ALIGN  ON DC 
FAULT  DC FAIL 

ALIGN Light
Illuminated (white) –
.  
steady – the related IRS is operating in the ALIGN mode, the initial ATT mode, or the shutdown cycle

.
flashing – alignment cannot be completed due to IRS detection of:

.  
significant difference between previous and entered positions or an unreasonable present position entry

.
no present position entry.

Extinguished –
.
IRS not in ALIGN mode

.  
with mode selector in NAV, alignment is complete, and all IRS
information is available

.  
with mode selector in ATT, attitude information is available. Heading
information is available following entry of initial magnetic heading.

Copyright . The Boeing Company. See title page for details.
11.10.16   March 28, 2005

Flight Management, Navigation -Controls and Indicators 737 Flight Crew Operations Manual

FAULT Light
Illuminated (amber) – a system fault affecting the related IRS ATT and/or NAV modes has been detected.

Inertial Reference System (IRS) Mode Selector
OFF –
.
alignment is lost

.  
all electrical power is removed from the system after a 30 second
shutdown cycle.

ALIGN –
.
rotating the selector from OFF to ALIGN initiates the alignment cycle

.  
rotating the selector from NAV to ALIGN automatically updates
alignment and zeroes ground speed error.

NAV (detented position) –
.  
system enters the NAV mode after completion of the alignment cycle and
entry of present position

.  
in NAV mode, all IRS information is available to airplane systems for
normal operations.

ATT – provides only attitude and heading information:
.  
attitude information is invalid (attitude flag in view) until ALIGN light is
extinguished

.  
heading information is invalid (heading flags in view) until the actual
magnetic heading is manually entered and the ALIGN light is
extinguished

.  
position and ground speed information is not available until the IRS is
aligned on the ground

.
the selector must be cycled to OFF before reselecting ALIGN or NAV.

ON DC Light
Illuminated (amber) –
.  
the related IRS is operating on DC power from the switched hot battery
bus (AC power not normal)

.  
if on the ground, the ground–call horn in the nose wheel well sounds,
providing an alert that a battery drain condition exists

.
momentary illumination is normal during alignment self–test.

Copyright . The Boeing Company. See title page for details.
Flight Management, Navigation -Controls and Indicators 737 Flight Crew Operations Manual

DC FAIL Light
Illuminated (amber) –
.
DC power for the related IRS is not normal

.  
if the other lights are extinguished, the IRS is operating normally on AC power.

IRS Transfer Switch

Inertial Reference System (IRS) Transfer Switch
BOTH ON L – switches the flight instruments attitude and heading source to left IRS.
NORMAL – flight instruments attitude and heading source is from default IRS.
BOTH ON R – switches the flight instruments attitude and heading source to right IRS.
Copyright . The Boeing Company. See title page for details.
11.10.18   March 28, 2005
Flight Management, Navigation -Controls and Indicators

Radio Navigation Systems Automatic Direction Finding (ADF) Control
YA613, YA626, YA801 - YA809, YD651 - YD655

Frequency Indicator
Shows the frequency selected with the related frequency selector. Shows if the system is in the ADF or antenna (ANT) mode.

Frequency Selector
Rotate – . outer knob sets the hundreds number
.
middle knob sets the tens number

.
inner knob sets the tenths and ones number.

Mode Selector Switch
ADF –
.
audio reception possible

.
ADF bearing sent to the DUs and the standby radio magnetic indicator. ANT –

.
audio reception optimized

.
no ADF bearing data available. OFF – removes power from selected receiver.

Copyright . The Boeing Company. See title page for details.
　
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