737 Flight Crew Operations Manual
Flight Instruments, Displays -
Head-Up Display System
Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
10.22.6 D6-27370-866-EGP
IMC Mode
The IMC mode is an alternate approach mode primarily intended for autopoilot
approaches. Like the PRI mode, the IMC mode guidance cue utilizes AFDS
derived guidance. The guidance cue is displayed when the Captain’s flight
director is active and both pitch and roll commands are valid.
Approach symbology format for the IMC mode is similar to the AIII approach
mode. Altitude and airspeed data is displayed as digital values and navigation raw
data is displayed in close proximity to the flight path vector.
VMC Mode
The VMC mode is intended for visual approach operations. No flight director or
HUD guidance is displayed. The flight path vector is used to control the approach
to the runway.
Approach symbology format for the VMC mode is similar to the AIII and IMC
modes. However, navigation data is not displayed.
The proper mechanical alignment of the combiner is critical during visual
operations. Combiner position is monitored by the combiner alignment detector,
to determine if the combiner is within allowable position tolerances while in the
IMC or VMC mode. If its position is out of tolerance, an ALIGN HUD message
is displayed on the combiner. Elimination of the message is accomplished by
gently pushing the combiner in the breakaway direction and releasing. This allows
the combiner to reposition itself. If the message cannot be removed, the IMC or
VMC mode should not be used.
TCAS Resolution Advisory
TCAS resolution advisories are displayed as preventive and corrective symbols,
and are similar to the pitch commands displayed on the attitude indicator.
Preventive advisories do not require any crew action, but indicate an unsafe zone,
displayed as a double lined bracket. On the unsafe side of the bracket, two angled
lines are extended from the corners. The position of the bracket is determined by
TCAS, and represents the vertical flight path position that is safe.
Corrective advisories require positive action by the crew and are indicated by a
double lined box. The position of the box is determined by the vertical speed
requirements from TCAS, and represents the vertical flight path position that is
safe.
For additional information on TCAS, refer to Chapter 15, Warning Systems.
September 26, 2013
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