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ST3400 TAWS/RMI PILOT’S GUIDE
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The ST3400 TAWS/RMI uses Sandel’s patented rear-projection display
technology. This technology allows the displayed image to extend to the
edges of the instrument’s bezel. Therefore, even though the Sandel display
is in a 3-inch form factor, its image is approximately the size of a 4”
primary display.
Class A and Class B
Various ST3400 models may be installed as “Class A” systems or as
“Class B” systems.
A Class A system requires airdata and radar altitude as system inputs and
provides the full complement of GPWS, FLTA and PDA alerting (see
following sections for a description). At the time of publication, a Class A
installation requires an STC and Class A is required for certain larger
classes of aircraft.
Class B installations, required for some smaller aircraft, have the same
FLTA and PDA capability but are not required to have the full complement
of GPWS alerts. However, some ST3400 models support enhanced Class
A alerting features even when installed on a Class B basis. One advantage
of Class B installations is that they may be installed as follow-on
installations without an STC.
The ST3400 supports the use of GPS altitude without airdata using
approved receivers; these represent the easiest installations and contain all
of the system features except some GPWS alerting modes.
If both GPS altitude and airdata are available in the aircraft, then both can
be supplied to the ST3400 for redundancy. GPS altitude will be used as
the primary source of altitude for TAWS alerts. Airdata will be used as the
primary source of altitude for GPWS alerts.
See your Airplane Flight Manual Supplement for the details of the specific
installation in your aircraft. When installed as Class B, consult your flight
manual supplement to determine what particular alerting modes your
ST3400 does or does not support.
Class B Without Radar Altitude and/or Airdata
In this POH, there are references to radar altitude, barometric altitude and
other airdata. If your aircraft is not so equipped, the ST3400 will substitute
GPS altitude and Height Above Terrain Cell from its database when
possible to supply the maximum alerting capability. The general
descriptions of ST3400 functions will remain the same.
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ST3400 TAWS/RMI PILOT’S GUIDE
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Alerts and Advisories
The ST3400 annunciates alerts for the following table of conditions, and
provides alert messages to the airplane audio system. Optional external
annunciators are also supported for these conditions. There are six
traditional/standard GPWS modes. One mode is based on downward
deviation from the ILS glideslope. The other five are based on altitude
above the terrain directly beneath the aircraft. The altitude clearance is
measured by radar altitude and/or by barometric altitude compared with the
terrain height below the airplane.
There are two terrain modes that determine safe proximity to terrain based
on location to a suitable airport (PDA) and the distance to and closure to
the terrain based on the airplane flight path (FLTA). In common usage
these two
terrain
database modes are generically called “TAWS modes” in
distinction to the “GPWS modes” because they rely on the terrain database
whereas the classic GPWS modes do not.
GPWS ALERTS
ERD
Mode 1 (Excessive Rate of Descent)
Uses a combination of barometric altitude and radar altitude,
alerts excessive barometric rate of descent when close to the
ground. When radar altitude is not available, the calculated
height above terrain from the terrain database is substituted.
ECRT
Mode 2 (Excessive Closure Rate to Terrain)
Alerts on high rates of change of radar altitude when close to the
ground. (Radar Altitude equipped aircraft only)
ALAT
Mode 3 (Altitude Loss After Takeoff or Missed Approach)
Uses radar altitude and barometric altitude to detect accumulated
altitude loss after take off or a missed approach. The height
above takeoff altitude is used. The takeoff alert is disabled after
climbing 770’ above takeoff elevation; the go-around alert is
disabled when reaching 1000’ radar altitude (radar altitude
equipped aircraft only).
FITNL
Mode 4 (Flight Into Terrain Not in Landing Configuration)
Uses radar altitude to detect too low an altitude without gear
and/or flaps in landing configuration. (Radar Altitude equipped
aircraft only)
EDGSD Mode 5 (Excessive Downward Glideslope Deviation)
When in landing configuration, provides an alert in the event of
an excessive downward deviation from an ILS Glideslope when