82046-PG-B1
ST3400H PILOT’S GUIDE
Page 4-1
4 SYSTEM
OVERVIEW
4.1
“Design Cruise Altitude”
The ST3400H introduces the concept of “Design Cruise Altitude”. This is
the nominal cruise altitude at which the ST3400H is designed to give
nuisance-free alerts with a black (no terrain showing) relative altitude
display.
4.1.1 Sensitivity
To facilitate low altitude operations unique to helicopters, the ST3400H
supports two pilot selectable alert sensitivity modes: Normal Sensitivity
and Low Sensitivity.
In NORM Sensitivity the Design Cruise Altitude is 500’ AGL. In LOW
Sensitivity, the Design Cruise Altitude is 300’ AGL - allowing standard
operations closer to the ground.
In addition to changing the alerting criteria, the selected Sensitivity adjusts
the relative altitude display colors to provide a black display screen at the
design cruise altitude to prevent color flooding.
4.2 Off
Airport
Landings
In addition, an Off Airport Mode is pilot selectable which operates at either
Sensitivity.
Alerts are normally automatically suppressed during the landing phase at
an airport or helipad. OFF-APT mode further suppresses alerts for landing
at random non-airport locations, such as for EMS operations. When this
mode has been selected, no further pilot action is required and no nuisance
alerts will be generated when landing anywhere. Normal alerting criteria
are automatically established when not landing or in cruise flight.
4.3
Alerts, Warnings and Cautions
An Alert is defined as either a Caution or Warning, generated by the
GPWS computer or the FLTA computer. A Caution is defined as an alert
which indicates that pilot action will be needed
shortly
; a Warning alert
indicates that pilot action is required
immediately
.
If any alert occurs, the alert text is shown at the bottom of the screen and
an audible alert message will occur on the cockpit audio system. The REL
