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Part Three: Section 3
TAWS Alerts
Section 3: TAWS Alerts
Alerts are issued when flight conditions meet
parameters that are set within TAWS software
algorithms. TAWS alerts typically employ either a
CAUTION or a WARNING alert severity level, or
both. When an alert is issued, visual annunciations
are displayed. Aural alerts are simultaneously issued.
Annunciations appear in a dedicated field in the lower
left corner of the display.
TAWS Annunciation Field
TAWS Annunciation Field
Annunciations are color-coded according to the
TAWS Alert Summary table. Pop-up terrain alerts can
also appear during an alert, but only when the TAWS
Page is not displayed. There are two options when
an alert is displayed:
To acknowledge the pop-up alert and
return to the currently viewed page:
Press the CLR button.
To acknowledge the pop-up alert and
quickly access the TAWS Page:
Press the ENT button.
NOTE: To further capture the attention of the pilot,
TAWS issues aural (voice) messages that accompany
visual annunciations and pop-up alerts. Some aural
messages are configurable during installation of the
system. For a summary of aural messages, see the
TAWS Alert Summary table in Appendix A.
Forward Looking Terrain Avoidance
The Forward Looking Terrain Avoidance alert,
or FLTA, is used by TAWS and is composed of two
elements:
Reduced Required Terrain Clearance and Reduced
Required Obstacle Clearance
Reduced Required Terrain Clearance (RTC) Avoidance
—
Reduced Required Terrain Clearance (RTC)
and Reduced Required Obstacle Clearance (ROC)
alerts are issued when the aircraft flight path is
above terrain, yet is projected to come within the
minimum clearance values shown below. When
an RTC alert is issued, a potential impact point is
displayed on the TAWS Page.
CAUTION—Estimated potential impact in approximately 60
seconds after pop-up alert and annunciation. RTC/ITI caution
alerts are accompanied by the aural message “Caution Ter
-
rain; Caution Terrain” OR “Terrain Ahead; Terrain Ahead”.
Similarly, a “Caution Obstacle; Caution Obstacle” or “Obstacle
Ahead; Obstacle Ahead” alert is also provided.
Imminent Terrain Impact and Imminent Obstacle
Impact
Imminent Terrain Impact (ITI) and Imminent
Obstacle Impact (IOI) alerts are issued when the
aircraft is below the elevation of a terrain or obstacle
cell in the aircraft’s projected path. ITI and IOI alerts
are accompanied by a potential impact point displayed
on the TAWS Page. The alert is annunciated when
the projected vertical flight path is calculated to come
within minimum clearance altitudes shown below.