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:

. airplane movement (on some airplanes)
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11.10.10   June 6, 2003

Flight Management, Navigation -Controls and Indicators 737 Operations Manual
.  
significant difference between previous and entered positions
(unreasonable present position) or

.
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.

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 – 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.

Flight Management, Navigation -Controls and Indicators 737 Operations Manual

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.

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.
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11.10.12   December 1, 2000

Flight Management, Navigation -Controls and Indicators
Instrument Transfer Switch Light

Instrument Transfer Switch Light (INSTR SWITCH)
Illuminated (amber) – one or both of the instrument transfer switches (EFI or IRS) has been moved from the normal position.
Flight Management, Navigation -Controls and Indicators 737 Operations Manual

Intentionally
Blank

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11.10.14  December 1, 2000

Flight Management, Navigation -Controls and Indicators
Radio Navigation Systems Automatic Direction Finding (ADF) Control

FREQUENCY Indicator
Indicates the frequency selected with the related frequency selector.

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
OFF – removes power from selected receiver.
ANT – receiver sends only station audio.
ADF – receiver sends bearing and station audio.
GAIN – adjusts receiver gain.
　
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