Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 M o d u l e 1 3-0 8 k A i r c r a f t A e r o d y n a m i c s, S t r u c t u r e s a n d S y s t e m s I n s t r u m e n t S y s t e m s - A T A 3 1 G r o u n d P r o x i m i t y W a r n i n g S y s t e m s ( G P W S ) 13 08k- 1
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 T a b l e o f c o n t e n t s GROUND PROXIMITY WARNING SYSTEMS... 3 1. HOW GPWS WORKS:... 4 2. MODES:... 4 3. GPWS AURAL WARNING SYSTEMS, LIGHT WARNING AND SWITCHES:... 4 4. MODE 1 EXCESSIVE DESCENT:... 5 5. MODE 2 EXCESSIVE TERRAIN CLOSURE RATE:... 7 5.1. Mode 2A:... 8 5.2. Mode 2B:... 11 6. MODE 3 EXCESSIVE ALTITUDE LOSS DURING CLIMB-OUT:... 12 7. MODE 4 UNSAFE TERRAIN CLEARANCE:... 14 7.1. Mode 4A:... 15 7.2. Mode 4B:... 17 8. MODE 5 EXCESSIVE DEVIATION BELOW GLIDESCOPE:... 19 9. GPWS MODES AND ANNUNCIATORS:... 21 10. ENHANCED GROUND PROXIMITY WARNING SYSTEMS:... 22 10.1. Envelope modulation:... 23 10.2. Terrain clearance floor:... 23 11. TERRAIN LOOK AHEAD ALERTING:... 24 11.1. Standard terrain alerting and display:... 26 11.2. Peak terrain alerting and display:... 27 12. MODE 6 ALTITUDE CALLOUT:... 27 12.1. Altitude alert:... 27 12.2. Excessive bank angle alert:... 27 13. MODE 7 WINDSHEAR ALERTING:... 28 13.1. Windshear Caution alert:... 29 13.2. Windshear Warning alert:... 29 13 08k- 2
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 GROUND PROXIMITY WARNING SYSTEMS The purpose of the Ground Proximity Warning System (GPWS) is to alert the flight crew to the existence of an unsafe condition due to terrain proximity. GPWS is a system developed to help prevent CFIT (Controlled flight into terrain) accidents. In the event of a loss of situational awareness by the crew GPWS is a last resort lifeline to warn of approaching terrain. The pilots are alerted through aural and visual warnings and in the case of EGPWS a visual display. GPWS computer 13 08k- 3
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 1. HOW GPWS WORKS: The heart of the GPWS is a computer processor which interprets data from a number of sources: Radar altimeter, Air data computer, UHF navigation receiver, Gear and flap indicating system, Roll attitude input sensor, The computer analyzes a number of parameters including aircraft configuration, speed, proximity to terrain, and descent rate in order to issue appropriate warnings. If the aircraft is in landing configuration at approach speed and approaching the ground it is deemed a warning is unnecessary. 2. MODES: The various hazardous conditions that can be encountered in flight are divided into five modes. Mode 1: Excessive descent rate. Mode 2: Excessive closure rate with respect to rising terrain. Mode 3: Excessive altitude loss during climb-out (in takeoff or during go-around) when not in landing configuration (landing gear up and/or flaps less than 25 ). Mode 4: Insufficient terrain clearance when not in landing configuration (landing gear up and/or flaps less than 25 ). Mode 5: Excessive deviation below glide slope when making a front course approach with the gear down. The Ground Proximity Warning System modes are annunciated to the flight crew in the flight deck by means of aural messages and visual indications. The various modes, methods of annunciation and override functions vary on different airplanes. 3. GPWS AURAL WARNING SYSTEMS, LIGHT WARNING AND SWITCHES: Some typical GPWS warnings are: SINK RATE TERRAIN, TERRAIN 13 08k- 4
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 DON T SINK TOO LOW, TERRAIN TOO LOW GEAR PULL UP WHOOP, WHOOP, PULL UP, PULL UP These aural warnings will be accompanied by illumination of a GPWS annunciator. In the event of a PULL UP warning a recovery procedure must be initiated. 4. MODE 1 EXCESSIVE DESCENT: Mode 1 applies to excessive descent rate with respect to terrain clearance. This mode is independent of landing gear and flap positions. Mode 1 indications occur below 2,450 feet radio altitude down to 50 feet, when the barometric altitude rate exceeds a threshold value as indicated on the graph. The Mode 1 envelope is divided into two areas: The initial penetration area ("SINK RATE" area), and the inner warning area ("PULL UP" area). The specific initial penetration area and the inner warning area boundaries are as shown on the graph. Initial penetration of the Mode 1 envelope is annunciated by the illumination of the GND PROX G/S INHB light switch (amber) and the repeated aural message "SINK RATE". Penetration of the inner warning area is annunciated by the PULL UP light (red), the MASTER WARNING LIGHTS (red), and the repeated aural message PULL UP, PULL UP. Note: Pull Up may be preceded by Whoop, Whoop in some configurations based on the audio menu option selected. WHOOP, WHOOP, PULL UP, PULL UP. 13 08k- 5
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Mode 1 MODE 1 in few words: Warns of excessive descent rate. A GPWS warning light will illuminate and SINK RATE, SINK RATE will be heard. If the situation is not corrected PULL UP, PULL UP or WHOOP, WHOOP, PULL UP, PULL UP will be heard. 13 08k- 6
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Example of a Mode 1 envelope 5. MODE 2 EXCESSIVE TERRAIN CLOSURE RATE: Mode 2 applies to excessive closure rate with respect to rising terrain. 13 08k- 7
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 This mode consists of two submodes: If the flaps are not down 25, mode 2A is annunciated; if the flaps are down 25 or more, mode 2B is annunciated. 5.1. Mode 2A: Mode 2A is active during climbout, cruise, and initial approach (flaps not in the landing configuration and the aircraft not on glideslope centerline). If the aircraft penetrates the Mode 2A caution envelope, the aural message TERRAIN, TERRAIN is generated and cockpit EGPWS caution lights will illuminate. If the aircraft continues to penetrate the envelope, the EGPWS warning lights will illuminate and the aural warning message PULL UP is repeated continuously until the warning envelope is exited. If airspeed is less than 190 knots, the upper boundary is 1,650 feet radio altitude, and the lower boundary is 50 feet. If airspeed exceeds 250 knots, the upper boundary is 2,450 feet radio altitude, and the lower boundary is 50 feet. Between 190 knots and 250 knots, the upper boundary varies according to an airspeed expansion function. The specific boundary limits for various closure rates is as shown on the graphic (see next figures). Penetration of the mode 2A envelope can be either on the slope or from the top. The envelope is divided into two areas: the initial penetration area and the inner warning area. The inner warning area is entered after the initial penetration area message "TERRAIN" has been voiced twice upon initial penetration of the mode 2A envelope. Initial penetration area indications consist of the illumination of the GND PROX G/S INHB light switch (amber), and the aural message "TERRAIN" voiced twice. The indications of the inner warning area are the illumination of the PULL UP light (red), the Master Warning lights (red), and the repeated aural message "WHOOP, WHOOP, PULL UP, PULL UP Upon leaving the inner warning area, due to either terrain drop-off or a pull-up maneuver, the altitude gain function is activated. During this function, the indications change to the GND PROX G/S INHB light switch (amber) and the repeated aural message "TERRAIN". The indications continue until the aircraft has gained 300 feet of barometric altitude, or when the landing gear is lowered. 13 08k- 8
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Mode 2A MODE 2A in few words: Warns crew when closure rate with terrain is too high. Designed to warn crew when rising terrain is a threat. terrain, terrain whoop, whoop, pull up, pull up There may be no change in barometric altitude but the radar altitude is decreasing. 13 08k- 9
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Example of a Mode 2A envelope The graph shows how the upper boundary of the Mode 2 alert envelope varies as a function of the aircraft speed. As airspeed increases from 220 knots to 310 knots, the boundary expands to provide increased alert times at higher airspeeds. 13 08k- 10
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 5.2. Mode 2B: Mode 2B applies to excessive closure rate with respect to rising terrain with the flaps down 25 or more. It is an advisory-only mode. The Mode 2B indications occur below 789 feet radio altitude and down to 200-600 feet, depending upon the barometric rate of descent, when the closure rate exceeds threshold values as shown on the graph (see next figures). Mode 2B indications consist of the illumination of the GND PROX G/S INHB light switch (amber), and the repeated aural message "TERRAIN". Mode 2B 13 08k- 11
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Example of a Mode 2B envelope 6. MODE 3 EXCESSIVE ALTITUDE LOSS DURING CLIMB-OUT: Mode 3 applies to excessive barometric altitude loss after takeoff, if the flaps are less than 25 or the landing gear is raised; or below 200 feet during a missed approach. It is an advisory-only mode. In general, the altitude loss threshold value is about 10% of the current altitude. 13 08k- 12
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 During landing approach, mode 3 is armed after the aircraft has descended below 200 feet in landing configuration (flaps down more than 25 and landing gear down). Modes 3 and 4 are mutually exclusive: In climb-out, Mode 3 is disabled and Mode 4 is armed after the aircraft has climbed above 700 feet. Mode 3 indications occur below 700 feet radio altitude and down to 50 feet, when the barometric altitude loss exceeds the threshold values as shown on the graphic (see next figure). Mode 3 indications include illumination of the GND PROX GIS INHB light switch and the repeated aural message "DON'T SINK. Mode 3 MODE 3 in few words: Warns of loss of altitude after take-off, or go-around. Within the first 1000 AGL if the aircraft starts to sink rather than climb. If the aircraft sinks 10 percent of its radar altitude don t sink will be heard. 13 08k- 13
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 7. MODE 4 UNSAFE TERRAIN CLEARANCE: Example of a Mode 3 envelope Mode 4 usually applies during the landing phase of flight. It is armed above 700 feet after takeoff. It is annunciated in the event of insufficient terrain clearance when the aircraft is not in the proper landing configuration. Mode 4 consists of two main submodes: When the landing gear is up, mode 4A is annunciated. When the landing gear is down, but the flaps are less than 25, mode 4B is annunciated. Remark: The complementary Mode 4C alert is intended to prevent inadvertent controlled flight into the ground during takeoff climb into terrain that produces insufficient closure rate for a Mode 2 alert. After takeoff, Mode 4A and 4B provide this protection. 13 08k- 14
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 7.1. Mode 4A: Mode 4A is active during cruise and approach with gear and flaps up. This provides alerting during cruise for inadvertent flight into terrain where terrain is not rising significantly, or the aircraft is not descending excessively. Mode 4A It also provides alerting for protection against an unintentional gear-up landing. MODE 4A in few words: If the aircraft is too low and slow, with landing gear retracted. too low, gear 13 08k- 15
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 If the airspeed is higher the warning will be too low, terrain Example of a Mode 4A envelope If airspeed exceeds 190 knots, the mode 4A threshold radio altitude increases from 190 knots to 250 knots. Above 250 knots, the threshold radio altitude is 1,000 feet. If the airspeed is less than 190 knots, the threshold radio altitude is 500 feet. The lower boundary of the mode 4A envelope is 50 feet radio altitude at all airspeeds 13 08k- 16
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 In the high-airspeed advisory area, the aural message is the repeated "TOO LOW, TERRAIN". The visual indication in both advisory areas is the illumination of the GND PROX G/S INHB light switch (amber). Below 500 feet and less than 190 knots airspeed, the Mode 4A aural alert is TOO LOW, GEAR. The visual indication in both advisory areas is the illumination of the GND PROX G/S INHB light switch (amber). For either Mode 4A alert, subsequent alert messages occur for each 20% degradation in altitude. EGPWS caution lights extinguish and aural messages cease when the Mode 4A alert envelope is exited. If the aural signal is disabled, mode 4A alert messages are repeated continuously until the Mode 4A envelope is exited. 7.2. Mode 4B: In mode 4B, if airspeed exceeds 154 knots, the threshold radio altitude increases linearly as the airspeed increases from 154 knots to 250 knots. Above 250 knots, the threshold radio altitude is 1,000 feet, as in the case of mode 4A If airspeed is less than 154 knots, the threshold altitude is 200 feet radio altitude. The lower boundary of the mode 4B envelope is 50 feet radio altitude at all airspeeds. In the high-airspeed advisory area, the aural message is the repeated "TOO LOW, TERRAIN". In the low-airspeed advisory area, it is the repeated "TOO LOW, FLAP". The visual indication in both advisory areas is the illumination of the GND PROX G/S INHB light switch (amber). Mode 4B 13 08k- 17
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 MODE 4B in few words: When the gear is selected down, but the flaps are still retracted too low, flaps. This warning can be canceled by the pilot in the event of flapless landing. Example of a Mode 4B envelope 13 08k- 18
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 8. MODE 5 EXCESSIVE DEVIATION BELOW GLIDESCOPE: Mode 5 applies to excessive deviation below the glide path when making a front-course approach with the gear down. In a back-course landing condition, mode 5 is inhibited. Initial penetration of mode 5 envelope results in a low-level aural annunciation. A penetration of the inner advisory area is indicated by a normal-level aural annunciation. The mode 5 envelope is divided into two advisory areas: the low-level (initial penetration) advisory area, and the normal-level (inner) advisory area. The low-level advisory area indications occur below 1,000 feet of radio altitude and down to 50 feet, when the glide slope deviation exceeds 1.3 dots (0.46 degrees). The specific area boundaries are as shown in next Figure. Mode 5 MODE 5 in few words: Warns the crew of glideslope deviations. When the aircraft receives a valid glideslope and sinks two dots below glideslope will be heard. The warning will continue with increasing intensity if the problem is not corrected. This warning may be canceled by the pilot. 13 08k- 19
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Normal-level advisory area indications occur only below 300 feet radio altitude and down to 50 feet, and when the glide slope deviation exceeds 2.0 dots (0.7 degrees). The specific area boundaries are as shown in figure below. Mode 5 is annunciated by the illumination of the GND PROX G/S INHB light switch (amber) and the repeated aural message "GLIDESLOPE." The sound level in the normal-level advisory area is the same as in modes 1 through 4, and it is six decibels lower in the low-level advisory area. The "GLIDESLOPE" message is repeated more rapidly as the terrain clearance decreases and/or the glide slope deviation increases. Mode 5 indications may be cancelled by pressing the GND PROX G/S INHB light switch when the radio altitude is less than 1,000 feet. Both the aural message and the light indication are cancelled. The mode is automatically rearmed when climbing above 1,000 feet radio altitude, or descending below 50 feet radio altitude. Example of a Mode 5 envelope 13 08k- 20
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 9. GPWS MODES AND ANNUNCIATORS: MODE CONDITION AURAL MESSAGE PULL UP LIGHT GND PROX G/S INHB LIGHT SWITCH 1 Initial penetration area SINK RATE ON Inner warning area WHOOP, WHOOP, PULL UP 2A Flaps up Initial penetration area TERRAIN, TERRAIN ON Inner warning area Altitude gain function: Starts when the airplane exits the warning area, Ends when 300 ft in the altitude have gained, Is inhibited when gear is extended. WHOOP, WHOOP, PULL UP TERRAIN, TERRAIN 2B Flaps > 25 TERRAIN, TERRAIN ON 3 Flaps < 25 or gear up DON T SINK ON 4A Gear up Airspeed < 190 KTS TOO LOW, GEAR ON 4B Gear down Flaps < 25 Airspeed > 190 KTS TOO LOW, TERRAIN ON Airspeed < 154 KTS V Airspeed > 190 KTS Note: When gear is retracted after being extended, TO LOW, GEAR will be annunciated on the mode 4B. 5 Gear down GLIDESLOPE ON ON ON ON ON ON ON CAPT MASTER WARNING LIGHTS ON ON 13 08k- 21
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 10. ENHANCED GROUND PROXIMITY WARNING SYSTEMS: The Enhanced GPWS incorporates the functions of the basic Ground Proximity Warning System (GPWS) modes 1 through.5 and adds addition modes, callouts as well as display of terrain. The EGPWS uses aircraft inputs including geographic position, attitude, altitude, airspeed, and glideslope. These are used with internal terrain, obstacles, and airport databases to predict a potential conflict between the aircraft flight path and terrain or an obstacle. A terrain or obstacle conflict will result in the EGPWS providing a visual and audio caution or warning alert. Additionally, the EGPWS provides (Mode 6) alerts for bank angle and altitude callouts based on system program pin selection. Detection of severe windshear (Mode 7) conditions is also provided for selected aircraft types when enabled. This feature can use Doppler enabled "X" band weather radar to predict windshear (Predictive Windshear) in addition to the reactive windshear function in which the windshear is detected as the aircraft flies through the condition. The EGPWS incorporates several "enhanced" features: Terrain Alerting and Display (TAD) provides a graphic display of the surrounding terrain on the Weather Radar Indicator, EFIS, or a dedicated display. "Peaks" is a TAD supplemental feature providing additional terrain display features for enhanced situational awareness, independent of the aircraft's altitude. This includes digital elevations for the highest and lowest displayed terrain, additional elevation (color) bands, and a unique representation of 0 MSL elevation (sea level and its corresponding shoreline). "Obstacles" is a feature utilizing an obstacle database for obstacle conflict alerting and display. EGPWS caution and warning visual and audio alerts are provided when a conflict is detected. Additionally, when TAD is enabled, Obstacles are graphical displayed similar to terrain. "Terrain Clearance Floor" feature adds an additional element of protection by alerting the pilot of possible premature descent. This is intended for non-precision approaches and is based on the current aircraft position relative to the nearest runway. Windshear alerting (Mode 7) is provided for specific aircraft types. Mode 7 provides windshear caution and/or warning alerts when an EGPWS windshear threshold is exceeded. The EGPWS adds to these 7 basic functions the ability to compare the aircraft position to an internal database and provide additional alerting and display capabilities for enhanced situational awareness and safety (hence the term "Enhanced" GPWS). The EGPWS internal database consists of four sub-sets: A worldwide terrain database of varying degrees of resolution. An obstacles database containing cataloged obstacles 100 feet or greater in height located within North America and portions of the Caribbean. 13 08k- 22
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 A worldwide airport database containing information on hard-surface runways 3500 feet or longer in length. An envelope modulation database. Notification of a database update is accomplished by Service Bulletin. Database updates are distributed on PCMCIA data cards and downloaded via a card slot in the front panel of each EGPWS computer. With the use of accurate GPS or FMS information, the EGPWS is provided present position, track, and ground speed. With this information the EGPWS is able to present a graphical plan view of the aircraft relative to the terrain and advise the flight crew of a potential conflict with the terrain or obstacle. Conflicts are recognized and alerts provided when terrain violates specific computed envelope boundaries on the projected flight path of the aircraft. Alerts are provided in the form of visual light annunciation of a caution or warning, audio enunciation based on the type of conflict, and color enhanced visual display of the terrain or obstacle relative to the forward look of the aircraft. The terrain display is provided on the Weather Radar Indicator, EFIS display, or a dedicated EGPWS display and may or may not be displayed automatically. 10.1. 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. With the introduction of accurate position information and a terrain and airport database, it is possible to identify these areas and adjust the normal alerting process to compensate for the condition. Modes 4, 5, and 6 are expanded at certain locations to provide alerting protection consistent with normal approaches. Modes 1, 2, and 4 are desensitized at other locations to prevent nuisance warnings that 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. 10.2. Terrain clearance floor: The Terrain Clearance Floor (TCF) function (when enabled) enhances the basic GPWS Modes by alerting the pilot of descent below a defined "Terrain Clearance Floor" regardless of the aircraft configuration. The TCF alert is a function of the aircraft's Radio Altitude and distance (calculated from latitude/longitude position) relative to the center of the nearest runway in the database. TCF alerts result in illumination of the EGPWS caution lights and the aural message "TOO LOW TERRAIN". The audio message is provided once when initial envelope penetration occurs and again only for additional 20% decreases in Radio Altitude. The EGPWS caution lights will remain on until the TCF envelope is exited. 13 08k- 23
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Terrain clearance floor alert envelope 11. TERRAIN LOOK AHEAD ALERTING: Another enhancement provided by the internal terrain database, is the ability to look ahead of the aircraft and detect terrain or obstacle conflicts with greater alerting time. This is accomplished based on aircraft position, flight path angle, track, and speed relative to the terrain database image forward the aircraft. Through sophisticated look ahead algorithms, both caution and warning alerts are generated if terrain or an obstacle conflict with "ribbons" projected forward of the aircraft (see illustration). 13 08k- 24
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 A terrain conflict intruding into the caution ribbon (see next figure) activates EGPWS caution lights and the aural message "CAUTION TERRAIN, CAUTION TERRAIN" or "TERRAIN AHEAD, TERRAIN AHEAD". An obstacle conflict provides a "CAUTION OBSTACLE, CAUTION" OBSTACLE" or OBSTACLE AHEAD, OBSTACLE AHEAD" message. The caution alert is given typically 60 seconds ahead of the. terrain/obstacle conflict and is repeated every seven seconds as long as the conflict remains within the caution area When the warning ribbon is intruded (typically 30 seconds prior to the terrain/obstacle conflict), EGPWS warning lights activate and the aural message "TERRAIN, TERRAIN, PULL UP" or "OBSTACLE, OBSTACLE, PULL UP" is enunciated with "PULL UP" repeating continuously while the conflict is within the warning area. When a compatible Weather Radar, EFIS, or other display is available and enabled, the EGPWS Terrain AND Alerting and Display (TAD) feature provides an image of the surrounding terrain represented in various colors and intensities. There are actually two types of TAD displays depending on the options selected. The first provides a terrain image only when the aircraft is 2000 feet or less above the terrain ("standard"). A second feature called "Peaks enhances the standard display characteristics to provide a higher degree of terrain awareness independent of the aircraft's altitude. 13 08k- 25
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 11.1. Standard terrain alerting and display: The Standard TAD provides a graphical plan-view image of the surrounding terrain as varying density patterns of green, yellow, and red. The selected display range is also indicated on the display, and an indication that TAD is active is either indicated on the display (e.g., "TERR") or by an adjacent indicator. Each specific color and intensity represents terrain (and obstacles) below, at, or above the aircraft's altitude based on the aircraft's position with respect to the terrain in the database. If no terrain data is available in the terrain database, then this area is displayed in a low-density magenta color. Terrain more than 2000 feet below the aircraft, or within 400 (vertical) feet of the nearest runway elevation, is not displayed (black). When a caution alert is triggered, the terrain (or obstacle) that created the alert is changed to solid yellow (100% density). When a warning alert is triggered, the terrain (or obstacle) that created the alert is changed to solid red (100% density). 13 08k- 26
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 11.2. Peak terrain alerting and display: Peaks display has all the characteristics of the standard display but with additional terrain display features for enhanced situational awareness independent of the aircraft s altitude. The principle additions are: The digital display of the highest and lowest terrain/obstacle elevations currently displayed, The display of additional solid or lower density color bands, including the addition of the graphic representation of sea level (0 feet MSL). 12. MODE 6 ALTITUDE CALLOUT: EGPWS Mode 6 includes both altitude and excessive bank angle callouts. 12.1. Altitude alert: Altitude callouts, which have become a popular feature with many airlines on new aircraft, are available in the EGPWS. They are pin-selectable at the rear connector and there are several menus available for the purpose of increasing altitude awareness on final approach. Tones are also available. Automatic audio level increase is available when windshield rain removal is in use. AlliedSignal recommends the use of a few automatic callouts near the runway and a "smart" callouts, which would rarely be heard, for most ILS landings. AlliedSignal recommends that the minimums callout be utilized. 12.2. Excessive bank angle alert: Bank Angle can be used to alert crews of excessive roll angles. The bank angle limit tightens from 40 degrees at 150 feet AGL (Above Ground Level) to 10 at 30 feet AGL to help alert the crew on landing of excessive roll corrections which might result in wing tip or engine damage. Bank Angle is also useful to help alert the pilot of severe over banking which might occur from momentary disorientation during initial climb out. The callout BANK ANGLE, BANK ANGLE advises of an excessive roll angle. The EGPWS provides several excessive bank angle envelopes supporting Air Transport, Business, or Military aircraft types (only Air Transport and Business are addressed below). 13 08k- 27
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Example of Mode 6 One envelope is defined for turbo-prop and jet business aircraft (see graph below). Bank angles in excess of: ±10 between 5 and 30 feet, ±10 to 40 between 30 and 150 feet, ±40 to 55 between 150 and 2450 feet. 13. MODE 7 WINDSHEAR ALERTING: Mode 7 is designed to provide alerts if the aircraft encounters windshear. 13 08k- 28
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Two alerting envelopes provide either a WINDSHEAR CAUTION alert or a WINDSHEAR WARNING alert each with distinctive aural and visual indications to the flight crew. EGPWS windshear is provided for certain (not all) aircraft types and is a function of certain additionally required input signals and enabled internal detection algorithms. These are established during the initial installation and addressed in the appropriate Airplane Flight Manual (AFM) or EGPWS Airplane Flight Manual Supplement (AFMS). 13.1. Windshear Caution alert: Windshear Caution alerts are given if an increasing headwind (or decreasing tailwind) and/or a severe updraft exceed a defined threshold. These are characteristic of conditions preceding an encounter with a microburst. A Windshear Caution (if enabled) results in illumination of amber Windshear Caution lights and may (if separately enabled) also be accompanied by the aural message CAUTION, WINDSHEAR. The lights remain on for as long as the aircraft is exposed to conditions in excess of the caution alert threshold. 13.2. Windshear Warning alert: The Windshear Caution alerting can be disabled by EGPWS program pin selection so that only Windshear Warning alerts are provided. Windshear Warning alerts are given if a decreasing headwind (or increasing tailwind) and/or a severe downdraft exceed a defined threshold. These are characteristic of conditions within or exiting an encounter with a microburst. Windshear Warning results in illumination of red Windshear Warning lights and an aural siren followed by the message WINDSHEAR, WINDSHEAR, WINDSHEAR. The lights remain on for as long as the aircraft is exposed to conditions in excess of the warning alert threshold. The aural message will not repeat unless another separate windshear event is encountered. The threshold is adjusted as a function of available climb performance, flight path angle, airspeeds significantly different from normal approach speeds, and unusual fluctuations in Static Air Temperature (typically associated with the leading edge of a microburst). Mode 7 Windshear alerting is active under the following conditions: During takeoff; from rotation until an altitude of 1500 feet AGL is reached, During approach; From an altitude of 1500 feet down to 10 feet AGL, During a missed approach; until an altitude of 1500 feet AGL is reached. 13 08k- 29
Category A B1 B2 B3 08 Instrument systems (ATA 31) Level 1 2 3 Example of Mode 7 13 08k- 30