I
From the lateral gain programmer, the radio signal is filtered
and summed with the course error signal. The sum of course
error and radio deviation is then sent to a course cut limiter.
The course cut limiter functions primarily when approaching the
desired VOR radial at an intercept angle greater than 45
degrees and at high speed. Its function is to limit steering
commands to 45 degrees which forces a flightpath to get on the
selected radial sooner to prevent overshooting beam center.
Typically, the roll command will make an initial heading
change, then level out and fly toward the beam, then make a
second heading change to get lined up on the center of the
selected radial.
When the aircraft meets the VOR ON TRACK criteria, the (VOR
TRK . CE < 45”) switch opens.
This removes course error from
the roll command, leaving radio deviation, roll attitude and
lateral acceleration from the
IRS, to compensate for beam
standoff in the presence of a crosswind.
As the aircraft approaches the VOR
station, it will enter a
zone of unstable radio signal. This zone of confusion radiates
upward from the station in the shape of a truncated
cone. In
this area, the radio signal becomes highly erratic and it is
desirable to remove it from the roll command. The over station
sensor monitors for entry into the zone of confusion and opens
the 0SS switch, removing radio deviation from the roll command.
From the course cut limiter, the VOR SEL command is routed
to Figure 259, sheet 4, and is processed as discussed in
paragraph 3.B. (7)(g).
Should the pilot select FMS as his navigation source on the
DC-884 Display Controller, the system flys desired track from
present position to the next waypoint, with the following
differences:
. Instead of using course error and radio deviation from the
symbol generator, a composite lateral steering command is
utilized from the NZ-920 Navigation Computer.
. This lateral steering command is lateral gain programmed
in the NZ-920 and therefore is not gain programmed again in
the FZ-820.
. When FMS is selected as the navigation source on
the DC-884
to perform the VOR intercept,
the mode annunciation on the
PFD will be FMS.
22-14-00
Page 298.90
Apr 15/93
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