Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: B SHEET 105
6.9.3.2 Windshear Discrete (Lamp) Outputs
The Mode 7 Windshear detection warning and caution functions activate separate lamp outputs. Priority logic, described in
section 6.5, prevents windshear caution during a windshear warning condition and provides an inhibit which turns off the
EGPWS alert and warning lamps.
6.9.3.3 Audio On Discrete
The Audio On output is activated whenever the EGPWS is talking. It will stay on until the voice is completed. This output
can be used to inhibit other audio systems during GPWS alerts and callouts. In addition it can be used to drive the audio key
line input provided on some aircraft audio systems.
6.9.3.4 Terrain / Obstacle Awareness Alert Discretes
Terrain Awareness provisions for 2 discrete alert outputs, one for terrain and obstacle cautions and one for terrain and
obstacle warnings. For the MKVI and MKVIII these outputs contribute to the GPWS warn lamp.
The TA & TCF inhibit discrete logic always disables the setting of this discrete due to Terrain Awareness.
6.9.3.4.1 Terrain / Obstacle Caution Discrete
Terrain/obstacle caution will activate a discrete output. The alert will activate the GPWS Warn Lamp if Lamp Format 1 is
selected or the GPWS Caution Lamp if Lamp Format 2 is selected. In addition, ARINC output discrete bits for each of
Terrain and Obstacle Cautions are included.
6.9.3.4.2 Terrain / Obstacle Warning Discrete
Terrain/Obstacle Warning will activate a discrete output. The alert will activate the GPWS Warn Lamp. In addition, ARINC
output discrete bits for each of Terrain and Obstacle Warnings are included.
6.9.3.5 Monitor Discretes (GPWS INOP, Terrain INOP & Terrain Not Available)
The EGPWC produces two discrete monitor outputs. These discretes reflect the following functions, GPWS INOP, and
Terrain INOP or Terrain Not Available. Both of these discretes activate with loss of EGPWC power. The status of the three
inputs to these discretes is also contained on an ARINC 429 output word.
6.9.3.6 Terrain Display Switching Discretes
The EGPWC produces two discrete outputs for controlling the terrain display. They can be used either to control picture bus
switching relay(s) or connected directly to the symbol generators. Refer to section 6.9.4.2.
6.9.3.7 Steep Approach Discrete
For those Discrete I/O IDs that include a momentary Steep Approach input discrete, an associated Steep Approach Activated
lamp output is also supplied. This discrete output is turned on whenever Steep Approach is activated, either via pilot
selection, or if Steep Approach is automatically activated via Envelope Modulation.
6.9.4 Display Output and Control
The Terrain Display (EGPWD) component of the EGPWS is divided into the functional blocks shown in Figure 6.7-1.
Terrain display data and range scale settings for up to two weather displays are delivered to the Display Signal Processor
(DSP) from the Terrain Threat Detection and Display Processing and Display Control Logic blocks. The DSP performs the
real-time rendering of the EGPWD synthetic radar sweep and provides outputs for both ARINC-708 display buses. The
Display Control Logic also provides discrete signals and an ARINC-429 status bus to the external display system to control
final selection and annunciation of the EGPWD or Weather image. As described in each related sub-section, these outputs
are wired as required for the specific aircraft installation.
6.9.4.1 Display Signal Processor
The Display Signal Processor (DSP) receives aircraft-local terrain data from the Terrain Threat Detection and Display
Processing block. These data are contained in a set of display matrix overlays that hold display attributes rather than altitude
for each matrix element. These attributes have been computed by the Terrain Threat Detection and Display Processing block
for the background and terrain threat areas and kept small to reduce memory requirements and transfer time to the DSP.
The attributes within the display matrix overlays identify caution and warning threat areas and background terrain. Threats
are highlighted by the DSP in unique, solid colors while background terrain is displayed using fractal-like dot patterns. These
dot patterns vary in density to convey approximate terrain altitude with respect to the aircraft. Areas with no terrain data
available are also displayed with a fractal-like dot pattern but with a unique color. (Refer to section 6.7.4).