be entered.
During IRS initialization, the IRS ALIGNING DO NOT TAXI message appears on
the Primary Flight Displays (PFDs). When alignment is complete, the PFD message
goes out and position entry is no longer accepted. IRS alignment cannot be
accomplished in flight.
If possible, use of the GPS coordinates is recommended for
initialization since they provide the most accurate aircraft
position.
PFD IRS Aligning Annunciation
Figure 17-4
NOTE
P604_17_073
IRS ALIGNING
DO NOT TAXI
ATT
NAVIGATION SYSTEMS
For Training Purposes Only
May 03
17-9
P I LOT T R A I N I N G GU I D E
Low-Temperature Alignment
At an IRS internal temperature between -54°C and -40°C, the power supply will turn
on but normal alignment will not start until the IRS temperature is greater than -40°C.
The alignment mode is inhibited when the gyro temperature exceeds +80°C.
The following table shows the time to complete alignment when the gyro temperature
is below 0°C. IRU time to complete alignment is displayed on the FMS CDU POS
INIT page 3/3.
Alignment time is extended beyond 16 minutes if the gyro
temperature has not reached at least -40°C. The system will not
go into NAV mode until the gyro temperature reaches -15°C.
Extended 15-Minute Alignment
The extended 15-minute alignment procedure allows the system to align at latitudes up
to 80° north and south.
After NAV has been selected, wait 15 minutes before entering the present position.
Refer to the CL-604 Airplane Flight Manual - Supplement 7, FMS Navigation in Polar
Regions, for additional navigation procedures when operating in polar regions.
IRU INTERNAL TEMP
(°C)
TIME TO COMPLETE
ALIGNMENT (MIN.)
< -12.5 16 (see note)
-12.5 to -10.0 15
-10.0 to -7.5 14
-7.5 to -5.0 13
-5.0 to -2.5 12
-2.5 to 0 11
>0 7
Low-Temperature Alignment Times
Table 17-2
NOTE
NAVIGATION SYSTEMS
17-10 For Training Purposes Only
May 03
P I LOT T R A I N I N G GU I D E
IRS Rapid Realignment
When the IRS is operating in the NAV mode, it is possible to perform a rapid
realignment whenever the aircraft is on the ground. If the MSU selector switch is
rotated from NAV to OFF and back to NAV within 5 seconds, the system will
sequence into the rapid realignment mode. Velocity components are set to zero, a
30-second leveling mode corrects the pitch and roll angles, and no gyro compassing is
performed (the last heading from the NAV mode is used). The total rapid realignment
sequence takes approximately 32 seconds. Present position must be reentered.
If excessive motion is detected during rapid realignment, the
system restarts rapid realignment and resets the time remaining
to align to 30 seconds.
IRS Attitude (ATT) Mode
Attitude mode is normally used when an IRS malfunction occurs. It may also be used
if all power to the IRS (including battery backup power) is lost then restored during
flight. In attitude mode, the IRS provides only pitch, roll, and heading outputs.
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