Figure: G450 HUD Symbology Overview, from Eddie's notes.

Eddie Sez:

The manuals on the G450 Heads Up Display are poorly written and missing a lot of detail. You can get by without them, I suppose, but the system is capable of much more than just what we absorb through a few days in school and from day-to-day use. I've tried to organize what does appear in print so it makes more sense, adding what we've learned along the way.

Knowing the what all those symbols are trying to tell you is an excellent first step. From there you should consider:

What follows are quotes from the references listed below, but most of this is pure technique, shown in blue.


Airport Symbol

Figure: G450 HUD Airport Symbol, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 33.] The conformal airport symbol is displayed at the end of the runway centerline when the aircraft is on an ILS or MLS approach course and 2000 ft above the airport. The display is the equivalent of an airport 800 feet across. At 2000 feet and a -3° reference FPA, the symbol is at its narrowest and at 1200 feet it widens to show the perspective of the approaching airport. It is at its widest at 325 feet AGL. Accurate placement of the airport symbol requires that FPA is set, lateral deviation is less than two dots, valid vertical deviation is less than three dots, AUTO is selected on the display controller HUD menu page, NAV source is LOC or MLS, altitude is between 325 ft and 2000 ft AGL, and the FPV is below -1° pitch. NOTE: The airport symbol is displayed correctly if the runway elevation has been entered on the display controller HUD menu. If runway elevation has not been entered, the airport display may be displayed too soon or too late, depending on the difference between the actual runway elevation and the default runway elevation that is used by the HUD software.

[G450 Aircraft Operating Manual, §2B-18-10, page 7.] The [Display Driver Unit] computes and displays synthetic airport and runway symbols using glideslope and localizer information, making the lower end of the displayed runway the touchdown zone. The airport symbol is based on an 800-foot wide airport. The runway display is based on a 150-footwide 8000-foot long runway. The pilot must set the runway threshold elevation and glideslope angle using the HUD menu on the DC to ensure accurate symbol placement. Runway heading is determined from the localizer course selected by the pilot.

[G450 Aircraft Operating Manual, §2B-18-10, page 9.] [The display controller] RW ELEV Key is used to set the runway elevation of the destination airport between --1500 and 16,000 feet. This information is used to calculate at what altitude the airport and runway symbols are displayed. If the runway elevation is not properly set, the airport and runway symbols may be incorrect (i.e., without runway elevation).

The airport symbol only appears if you have everything dialed in to fly an ILS or MLS approach and once you descend below 2,000 feet. It doesn't look like an airport, it looks like a fat runway. In fact, it turns into a runway at 350 feet above the runway. That begs the question, how do you tell them apart. Here's how:

Figure: G450 HUD Symbology Airport versus Runway Symbols, from Eddie's notes.

Reading between the lines: the airport symbol uses the localizer or MLS beam for geographical placement, the FMS for perspective, the radio altimeter for vertical placement, and the guidance panel course selection for runway heading. The airport symbol attempts to show you where the runway is, using a larger than the runway perspective, until 325' radio altimeter height, at which point it changes to the runway symbol. The touchdown zone of the runway symbol is determined by the glide slope beam.

Photo: G450 Display Controller HUD Menu - Rwy Elev, from Eddie's aircraft.

The RW ELEV entry in the display controller HUD menu should always be made using QNH altitude, even if the PFD is using QFE. This isn't written anywhere, but we've noticed that if you enter 0' when flying QFE, the airport and runway symbols will appear late by the difference between QFE and QNH.

If, for example, the runway elevation is 100' MSL for a QFE airport you would adjust your PFD altimeter to the proper QFE and it will read 0' on touchdown. If you were to set your display controller HUD RWY ELEV to 0', the airport symbol will appear at 2,000 - 100 = 1900' and the runway symbol will appear at 325' - 100' = 225'. We've tested this and one of these days we'll test an airport greater than 325' MSL to see if the runway symbol fails to appear completely.


Airspeed Dial

Figure: G450 HUD Airspeed Dial, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 19.]

  • The current IAS/Mach is displayed digitally in the center of the analog IAS/Mach dial. The dial consists of 10 unlabeled dots with a dot at the 12 o’clock position that acts as a zero point. Each dot represents 10 knots or 0.01 M, depending on the speed mode selected on the guidance panel. The pointer rotates within the dial and points to the current IAS/Mach.

  • The airspeed bug is set manually using the guidance panel or automatically through the FMS. The selected airspeed is displayed digitally above the airspeed dial. The bug is displayed on the airspeed dial when the selected airspeed is within 50 knots of actual airspeed.

  • The secondary airspeed is a digital readout of the current airspeed. If the primary dial is displaying MACH, the secondary dial is IAS. The display is a three-digit readout for IAS and, if selected, the MACH readout is a two-digit value preceded by a zero and a decimal point. If the MACH value is less than 0.40, the digits are removed.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 21.] The VSPEEDS are annunciated around the analog airspeed dial and on the speed error tape. When selected and boxed on the DC, the VSPEEDS VR, V1, V2, VFS, VSE, and VRF are indicated with an R, 1, 2, FS, SE, and RF, respectively.

If you have EVS/FLIR turned on, the dial and pointer will disappear and all you will have is the box with the numbers, the selected and secondary speeds. (Nothing in writing says this, but it is so.)


Altitude Awareness Bug

Figure: G450 HUD Altitude Awareness Bug, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 17.] The altitude awareness bug displays the difference between the selected altitude and the barometric altitude. It is displayed to the right of the FPV and it moves vertically relative to the horizon line. The bug moves vertically 1° per 100 ft. Half of the bug is displayed when the difference is greater than ±1000 ft. The bug is removed when the difference is less than ±10 feet. However, it is redisplayed when the difference reaches ±100 ft. The bug is not displayed when the FD vertical capture mode shows GS or GP.


Altitude Dial

Figure: G450 HUD Altitude Dial, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 16.] The current barometric altitude is digitally displayed in the center of the analog altitude dial. The dial consists of 10 unlabeled dots with one dot at the 12 o’clock position to indicate the zero point. Each dot represents 100 ft barometric altitude, so one full rotation of the dial indicates 1000 ft. The altitude indicator arrow rotates within the dial and indicates current barometric altitude. The selected altitude readout is displayed digitally above the dial.

If you have EVS/FLIR turned on, the dial and pointer will disappear and all you will have is the box with the numbers, and the selected altitude above. (Nothing in writing says this, but it is so.)


Boresight

Figure: G450 HUD Boresight, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶2, page 5.] Overhead Unit (OHU). The OHU is located above and slightly behind the pilot’s head. It is mounted in a one-piece tray with the combiner. The tray is boresighted to the aircraft during its initial installation.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 12.] The aircraft reference symbol serves as a stationary representation of the longitudinal axis of the aircraft.

The boresight is the nose of the airplane, it never changes. You can think of it as the pointy end of the airplane and the pointy end of the airport symbol on a conventional attitude indicator. The only time I look at the boresight is when flying a stall recovery, wind shear, or CFIT.


Conformal Lateral Deviation Indicator, Scale, Centerline

Figure: G450 HUD Conformal Lateral Deviation Indicator, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶2, page 26.] The [Conformal Lateral Deviation Scale] is described for various navigation sources in [the table below]. The centerline is the indicator of aircraft position along the lateral deviation scale.

Deviation VOR/TACAN LOC/MLS FMS 1/2/3 FMS 1/2/3 APP
2nd dot right 10° 5 NM Based on RNP
1st dot right 2.5 NM Based on RNP
Center 0 NM Based on RNP
1st dot left 2.5 NM Based on RNP
2nd dot left 10° 5 NM Based on RNP

To see a conformal lateral deviation display like this, you need to select LSK 5L AUTO from the display controller HUD menu. Once you are within 12° of course the HSI or CDI displayed (depending on LSK 4L) will switch to the conformal display.

Figure: G450 Display Controller HUD Page, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 9.] Pushing [the LSK 5L] key scrolls through AUTO, ON, and OFF. This key selects the lateral display format from one of the following HUD displays:

  • HSI
  • CDI
  • Conformal lateral deviation
  • Non-conformal deviation.

AUTO -- Selects one of three positions, and the effect of the selected position depends on whether the CDI or the HSI is selected. [The table below] describes this key selection relative to the selected display.

ON -- Selects full HSI or CDI display format depending on what was selected on LSK 4L.

OFF -- Results in a non-conformal CDI display only.

  Course Select/Desired Track Error < 12° Course Select/Desired Track Error > 12°
AUTO Conformal only Full HSI or CDI (Note 1)
ON Full HSI or CDI (Note 1) Full HSI or CDI (Note 1)
OFF Non-conformal CDI only Non-conformal CDI only
NOTES:
1. Depends on the selection made with the HSI/CDI line select key.
2. For a typical ILS approach, select AUTO and CDI. As the localizer
moves to less than 12°, the display automatically switches to the
conformal CDI display if it was not previously selected.
3. The power-up setting is the combination set when the aircraft was
last powered-down.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 8.] When the AUTO has been selected ON, pushing the CDI/HSI key toggles HUD display between the CDI display and the HSI display format.


Course Deviation Indicator, Scale, To/From

Figure: G450 HUD CDI, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶2, page 23.] The scale consists of four dots (two dots of deviation to the left and two to the right centered about the FPV). The deviation pointer indicates the amount of deviation from the selected NAV source. The arrow on the pointer indicates the selected course. The CDI rotates around the FPV based on the course selected using the CRS select knob on the guidance panel. TO is indicated by a circle near the arrow’s point. FROM is indicated by a circle near the arrow’s tail.

If you want to see a CDI like this at all times, you need to select LSK 5L ON and LSK 4L CDI from the display controller HUD menu. If you select LSK 5L AUTO and LSK 4L CDI, you will get the CDI display until you get within 12° of course, at which time you will get the conformal display.

Figure: G450 Display Controller HUD Page, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 9.] Pushing [the LSK 5L] key scrolls through AUTO, ON, and OFF. This key selects the lateral display format from one of the following HUD displays:

  • HSI
  • CDI
  • Conformal lateral deviation
  • Non-conformal deviation.

AUTO -- Selects one of three positions, and the effect of the selected position depends on whether the CDI or the HSI is selected. [The table below] describes this key selection relative to the selected display.

ON -- Selects full HSI or CDI display format depending on what was selected on LSK 4L.

OFF -- Results in a non-conformal CDI display only.

  Course Select/Desired Track Error < 12° Course Select/Desired Track Error > 12°
AUTO Conformal only Full HSI or CDI (Note 1)
ON Full HSI or CDI (Note 1) Full HSI or CDI (Note 1)
OFF Non-conformal CDI only Non-conformal CDI only
NOTES:
1. Depends on the selection made with the HSI/CDI line select key.
2. For a typical ILS approach, select AUTO and CDI. As the localizer
moves to less than 12°, the display automatically switches to the
conformal CDI display if it was not previously selected.
3. The power-up setting is the combination set when the aircraft was
last powered-down.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 8.] When the AUTO has been selected ON, pushing the CDI/HSI key toggles HUD display between the CDI display and the HSI display format.


Flare Cue

Figure: G450 HUD Flare Cue, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶5., page 7.] The radio altitude is used to calculate runway symbol and flare cue placement.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 35.] The flare cue is armed, but not displayed, when the aircraft is airborne, and RA is +400 ft for 5 seconds. Once armed, when the radio altimeter (RA) is <100 ft AGL, the flare cue is displayed. When the flare cue is activated, it moves up from below the FPV. As the aircraft descends to 50 feet RA, the flare cue rises to surround the FPV. When the aircraft descends below 50 ft AGL, the cue switches from glideslope to the FD vertical command. The FD vertical command also drives the flare cue below 50 ft. If the pilot maintains the wings of the FPV between the parallel lines of the flare cue and pulls power to idle, the aircraft flares to a landing. Touchdown and roll out are performed using normal visual procedures.

The book doesn't explain which "FD vertical command" is used to flare the aircraft but it appears to be level flight at 0' feet, which means it doesn't land the airplane properly. The key phrase here is "using normal visual procedures."

Photo: HUD FPA in flare, KPSM, from Eddie's HUD.

We have found that following the flare cue until touchdown usually leads to a long landing. See Procedures & Techniques / Landing / Flare for a better way to do this.

Video: KBED - KPSM with HUD.


Flight Director

Figure: G450 HUD Flight Director, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 8.]

  • The FD command symbol moves laterally and vertically for guidance. To capture the FD guidance, the pilot maneuvers the aircraft to place the FPV over the FD, both vertically and laterally. If a single cue flight director is selected on the DC, the diamond is displayed with wings and the symbol rolls and moves sideways to indicate lateral commands. When the cross-pointer flight director is selected on the DC, the diamond is displayed with out wings and it does not roll. In both cases, the FD is satisfied by centering the FPV over the FD.
  • FD modes come from the priority AFCS, and autothrottle modes come from the priority performance computer. Both armed and captured modes are displayed, with captured modes being displayed inside a box. When a mode is captured, a box is drawn around it, and it flashes for 5 seconds and then goes on steady. If an unusual attitude exists, the modes are removed from the display and FD FAIL is displayed. Flight director modes are described in [the table below].
Lateral Mode Annunciator
Heading select HDG
LNAV FMS FMS
LNAV VOR VOR
Approach VOR VORAP
LNAV NMS NMS
Approach ILS LOC
Back Course BC
Emergency Descent EDM
Overstation OS
TACAN TCN
Approach TACAN TCNAP
Autothrottle Mode Annunciator
Takeoff TO
Go Around GA
Flight Level Change FLCH
Speed IAS IAS
Speed Mach MACH
Retard RTD
Hold Mode HOLD
Override OVRD
VMO Limited VMO
MMO Limited MMO
Power Limited POWER
Flap Limited FLAPS
Gear Limited GEAR
VMIN Limited VMIN
Vertical Mode Annunciator
Altitude Hold ALT
Vertical Speed VS
Altitude Select ASEL
FLCH IAS IAS
FLCH MACH MACH
Approach ILS GS
Approach MLS GP
Takeoff TO
Go Around GA
VNAV ALT Preselect VASEL
VNAV ALT Hold VALT
VNAV FLCH IAS VIAS
VNAV FLCH MACH VMACH
VNAV ARM VNAV
VNAV Path VPATH
Flight Path Angle FPA
VMAX VMAX

Flight Path Vector

Figure: G450 HUD Flight Path Vector, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 14.] The FPV is the primary symbol for control of the aircraft. The FPV displays the current velocity vector of the aircraft. The lateral displacement vector is calculated from the selected IRS drift angle and the vertical vector is calculated from the IRS flight path angle. Inputs from the GPS system (if installed) are used to improve the accuracy of the IRS data. The FPV does not display nose attitude as does the normal attitude indicator. If the aircraft is descending, the FPV is displayed below the HUD horizon at the current flight path angle of the aircraft. If the aircraft is climbing, the symbol is above the horizon line at the current flight path angle. Displacement of the FPV laterally indicates drift. Full-scale deflection indicates 12° of drift. The lateral and vertical motion of the symbol are restricted to ±12° in the uncaged mode, and 0° laterally in the caged mode. The FPV flashes when it is at its limit. The FPV becomes active when the IAS is 63 knots or greater, disabled when IAS is 60 knots or less.

The IRU drives the flight path vector, telling it how high above the local horizon to be based on the aircraft's vertical motion and how far right or left of center based on drift angle.

The flight path vector is my favorite bit of technology on the airplane and I use it for all my instrument flying needs. In fact, the only time I ignore it and revert to the the old fashioned boresight is for stall recoveries, wind shear escape maneuvers, and CFIT avoidance. In these cases the flight path vector is jumping around too erratically to follow.

Figure: G450 HUD Angle of Attack, from Eddie's notes.

You can think of the boresight as being attached to the wing and the flight path vector as where the aircraft is heading. It is the angle of attack that separates the two. The only time you will see the boresight below the flight path vector in a G450 is:

  • Prior to takeoff rotation.

  • After landing touchdown,

  • You or the autopilot have mismanaged a climb or descent and your vector exceeds aircraft performance. For example, the autopilot sometimes pulls the airplane up into a unsustainable climb, as much as 8,000 fpm. You know the airplane can't keep that up at altitude. The flight path vector will be above the boresight, that means you will soon run out of airspeed and it is time to lower the nose.

  • You've lost control of the airplane. Don't do that.

    More about this: Basic Aerodynamics / Angle of Attack.


Ghost Flight Path Vector

Figure: G450 HUD Ghost Flight Path Vector, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 14.] The ghost FPV is displayed when the caged mode is selected on the DC HUD menu, and the drift angle (the difference between the actual velocity vector and the caged FPV) is 1.5° or greater. The ghost FPV is used during high crosswind conditions. This means the pilot can observe the actual flight path while the FPV symbol and associated symbols are caged to the center of the display. The ghost FPV flashes and remains in view when it reaches the lateral limits of the display.

When the flight path vector is uncaged, it points to where the aircraft is headed up to the limits of the viewing angle on the HUD and then it flashes to let you know it would actually be further left or right if it could. Even at these limited extremes it can be difficult to see so you have the option of caging the flight path vector to the center of the HUD. In this case, the ghost flight path vector shows you where the aircraft is actually headed, again up to the limits of the viewing angle of the HUD.


Heading Bug

Figure: G450 HUD Heading Bug, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 16] The heading select bug indicates the heading that was selected using the HDG SEL knob on the guidance panel. When the selected heading is off the displayed heading scale, the bug is displayed as a half-bug parked on the side of the heading scale closest to the selected heading. The digital readout indicates the numerical value (in degrees) of the heading select bug. The readout consists of three digits preceded by the HDG annunciator.


Heading Tape

Figure: G450 HUD Heading Tape, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 15.] The heading tape is a 40° non-conformal scale that moves horizontally left and right. The scale has labeled tick marks every 10°, with shorter tick marks every 5°. Heading readouts are two-digit numbers that leave off the least significant digit (i.e., 30 equals 300°). The scale indicates in magnetic unless the true mode is selected on the FMS. When true heading is selected, a TRU annunciator is displayed above the selected heading. In the CLEAR mode, the scale is replaced with a three-digit indication of actual heading.


Horizontal Situation Indicator

Figure: G450 HUD HSI, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶2, page 24.] The standard HSI display is selected using the DC HUD menu. The arrow points to the selected course. The TO/FROM indicator is a triangle that is attached to the head (TO) or tail (FROM) of the arrow. The lateral deviation scale is centered on the aircraft symbol with the deviation bar indicating course deviation. The selected heading is displayed as a bug on the outside of the heading dial.

If you want to see an HSI like this at all times, you need to select LSK 5L ON and LSK 4L HSI from the display controller HUD menu. If you select LSK 5L AUTO and LSK 4L HSI, you will get the HSI display until you get within 12° of course, at which time you will get the conformal display.

The HSI display is only available with the EVS/FLIR turned off. (Nothing says this, but that has been our experience in actual practice.)

Figure: G450 Display Controller HUD Page, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 9.] Pushing [the LSK 5L] key scrolls through AUTO, ON, and OFF. This key selects the lateral display format from one of the following HUD displays:

  • HSI
  • CDI
  • Conformal lateral deviation
  • Non-conformal deviation.

AUTO -- Selects one of three positions, and the effect of the selected position depends on whether the CDI or the HSI is selected. [The table below] describes this key selection relative to the selected display.

ON -- Selects full HSI or CDI display format depending on what was selected on LSK 4L.

OFF -- Results in a non-conformal CDI display only.

  Course Select/Desired Track Error < 12° Course Select/Desired Track Error > 12°
AUTO Conformal only Full HSI or CDI (Note 1)
ON Full HSI or CDI (Note 1) Full HSI or CDI (Note 1)
OFF Non-conformal CDI only Non-conformal CDI only
NOTES:
1. Depends on the selection made with the HSI/CDI line select key.
2. For a typical ILS approach, select AUTO and CDI. As the localizer
moves to less than 12°, the display automatically switches to the
conformal CDI display if it was not previously selected.
3. The power-up setting is the combination set when the aircraft was
last powered-down.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 8.] When the AUTO has been selected ON, pushing the CDI/HSI key toggles HUD display between the CDI display and the HSI display format.


Instantaneous Acceleration Caret

Figure: G450 HUD Instantaneous Acceleration Caret and Speed Error Tape, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 22.] The caret indicates current acceleration/deceleration of the aircraft along the current flight path. With its zero position at the end of the FPV left wing, it indicates above the wing when airspeed is increasing, and below the wing when airspeed is decreasing. The caret is primarily used to control airspeed. It is also scaled so that its position gives an indication of the aircraft flight path angle so that, if flown, current airspeed would be maintained at the current power setting.

Using the speed error tape in conjunction with the instantaneous acceleration caret gives you a wealth of information on the aircraft's energy state:

Figure: G450 HUD Speed Cues, from Eddie's notes.


Local Horizon

Figure: G450 HUD Local Horizon, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 12.] The horizon line is drawn across the HUD display with a gap in the center to allow room for the FPV to move vertically. The horizon line is held on-screen and flashes if the pitch-up exceeds 13° or the pitch-down exceeds 6°. The horizon line is displayed at 0° angle of pitch on the pitch tape. NOTE: The horizon line indicates the aircraft’s local horizon. At high altitudes, the line appears above the visual horizon line because of the curvature of the earth.


Non-conformal Lateral Deviation Indicator, Scale, To/From

Figure: G450 HUD Non-conformal Lateral Deviation Indicator, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶2, page 25-26.] The non-conformal deviation scale is centered on the aircraft boresight and below the FPV symbol. It is displayed 3.5° below the reference FPA, if the selected NAV 1/2 and the selected NAV source are tuned-to-localizer, or if it is MLS. The deviation scale is displayed 6° below the horizon line if the selected NAV source is VOR, NAV 1/2, or FMS. It is displayed only when the display controller HSI/CDI mode is selected OFF or the conformal display moves off the bottom of the display (typically, during a go-around). The deviation pointer indicates as described in [the table below]. The TO indicator is displayed above the aircraft symbol, and the FROM indicator is displayed below it.

Deviation VOR/TACAN LOC/MLS FMS 1/2/3 FMS 1/2/3 APP
2nd dot right 10° 5 NM Based on RNP
1st dot right 2.5 NM Based on RNP
Center 0 NM Based on RNP
1st dot left 2.5 NM Based on RNP
2nd dot left 10° 5 NM Based on RNP

If you want to see a non-conformal lateral deviation display like this at all times, you need to select LSK 5L OFF from the display controller HUD menu. You could also see this if you were in AUTO and pitched high enough to make the conformal scale disappear from view.

Figure: G450 Display Controller HUD Page, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 9.] Pushing [the LSK 5L] key scrolls through AUTO, ON, and OFF. This key selects the lateral display format from one of the following HUD displays:

  • HSI
  • CDI
  • Conformal lateral deviation
  • Non-conformal deviation.

AUTO -- Selects one of three positions, and the effect of the selected position depends on whether the CDI or the HSI is selected. [The table below] describes this key selection relative to the selected display.

ON -- Selects full HSI or CDI display format depending on what was selected on LSK 4L.

OFF -- Results in a non-conformal CDI display only.

  Course Select/Desired Track Error < 12° Course Select/Desired Track Error > 12°
AUTO Conformal only Full HSI or CDI (Note 1)
ON Full HSI or CDI (Note 1) Full HSI or CDI (Note 1)
OFF Non-conformal CDI only Non-conformal CDI only
NOTES:
1. Depends on the selection made with the HSI/CDI line select key.
2. For a typical ILS approach, select AUTO and CDI. As the localizer
moves to less than 12°, the display automatically switches to the
conformal CDI display if it was not previously selected.
3. The power-up setting is the combination set when the aircraft was
last powered-down.

[G450 Aircraft Operating Manual, §2B-18-10, ¶6, page 8.] When the AUTO has been selected ON, pushing the CDI/HSI key toggles HUD display between the CDI display and the HSI display format.


Pitch Limit Indicator (PLI)

Figure: G450 HUD PLI, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 13.] The PLI is displayed when the normalized AOA is greater than 0.7 and is used as a visual cue to alert the pilot to an impending stick shaker. As the FPV approaches the PLI, the pilot is approaching stick shaker activation. The distance between the PLI and FPV is zero when the stick shaker is activated.


Pitch Tape

Figure: G450 HUD Pitch Tape, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 12.] The pitch tape displays the conformal attitude at all times. The tape has solid reference marks for positive pitch and dashed reference marks for negative pitch. The pitch tape moves as earth referenced over a range of ±90° pitch and ±180° roll. The -5° pitch reference is removed when the reference FPA is displayed below the horizon line.


Reference Flight Path Angle

Figure: G450 HUD Reference Flight Path Angle, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 32.] The reference FPA line is a dashed line that is positioned above or below the horizon line to display the selected FPA. The gap in the line is centered and moves laterally with the FPV. The FPA line is always parallel to the horizon line. The FPA is limited to ±9°. FPA can be selected on the display controller HUD menu page or on the guidance panel. If a reference FPA is seen on both the display controller HUD menu and the guidance panel, the priority is the display controller value. The FPA (vertical angle) is selected on the display controller when the value is boxed. To set the reference FPA on the guidance panel, first select FPA (boxed) on the display controller DISP menu, then set the FPA angle on the guidance panel. The FPA value from the guidance panel is used by HUD if the vertical angle on the display controller HUD menu page is not boxed.

[G450 Aircraft Operating Manual, §2B-18-10, page 9.] [The display controller] VERT ANG Key is used to set the position of the reference flight path angle symbol on the HUD. The maximum allowable range is +9.9° to -9.9°. The corresponding FT/NM is displayed below the vertical angle.

Figure: HUD 3° line, from Eddie's notes.

The HUD draws a line from the airplane down to the ground or up to the sky at whatever angle you command up to 9.9°. This angle comes from the airplane and the airplane's attitude does not matter. In the case of a downward angle, the line it draws on the ground shows where your airplane will end up if you follow that angle.

Understanding that the line, when negative, comes from the aircraft and not the ground is vital to using the line to your advantage for glide path control. In each of the three examples to follow, the flight path vector is right on the touchdown zone of the runway. So the airplane is headed to the correct spot but the angle is different.

Figure: FPA short, from Eddie's notes.

If the line is short of the runway, you need to “walk the line up” by reducing your angle of descent. In the drawing you have raised your pitch to the touchdown zone but your flight path angle is still short of the runway. This means you will indeed land in the touchdown zone, but at too shallow an angle. You should further reduce your angle to "return to glide path."

Figure: FPA long, from Eddie's notes.

If the line is beyond the touchdown zone of the runway, you need to “walk the line back” by increasing your angle of descent. In the drawing you have decreased your pitch so that the flight path vector is on the touchdown zone. This means you will land in the touchdown zone, but at too steep an angle. If time permits and you are above Stabilized Approach height, you should further increase your descent angle to "return to glide path."

Figure: FPA good, from Eddie's notes.

If the line is on top of the touchdown zone of the runway, that is where you will end up if you don't flare. A proper flare consumes less than 500'.


Runway Symbol

Figure: G450 HUD Runway Symbol, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, page 34.] The runway symbol is displayed on an ILS or MLS approach when the aircraft is less than 350 feet above the runway and it remains displayed until 60 feet on the RA. The runway symbol represents a runway width of 150 ft with two indentations at the touchdown point, which is assumed to be 1000 ft from the runway threshold. The runway symbol requires that FPA is set, lateral deviation is valid and less than two dots, and vertical deviation is valid and less than two dots. NOTE: The runway symbol is displayed correctly during an ILS or MLS approach if the runway elevation has been entered on the display controller HUD menu and the AUTO mode has been selected. If runway elevation has not been entered, the runway display may be displayed too soon or too late, depending on the difference between the actual runway elevation and the default runway elevation that is used by the HUD software.

[G450 Aircraft Operating Manual, §2B-18-10, ¶5., page 7.] The radio altitude is used to calculate runway symbol and flare cue placement.

[G450 Aircraft Operating Manual, §2B-18-10, page 9.] [The display controller] RW ELEV Key is used to set the runway elevation of the destination airport between -1500 and 16,000 feet. This information is used to calculate at what altitude the airport and runway symbols are displayed. If the runway elevation is not properly set, the airport and runway symbols may be incorrect (i.e., without runway elevation).

[G450 Aircraft Operating Manual, §2B-18-10, page 7.] The [Display Driver Unit] computes and displays synthetic airport and runway symbols using glideslope and localizer information, making the lower end of the displayed runway the touchdown zone. The airport symbol is based on an 800-foot wide airport. The runway display is based on a 150-footwide 8000-foot long runway. The pilot must set the runway threshold elevation and glideslope angle using the HUD menu on the DC to ensure accurate symbol placement. Runway heading is determined from the localizer course selected by the pilot.

[G450 Aircraft Operating Manual, §2B-18-10, page 9.] [The display controller] RW ELEV Key is used to set the runway elevation of the destination airport between --1500 and 16,000 feet. This information is used to calculate at what altitude the airport and runway symbols are displayed. If the runway elevation is not properly set, the airport and runway symbols may be incorrect (i.e., without runway elevation).

The airport symbol only appears if you have everything dialed in to fly an ILS or MLS approach and once you descend below 2,000 feet. It doesn't look like an airport, it looks like a fat runway. In fact, it turns into a runway at 350 feet above the runway. That begs the question, how do you tell them apart. Here's how:

Figure: G450 HUD Symbology Airport versus Runway Symbols, from Eddie's notes.

Reading between the lines: the airport symbol uses the localizer or MLS beam for geographical placement, the FMS for perspective, the radio altimeter for vertical placement, and the guidance panel course selection for runway heading. The airport symbol attempts to show you where the runway is, using a larger than the runway perspective, until 325' radio altimeter height, at which point it changes to the runway symbol. The touchdown zone of the runway symbol is determined by the glide slope beam.

Photo: G450 Display Controller HUD Menu - Rwy Elev, from Eddie's aircraft.

The RW ELEV entry in the display controller HUD menu should always be made using QNH altitude, even if the PFD is using QFE. This isn't written anywhere, but we've noticed that if you enter 0' when flying QFE, the airport and runway symbols will appear late by the difference between QFE and QNH.

If, for example, the runway elevation is 100' MSL for a QFE airport you would adjust your PFD altimeter to the proper QFE and it will read 0' on touchdown. If you were to set your display controller HUD RWY ELEV to 0', the airport symbol will appear at 2,000 - 100 = 1900' and the runway symbol will appear at 325' - 100' = 225'. We've tested this and one of these days we'll test an airport greater than 325' MSL to see if the runway symbol fails to appear completely.


Selected Altitude

Figure: G450 HUD Selected Altitude, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A.] The selected altitude bug travels around the outside of the altitude analog scale. The selected altitude range is -2000 to 65,000 ft barometric altitude. The bug is displayed when the aircraft is within ± 500 feet from the selected altitude. The bug is not displayed when the FD vertical capture mode shows GS or GP. The digital readout is the digital value of the bug position. This display can be in metric or English values.


Speed Error Tape

Figure: G450 HUD Instantaneous Acceleration Caret and Speed Error Tape, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 21.]

  • This tape rises or descends from the left wing of the FPV. It represents the difference between the selected airspeed and the current airspeed. If the tape is below the wing, current airspeed is less than the selected airspeed. If the current airspeed is greater than the selected airspeed, the tape is above the wing. The tape is designed so that if the speed error tape is not displayed, the selected airspeed is being maintained.
  • If V1, VR, or V2 are within the range of the speed error tape, they are displayed to the left of the speed error tape. The indicator moves vertically along the speed error tape, so that the distance between the FPV wing and the VSPEED indicator is proportional to the speed error tape scale. The V1 and VR values are parked at the bottom of the speed error tape if their values place them outside the displayed values on the tape.

Using the speed error tape in conjunction with the instantaneous acceleration caret gives you a wealth of information on the aircraft's energy state:

Figure: G450 HUD Speed Cues, from Eddie's notes.


Vertical Deviation

Figure: G450 HUD Vertical Deviation, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 27.] The vertical deviation scale displays either VPATH or glideslope deviation. The scale moves laterally with the FPV. The deviation scale uses the FPA line as its center point when the selected NAV source is NAV 1/2 and it is tuned-to-localizer, or if it is MLS. The pointer moves up and down the scale with a sensitivity of 0.35°/dot for glideslope deviation. If the NAV source is FMS 1/2/3, the pointer is driven by the selected FMS vertical deviation, and the deviation scale center point is at -3°.


Vertical Speed

Figure: G450 HUD Vertical Speed, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A., page 18.] The vertical speed digital readout is the vertical speed in terms of feet per minute (FPM). The vertical speed worm indicates the vertical speed. The worm is an arc that originates from the 9 o’clock position of the altitude dial and moves clockwise (cw) for positive vertical speed and counterclockwise (ccw) for negative vertical speed. The scaling is 1000 ft/min per mark for the first 54° of arc, 2000 ft/min per mark for the next 36°, and 3000 ft/min per mark for the next 36°.


Wind Vector

Figure: G450 HUD Wind Vector, from Eddie's notes.

[G450 Aircraft Operating Manual, §2B-18-20, ¶2.A.] The wind vector can be displayed in either the X-Y or vector format, as selected on the DC. Wind data comes from the selected IRS. NOTE: The wind display is the standard wind vector format selection on the DC. It is not a HUD-specific selection. However, this is a non-filtered instantaneous wind vector and it can vary slightly from the ND and MCDU wind values.


References

Gulfstream G450 Aircraft Operating Manual, Revision 35, April 30, 2013.