Photo: Three views of the same approach at 190 feet, from Eddie's aircraft.

Eddie Sez:

The Heads Up Display puts your eyes where they need to be for an approach in low visibility: on the runway. It is a definite plus. The infrared camera (FLIR)? Not so much. Sometimes it works, sometimes it doesn't. The photo above was one of those rare times for us where it did, giving us maybe an extra five seconds. FLIR or not, knowing how to use the HUD for an approach will make your life easier, and safer.

If you are new to this, you might want to watch this short three-minute video showing an approach to minimums using the EVS: EVS vs. Visual (Approach). (Watch the behavior of the airport symbol-turned-runway symbol and start looking for the runway on EVS around 300 feet.)

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


Set Up

Photo: EVS at minimums, from Eddie's aircraft.

The best use of the HUD is to get the airplane in a stable position for landing, and to that end it will help you for lateral and vertical alignment. To get symbols helpful to your approach and landing, you will have to set things up accordingly. What you end up with, depends on what you start with. The following notes start with the bare minimum to get HUD guidance on approach and end with the best you can do.

Runway in FMS Database

Photo: DU map display on final flight segment, from Eddie's aircraft.

If you select the approach runway from the FMS database, even if there are no instrument approaches listed, you can still get course guidance and a VNAV-capable glide path on the HUD. See G450 Procedures & Techniques / Visual Approach Guidance for instructions on how to do this.

The resulting guidance is suitable for backing up a visual approach but the RNP will be 1.0 and even that could be suspect, depending on the accuracy of the runway's position in the database and the country's GPS coordinates. See International Operations / WGS-84 for more about this issue.

Reference Flight Path Angle

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

You can improve upon the simple VNAV line to the runway by comparing it to a 3° line drawn from the airplane to the ground. More about this explained below: Reference Flight Path Angle.

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'.

Conformal Lateral Deviation Indicator, Scale, Centerline

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

You can improve the accuracy of your lateral centerline and course deviation indicator by improving the guidance to the airport. Your best choice is an ILS or MLS, followed by an LPV, then the other approach options.

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

You may have come to appreciate an LPV approach more than an ILS, but the ILS gives the HUD more to work with, as you will now see below: Airport and Runway Symbols.

Vertical Deviation

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

The vertical deviation scale is available to you for either VPATH or glide slope deviation, but its accuracy varies with source. Your best bet is an ILS or MLS, followed by an LPV. More about this below: Vertical Deviation.

Airport and Runway Symbols

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

If you have an ILS localizer or an MLS dialed in and set up properly, the HUD will draw you an airport symbol where it believes the runway is and it will do this 2,000 feet above the runway. When you get to 350 feet of the runway, it draws a runway symbol, complete with touchdown zone:

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

More about this below: Runway Symbol.


Symbology Notes

Extracted from: G450 Normal Procedures & Techniques / HUD - Symbology.

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.

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.

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.

HUD Display Controller Runway Elevation

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

[G450 Airplane Flight Manual, §02-08-80, ¶1.C.] When conducting QFE, ILS or LPV approaches using the HUD, set the runway elevation to zero on the display controller HUD menu page.

This isn't something you need to set to the nearest 10 feet, erring on the plus side. It is used to determine when the airport and runway symbols appear. If it isn't set, they won't come up at all. If they are set to QNH when QFE is being used, they may come up late.

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°.


References

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

Gulfstream G450 Airplane Flight Manual, Revision 36, December 5, 2013