Garmin GNC 420AW Pilot's Manual

Also see for GDL 69: Pilot's guide addendum Pilot's guide addendum Activation Instructions Activation Instructions Pilot's guide addendum

Contents

Garmin GNC 420AW Pilot's Manual Manual pdf 54 page image

48Part Four: Section 2HTAWS OperationInhibit ModeHTAWS provides an “inhibit mode”. This mode isdesigned to deactivate aural and visual alerts when theyare deemed unnecessary by the aircrew. Pilots shoulduse discretion when inhibiting the HTAWS system andalways remember to enable the system when appropri-ate. VCO’s are not inhibited in Inhibit Mode. See section3 for more information on HTAWS alerts. When alertingis inhibited, all FLTA aural and visual alerting is sup-pressed. HTAWS should only be inhibited when in visualcontact with terrain and when the pilot can be assuredof maintaining clearance from terrain and obstacles.When conducting en route operations and operationsfrom published airports and heliports HTAWS should beoperated in Normal mode. HTAWS configured units willalways start up with HTAWS alerts uninhibited.Inhibiting HTAWSTo inhibit HTAWS alerts:1. Select the HTAWS Page and press MENU.“Inhibit HTAWS?” is selected by default.2. Press ENT. The HTAWS alerts are inhibited. Theannunciation is displayed in theterrain annunciator field whenever HTAWS isinhibited.NOTE: When the ground speed falls below 30 knotsHTAWS will automatically display the “TAWS INHB”annunciation. This indicates that HTAWS is no longerproviding CFIT protection.This automatic “TAWS INHB” cannot be removed bymenu option selection. In fact, the menu option canstill list the “Inhibit HTAWS” option when HTAWS isautomatically inhibited due to speed.If the pilot selects any mode on the Menu while theunit is Auto-Inhibited because it is less than 30 knotsthen the unit will enter that mode once ground speedexceeds 30 knots. Hence the presence of these selec-tions on the Menu.External HTAWS Inhibit ControlAn optional installation is allowed for providing anexternal HTAWS Inhibit switch. Pressing the externalHTAWS Inhibit switch toggles the HTAWS inhibit onand off in the same manner as using the Page Menuselection.Reduced Protection ModeThe Reduce Protection (RP) functionality allowsoperating 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 numberof alerts while continuing to provide protection fromterrain and obstacles. Reduced Protection should onlybe selected when operating in visual contact with theterrain as alerting times are significantly less than innormal mode. There is support for an external RPMode switch and an external Mute Caution switch.190-00356-30 Rev H