Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: B SHEET 106
The DSP performs a rho-theta conversion of the display matrix overlays using current aircraft position and aircraft heading
and synthesizes a radar-like sweep ahead of the aircraft. This sweep can feed two display outputs with independent range
scale settings.
6.9.4.1.1 Output Display Buses
The EGPWS provides two output buses that conform electrically to ARINC-453 and implement the ARINC-708 data formats
used by weather radar. The EGPWS output formats are configurable for the type of display and provide the capability to
drive two independent radar displays using either of two ARINC-708 display addressing standards:
• Time Shared: single multiplexed data stream for two independent displays.
• Space Addressed: two individual output data streams for two independent displays.
The “time shared” configuration is normally used by Multi-function Display (MFD) systems such as an EFIS providing a
single output display bus with data for two independent displays. The “space addressed” configuration provides two separate
and independent outputs for driving combinations of displays comprising weather radar indicators and/or MFDs. The second
display output bus may be wired as needed for the specific aircraft installation.
6.9.4.1.2 KC Picture Bus (KCPB)
The KC Picture Bus, KCPB, is the specification of a family of proprietary data formats intended for the transport of digital
image pixel data, such as terrain data. Digital image pixel data is in the form of rasterized or X/Y format. This format does
not require a rho-theta to X/Y conversion that can introduce conversion and overlap errors and allows use of the entire X/Y
screen of the display. Text data consist of data generated for range, mode, heading, Peaks altitude, test status, and alerts.
For a detailed description of the KCPB specification see EGPWS Interface Methodology, 060-4303-000. The KCPB
specification defines the header structure of the bus as well as what types of representation may be used for the pixel coding.
Minimum KCPB implementations must include raster image data and display support of query or continuous response. A
typical KCPB implementation will also include key press data. A full up KCPB implementation will support palette
definition and text data.
All KCPB compatible displays support either the query response (on-demand) or the continuous response. The query
response interactive protocol is used for displays that support a dedicated KCPB input bus. For all other displays, KCPB
compatibility is ensured by having the respective displays continuously output their configuration on ARINC 429.
The EGPWC will query the display for type information to setup the display interface. The KCPB compatible display will
either respond to this query, or provide a continuous response. At power up, the EGPWC will monitor the activity of the bus
on which the response comes in on and will use it to detect that the display system is powered and connected. Upon detection
of bus activity, the EGPWC will send a query via ARINC 453 asking the display to respond with configuration information,
and then it will listen for a response (query or continuous) via ARINC 429. For dual display configurations each side queries
independent of the other. If, after several attempts to receive the display configuration data, there is no response after a set
time, or the response is invalid or unintelligible, then the EGPWC will display a configuration failure on the respective
display and will advise the display that it’s not functioning properly.
6.9.4.2 Display Selection and Control Outputs
The display control logic block, shown in the previous Figure 6.7-1, provides signals to control the selection of EGPWD or
weather display for each display and also to control EGPWD range selections depending on cockpit switch selections, current
EGPWD threat conditions. The EGPWD may also be configured to automatically optimize the range scale of the EGPWD
display when a terrain alert is detected.
The display control logic makes use of configuration input data and provides several outputs that may be wired as required for
specific aircraft installations.
6.9.4.2.1 Wx/EGPWD Select and Pop-Up Discretes
Provision is made to support two means of selecting between weather and EGPWD displays:
1. Discrete Cockpit Selection Switch(s) for each display.
2. Selection made within the display controller(s).
Two ground seeking discrete outputs are provided for control of the selection between weather and EGPWD on each display.
These discretes perform different functions depending on the display configuration.