NAVIGATION AND
COMMUNICATION
AIRPLANE
OPERATIONS
MANUAL
2-18-75
Page
8
Code
01
REVISION 39
AOM-145/1114
LOW-VISIBILITY TAKEOFF
The Primary mode includes special symbology used for a low-visibility
guided takeoff that provides guidance information that supplements
visual runway centerline tracking and enhances situational awareness.
The low-visibility takeoff display and Ground Roll Guidance Cue are
automatically provided to the pilot once the following conditions have
been established:
− Primary mode selected;
− IRS in NAV mode;
− All NAV receivers tuned to same ILS frequency;
− Runway length set between 6000 and 13500 ft;
− Selected heading bug set to runway heading;
− Selected course set to runway heading or approach course.
NOTE: Misleading/removal of the guidance is not annunciated. Safe
operation in this condition was demonstrated and is predicated
on the pilot’s ability to see external visual references.
AIII MODE
The HGS AIII mode is designed for precision, manual ILS approach
and landing operations to CAT IIIa minimums. Additionally, the AIII
mode can be used for CAT II approaches.
During a Category IIIa approach, the HGS monitors its capability to
provide accurate guidance and airplane deviation from the desired
approach path. If this monitor indicates that the system is incapable to
provide accurate guidance, it is removed from the display and a
capability loss indication is annunciated. If the monitor indicates that
the airplane is on an unacceptable approach path, the HGS displays a
clear indication that a go-around should be performed.
The AIII display is de-cluttered by removing the altitude and airspeed
tape displays and replacing with digital values in order to maximize
visibility. The HSI is also removed, with raw ILS data (localizer and
glideslope deviation) being displayed in proximity to the flight path
group around the center of the display. In the AIII mode, guidance
information is shown as a circular cue whose position is calculated by
the HGS.
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