Overview
The Enhanced Ground Proximity Warning System (EGPWS) provides alerting in seven modes to prevent accidents caused by controlled flight into terrain (CFIT) or severe wind shear.
EGPWS provides seven alerting modes, terrain/obstacle awareness alerting and display (TAAD), and terrain clearance floor (TCF).
The system achieves this aim by accepting a variety of aircraft parameters as inputs, applying alerting algorithms, and providing the flight crew with aural and visual alerts in the event that any of the boundaries of the alerting envelopes are exceeded. EGPWS also supplies a visual display of terrain on the MFDs for terrain awareness alerting.
The system is designed to be fully compatible with normal operation of other systems on the aircraft. False alerts will be rare if the flight crew maintains situational awareness with respect to the terrain, and if the crew follows correct avoidance procedures for any significant wind shear activity.
05/05/16
EGPWS Computer
The EGPWS computer is the primary component of the system. The computer receives power from DC BUS 1 through SPDA 3. The computer receives ARINC and discrete format input-data from the systems that follow:
- Stall Protection System
- Inertial Reference System (IRS)
- Radio Altimeter System
- Air-Data Computer System
- Integrated Avionics Computer System (IAC)
- Global Positioning System (GPS)
- Landing-Gear Control
- Flap System
- Data Acquisition Unit
- Central Aircraft-Information and Maintenance-System (CAIMS)
The EGPWS computer supplies ARINC and discrete format data to the components/systems that follow:
- Multifunction Display (MFD) 1 and MFD 2
- Audio Integrating System
- Data Acquisition Unit (DAU) 3
The EGPWC is installed on the left side of the under floor main avionics bay in the Global Express/XRS and in the above floor avionics rack in the Global 5000.
The computer has a port in the front for connecting a personal computer modular interface adapter (PCMIA) card, a RS 232 port to interface with a portable computer, a test switch to start a self-test and LEDs to indicate system status.
The computer is a solid-state processor. It supplies the visual and aural warnings related to a dangerous flight path, aircraft configuration, or wind shear condition. The computer has continuous self-test functions and automatically sends system failure data to the EICAS display.
The EGPWS computer operates in three basic functions that follows:
- Basic ground proximity
- Terrain warning
- Wind shear
The functions operate independently from each other. The failure of one function does not have an effect on the other two. If the failure is caused by an input that is required by all three functions, then all three functions fail.
For aircraft that have the SBAS GNSSU(s) installed the EGPWS is configuration strapped to enable the reception of high speed (100kHz) ARINC 429 data from the SBAS GNSSU. (The original GPS unit uses a low speed bus (12.5 kHz).).
05/04/16
EGPWS Control Panel
On A/C 9001, 9002, 9004 to 9074 for Global Express:
The EGPWS control panel is installed in the overhead panel in the flight compartment.
On Global 5000/XRS and on A/C 9003, 9075 and Subs for Global Express:
The EGPWS control panel is installed in the center pedestal above and to the right of the throttles quadrant.
The three switch/lights on the panel are identified as G/S WARN, FLAP OVRD and TERRAIN. When the G/S WARN switch/light is pushed, the GLIDESLOPE aural warning stops and the MUTE light comes on. The MUTE light shows that the aural warning was cancelled, although the warning is still present. The MUTE light stays on until:
- The aircraft configuration changes (gear or flaps up)
- The aircraft is on the ground
- The flight crew pushes and holds the switch five seconds or more after the switch was first pushed
When the FLAP OVRD switch/light is pushed, the TOO LOW, FLAPS, and TERRAIN aural warnings stop, and the OVRD light comes on. The TOO LOW, FLAPS aural warning comes on when the aircraft is landing and the flaps are not in normal landing configuration. The TERRAIN warning comes on if the aircraft is operated near the terrain during daylight VFR conditions. The OVRD light stays on until the flight crew manually reset the FLAP OVRD switch.
When an aircraft lands at an airport that is not in the terrain database, the EGPWS can give nuisance warning. The TERRAIN OFF switch will stop the nuisance warnings. When the TERRAIN switch/light is pushed, the MFDs show a TERR OFF annunciation and an EGPWS TERR OFF status message shows on the EICAS display, and the TERRAIN OFF PBA light stays on until the flight crew pushes the TERRAIN switch/light. When the EGPWS is operating normally, a TERR annunciation shows on the MFD.
Global 5000/XRS
09/29/20
System Operation
The EGPWS receives input parameters from the air data systems, radio altimeters, GPS, IRS, SPS (flap angle, AOA), FWC (GS, LOC, DN), nose gear downlock (state of the landing gear) and the EGPWS panel (for mute and inhibit function).
The EGPWS provides predictive terrain warnings based on the aircraft position supplied by the GPS and the EGPWC projection of the aircraftflight path based on current aircraft position.
The EGPWS contains terrain, airports and obstacle databases. The EGPWS provides aural audio to the audio panels, visual annunciations to the PFDs and EICAS via the DAU. The EGPWS computer outputs a display of terrain data in ARINC 453 data format.
EGPWS Warning Modes
The EGPWS functions monitor and supply warnings related to the following flight parameters/conditions:
| MODE | NAME | VOICE OUTPUTS |
|---|---|---|
| 1 | Excessive Descent Rate | "SINKRATE" PULL UP |
| 2 | Excessive Terrain Closure Rate | "TERRAIN TERRAIN" "PULL UP" |
| 3 | Sink After Takeoff | "DON’T SINK!" |
| 4 | Too close To Terrain | "TOO LOW- TERRAIN " "TOO LOW-GEAR" "TOO LOW - FLAPS" |
| 5 | Excessive Deviation Below Glideslope | "SINKRATE" "GLIDESLOPE" |
| 6 | Excessive bank Angle Altitude Callouts Decision Height |
"BANK ANGLE " "(selected) " "MINIMUMS " |
| 7 | Wind shear | "WINDSHEAR, WINDSHEAR WINDSHEAR " PULL UP |
Mode 1 Excessive Descent Rate
This mode operates independently of the aircraft configuration. It provides alerts when the aircraft has excessive descent rate close to the terrain. If the aircraft penetrates an "outer" alert boundary, the computer generates an aural message "SINKRATE" and sends alert discretes to drive the PFD "GND PROX" annunciations. Mode 1 is set when the altitude of the aircraft is less than 2,500 ft Above Ground Level (AGL). If the aircraft penetrates the envelope further, the aural message "WHOOP PULL UP" and visual alert discretes are also generated. The alert boundaries are defined in terms of aircraft vertical speed (Barometric Vertical Speed supplemented by Inertial Vertical Speed) and Radio Altitude.
Optional variations to the Mode 1 alert boundaries are available by strapping. These options include Envelope Modulation, Glideslope Deviation Bias, and Steep Approach Bias to decrease unwanted alerts in special situations.
Mode 2 Excessive Closure to Terrain
Mode 2 is a function of aircraft altitude, phase of flight, and speed. It provides alerts to help protect the aircraft from impacting the ground when rapidly rising terrain with respect to the aircraft is detected. Mode 2 is based on Radio Altitude and on how rapidly Radio Altitude is decreasing (closure rate). Mode 2 exists in two forms, 2A and 2B.
Mode 2 has two submodes referred to as Mode 2a and Mode 2b. The active submode is determined by the aircraft’s configuration.
Mode 2A
Mode 2A is active during climb out, cruise, and initial approach (flaps not in the landing configuration and the aircraft not on glideslope centerline). If the aircraft penetrates the Mode 2a alerting envelope, the aural message "TERRAIN TERRAIN" is generated initially, and alert discretes are output to show "PULL UP" annunciation on the PFD.
If the aircraft continues to penetrate the envelope, the aural message "WHOOP PULL UP!" is repeated continuously until the warning envelope is exited. At this point, an altitude gain function activates. The aural message reverts to "TERRAIN TERRAIN", but will only be given if the terrain clearance still continues to decrease. The visual alert will remain on until the aircraft has gained enough barometric altitude or the altimeter goes out of track, when all visual and aural alerts stop.
The aural and visual warnings stop for the conditions that follow:
- The aircraft climbs 300 feet
- The FLAP OVRD switch is set to OVRD
- Forty-five seconds pass after the aircraft leaves the warning envelope
Mode 2B
Mode 2b provides a "desensitized" alert envelope, permitting normal landing approach maneuvering close to the terrain without producing unwanted alerts. Mode 2b is enabled whenever flaps are selected to landing position and is also enabled (independent of flap position if the aircraft is performing an ILS approach and is within ±2 dots of both Localizer and Glideslope centerlines. If the aircraft penetrates the Mode 2b envelope with either Gear or Flaps not in landing configuration, the aural message "TERRAIN, TERRAIN" is generated initially, and alert discretes are output for driving "PULL UP" visual annunciators. If the aircraft continues to penetrate the envelope, then the aural message "WHOOP WHOOP PULL UP" is repeated continuously until the warning envelope is exited. If the aircraft penetrates the Mode 2b envelope with both Gear and Flaps in landing configuration, the aural message "Terrain" is repeated until the envelope is exited.
The G/S WARN light goes off between a radio altitude of 200 and 600 ft when the flaps are in the landing configuration. The altitude at which the alerts go off is a function of the aircraft rate of descent. The PULL UP aural warning and the G/S WARN light go off at an altitude of 30 ft when the flaps are not down and the aircraft is on an ILS approach.
Mode 3 Altitude Loss after Takeoff
Mode 3 provides alerts when the aircraft loses a significant amount of altitude immediately after takeoff or during a missed approach. The altitude loss variable is based on the altitude value from the time of the beginning of the inadvertent descent. The amount of altitude loss, which is permitted before an alert is given, is a function of the height of the aircraft above the terrain. Mode 3 is enabled after takeoff or go around when the landing gear is up and the flaps are in other than the landing position, and stays enabled until the computer detects that the aircraft has gained sufficient altitude to indicate that it is no longer in the takeoff phase.
If the aircraft penetrates the Mode 3 boundary, the aural message "DON’T SINK" is generated, and alert discretes are provided for activation a "GND PROX" annunciation on the PFD.
The "Don’t Sink" Message is repeated only if the situation continues to degrade, but the visual annunciators remain active, until a positive rate of climb is re-established. Mode 3 is disarmed when the radio altitude goes above 1,500 ft.
Mode 4 Unsafe Terrain Clearance
Mode 4 provides alerts and warnings for insufficient terrain clearance with respect to phase of flight and speed. Mode 4 exists in three forms, 4A, 4B, and 4C. Mode 4A is active during cruise and approach with Gear not in landing configuration. Mode 4B is also active in cruise and approach, but with Gear in landing configuration. Mode 4C is active during the takeoff phase of flight with either Gear or Flaps not in landing configuration.
Mode 4A
Mode 4a is based on a Radio Altitude envelope. If the aircraft penetrates the Mode 4A envelope upper boundary with the gear still up the voice message will be "TOO LOW GEAR". At higher aircraft speeds the upper boundary is increased linearly. Penetrating this boundary produces a "TOO LOW TERRAIN" message and a visual "GND PROX" annunciation on the PFD.
Mode 4B
With the landing gear lowered, the upper boundary will decrease. Penetration at lower speeds results in the "TOO LOW GEAR" message with Gear up or the "TOO LOW FLAPS" message with Gear Down and Flaps not in landing configuration. A visual "GND PROX" annunciation shows on the PFD with either of the above conditions. Should the pilot wish to land with less than full flaps, a FLAP OVERRIDE switch on the center pedestal will cancel the call out. An EICAS advisory message "FLAP OVERRIDE" will be displayed while the callouts is canceled. At higher speeds the message is "TOO LOW TERRAIN".
Mode 4C
Mode 4C is based on a minimum terrain clearance, or floor, that increases with Radio Altitude during takeoff. A value equal to 75% of the current Radio Altitude is accumulated in a long-term filter. Any decrease of Radio Altitude below the filter value with Gear or Flaps up will result in the warning "TOO LOW TERRAIN".
Mode 5
Mode 5 provides two levels of warning when the aircraft flight path descends below the Glideslope beam on front course ILS approaches.
The first alert activation occurs whenever the aircraft is below a set deviation for its minimum terrain clearance and is called a "soft" Glideslope alert because the volume level of the warning is roughly one half the level of the other warnings.
A second alert boundary at lower altitude with greater than two dots deviation is called "loud" or "hard" Glideslope alert because the volume level is increased to the same level as the other warnings. Pushing a GS CANCEL button on the center pedestal can silence the voice callouts. An EICAS advisory message "GS MUTED" will be displayed while the GS callouts is muted.
The aural messages can be reset if the G/S WARN switch/light is pushed five seconds or more after the switch was first pushed to stop the alarm. The aural messages are automatically reset after the landing gear or flap configuration changes, or after the aircraft is in a weight-on-wheels configuration.
Mode 6
Mode 6 provides alerts and callouts for descent below predefined altitudes, Decision Height (DH), Minimums and Approaching Decision Height, Approaching Minimums. Alerts for excessive roll or bank angle are also provided as part of this mode. Specific callouts are program pin selectable from predefined menus. Mode 6 alerts and callouts produce aural and ARINC 429 output indications, but do not produce visual indications.
A "Smart" 500 ft. callouts is selected for the GEX. This callouts will only be issued when the system detects that a Non-Precision Approach is being performed or that the aircraft is outside ± 2 dots Glideslope or Localizer deviation.
Strapping enables Smart Callouts plus "50, 30, and MINIMUMS-MINIMUMS" (ref SB 700-31-024). Pin PPCNF8 is left open which selects the Basic Voice Menu in the following table:
Mode 6 Callouts
| ALERT/WARNING CONDITION | BASIC VOICE MENU |
|---|---|
| MODE 7 WINDSHEAR WARNING | (SIREN) WINDSHEAR, WINDSHEAR WINDSHEAR |
| MODE 1 PULL UP | WHOOP, WHOOP, PULL UP |
| MODE 2 PULL UP | WHOOP, WHOOP, PULL UP |
| MODE 2 PULL UP PREFACE | TERRAIN, TERRAIN |
| TERRAIN AWARENESS PULL UP | TERRAIN AHEAD PULL UP |
| MODE 2 TERRAIN | TERRAIN |
| MODE 6 MINIMUMS MINIMUMS | MINIMUMS, MINIMUMS |
| MODE 6 MINIMUMS | MINIMUMS |
| MODE 6 DECISION HEIGHT | DECISION HEIGHT |
| TERRAIN AWARENESS CAUTION | CAUTION TERRAIN |
| MODE 4 TOO LOW TERRAIN | TOO LOW TERRAIN |
| TCF TOO LOW TERRAIN | TOO LOW TERRAIN |
| MODE 6 ALTITUDE CALLOUTS | Different altitude aural indications |
| MODE 6 SMART CALLOUT | (Disabled) |
| MODE 4 TOO LOW GEAR | TOO LOW, GEAR |
| MODE 4 TOO LOW FLAPS | TOO LOW, FLAPS |
| MODE 1 SINKRATE | SINKRATE (PAUSE) SINKRATE |
| MODE 3 DON’T SINK | DON’T SINK (PAUSE) DON’T SINK |
| MODE 5 GLIDESLOPE | GLIDESLOPE |
| MODE 6 APPROACHING MINIMUMS | APPROACHING MINIMUMS |
| MODE 6 APPROACHING DECISION HEIGHT | APPROACHING DECISION HEIGHT |
| MODE 6 BANK ANGLE BANK | ANGLE BANK ANGLE (PAUSE) BANK ANGLE |
| MODE 7 WINDSHEAR ALERT | QUIET |
Bank Angle
Bank Angle provides protection from over banking during maneuvering on approach or climb out. The "Bank Angle" aural alerts are given twice and then suppressed unless the roll angle increases by an additional 20%. If the bank angle increased by more than 40 percent of the normal value, the message is transmitted continuously until the angle is decreased.
Windshear Alerting
Mode 7 produces alerts for flight into an excessive Windshear condition during takeoff or final approach. The Windshear Caution, or pre-alert provides visual and ARINC 429 output indication. This mode can be de-selected with a program pin strap.
Windshear detection is active between 10 and 1,500 feet AGL during the initial takeoff and final approach phases of flight. Alerts and warnings are provided when the level of windshear exceeds predetermined threshold values.
The actual windshear value measured represents the vector sum of inertial vs. air mass accelerations along the flight path and perpendicular to the flight path. These shears result from vertical winds and rapidly changing horizontal winds.
Windshear warnings are given for decreasing head wind (or increasing tail wind) and severe vertical downdrafts.
Windshear alerts are given for increasing head wind (or decreasing tail wind) and severe up drafts.
Enhanced Functions
Envelope Modulation
Due to terrain features at or near certain specific airports around the world, normal operations have resulted in nuisance or missed alerts at these locations in the past.
The envelope modulation feature provides improved alert/warning protection at some key locations throughout the world, while improving nuisance margins at others. This is made possible with the use of navigation data from inertial navigation equipment. The system optionally utilizes GPS or updated Flight Management System navigation signals when available. All position data is cross checked to ground based navigational aids, altimeter and heading information, and stored terrain characteristics prior to being accepted for envelope modulation purposes. This guards against possible navigational position errors.
Modes 4, 5, and 6 are expanded at some locations to provide alert/warning protection consistent with normal approaches. Modes 1, 2, and 4 are desensitized at other locations to prevent nuisance warnings, which result from unusual terrain or approach procedures. In all cases, very specific information is used to correlate the aircraft position and phase of flight prior to modulating the envelopes. The tables, which store the Envelope Modulation data, are maintained in non-volatile memory.
Terrain Clearance Floor
The Terrain Clearance Floor (TCF) alert adds an additional element of protection to the standard Ground Proximity Warning modes. It creates an increasing terrain clearance envelope around the intended airport runway to provide protection against CFIT situations beyond those, which are currently provided. TCF alerts are based on current aircraft location, nearest runway center position and radio altitude.
TCF is active during takeoff mode when mode 4 protection is not available, and during cruise and final approach. This alert mode complements the existing Mode 4 protection by providing and alert based on insufficient terrain clearance even when in landing configuration. Alerts for TCF illuminate GPWS annunciations on the PFDs and produce aural messages.
When an aircraft penetrates the TCF alert envelope the aural message "TOO LOW TERRAIN" will be given. This aural message will occur two times when initial envelope penetration takes place and one time thereafter for each 20% degradation in Radio Altitude. At the same time the warning lamps will illuminate. The lamps will remain on until the alert envelope is exited.
Terrain Alerting and Display
A major feature of the EGPWS is the incorporation of the Terrain Alerting and Display (TAD) functions. These functions use aircraft geographic position, aircraft altitude and a terrain database to predict potential conflicts between the aircraft flight path and the terrain, and to provide graphic displays of the conflicting terrain
Terrain Alerting
The Terrain Awareness Alerting algorithms continuously compute clearance envelopes ahead of the aircraft. If the boundaries of these envelopes conflict with terrain elevation data in the terrain database, then alerts are issued. Two envelopes are computed, one corresponding to a Terrain Advisor Alert level and the other to a Terrain Warning Alert level.
The Advisory and Warning envelopes use the Terrain Clearance Floor as a baseline, and "look ahead" of the aircraft in a volume which is calculated as a function of airspeed and flight path angle.
The computer uses data from the radio altimeter, GPS, FMS, IRS, and VHF navigation system to change the flight envelopes for specified airports. These are airports where the topography can cause intermittent warnings, or where the usual flight envelope will not supply sufficient warnings or cautions.
If the aircraft penetrates the Advisory envelope boundary, the aural message "Caution, Terrain" is generated, and alert discretes are provided for activation of visual annunciators.
Simultaneously, after the TERRAIN switch is pushed on the MFD controller, terrain areas, which conflict with the caution criteria, are shown in solid yellow color on the MFD Terrain Display.
If the aircraft penetrates the Warning envelope boundary, the aural message "Terrain Ahead, Pull Up!" is generated and alert discretes are provident for activation of visual annunciators. Simultaneously, terrain areas, which conflict with the warning criteria, are shown in solid red color on the Terrain Display.
Terrain Display
The EGPWS computer outputs a display of terrain data in ARINC 708/453 data format (Weather Radar). The terrain data is displayed on an Electronic Flight Instrument System (EFIS), on the Multifunction Display (MFD). When the Terrain Display is present and the TERRAIN switch is pushed on the MFD controller, it replaces the Weather Radar display. The Terrain Display can be made available to the flight crew at any time or only when a Terrain Alert occurs.
Areas of terrain that satisfy the Terrain Caution Alert criteria are shown in solid yellow, and areas of terrain that satisfy the Terrain Warning Alert criteria are shown in solid red. Terrain which is significantly close to the aircraft, but which satisfies neither the Caution or Warning criteria, is shown as follows:
- Terrain 2,000 feet or more above the aircraft is displayed with a high density red.
- Terrain 1,000 to 2,000 feet above the aircraft is displayed with a high density yellow.
- Terrain 100 feet below to 1,000 feet above the aircraft is displayed with a medium density yellow.
- Terrain 100 foot to 1,000 feet below the aircraft is displayed with a medium density green.
- Terrain 1,000 to 2,000 feet below the aircraft is displayed with a light density green.
- Terrain 2,000 feet or more below the aircraft is black.
- Unknown terrain data below the aircraft is displayed in light density magenta.
EGPWS Indications
PFD Annunciations
Unlike previous aircraft, the Global has no dedicated warning and alert lights. The GPWS warnings and cautions are displayed on the PFD. A red GPWS annunciation will appear below and to the left of the ADI sphere for Modes 1 through 4 Warnings. The annunciation will flash for five seconds and then turns steady. It remains as long as the warning is valid.
The Mode 5 Caution BELOW GLIDESLOPE will be displayed to the left of the Glideslope scale on the right side of the attitude sphere. The color is Amber and like the warning, it will flash for five seconds and turn steady while the caution is valid.
The Windshear Caution and Warning annunciations will be shown inside a box above the horizon line on the left side of the ADI sphere. The letters will be "WNDSHR" in red for a warning and amber for a caution. They will also flash for five seconds and then turn steady while the mode is valid.
MFD Displays
The terrain data from the terrain database will be displayed on the MFDs after the TERRAIN switch is pushed during a terrain alert. The display colors and conditions were previously discussed and illustrated in the terrain display section.
System Interface
The EGPWC supports ARINC 429 interactive protocols to provide maintenance information, including fault history, for aircraft installations that use an on-board central maintenance system. If date, time, flight number, aircraft ID are provided, then this information can also be tagged to fault history records. In addition, maintenance system test commands can be used to initiate EGPWS Self-Test. In the Global Express this process is handled by the Central Aircraft Information Maintenance System (CAIMS).
Front Panel Test Interface
The EGPWC has a front panel test connector which can be connected to a portable PC to both receive and control internal data. This test interface can be used for engineering and production testing, both on the bench and at the aircraft.
The LRU front panel also contains a test switch, 600 ohm headset jack, and several fault LEDs. The test switch and audio jack allow for initiating tests from the LRU. This test operates the same as the Cockpit Self-Test. The status LEDs include Input Fault, Computer OK, and Computer Fail.
PCMIA Interface
The PCMIA Interface is a standard Type II connector. Any card that is capable of memory mapped operation may be plugged into this connector. The most common use of this interface is for upload and download of application software, databases, and history data. Many safety checks are built-in to prevent any errors during the upload process.
ARINC Inputs
The EGPWS System Interfacing diagram shows the connections with other systems. There are 16 ARINC 429 inputs from the following associated systems:
- IRS 1 and 2
- ADC 1 and 2
- RAD ALT 1 and 2
- GPS 1 and 2 (opt)
- TALL 1 and 2
- FMS 1 and 2, FWC 1, 2 and 3
- DAU 3
ARINC 429 inputs from systems No. 2 and No. 3 carry the same labels and data, only the pin numbers and the bus numbers change.
Inputs and Outputs
The Digital EGPWC Internal Block Diagram illustrates a breakdown of the main assemblies used in the system. The main processor is a 486 CPU with a 512k cache memory. Other assemblies are used for inputs circuits, memory, output circuits, audio circuits, and video generation.
ARINC 429 input, and output channels are provided. The inputs can be software programmed for either high or low speed operation. The capability exists to accommodate four DC analog input channels. Twenty ground activated input discretes and eight +28 VDC activated input discretes are provided. Seventeen program pin inputs are used to select configuration and optional features. Two audio outputs are provided, a 600 ohm interphone output in the rear connector sends audio to the Audio Control Panels and a 600 ohm audio jack is also available at the LRU front panel.
The audio volume levels are software controlled. An RS 232 interface is also provided via the LRU front panel to aid in maintenance troubleshooting, engineering and production testing. This interface allows for access and control of internal EGPWS data and outputs. A front panel self-test switch, audio jack, and status LEDs are provided for maintenance and fault isolation.
System Outputs
There are two ARINC 429 output buses to DAU 3A and 3B with data for the EFIS, EICAS and CAIMS systems.
There are two ARINC 453 output buses to send the terrain displays to the MFDs.
One discrete output is used to silence the TCAS while the EGPWC is sending an audio warning. Program pins inform the EGPWC of the type of aircraft. The ID for the Global is 97 and the audio menu and altitude callouts selection ID for the Global is 257. The 600 ohm audio output is sent directly to the Audio Panels. Power input is 28 VDC from the Secondary Power Distribution Assembly No. 3 DC Bus 1.
CAIMS
Inputs
The following 429 inputs are recognized by the EGPWC and used in the maintenance function for storing/reporting faults and running maintenance tests:
Command Word input comes from an ARINC 429 source. The data contained in this word is the Equipment Code and Command Code. When a valid command is recognized the EGPWC performs the desired Self-Test Level or the System Flight Fault Summary mode is initiated and fault data is retrieved.
Date input comes from an ARINC 429 source. The date (Day, Month, Year) is extracted from the word in 4 BCD input characters and 2 discrete fields. This data is used to date stamp faults in fault history.
SFFS Date input comes from an ARINC 429 source. The date (Day, Month, Year) is extracted from the word in 4 BCD input characters and 2 discrete fields. This data is used to retrieve fault data from fault history.
Universal Time Correlation (UTC) input comes from an ARINC 429 source. This word contained the CAIMS time (Hour and Minutes) and is used to time stamp faults in fault history.
Flight Number Word input comes from an ARINC 429 source. This flight number is extracted from the word in 2 BCD input values. This word also contains the CAIMS Active flag value. The flight number is used to tag faults in fault history. The CAIMS Active flag determines whether normal operation or interactive mode is active.
Aircraft Serial Number Word input come from an ARINC 429 source. The A/C Serial Number is extracted from the word in 4 BCD input values.
This data forms the aircraft tail number (4 digits) for tagging faults in fault history. This word also contains the fault storage allowed flag and the NVM flight zone indicator.
Outputs
The EGPWS outputs ten 429 words for interface with CAIMS. Label 350 Fault Flag word used to indicate whether faults have been detected by the EGPWC, status for fault storage area 90 percent written, and if the EGPWC is performing a system test. Labels 354, and 355 are Fault Diagnostic words listing the current faults detected by the EGPWC. Labels 278 and 279 are Discrete Status words showing the current status of all the analog discrete inputs. Labels 275, 276 and 277 are Program Pin Status words displaying the current program pin options selected.
Databases
The EGPWS contains the following types of databases, which can be loaded via the EGPWC front panel PCMCIA interface independent of the system software. Updates to each database will be made available on request. Current database release information is available on the EGPWS website (www.egpws.com).
- Envelope Modulation Database
- Runway Database
- Terrain Database
- Obstacle Database
System Test
Maintenance Concept
The EGPWS performs both event initiated and continuous BIT (built-in test) functions. Event initiated refers to both power-up tests and manually activated self-tests. System status monitors are provided to indicate whenever any fault is detected which affects system functionality.
The cockpit Self-Test is provided both to test the cockpit interface and to annunciate system configuration status.
Acceptance Test Procedure consists of internal BITE tests ant interface tests. These tests are performed in an order, which assures the integrity of the testing hardware before it is used to test other hardware.
System Status
Current Configuration
Current Configuration indicates the current hardware, software, databases and program pin inputs detected by the EGPWS. This information is available from the level 3 Self-Test to the PMAT via RS 232 bus or to the front panel RS 232 test connector interface.
Current Faults
Faults and failures in the system are divided into two main categories, Internal Faults and External Faults. These two main categories are used to distinguish faults for different processing requirements.
Faults are further broken down into sub-categories: Discrete Faults, ARINC 429 bus activity faults, Analog Input Wire Monitoring Faults, ARINC 429 Signal Faults, Analog Signal Faults and Program Pin Faults.
Internal Faults
Internal Faults are those that originate within the EGPWC. The specific BITE failure will be annunciated.
External Faults
External Faults are those that originate from outside the EGPWC. The following faults are categorized as external faults: ARINC 429 bus activity faults, Analog Input Wire Monitoring faults, ARINC 429 Signal faults, and Analog Signal faults.
System Monitors
The system provides three discrete outputs indicating the status (whether a function is valid or not). Detected data failures and internal computer failures will activate these outputs. The digital version of these outputs, used in the Global Express, will set bits in ARINC 429 words to indicate the type of failure. The ARINC 429 outputs set by these monitors is sent to DAU 3 and converted to ASCB for the CAIMS and the Fault Warning Computer. There are 4 CAS advisory message outputs from the Fault Warning Computer: "GND PROX FAIL", "WINDSHEAR FAIL", "TERR FAIL" and "GPWS SYSTEM FAIL". "Computer OK" and "Computer Fail", will also indicate the status of the system after a self-test.
- EGPWS Monitor: This monitor is activated by failures, which affect the system performance for non-wind shear functions
- Wind shear Monitor: This monitor is activated by failures, which affect the Wind shear function
- Terrain Alerting Monitor: This monitor is activated by the Terrain Alerting Functions and is encoded in an ARINC 429 word
LRU Operational History Recording
Fault history is stored in-nonvolatile memory in the form of fault history records. Fault history information can be reviewed through the use of voice output, RS 232 test interface, or PCMIA interface.
Fault recording is not enabled until at least 25 seconds have elapsed after power up. For multiple occurrences of the same fault during the same flight leg only one fault record will be stored.
When "In the Air" status is false, only internal faults are stored. When this status is true, both internal and external faults are stored. The system is capable of storing a minimum of 256 Fault History Records and 64 fault legs in non-volatile memory or an average of 4 faults per flight leg.
Note:
The cockpit Self-Test capability has not been implemented on the Global. The 6 levels of self-tests are available through the CAIMS, or by pressing the test switch behind the front panel on the EGPWC.
Initiated Built-In Test – CAIMS
The CAIMS interface provides the means to view faults and initiate EGPWS test through the PMAT.
The procedure consists in entering the CAIMS MAIN MENU and selecting SYSTEM DIAG function. From ATA SELECTION display, select ATA 34 and then from the list of LRUs select COMPUTER (GPWS).
Initiated Built-In Test – EGPWS Computer
The front panel also contains a test switch, a headset jack, and several fault LEDs. The test switch and audio jack allow for conducting tests from the computer.
Several levels of information may be voice annunciated via the audio system. These can also be heard via the headset audio jack on the front panel. The test sequences have been divided into six levels to aid in testing and troubleshooting the EGPWC.
Instructions are annunciated on the PMAT EGPWS pages. The results of performing a short or long cancel are defined below for each self-test level.COMPUTER OK and COMPUTER FAIL also indicate the status of the system after a self-test.
