Inhibit Mode; External Htaws Inhibit Control; Reduced Protection Mode - Garmin GNC 420AW Pilot's Manual

Part Four: Section 2
HTAWS Operation

Inhibit Mode

HTAWS provides an "inhibit mode". This mode is
designed to deactivate aural and visual alerts when they
are deemed unnecessary by the aircrew. Pilots should
use discretion when inhibiting the HTAWS system and
always remember to enable the system when appropri-
ate. VCO' s are not inhibited in Inhibit Mode. See section
3 for more information on HTAWS alerts. When alerting
is inhibited, all FLTA aural and visual alerting is sup-
pressed. HTAWS should only be inhibited when in visual
contact with terrain and when the pilot can be assured
of maintaining clearance from terrain and obstacles.
When conducting en route operations and operations
from published airports and heliports HTAWS should be
operated in Normal mode. HTAWS configured units will
always start up with HTAWS alerts uninhibited.
Inhibiting HTAWS
48
To inhibit HTAWS alerts:
1. Select the HTAWS Page and press MENU.
"Inhibit HTAWS?" is selected by default.
Press ENT. The HTAWS alerts are inhibited. The
2.
terrain annunciator field whenever HTAWS is
inhibited.
NOTE: When the ground speed falls below 30 knots
HTAWS will automatically display the "TAWS INHB"
annunciation. This indicates that HTAWS is no longer
providing CFIT protection.
This automatic "TAWS INHB" cannot be removed by
menu option selection. In fact, the menu option can
still list the "Inhibit HTAWS" option when HTAWS is
automatically inhibited due to speed.
If the pilot selects any mode on the Menu while the
unit is Auto-Inhibited because it is less than 30 knots
then the unit will enter that mode once ground speed
exceeds 30 knots. Hence the presence of these selec-
tions on the Menu.

External HTAWS Inhibit Control

An optional installation is allowed for providing an
external HTAWS Inhibit switch. Pressing the external
HTAWS Inhibit switch toggles the HTAWS inhibit on
and off in the same manner as using the Page Menu
selection.

Reduced Protection Mode

The Reduce Protection (RP) functionality allows
operating with a reduction in the alerting thresholds,
and suppresses visual and aural annunciation of cau-
tion alerts. Reduced protection allows low level opera-
tions and landings off airport with a minimum number
of alerts while continuing to provide protection from
terrain and obstacles. Reduced Protection should only
be selected when operating in visual contact with the
terrain as alerting times are significantly less than in
normal mode. There is support for an external RP
Mode switch and an external Mute Caution switch.
190-00356-30 Rev H
annunciation is displayed in the