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Gulfstream G450 Systems

[G450 AOM, § 2A-34-10] The navigation system provides the flight crew with indications of position in three dimensions and vector information for management of the flight environment, supplemented with aural and visual alerts to prevent controlled flight into terrain (CFIT) and collision with other airborne traffic.


 

Digital Air Data Computing (DADC) System

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The AOM starts off calling this the "Flight Environment Data System, a term you will be hard pressed to find anyplace else. Most of the AOM and just about every other source calls this the Digital Air Data Computing (DADC) system. We'll stick with that here.

[G450 AOM, § 2A-34-20] The air data system (ADS) is composed of sensors, probes and modules dedicated to the acquisition and processing of environmental data and the software applications translating the data into appropriate digital formats. Pitot probes and static ports provide analog environmental data to three Air Data Modules (ADMs) that convert the analog information into digital format. that is provided to three Air Data Applications (ADAs), each hosted in one of the Modular Avionics Units (MAUs)s. The ADAs refine the digital information from the ADMs using additional data from the Total Air Temperature (TAT) probes, Angle of Attack (AOA) probes and the barometric correction entered by the flight crew using the Display Controllers (DCs). The ADAs then provide the refined data to the ASCB-D bus for distribution to all airplane systems and installations that require environmental data for operation.

Air Data Module

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[G450 AMM, § 34-12-00 ¶3.A.] The ADM is a self-contained, linearized ARINC 429 output pressure transducer. The ADM contains the pressure sensing elements that interface with the external static ports and pitot pressure probes. The ADM senses and computes the absolute pressure being applied to the probes. The pressure information is transmitted via ARINC 429 buses to the Input / Output (I/O) modules. The ADM operates from +28 Vdc aircraft power. Three ADMs are installed as standard equipment. Redundancy requirements for the primary DADC system and backup air data displays determine the number of ADM installed. The ADM has discrete inputs to identify three different installations as follows:

  • Left: Pilot
  • Right: Copilot
  • Standby

Each ADM is a small electronic box that takes pneumatic tubing from a pitot tube and two static ports and converts those into digital data.

Pitot-Static System

[G450 AOM, § 2A-34-20 ¶2.B.] The pitot-static system samples the atmospheric environment to provide indications of airspeed and altitude. Three pitot probes are mounted of exterior of the airplane: two pitot probes are mounted forward of the cockpit windshield on either side of the windshield center post - a third probe is installed on the left side of the fuselage below the pilot side window. The probes are aligned forward to sense pitot (dynamic) air pressure that increases proportional to airplane velocity. Each of the pitot probes is connected to tubing that is plumbed to an Air Data Module (ADM) that converts sensed pitot pressure into a digital signal that is furnished to the ADAs. The left pitot probe forward of the windshield is plumbed to ADM #1, the right pitot probe forward of the windshield is plumbed to ADM #2 and the pitot probe on the left side of the fuselage (termed the standby pitot probe) is plumbed to ADM #3 and to the Standby Flight Display (SFD). Each pitot probe is electrically heated to prevent blockage by frozen precipitation. Drains are also incorporated to dispel liquid precipitation. Probe heat is selected with the PROBE switches the copilot side of the lowest panel on the cockpit overhead. The switch labelled PRIMARY powers probe heat for the left and right pitot probes (forward of the cockpit windshield) as well as heat for the left (#1) TAT probes. The switch labelled STANDBY powers probe heat for the standby pitot probe and the right (#2) TAT probe.

[G450 AOM, § 2A-34-20 ¶2.B.] Two static air pressure installations, one on either side of the fuselage just below the cockpit side windows, provide readings of ambient air pressure for comparison with pitot dynamic pressure by the ADMs. The static air pressure installations do not require anti-ice heating since they are flush with the contour of the fuselage and not prone to ice accumulation. Each static installation contains four inlet ports. Three are connected by tubing plumbed to each of the three ADMs with the fourth (standby) port plumbed to both the SFD and to a Cabin Pressure Acquisition Module (CPAM). The CPAM converts the standby port sensed ambient air pressure to digital format for use by the cabin pressure controller in maintaining the selected cabin altitude and cabin differential pressure. Each of the lines from the static air pressure inlet ports on the left side of the airplane is connected to the corresponding inlet port on the right side of the airplane so that each static air pressure inlet (ADM #1, #2, #3 and the standby) are plumbed together, compensating for any untrimmed flight condition around the vertical axis (such as a skid or slip) that would induce an increase in sampled static pressure due to the sensor being slightly aligned into the airplane slipstream.

SAT/TAT Sensing

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[G450 AOM, § 2A-34-20 ¶2.C.] The total air temperature (TAT) sensing system has two identical TAT probes mounted on either side of the airplane below the cockpit area. TAT probes provide the MAUs with temperature data. The design of the TAT probes allows them to subtract out the rise in temperature associated with the friction of air molecules impacting the probe that increases with airplane speed. The probes thus derive a static air temperature (SAT) value as well as a TAT (including the frictional rise). The TAT probes are electrically heated when the airplane is airborne (power to the probe heat elements is controlled by the WOW switches). The PROBE switches on the copilot side of the lower overhead panel control both pitot and TAT probe heat. On the ground when bleed air is available, the TAT probes are aspirated with bleed air, venting air through holes in the probe to induce outside air flow over the temperature sensing element. Air flow over the probe results in a more accurate reading of ambient conditions and avoids temperature increases associated with the heating effects of sunlight. TAT information is transmitted as an electrical signal to the ADAs in the MAUs. TAT #1 furnishes data to the ADA in MAU #1, TAT #2 provides data to the ADA in MAU #2, and the ADA in MAU #3 averages the data from both TATs. The ADAs format information that requires temperature data, such as density altitude, for distribution to temperature dependent systems / subsystems such as engine FADECs.

Standby Flight Instruments System

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[G450 AOM, § 2A-34-30 ¶1.] The Standby Flight Instruments provide a backup means of airplane control and navigation in instances where serious malfunctions prevent the use of normal flight displays or in the case of electrical failures that reduce the available power supply to the airplane emergency batteries. The Standby Flight Instruments are digital electronic displays with very low power requirements powered by the emergency DC bus that can be supplied by the emergency batteries if necessary. Together, the instruments provide a means for the flight crew to navigate to a destination and perform instrument approaches including VOR, and standard and back-course ILS using the VHF NAV #1 receiver on only emergency battery power.

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When looking for an independent indication of aircraft attitude, heading, altitude, and airspeed, the SFD is your go to location. The EBDI defaults to IRS #1 and is not a valid tie breaker unless you switch it to STBY.

Standby Flight Display (SFD)

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[G450 AOM, § 2A-34-30 ¶2.] The SFD display presents a standard Primary Flight Display (PFD) format with a airspeed tape and digital airspeed readout on the left and an altitude tape and digital altitude readout on the right. The SFD contains an independent internal reference system for attitude data, a stand-alone magnetic heading reference from a vertical stabilizer mounted magnetometer, and airspeed and altitude data derived from the dedicated connections to pitot/static system.

A menu access button, labelled “M”, located at the bottom center of the SFD face, provides instrument function and display options. Pushing the button brings up a menu display on the bottom of the SFD display. Menu scrolling is done by rotating the knob on the lower right of the instrument. Each menu item or function is highlighted as it is sequentially scrolled. A menu choice is selected by pressing the adjustment knob while the choice is highlighted. Some menu choices contain submenus that provide additional function options such as sub-menu choices for barometric settings in inches of mercury (in), millibars (mb) or HectorPacals (hPa). Other selected menu items require rotation of the knob to accomplish the required function, such as changing an altimeter setting or entering a desired navigation course.

  • FAST ERECT — Causes rapid alignment of the instrument vertical axis with the existing airplane vertical axis.
  • SET BRIGHTNESS OFFSET — Rotating knob increases or decreases instrument illumination level.
  • FAST ALIGN — Causes a 90 second internal sensor alignment with the existing airplane three-dimensional axes.
  • NAV — Selects the VHF NAV function ON or OFF. When NAV is selected ON and a valid frequency is tuned to VHF NAV #1, a course selector, TO/FROM indicator and a COURSE DEVIATION INDICATOR (CDI) will be displayed.
  • SET CRS — Rotating knob changes the indicated course selector.
  • ILS — Allows selection of a NORMAL or a Back Course (BC) approach
  • BARO TYPE — Allows selection to IN HG, MG, or HPA.

A heading tape at the bottom of the instrument display provides a readout of an independent standby magnetic heading source, called a magnetometer. The magnetometer is located in the airplane’s vertical stabilizer and has a three-axis magnetic sensor that converts magnetic field data into a digital format for display on the SFD.

The SFD has the capability to act as a complete PFD. The SFD determines airplane pitch, roll and side slip information from a self-contained internal three axis sensor cluster. The display includes a heading tape on the bottom, an artificial horizon with a standard airplane symbol, instrument navigation data display for enroute and approach navigation, and an unusual attitude display with declutter mode and a fast erect feature.

Instrument failures are displayed on the face of the instrument as text messages, indicators or the absence of data.

Electronic Bearing and Distance Indicator (EBDI)

[G450 AOM, § 2A-34-30 ¶3.] The Electronic Bearing and Distance Indicator (EBDI) is located to the right of the SFD on the lower center of the instrument panel. (See Figure 5.) The display incorporates a standard compass card with airplane symbol, two bearing pointer needles, two range / DME indicators and a digital heading indicator with heading reference notation. Below the compass card are a center-mounted menu pushbutton and two menu item select pushbuttons. Each select pushbutton designates a navigation source for the associated bearing pointer needle (VOR / TAC or ADF), the pushbutton on the lower left for NAV #1 radios, the button on the lower right for NAV #2 radios. The range / DME indicator associated with the select pushbutton will display distance to the selected navaid (except ADF). The menu pushbutton on the bottom center of the instrument allows manual selection of the heading source (magnetic from the SFD magnetometer or IRS #1 or #2).

During operation on emergency batteries, all three heading sources remain available, but only VOR / ILS #1 is available for navigation. Display brightness is set by selecting the brightness menu with the “M” pushbutton and subsequently adjusting brightness with the left and right pushbuttons - the left button decreases brightness, the right increases brightness. Once set, an autobrilliance sensor on the face of the instrument will automatically adjust display brightness for ambient light conditions. (The brightness of the “M” pushbutton is controlled by the COCKPIT LIGHTS MASTER CONTROL knob on the cockpit overhead.) A summary of the functions of the “M” menu pushbutton:

  • BRT ADJ — Adjusts display brightness using inputs with the up and down pointing triangles on either side of the “M” pushbutton.
  • MODE — Selects heading source to instrument. Selections include:
    • STBY - Magnetometer input from the SFD
    • HDG 1 - input from IRS #1
    • HDG 2 - input from IRS #2
    • AUTO - automatically selects heading source with a priority of IRS #1, IRS #2, or STBY
  • VIEW FAULTS — Selects display of instrument failure data for maintenance action.
  • VIEW ID — Selects display of instrument software identificationdata.

MEL Implications

SFD:

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EBDI:

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Except for the most basic flight, you really need the SFD for all operations. The EBDI isn't needed unless you are down an IRS.

Cold Weather Operations

[G450 AOM, §07-01-20 §3.A.(4)] When leaving the aircraft, if temperatures are expected to be below +65°F during the next power up, or prior to power up with temperature below +65°F, pull the SFD / EBDI circuit breakers:

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Radio Altimeter System

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You rarely have to worry about the radio altimeters, except that when they aren't working they impact the operations of other systems. WOW faults and auto-throttle warnings can often be traced to the radio altimeters. By the way, in a three-point attitude they indicate -5 feet. Why? When you touchdown they indicate 0 feet, as shown above.

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[G450 AOM, § 2A-34-40 ¶1.] Dual RT-300 radio altimeters have dedicated receiver / transmitter (R/T) unit, transmitting antenna and receiving antenna. The radio altimeters operate continuously when the airplane Main DC buses are powered, using high resolution, short-pulse radar signals that are accurate over wide variations of terrain, target reflectivity, weather and airplane altitude. The radio altimeters provide a continuous readout of airplane altitude above ground level in the operating range of 0 - 2,500 feet.

  • Accuracy of the altitude readout varies with height above ground, with the readout rounded to a resolution of five (5) feet when the airplane is below 200 feet and a resolution of 10 feet when above 200 feet.
  • Readings between 0 - 100 feet are accurate to within three feet, readings between 100 - 500 feet have an accuracy within 3%, and readings between 500 - 2,500 feet accurate within 4%.

Above 2,500 feet, the radio altimeters continue to operate, however radio altitude information is no longer displayed because of the increase in error margin at higher altitudes.

System Operation

[G450 AOM, § 2A-34-40 ¶2.]

  • Radio altitude is displayed as a digital readout on the Primary Flight Display (PFD) and is indicated by shading on the altitude tape display on the right side of the PFD.
  • The digital altitude readout is accompanied by a data source indication of RA 1 or RA 2 shown in white reversed video.
  • Radio altitude data source is selected on the DCs. If both PFDs are selected to the same radio altimeter for a data source, RA 1 or RA 2 will be shown in amber reversed video.
  • The altitude digital readout is shown in green unless a radio altitude decision height (DH) is selected and the airplane is less than 100 feet above the selected DH, in this instance the digital readout is shown in amber.
  • The altitude tape display format changes below a radio altitude of 600 feet, incorporating a yellow band and“ barber pole” stripes that intensify with decreases in altitude. If the airplane is between 400 and 600 feet radio altitude and is descending, the yellow bar on the altitude tape flashes at a rate of 1 second on and 1/2 second off.

Antennas

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[G450 AMM, § 34-43-00, Figure 3]

From front to back you have transmit antenna 1, receive antenna 2, receive antenna 1, and transmit antenna 2. If you are parked over ice, water, or other shiny surfaces that span the distance between an antenna's transmit and receive antenna, you could get erroneous indications enough to generate problems with other aircraft systems, such as the WOW or autothrottles. Moving the aircraft should clear the faults.

Enhanced Ground Proximity Warning System (EGPWS)

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Figure: G450 Typical EGPWM pop-up display, from G450 Aircraft Operating Manual, §2B-20-110, figure 32.

Before the "E" of EGPWS, pilots were programmed to ignore many GPWS warnings because the knew they were smarter than the electrons. The Enhanced GPWS changes all that. If the EGPWS says you are about to die, chances are if you don't do something quickly, you will. How do you react? Immediately. See: G450 Controlled Flight Into Terrain (CFIT).

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Figure: G450 EGPWS Simplified Block Diagram, from G450 Aircraft Operating Manual, §2B-20-10, figure 1.

[Honeywell EGPWS Pilot Guide, §1]

  • The EGPWS is a Terrain Awareness and Alerting system providing terrain alerting and display functions with additional features.
  • The EGPWS uses aircraft inputs including geographic position, attitude, altitude, airspeed, and glideslope deviation. 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 results in the EGPWS providing a visual and audio caution or warning alert.
  • Additionally, the EGPWS provides alerts for excessive glideslope deviation, too low with flaps or gear not in landing configuration, and optionally provides bank angle and altitude callouts based on system program pin selection. Detection of severe windshear conditions is also provided for selected aircraft types when enabled.
  • The "E" part of EGPWS gives you a terrain database so the system is doing more than just checking the radio altimeter. Among the features in this example (Honeywell) system . . .

  • Terrain Alerting and Display (TAD) provides a graphic display of the surrounding terrain on the Weather Radar Indicator, EFIS, or a dedicated display. Based on the aircraft's position and the internal database, the terrain topography (within the display range selected) that is above or within 2000 feet below the aircraft altitude is presented on the system display. This feature is an option, enabled by program pins during installation.
  • "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). This feature is an option, enabled by program pins during installation.
  • "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 graphically displayed similar to terrain. This feature is an option, enabled by program pins during installation.
  • A process feature called Envelope Modulation utilizes the internal database to tailor EGPWS alerts at certain geographic locations to reduce nuisance alerts and provide added protection.
  • A 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. This feature is enabled with the TAD feature.
  • In -210-210 and later versions, a Runway Field Clearance Floor (RFCF) feature is included. This is similar to the TCF feature except that RFCF is based on the current aircraft position and height above the destination runway based on Geometric Altitude (see next page). This provides improved protection at locations where the destination runway is significantly higher than the surrounding terrain.
  • An Aural Declutter feature reduces the repetition of warning messages. This feature is optional, and may be disabled by system program pins during installation.
  • Geometric Altitude, based on GPS altitude, is a computed pseudo-barometric altitude designed to reduce or eliminate altitude errors resulting from temperature extremes, non- standard pressure altitude conditions, and altimeter miss-sets. This ensures an optimal EGPWS alerting and display capability.
  • Runway Alerting & Advisory System (RAAS). The EGPWS also provides position awareness advisories relative to runways during ground operations and approach to land. This new feature is known as "Runway Awareness and Advisory System" - RAAS (only available in -218-218 or later versions).

Honeywell Terrain Database Subsets

[Honeywell EGPWS Pilot Guide, §1] The EGPWS internal database consists of four sub-sets:

  1. A worldwide terrain database of varying degrees of resolution.
  2. An obstacles database containing cataloged obstacles 100 feet or greater in height located within North America, portions of Europe and portions of the Caribbean (expanding as data is obtained).
  3. A worldwide airport database containing information on runways 3500 feet or longer in length. For a specific list of the airports included, refer to Honeywell document 060- 4267-000 or access on the Internet at website www.egpws.com.
  4. An Envelope Modulation database to support the Envelope Modulation feature discussed later.

Resolution Differences

[Honeywell EGPWS Pilot Guide, §2] Because the overwhelming majority of "Controlled Flight Into Terrain" (CFIT) accidents occur near an airport, and the fact that aircraft operate in close proximity to terrain near an airport, and to address prevention of airport runway/taxiway incursions, the terrain database contains higher resolution grids for airport areas. Lower resolution grids are used out- side airport areas where aircraft enroute altitude make CFIT accidents less likely and terrain feature detail is less important to the flight crew.

G450 Specifics

[G450 Aircraft Operating Manual, §2B-20-10, pg. 2] The EGPWS contains a worldwide terrain database. The resolution of the database varies not only with location around the world but also relative to the proximity to airports. The database also contains the locations of all runways longer than 3200 feet that have a published instrument approach. The system uses this database, and position data to supply enhanced terrain awareness computations which, in turn, supply enhanced terrain awareness information to the pilots.

The terrain database is labeled the "threat database" in the red disk update series. (See G450 Aircraft Operating Manual, §2B-20-50, ¶1.)

WGS-84

[Honeywell DirectTo Newsletter, December 2011, page 11] Unlike the FMS, the EGPWS system will continue to use GPS information even if DME/DME is being used for navigation. The EGPWS database uses a combination of WGS-84 terrain data and non WGS-84 data obtained from the AIP which is checked against GPS position information and then converted if necessary. Therefore, aural cautions and warnings associated with EGPWS will be annunciated accurately. Honeywell Synthetic Vision Systems (SVS) however, will automatically be inhibited whenever GPS is deselected as the primary source of navigation in the FMS.

More about this: World Geodetic System 84 (WGS-84).

Geometric Altitude

[Honeywell EGPWS Pilot Guide, §2, page 36]

  • Based on GPS altitude, geometric altitude is a computed pseudo-barometric altitude (Above Sea Level - ASL) designed to reduce or eliminate errors potentially induced in Corrected Barometric Altitude by temperature extremes, non-standard pressure altitude conditions, and altimeter miss-sets. This ensures an optimal EGPWS Terrain Alerting and Display capability. Geometric Altitude also allows EGPWS operations in QFE environments without custom inputs or special operational procedures.
  • Geometric Altitude requires GPS Altitude input with its associated Vertical Figure Of Merit (VFOM) and Receiver Autonomous Integrity Monitoring (RAIM) failure indication, standard (uncorrected) altitude, Radio Altitude, Ground Speed, Roll Angle, and aircraft position (Latitude and Longitude). Additionally, corrected Barometric Altitude, Static Air Temperature (SAT), GPS mode, and the number of satellites tracked are used if available.
  • The Geometric Altitude is computed by blending a calculated Non-Standard Altitude, Runway Calibrated Altitude (determined during takeoff), GPS Calibrated Altitude, Radio Altitude Calibrated Altitude (determined during approach), and Altitude Barometric Altitude (if available). Estimates of the VFOM for continued each of these are determined and applied in order to determine its weight in the final altitude. The blending algorithm gives the most weight to altitudes with a higher estimated accuracy, reducing the effect of less accurate altitudes. Each component altitude is also checked for reasonableness using a window monitor computed from GPS Altitude and its VFOM. Altitudes that are invalid, not available, or fall outside the reasonableness window are not included in the final Geometric Altitude value.
  • The Geometric Altitude algorithm is designed to allow continued operation when one or more of the altitude components are not available. If all component altitudes are invalid or unreasonable, the GPS Altitude is used directly. If GPS Altitude fails or is not present, then the EGPWS reverts to using Corrected Barometric Altitude alone.
  • The Geometric Altitude function is fully automatic and requires no pilot action.
G450 Specifics

[G450 Aircraft Operating Manual, §2B-20-40, ¶1.] Geometric altitude is a computed aircraft altitude designed to help ensure optimal operation of the EGPWM terrain awareness and display functions through all phases of flight and atmospheric conditions. Geometric altitude uses an improved pressure altitude calculation, GPS altitude, radio altitude, and terrain and runway elevation data to reduce or eliminate errors potentially induced in corrected barometric altitude by temperature extremes, non-standard altitude conditions, and altimeter miss-sets. Geometric altitude also permits continuous EGPWM operations in QFE environments without custom inputs or special operational procedures.

TCAS Interface

[Honeywell EGPWS Pilot Guide, §2, page 36] Audio outputs are provided as specific alert phrases, and altitude callouts or tones provided by an EGPWS speaker and via the cockpit Interphone system for headset usage. Several audio output levels are available. They are established during the installation of the EGPWS. These EGPWS audio outputs can be inhibited by other systems having higher priority (i.e., windshear) or cockpit switches in some cases. The EGPWS also has the ability to inhibit other system audio outputs such as TCAS.

G450 Specifics

[G450 Aircraft Operating Manual, §2A-34-50 ¶2.B.] When any EGPWS alerts are in progress, all TCAS messages are inhibited.

Terrain Clearance Floor

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Figure: Terrain clearance floor alert envelope, from Honeywell EGPWS Pilot Guide, §2, page 25.

[Honeywell EGPWS Pilot Guide, §2, page 25] The Terrain Clearance Floor (TCF) function (enabled with TAD) 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 (all runways greater than 3500 feet in length). The TCF envelope is defined for all runways as illustrated below and extends to infinity, or until it meets the envelope of another runway. The envelope bias factor is typically 1/2 to 2 nm and varies as a function of position accuracy.

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Figure: Improved terrain clearance floor alert envelope plan view, from Honeywell EGPWS Pilot Guide, §2, page 26.

[Honeywell EGPWS Pilot Guide, §2, page 26] In -210-210 and later versions, the TCF alert envelope and Envelope Bias Factor are improved. The alert envelope is limited to a minimum of 245 feet AGL adjacent to the runway as illustrated in the following diagrams. The Envelope Bias Factor is reduced (moved closer to the runway) when higher accuracy aircraft position and runway position information is available. This is typically 1/3 to 1 nm providing greater protection against landing short events. With version -218-218 and later models, the envelope bias factor is reduced to 1/4 nm if runway and position data is of high integrity.

G450 Specifics

[G450 Aircraft Operating Manual, § 2A-34-50 ¶2.A.] The TCF alert function adds an additional element of protection to the standard GPWS by alerting the flight crew of possible premature descent during non-precision approaches regardless of airplane configuration. It creates a terrain clearance envelope around the airport to provide protection against CFIT situations beyond that of basic GPWS. TCF alerts are based on current airplane location, nearest runway center point position and radio altitude. TCF is active during takeoff, cruise and final approach. When landing at an airport with no approved approach procedure, or where the longest runway is less than 3500 ft in length, or the airport is not included in the Jeppesen database, EGPWS may generate a Terrain Alert and the Terrain Awareness Display (TAD). At these airports the TERRAIN INHIBIT switch, located on the Standby Rudder/Yaw Damper panel, can be selected ON at the discretion of the flight crew to avoid nuisance alerts.

The EGPWS database is updated periodically on the red update disk. While you may not find yourself landing on a runway less than 3,500' the terrain or even the runway may have changed. (That happened to us landing in LGAV. The Athens airport moved several miles when they closed the older and opened the newer between two hills. The database was not aware the Greeks had bulldozed the hills.)

Runway Clearance Floor

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Figure: Runway clearance floor alert envelope, from Honeywell EGPWS Pilot Guide, §2, page 27.

[Honeywell EGPWS Pilot Guide, §2, page 27]

  • In -210-210 and later versions, a Runway Field Clearance Floor feature is included. This is similar to the TCF feature except that RFCF is based on the current aircraft position and height above the destination runway, using Geometric Altitude (in lieu of Radio Altitude). This provides improved protection at locations where the runway is significantly higher than the surrounding terrain [as illustrated]. With version -218-218 and later models, the RFCF envelope is moved from 1nm to 1/2nm if runway and position data is of high integrity.
  • TCF and RFCF 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.

Terrain Alerting

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Figure: Terrain look ahead alerting, from Honeywell EGPWS Pilot Guide, §2, page 28.

[Honeywell EGPWS Pilot Guide, §2, page 28]

  • 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 (when enabled) 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 continued warning alerts are generated if terrain or an obstacle conflict with "ribbons" projected forward of the aircraft (see following illustration). These ribbons project down, forward, then up from the aircraft with a width starting at 1/4 nm and extending out at ±3° laterally, more if turning. The look-down and up angles are a function of the aircraft flight path angle, and the look-down distance a function of the aircraft's altitude with respect to the nearest or destination runway. This relationship prevents undesired alerts when taking off or landing. The look-ahead distance is a function of the aircraft's speed, and distance to the nearest runway.
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[Honeywell EGPWS Pilot Guide, §2, page 29]

  • When a compatible Weather Radar, EFIS, or other display is available and enabled, the EGPWS Terrain Alerting and Display (TAD) feature provides an image of the surrounding terrain represented in various colors and intensities.
  • There are two types of TAD displays depending on the options selected. The original type provides a terrain image only when the aircraft is 2000 feet or less above the terrain. A second type called "Peaks" enhances the display characteristics to provide a higher degree of terrain awareness independent of the aircraft's altitude (available for selected display types in version -206-206 with additional displays added in later versions). In either case, terrain and obstacles (if enabled) forward of the aircraft are displayed. Obstacles are presented on the cockpit display as terrain, employing the same display-coloring scheme. TAD, Peaks and Obstacle functions are enabled by EGPWS program pin selection.
  • 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). With version -218-218 or later, the transition to black may occur below 400 feet based on runway and terrain database integrity for a given area.
  • The transition between green and yellow is below the aircraft in order to account for altimetry and/or terrain/obstacle height errors. Also, the transition altitudes between colors are biased upward proportional to the descent rate when greater than 1000 feet per minute. This provides approximately a 30 second advance display of terrain.
  • Essentially, pilots should note that any yellow or red painted terrain is at, or above the aircraft's altitude and appropriate terrain clearance needs to be provided.
G450 Specifics
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Figure: G450 Terrain clearance floor, from G450 Aircraft Operating Manual, §2B-20-110, figure 30.

[G450 Aircraft Operating Manual, § 2A-34-50 ¶2.B.] Terrain alerting predicts potential conflicts between the airplane flight path and the surrounding terrain and provides the flight crew with visual and aural alerts. To compute terrain awareness, the EGPWS software uses airplane geographic position, airplane altitude, and a terrain database to determine the relative position of the airplane in relation to the surrounding terrain, generating a clearance envelope as far as one minute ahead of the airplane. At the onset of a terrain caution, (approximately 60 seconds prior to potential terrain conflict), the terrain alerting function causes an amber TERRAIN icon to be displayed on the PFD and annunciates an aural“ TERRAIN, TERRAIN” callout. This is repeated every seven seconds as long as the airplane is within the caution envelope. At the onset of a terrain warning, (approximately 30 seconds prior to potential terrain conflict), the terrain alerting function causes red TERRAIN and PULL UP icons to be displayed on the PFD, a TAD on the HSI and annunciates aural “TERRAIN, TERRAIN” and “PULL UP, PULL UP” Callouts. The aural callout is repeated continuously while the airplane is within the warning envelope.

EGPWS Modes

Mode 1 - Excessive Descent Rate
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Figure: EGPWS Mode 1, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.A.]

[Honeywell EGPWS Pilot Guide, §2, page 8]

  • Mode 1 provides alerts for excessive descent rates with respect to altitude AGL and is active for all phases of flight. This mode has inner and outer alert boundaries as illustrated in [the diagram].
  • Penetration of the outer boundary activates the EGPWS caution lights and "SINKRATE, SINKRATE" alert enunciation. Additional "SINKRATE, SINKRATE " messages will occur for each 20% degradation in altitude.
  • Penetration of the inner boundary activates the EGPWS warning lights and changes the audio message to "PULL UP" which repeats continuously until the inner warning boundary is exited.
  • Note: "Pull Up" may be preceded by "Whoop, Whoop" in some configurations based on the audio menu option selected.

  • If a valid ILS Glideslope front course is received and the aircraft is above the glideslope centerline, the outer (sink rate) boundary is adjusted to desensitize the sink rate alerting. This is to prevent unwanted alerts when the aircraft is safely capturing the glideslope (or repositioning to the centerline) from above the beam.
  • If the Aural Declutter feature is disabled, the sink rate alert boundary remains fixed and the aural message "SINKRATE" repeats continuously until the outer boundary is exited.
  • The EGPWS offers a Steep Approach option for given aircraft types (typically bizjets) that desensitizes the alert boundaries to permit steeper than normal approaches without unwanted alerts.
EGPWS Mode 2A - Excessive Closure to Terrain
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Figure: EGPWS Mode 2A, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.B.]

[Honeywell EGPWS Pilot Guide, §2, page 9]

  • Mode 2 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 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.
  • Note: "Pull Up" may be preceded by "Whoop, Whoop" in some configurations based on the audio menu option selected.

  • Upon exiting the warning envelope, if terrain clearance continues to decrease, the aural message "TERRAIN" will be given until the terrain clearance stops decreasing. In addition, the visual alert will remain on until the aircraft has gained 300 feet of barometric altitude, 45 seconds has elapsed, or landing flaps or the flap override switch is activated.
  • With version -210-210 and later models, the Mode 2A upper limit is reduced to 1250 feet (950 feet with version -218- 218 and later) for all airspeeds when the Terrain Alerting and Display (TAD) function is enabled and available. This is due to the enhanced alerting capability provided with TAD, resulting from high integrity GPS Altitude and Geometric Altitude data. The Mode 2A envelope is lowered in order to reduce the potential for nuisance alerts during an approach.
EGPWS Mode 2B - Excessive Closure to Terrain
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Figure: EGPWS Mode 2B, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.B.]

[Honeywell EGPWS Pilot Guide, §2, page 11]

  • Mode 2B provides a desensitized alerting envelope to permit normal landing approach maneuvers close to terrain without unwanted alerts. Mode 2B is automatically selected with flaps in the landing configuration (landing flaps or flap over-ride selected) or when making an ILS approach with Glideslope and Localizer deviation less than 2 dots. It is also active during the first 60 seconds after takeoff.
  • With version -210-210 and later models, Mode 2B is selected when the aircraft is within 5nm (10nm with version -218- 218 and later) and 3500 feet of the destination airport (independent of configuration) and the Terrain Alerting and Display (TAD) function is enabled and available. This is due to the enhanced alerting capability provided with TAD, resulting from high integrity GPS Altitude and Geometric Altitude data. The Mode 2B envelope is selected in order to reduce the potential for nuisance alerts during an approach.
  • During an approach, if the aircraft penetrates the Mode 2B envelope with either the gear or flaps not in the landing configuration, the aural message "TERRAIN, TERRAIN" is generated and the EGPWS caution lights illuminate. If the aircraft continues to penetrate the envelope, the EGPWS warning lights illuminate and the aural message "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 the landing configuration, the aural "PULL UP" messages are suppressed and the aural message "TERRAIN" is repeated until the envelope is exited.
EGPWS Mode 3 - Altitude Loss After Takeoff
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Figure: EGPWS Mode 3, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.C.]

[Honeywell EGPWS Pilot Guide, §2, page 12]

  • Mode 3 provides alerts for significant altitude loss after takeoff or low altitude go-around (less than 245 feet AGL or 150 feet, depending on aircraft type) with gear or flaps not in the landing configuration. The amount of altitude loss that is permitted before an alert is given is a function of the height of the aircraft above the terrain as shown below. This protection is available until the EGPWS determines that the aircraft has gained sufficient altitude that it is no longer in the takeoff phase of flight. Significant altitude loss after takeoff or during a low altitude go-around activates the EGPWS caution lights and the aural message "DON'T SINK, DON'T SINK". The aural message is enunciated twice for each 20% degradation in altitude. Upon establishing a positive rate of climb, the EGPWS caution lights extinguish and the aural alert will cease.
  • If the Aural Declutter feature is disabled, the warning is enunciated continuously until positive climb is established.
EGPWS Mode 4A - Unsafe Terrain Clearance
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Figure: EGPWS Mode 4A, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.D.]

[Honeywell EGPWS Pilot Guide, §2, page 13]

  • Mode 4 provides alerts for insufficient terrain clearance with respect to phase of flight, configuration, and speed. Mode 4 exists in three forms, 4A, 4B, and 4C.
    • Mode 4A is active during cruise and approach with the gear and flaps not in the landing configuration.
    • Mode 4B is active during cruise and approach with the gear in the landing configuration and flaps not in the landing configuration.
    • Mode 4C is active during the takeoff phase of flight with either the gear or flaps not in the landing configuration.
  • Mode 4 alerts activate the EGPWS caution lights and aural messages.
  • To reduce nuisance alerts caused by over-flying another aircraft, the upper limit of the Mode 4A/B alerting curve can be reduced (from 1000) to 800 feet. This occurs if the airplane is above 250 knots with gear and flaps not in landing configuration and a sudden change in Radio Altitude is detected. This is intended to eliminate nuisance alerts while flying a holding pattern and an aircraft over-flight occurs (with 1000 foot separation).
  • With version -210-210 and later models, Mode 4 airspeed expansion is disabled (upper limit held at lowest airspeed limit) when the Terrain Alerting and Display (TAD) function is enabled and available. This is due to the enhanced alerting capability provided with TAD, resulting from high integrity GPS Altitude and Geometric Altitude data. This change to the Mode 4 envelopes reduces the potential for nuisance alerts when the aircraft is not in the landing configuration.
  • 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. It also provides alerting for protection against an unintentional gear-up landing.
  • Below 1000 feet AGL and above 190 knots airspeed, the Mode 4A aural alert is "TOO LOW TERRAIN". This alert is dependent on aircraft speed such that the alert threshold is ramped between 500 feet at 190 knots to 1000 feet at 250 knots.
  • Below 500 feet AGL and less than 190 knots airspeed, the Mode 4A aural alert is "TOO LOW GEAR".
  • 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 Declutter feature is disabled, mode 4A alert messages are repeated continuously until the Mode 4A envelope is exited.
EGPWS Mode 4B - Unsafe Terrain Clearance
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Figure: EGPWS Mode 4B, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.D.]

[Honeywell EGPWS Pilot Guide, §2, page 14]

  • Mode 4B is active during cruise and approach, with gear down and flaps not in the landing configuration.
  • Below 1000 feet AGL and above 159 knots airspeed, the Mode 4B aural alert is "TOO LOW TERRAIN". This alert is dependent on aircraft speed such that the alert threshold is ramped between 245 feet at 159 knots to 1000 feet at 250 knots.
  • Below 245 feet AGL and less than 159 knots airspeed, the Mode 4B aural alert is "TOO LOW FLAPS". For turboprop and select turbofan aircraft, the "TOO LOW FLAPS" warning curve is lowered to 150 feet AGL and less than 148 knots.
  • If desired, the pilot may disable the "TOO LOW FLAPS" alert by engaging the Flap Override switch (if installed). This precludes or silences the Mode 4B flap alert until reset by the pilot.
  • If the aircraft's Radio Altitude decreases to the value of the MTC, the EGPWS caution illuminates and the aural message "TOO LOW TERRAIN" is enunciated.
  • For either Mode 4B alert, subsequent alert messages occur for each 20% degradation in altitude. EGPWS caution lights extinguish and aural messages cease when the Mode 4B alert envelope is exited.
  • If the Aural Declutter feature is disabled, mode 4B alert messages are repeated continuously until the Mode 4B envelope is exited.
EGPWS Mode 4C - Unsafe Terrain Clearance
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Figure: EGPWS Mode 4C, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.D.]

[Honeywell EGPWS Pilot Guide, §2, page 15]

  • The 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.
  • Mode 4C is based on an EGPWS computed Minimum Terrain Clearance (MTC) floor, that increases with Radio Altitude. It is active after takeoff when the gear or flaps are not in the landing configuration. It is also active during a low altitude go-around if the aircraft has descended below 245 feet AGL (or 150 feet depending on aircraft type).
  • At takeoff the Minimum Terrain Clearance (MTC) is zero feet. As the aircraft ascends the MTC is increased to 75% of the aircraft's Radio Altitude (averaged over the previous 15 seconds). This value is not allowed to decrease and is limited to 500 feet AGL for airspeed less than 190 knots. Beginning at 190 knots, the MTC increases linearly to the limit of 1000 feet at 250 knots.
  • If the aircraft's Radio Altitude decreases to the value of the MTC, the EGPWS caution illuminates and the aural message "TOO LOW TERRAIN" is enunciated.
  • EGPWS caution lights extinguish and aural messages cease when the Mode 4C alert envelope is exited.
  • If the Aural Declutter feature is disabled, mode 4C alert messages are repeated continuously until the Mode 4C envelope is exited.
EGPWS Mode 5 - Excessive Glide Slope Deviation
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Figure: EGPWS Mode 5, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.E.]

[Honeywell EGPWS Pilot Guide, §2, page 17]

  • Mode 5 provides two levels of alerting for when the aircraft descends below glideslope, resulting in activation of EGPWS caution lights and aural messages.
  • The first level alert occurs when below 1000 feet Radio Altitude and the aircraft is 1.3 dots or greater below the beam. This turns on the caution lights and is called a "soft" alert because the audio message "GLIDESLOPE" is enunciated at half volume. 20% increases in the below glideslope deviation cause additional "GLIDESLOPE" messages enunciated at a progressively faster rate.
  • The second level alert occurs when below 300 feet Radio Altitude with 2 dots or greater glideslope deviation. This is called a "hard" alert because a louder "GLIDESLOPE, GLIDESLOPE" message is enunciated every 3 seconds continuing until the "hard" envelope is exited. The caution lights remain on until a glideslope deviation less than 1.3 dots is achieved.
  • To avoid unwanted Below Glideslope alerts when capturing the localizer between 500 and 1000 feet AGL, alerting is varied in the following ways:
    • Below Glideslope alerts are enabled only if the localizer is within 2 dots, landing gear and flaps are selected, Glideslope Cancel is not active, and a front course approach is determined.
    • The upper altitude limit for the alert is modulated with vertical speed. For descent rates above 500 FPM, the upper limit is set to the normal 1000 feet AGL. For descent rates lower than 500 FPM, the upper limit is desensitized (reduced) to a minimum of 500 feet AGL.
  • Additionally, both alert levels are desensitized below 150 feet AGL, to allow for normal beam variations nearer the ground, and reduce the possibility of nuisance alerts.
  • If the Aural Declutter feature is disabled, messages are repeated continuously until the Mode 5 envelope is exited.
  • Mode 5 alerts can be canceled by pressing the Glideslope Cancel switch (if installed). The EGPWS will interpret this switch one of two ways depending on the installation configuration.
    • A standard glideslope cancel switch allows for manually canceling Mode 5 alerting any time below 2000 feet AGL. This is automatically reset when the aircraft descends below 30 feet or climbs above 2000 feet AGL (1000 feet AGL for current Boeing production aircraft).
    • An alternate glideslope cancel switch allows for manually canceling Mode 5 alerting at any time and any altitude. The cancel is reset by again pressing the cancel switch, or automatically if gear or flaps are raised, or the aircraft is on the ground. Due to the nature of the alternate cancel switch, this method requires that there be a cockpit annunciation that glideslope cancel is in effect (this con- figuration is currently not allowed on aircraft operating under FAA part 121 rules).
  • EGPWS Mode 5 alerts are inhibited during back course approaches to prevent nuisance alerts due to false fly up lobes from the Glideslope. The EGPWC determines a back course approach if either: 1) the aircraft's magnetic track is greater than 90 degrees from the runways approach course, or 2) a glideslope inhibit discrete is set.
EGPWS Mode 6 - Advisory Callouts.
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Figure: EGPWS Mode 6, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.F.]

[Honeywell EGPWS Pilot Guide, §2, page 19]

  • Mode 6 provides EGPWS advisory callouts based on the menu-selected option established at installation (set by program pin configuration). These callouts consist of predefined Radio Altitude based voice callouts or tones and an excessive bank angle warning. There is no visual alerting provided with these callouts.
  • The following is a list of each of the possible altitude callouts or tones:
  • images
  • In some cases a callout is stated twice (e.g., "MINIMUMS, MINIMUMS") but in all cases a given callout is only enunciated once per approach.
  • Decision Height (DH) based callouts (Approaching Mini- mums, Minimums, etc.) require the landing gear to be down and occur when descending through the Radio Altitude corresponding to the selected DH. These also have priority over other altitude callouts when overlapping. For example, if DH is set to 200 and both "TWO HUNDRED" and "MINI- MUMS" are valid callouts, then only "MINIMUMS" will be called out at 200 feet AGL.
  • DH plus based callouts (e.g., Approaching Minimums) are only applicable for aircraft providing a Decision Height altitude to the EGPWS. Consequently, not all EGPWS installations can utilize these callout options.
  • Due to the variety of altitude callout choices available, it is not possible to identify every combination in this guide. Refer to an appropriate Airplane Flight Manual or EGPWS Airplane Flight Manual Supplement for callout identification in a specific application or contact Honeywell.
  • Another feature available in the Altitude Callouts (options) is a "Smart 500" foot callout. When selected, this callout assists pilots during a non-precision approach by enunciating "FIVE HUNDRED" feet in addition to any other altitude callout discussed above. The EGPWS determines a non-precision approach when Glideslope is greater than 2 dots deviation (valid or not) or a back-course approach is detected. This feature has the distinction of adding the 500-foot callout during non-precision approaches and removing the 500-foot callout on precision approaches when part of the callout option.
  • 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).
EGPWS Mode 7 - Severe Windshear
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Figure: EGPWS Mode 7, from G450 Aircraft Operating Manual, § 2A-34-50 ¶3.G.]

[Honeywell EGPWS Pilot Guide, §2, page 23]

  • Mode 7 is designed to provide alerts if the aircraft encounters windshear. 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).
  • Windshear Caution alerts are given if an increasing headwind Caution (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. The Windshear Caution envelope is illustrated in the figure below.
  • 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). The Windshear Warning envelope is illustrated in the figure shown on page 23.
  • 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.

Test Procedure

There is a lot of misinformation out there about the Honeywell EGPWS and no wonder, they do a lousy job of documenting their products. The newest available manual was written in 2003, though there is another that simply has a stamp "2011" with little or no updated content. The Honeywell EGPWS and RAAS Pilot Guide says there are 6 levels of test but only gives details for Level 1 and says "contact Honeywell" for the rest. Lots of luck doing that!

Looking at the G450 AOM you get a description of a Level 1 test, but nothing else. The way it is written leads you to believe that is the only level of test in this system.

[G450 AOM, §2B-20-140; ¶3]

In addition to power-up and continuous BIT, user activated tests, by discrete test switches, and/or maintenance system commands are supported.

The EGPWS provides a self--test capability for verifying and indicating intended functions. The self-test capability consists of one level to aid in testing and troubleshooting the EGPWS. This level is:

Level 1 - Go/No Go Test provides an overview of the current operational functions and an indication of their status.

For this sequence, when the test switch is activated, the cockpit visuals are activated and voices are issued to indicatewhat functions are correctly operating. For example, if no faults exist on an installation that uses the terrain awareness function in addition to basic GPWS and windshear, then the result of the self--test would typically be:

“Glideslope--Pull Up--Windshear Windshear Windshear--Terrain Terrain, Pull Up”

However, if no valid glideslope input was present then the sequence would be:

“Glideslope INOP--Pull Up--Windshear Windshear Windshear--Terrain Terrain, Pull Up”

The following phrases are used to report system status during the system self-test:

  • GPWS INOP
  • GLIDESLOPE INOP
  • WINDSHEAR INOP
  • TERRAIN INOP
  • BANK ANGLE INOP
  • CALLOUTS INOP
  • GPWS INHIBITED
  • TERRAIN INHIBITED
  • SELF-TEST INHIBITED.

During system self-test, all INOP annunciators are activated and TERR TEST in shown on the INAV.

Level 1 self-test is used to verify proper operation of the EGPWS on the ground as follows:

  1. Ensure that adequate aircraft power is available and the EGPWS and associated systems are powered.
  2. Ensure that any EGPWS inhibiting switches are in the normal (non--inhibiting) position.
  3. Verify that EGPWS inoperative annunciators are out. If an inoperative annunciation is indicated, perform the EGPWS self--test (below) and then seek corrective action if the inoperative condition persists.
  4. If a terrain display is enabled, select terrain to be displayed.
  5. Momentarily push the EGPWS self-test switch.
  6. When a self-test is initiated, the EGPWM first checks for any configuration (installation or database) errors. If any are detected it is audibly enunciated and the test is terminated. If no errors are detected, the test continues through a sequence resulting in turning on and off all system annunciators, and enunciating specific audio messages. Any functions determined inoperative are also enunciated (e.g., GLIDESLOPE INOP). The self-test terminates automatically at its conclusion.

    The following is the self-test sequence:

    • The white TERR TEST message is displayed on INAV.
    • The blue GPWS 1--2 FAIL message is displayed on the CAS.
    • The blue WINDSHEAR 1--2 FAIL message is displayed on the CAS.
    • The blue EGPWM SYS 1--2 FAIL message is displayed on the CAS.
    • All fail messages are turned off.
    • The amber GND PROX message is displayed on the PFDs.
    • The aural “GLIDESLOPE” message is enunciated.
    • The amber GND PROX display message turns off.
    • The red PULL UP message is displayed on the PFDs.
    • An aural “PULL UP” message is enunciated.
    • The red PULL UP display message turns off.
    • The red WINDSHEAR message is displayed on the PFDs.
    • The aural “WINDSHEAR, WINDSHEAR, WINDSHEAR” message is enunciated.
    • The red WINDSHEAR message is turned off.
    • The amber WINDSHEAR message is displayed momentarily on the PFDs.
    • The red PULL UP message is displayed on the PFDs,
    • INAV is displayed to the 5NM range ring.
    • An aural “TERRAIN, TERRAIN, PULL UP” message in enunciated.
    • The red PULL UP display message turns off.
    • The amber GND PROX message is displayed on the PFDs
    • The aural RUNWAY AWARENESS OK message is annunciated in one of thefollowing methods based on APM selection:
      • RUNWAY AWARENESS OK, feet (female voice)
      • RUNWAY AWARENESS OK, feet (male voice)
      • RUNWAY AWARENESS OK, meter (female voice)
      • RUNWAY AWARENESS OK, meter (male voice).
  7. Verify expected indications and enunciations during test, repeating as necessary noting any erroneous conditions.

A successful test is accomplished if all expected indications are observed and no inoperative functions or display anomalies are indicated or observed.

So why are those other modes missing? Reading further we see this:

[G450 AOM, §2B-20-140; ¶5] Maintenance Interface with the CMC

  • The EGPWM maintenance philosophy is to provide information that encourages the line mechanic to correct the real problem (analyze the correct LRU/LRM) by indicating whether the failure is within the EGPWM or one of the input sources. The EGPWM provides extremely clear (not necessarily detailed) fault messages and gives them with minimum effort on the part of the maintenance crew.
  • The EGPWM supports an interface to the central maintenance computer. The CMC is used by maintenance personnel to examine the status of the various LRUs and modules onboard the aircraft in order to facilitate correction of failures.

The G450 Maintenance Manual contains a brief procedure that is nothing more than the pilot's Level 1 test. But if you drill down through the CMC, you can find a diagnostic. Here are screen shots from just that:

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Phot: CMC Main Menu, from Eddie's aircraft.

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Phot: CMC System Diagnostics Menu, from Eddie's aircraft.

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Phot: CMC System Diagnostic Menu / 34 Navigation, from Eddie's aircraft.

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Phot: CMC 34 Navigation / 46 Enhanced Ground Prox Warning 1, from Eddie's aircraft.

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Phot: CMC Data: EGPWM 1 AC Config APM Options, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 1/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 2/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 3/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 4/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 5/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 6/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 7/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 8/9, from Eddie's aircraft.

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Phot: CMC EGPWM1 AC Config Options 9/9, from Eddie's aircraft.

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Phot: CMC DATA EGPWM2 Cockpit Selections, from Eddie's aircraft.

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Phot: CMC EGPWM1 Cockpit Selections, from Eddie's aircraft.

If anyone can offer a better explanation for the EGPWS test procedure, please "Contact Eddie" below. If anyone from Honeywell can offer an up-to-date manual, please "Contact Eddie" below. (He is willing to pay for it. He is still a bit sore about spending $500 for the Honeywell manuals he has, but he gets over things quickly.)

See Also:

Traffic and Collision Avoidance System (TCAS)

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I first discovered TCAS when I was at the Pentagon as a budget programmer for airlift aircraft. I found the money to install it on several of the aircraft in my program. As a lieutenant colonel program element monitor I was two levels removed from the head officer for all Air Force budget matters, a lieutenant general. He argued that the best collision avoidance system was the pilot's eyes. Of course he won the argument. Three years later the Air Force lost C-141 65-9405 off the coast of Namibia by a German aircraft flying at the wrong altitude. Now TCAS is mandatory when flying internationally.

[G450 AOM, §2A-34-60] The Honeywell Traffic and Collision Avoidance System (TCAS-2000) is production installed on the G450 airplane. TCAS provides the flight crew with notifications of the presence of other transponder equipped traffic in the vicinity that may present a collision hazard. TCAS can track up to fifty (50) airplanes simultaneously, however the display can accommodate only thirty-two (32) traffic symbols. The system provides aural alerts to the presence of traffic, visual plots of the relative location of other airplanes on cockpit displays, and aural and visual cues for evasive maneuvers if collision is imminent. If both converging airplanes are equipped with TCAS and Mode S transponders, the systems mutually coordinate evasive maneuvers to ensure diverging flight paths.

TCAS can exchange data with other airplanes having Mode S transponders at a range of forty nautical miles (40 NM) and can detect (but not communicate with) Mode S equipped targets up to one hundred twenty miles (120 NM). For targets with Mode A or Mode C transponders, the range is twenty nautical miles (20 NM).

Antennas:

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Symbology:

TCAS symbology is the same on both the HSI, 1/6 window and MAP display. Traffic is represented in different icon shapes and colors corresponding to the potential threat of collision:

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Control:

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Relative Altitude Limits:

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Do you have to have it?

MEL Says No...

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ICAO Says Yes. [ICAO Annex 6, §6.18.]

6.18.1 From 1 January 2003, all turbine-engined aeroplanes of a maximum certificated take-off mass in excess of 15 000 kg or authorized to carry more than 30 passengers shall be equipped with an airborne collision avoidance system (ACAS II).

6.18.2 From 1 January 2005, all turbine-engined aeroplanes of a maximum certificated take-off mass in excess of 5 700 kg or authorized to carry more than 19 passengers shall be equipped with an airborne collision avoidance system (ACAS II).

6.18.3 Recommendation.— All aeroplanes should be equipped with an airborne collision avoidance system (ACAS II). 6.18.4 An airborne collision avoidance system shall operate in accordance with the relevant provisions of Annex 10, Volume IV.

Enhanced Vision System (EVS) II

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FLIR vs EVS vs EFVS, from Eddie's notes.

An "Enhanced Vision System" (EVS), an "Enhanced Flight Vision System" (EFVS), and a "Forward Looking Infrared Receiver" (FLIR) might refer to the same thing or maybe completely different, depending on what you are reading. The distinction can be important:

  • The FAA thinks of EFVS as the infrared system viewed through a HUD while an EVS is viewed through a PFD. An EFVS can be used, under some conditions, to fly below published minimums. An EVS cannot.
  • The European Union uses EVS to refer to what our FAA calls EFVS. ([EU Ops 1, Subpart E, Section OPS 1.430, Appendix 1, ¶(h)])
  • Gulfstream calls its EFVS an EVS, while the FLIR is simply the camera. When reading a Gulfstream manual, EVS is EFVS.

Whatever you call it, EFVS (EVS in the G450) can lower your approach minimums under some circumstances, see Enhanced Flight Vision Systems for more on this.

Here's a video of the EVS in action: It's Magic.

[G450 Aircraft Operating Manual §2A-34-90 ¶1.]

  • The Enhanced Vision System (EVS) increases the ability of the pilot to see the external environment during periods of low light or reduced visibility by converting infrared radiation frequencies into visible imagery viewed on the Head Up Display (HUD). While normal human sight is limited to the 400 - 800 nanometer frequencies, the Forward Looking Infrared Receiver (FLIR) camera in the EVS detects frequencies down to the 1,300 - 4,900 nanometer range. The composite display imagery of flight guidance cues and infrared heat sources is particularly effective in low visibility approaches since the frequency range of the EVS encompasses the heat given off by runway and taxiway lighting and the higher temperature levels of the paved surfaces warmed by airplane ground operations. The EVS incorporates selective filtration to attenuate or lessen the heat bloom from runway lights and sequenced flashers, providing a more refined view of the airport environment.
  • The infrared camera field of view is thirty degrees (30°) horizontally and twenty degrees (20°) vertically. Imagery captured by the camera is routed through a processor that converts the infrared picture to a raster format and communicates the formatted data to the HUD overhead unit. The overhead unit synchronizes the data with the navigational and situational symbology presented on the HUD combiner to display a congruent image with an extended visual range. The composite display imagery of flight guidance cues and infrared heat sources is particularly effective in low visibility approaches since the frequency range of the EVS encompasses the heat given off by runway and taxiway lighting and the higher temperature levels of the paved surfaces warmed by airplane ground operations. The EVS incorporates selective filtration to attenuate or lessen the heat bloom from runway lights and sequenced flashers, providing a more refined view of the airport environment.

Infrared Camera (FLIR)

[G450 Aircraft Operating Manual §2A-34-90 ¶2.B]

  • The infrared camera is mounted in the nose of the airplane behind the EVS window. The installation of the camera requires careful alignment with transits and levels to focus the camera in the same line of sight as the Head Up Display (HUD) in order that the infrared image will conform to the data displayed on the HUD combiner. The camera assembly incorporates a series of lenses to focus the infrared energy received through the window onto a sensor plate. The sensor plate is composed an array of pixels arranged in a 320 X 240 format. The individual pixels are 30,000 nanometers square and detect infrared radiation. The patterns of infrared detected by the pixels are amplified and converted into electrical signals that forwarded to the system processor where they are formatted into raster images.
  • The camera is enclosed within a casing that is temperature controlled by a cooling unit. The actual camera operating temperature is seventy-seven degrees Kelvin (77°K) or minus three hundred twenty-one degrees Fahrenheit (-321°F) / minus one hundred ninety-six degrees centigrade (-196°C). When the EVS system is initially selected ON, a time delay of approximately thirty (30) minutes is required for the cooling unit to reduce the temperature within the camera enclosure to operating range.
  • The exterior of the camera enclosure, window hardware and processor also require cooling airflow to ensure proper operation. A duct routing conditioned air to the components provides an air supply at lower airplane operating altitudes. The valve, located in the lower cockpit supply duct, closes at eighteen thousand feet (18,000 ft) since temperatures at that flight level are low enough for ambient cooling and the EVS is not normally required above that altitude. The air supply valve is controlled by the same relay that extinguishes the landing lights.

Display Controller Menu

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Figure: G450 Display Controller HUD Menu, from Eddie's aircraft.

The Display Controller HUD menu controls both the HUD and the Enhanced Vision System (EVS). The HUD options are discussed here: G450 Systems / Heads Up Display System / Display Controller Menu. The EVS options are as follows:

[G450 Aircraft Operating Manual, §2A-34-100, figure 31.] EVS SELECTIONS ON HUD MENU:

  • NUC (Non-Uniformity Correction): Selects NUC ON and OFF. Default is OFF.
  • FLIR: Selects FLIR camera ON and OFF. Selecting FLIR camera OFF also selects EVS OFF (if it is ON). It may take up to 10 minutes to appear when FLIR is selected ON.
  • EVS: Selects EVS ON and OFF. Selecting EVS ON also selects FLIR camera ON (if it is OFF).
  • AUTO / H / L: Toggles FLIR camera through AUTO, high (H) and low (L) gain settings. Default is AUTO.

The description notwithstanding, the EVS selections are actually not too difficult:

  • The system does a NUC for you at certain times but you can force it to do one anytime you like by pressing this button.
  • The FLIR is the camera alone. You can turn the FLIR on by itself with no EVS, but if you turn the FLIR off, the EVS isn't going to work so it will turn itself off.
  • The EVS is the infrared system that gets you below minimums and it can't work without the FLIR. So if you turn on the EVS and the FLIR is off, both systems come on.
  • The FLIR gain can be forced into high setting if you find the need to do so.

Non Uniformity Corrections (NUCs)

[G450 Aircraft Operating Manual §2A-34-90 ¶2.C.]

  • The [EVS processor] monitors window heat states and performance, initiates camera enclosure cooling, performs camera pixel sensitivity level tests called Non Uniformity Corrections (NUCs), and initiates a Built In Test (BIT) on command of the Monitor and Warning System (MWS) at EVS start up.
  • The processor controlled NUC tests are essential to maintaining a proper signal to noise ratio for the camera sensor plate. The tests correct the sensitivity of each pixel to a normal response value at a standard temperature. When the EVS is initially powered, the processor initiates an extended NUC that involves calibrating pixel response at two distinct temperature levels that requires four (4) minutes to complete. During an approach when flaps are extended past ten degrees (10°), the MWS prompts a shorter duration NUC at a single temperature level to prepare the EVS for use during landing. A NUC can be manually selected at any time with a Line Select Key (LSK) on the HUD page of the Display Controller.

Qualification to Lower Minimums

[FAA GIV-X/GV/GV-SP FSB report, ¶1.9.3.] From February 1998 to August 2001 the GV FSB Chairman participated with the FAA Los Angeles Aircraft Certification Office in EVS development, proof of concept, and certification flight tests. Those flights included over 50 EVS approaches conducted at approximately 15 different airports during day, night, Visual Meteorological Conditions (VMC) and Instrument Meteorological Conditions (IMC). Gulfstream’s GV EVS Airplane Flight Manual Supplement was evaluated and found acceptable during the certification flight tests. In September 2001 two GV FSB members received EVS ground school, simulator, and airplane training from Gulfstream Aerospace Corp. (GAC), in Savannah, GA. It was found to be operationally suitable. EVS meets the requirements of EFVS (Enhanced Flight Vision System) as defined in FAR 91.175.

[FAA GIV-X/GV/GV-SP FSB report, Appendix 7] EVS meets the requirements of EFVS (Enhanced Flight Vision System) as defined in FAR 91.175. Flight crewmembers may use EVS to meet the visibility requirements of Title 14 CFR Section 91.175 provided that vertical guidance with reference to an obstacle-free path is used.

The G450 EVS can be used to fly below published minimums under specific conditions. Refer to Enhanced Flight Vision System for more on this, as well as 14 CFR 91.175.

Training Requirements

[FAA GIV-X/GV/GV-SP FSB report, Appendix 7]Flight crewmember training must include a review of Title 14 CFR Section 91.175 and a review of the associated EVS AFM system description, limitations, and procedures. Flight crewmember training must be accomplished using a level 'C' simulator, with a daylight visual display, or a level 'D' simulator that has been qualified by the National Simulator Program for EVS, or the aircraft. The FSB has determined that each pilot in command of an aircraft equipped with EVS should receive a minimum of 4 hours of ground school training followed by a minimum of 2 hours of simulator training in the left seat of a level 'C', with a daylight visual display, or level 'D' simulator. An EVS equipped aircraft may also be used in lieu of a simulator for training. In-flight training should consist of a minimum of 2 hours of flying in the left seat of the EVS equipped aircraft. The flight portion of the training should consist of a minimum of two (2) day and two (2) night approaches each with vertical guidance.

Checking requires a proficiency check conducted in a level 'C' simulator, with a daylight visual display, in a level 'D' simulator, that has been qualified by the National Simulator Program for EVS, or on an EVS equipped aircraft. The proficiency check will include at least one instrument approach to published minimums and landing utilizing the EVS. This check can be accomplished concurrently with a proficiency or competency check under 61.57, 61.58, 121.441, 135.293, or 135.297. Currency: If 61.57 (c) is being used for currency, at least one of the 6 required instrument approaches must be accomplished using EVS to published minimums.

EVS Window and Heating Controls

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[G450 Aircraft Operating Manual §2A-34-90 ¶2.A.] The EVS window is manufactured from one quarter inch thick synthetically grown sapphire is highly transparent to infrared thermal frequencies, allowing 98% transmissivity to airfield and approach lighting systems. The window is mounted in an aluminum frame beneath the radome and incorporates a grid of resistive metallic elements and three thermostats. The window is heated to a temperature between 12° - 14°C to prevent the formation of ice and to ensure uniform radiation transparency.

EVS Camera

[G450 Aircraft Operating Manual §2A-34-90 ¶2.B.] The camera is enclosed within a casing that is temperature controlled by a cooling unit. The actual camera operating temperature is -321°F. When the EVS system is initially selected ON, a time delay of approximately 30 minutes is required for the cooling unit to reduce the temperature within the camera enclosure to operating range.

EVS II Power On Operation

[G450 Aircraft Operating Manual §2A-34-100 ¶2.A.] When power is applied to the EVS II system and the airplane is on the ground, a Power-up BIT (PBIT) is performed, taking 15 seconds. When power is applied in the air, the EVS II skips the Power-up BIT and completes initialization within 5 seconds. Then an automatic Built-In-Test (BIT) sequence is initiated; all system functions are checked. The BIT takes approximately 1 minute. When initially powered, the EVS II FLIR may take up to 15 minutes to cool its detector to operating temperature and activate for an initial power-on. If the EVS has been previously activated, this activation period may be shorter depending on the deviation from nominal operating conditions that has occurred since power-off. When the aircraft is parked overnight in temperatures below -40°C, the EVS II FLIR may take up to 35 minutes to heat the electronics to operating temperature and to cool the detector to operating temperature. Once the FLIR is cooled to temperature, the EVS II will perform a NUC and then enable video to be displayed on the HUD. The NUC completes its cycle within 1 minute.

EVS II Failure to Power-up

Enhanced Vision System (EVS) II have been experiencing a nuisance failure upon application of electrical power. The symptoms of the condition are the amber EVS Fail (A) and blue EVS Maintenance Required (B) Crew Alerting System (CAS) messages, accompanied by the Central Maintenance Computer (CMC) Active Maintenance Message "FLIR Rx Fiber Fault". After cycling power as described below, the system behaves normally.

  • Ensure EVS is commanded ON (not STANDBY) (Display Controller Head-Up Display [HUD] Menu) then pull Forward-Looking Infra-Red (FLIR) camera and processor Circuit Breakers (CBs) for one second (pilot's overhead CB panel).
  • Close FLIR CB then the processor CB.
  • Allow up to 15 minutes (most likely around 10 minutes) for FLIR to cool and video to be valid before selecting EVS on the HUD.

The operator may choose to view EVS temperatures on the CMC screen during the FLIR cool down to check that FLIR-to-processor communications are working. If the FLIR temperature is 127 degrees Celsius or higher, FLIR-to-processor communications are not operating properly. If valid temperatures are displayed, FLIR-to-processor communications are functioning normally.

EVS II Limitations

[G450 Aircraft Operating Manual §2A-34-100 ¶5]

  1. The HUD or HUD II section of the G450 Operating Manual must be immediately available to the flight crew whenever use of the EVS system is contemplated.
  2. At 100 feet HAT, visual cues must be seen without the aid of EVS or EVS II to continue descent to landing.
  3. EVS may be used only by qualified pilots who have been trained in accordance with requirements listed in the FAA G450 Flight Standardization Board (FSB).
  4. Flight Director or autopilot with vertical guidance is permitted for all IMC EVS approaches.
  5. EVS, as installed, meets the requirements of EFVS (Enhanced Flight Vision System) as defined in 14 CFR Part 91.175.

For more details on the requirements of 14 CFR 91.175 and the ability to continue an approach to 100 feet HAT, see Enhanced Flight Visions Systems.

References

14 CFR 91, Title 14: Aeronautics and Space, General Operating and Flight Rules, Federal Aviation Administration, Department of Transportation

European Union Regulation No 859/2008, Technical requirements and administrative procedures applicable to commercial transportation by aeroplane, 20 August 2008

Flight Standardization Board (FSB) Report, Gulfstream GIV-X, GV, GV-AP, Revision 8, 08/01/2012

Gulfstream G550 Aircraft Operating Manual, Revision 27, July 17, 2008

* Honeywell Direct-To, FMS Quarterly Update and Newsletter, December 2011

* Honeywell Enhanced Ground Proximity Warning System (EGPWS) and Runway Awareness Advisory System (RAAS) Pilot Guide, 060-4241-0000, Rev. E - December 2003, MK V & MK VII EGPWS Pilot Guide

ICAO Annex 6 - Operation of Aircraft - Part 1 Commercial Aircraft, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part I, 9th edition, July 2010

ICAO Annex 6 - Operation of Aircraft - Part 2 General Aviation, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part II, 8th edition, July 2014

ICAO Annex 6 - Operation of Aircraft - Part 3 Helicopters, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part III, 7th edition, July 2010

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—Eddie

Revision: 20150722
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