AIRPLANE
OPERATIONS
MANUAL
NAVIGATION AND
COMMUNICATION
MARCH 30, 2001
2-18-22
Page
1
Code
03
THIRD VHF NAVIGATION SYSTEM
The airplane may be equipped with a third VHF Navigation System.
The third Navigation receiver is required to perform CAT-IIIa
operations. It feeds the HGS with high reliability ILS data, which are
compared with those received from Navigation receiver #1. In case of
a miscomparison between both signals, the HGS will not be able to
engage CAT-IIIa mode.
All functions of the Collins VIR-433 System are controlled by the
CTL-32 VHF Control Panel located at the pedestal.
The Avionics Master DC Bus 1 supplies the third VHF Navigation
System with a protective 5A circuit breaker.
THIRD VHF NAV CONTROLS AND INDICATORS
1 - ACTIVE FREQUENCY DISPLAY
− Displays the active frequency (frequency to which the equipment
is tuned) and diagnostics messages.
2 - XFR/MEM SWITCH
− This is a 3-position, spring-loaded toggle switch.
− When held to the XFR position, the preset frequency is
transferred up to the active display and the equipment retunes.
The previously active frequency becomes the new preset
frequency and is displayed in the lower window.
− When held to the MEM position, one of the four stacked
memory frequencies is loaded into the preset display.
− Successive pushes cycle the four memory frequencies through
the display.
3 - FREQUENCY SELECT KNOBS
− Two concentric knobs control the preset or active frequency
displays.
− The large knob changes the digits to the left of the decimal point
in 1 MHz steps.
− The smaller knob changes the digits to the right of the decimal
point in 0.05 MHz steps.
− Numbers roll over at the upper and lower frequency limits.
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