Figure: HUD brightness control panel, from G450 Aircraft Operating Manual, §2B-18-10, page 6.

Eddie Sez:

The G450 Heads Up Display brightness control panel impacts controls the HUD display with and without the EVS. In the Gulfstream world, the Enhanced Vision System means the Forward Looking Infrared (FLIR) camera displayed through the HUD. For a look at the other hardware aspects of the HUD, refer to G450 Systems / HUD. For a look at the operational aspects of the HUD, refer to G450 Procedures & Techniques / Heads Up Display.

What follows are quotes from the references listed below, with a few comments, shown in blue.

. . . working . . .


The HUD Side

MAN/NORM

Figure: HUD brightness control panel, MAN/NORM, from G450 Aircraft Operating Manual, §2B-18-10, page 6.

[G450 Aircraft Operating Manual, §2B-18-10 ¶3.]

  • The MAN/NORM switch operates the same as when EVS is not installed. When the switch is in the NORM position, the display brightness is automatically adjusted for ambient light changes.

  • When the mode switch is in the MAN position, the display brightness can be manually adjusted from zero to full intensity with the system dimming (SYM DIM) (or EVS/SYM DIM) knob. When the switch is in the NORM position, the display brightness is set for ambient light conditions with the SYM DIM (or EVS/SYM DIM) knob and the brightness is automatically adjusted for changes in ambient light conditions. If EVS is installed, the brightness control panel on the combiner assembly has two knobs for controlling the EVS video contrast and brightness.

You can think of the MAN/NORM switch as the switch that enables the two DIM switches. In the NORM position they don't work and you are at the mercy of what the computer thinks you should be seeing. It has been my experience that most pilots don't trust it, since having it decide you need full brightness at the darkest part of an approach could be a big problem. Leaving the switch in MAN gives you control of the bottom two switches.

Figure: HUD brightness control panel, SYM DIM, from G450 Aircraft Operating Manual, §2B-18-10, page 6.

SYM/DIM

[G450 Aircraft Operating Manual, §2B-18-10 ¶3.] SYM DIM Knob — The SYM DIM knob controls the brightness of the HUD symbols. This lets the pilot adjust the brightness level between the symbols and the video.

The SYM DIM switch only controls the brightness of the HUD symbology and can be overwhelmed by the EVS brightness. If you find the switch doesn't seem to work, first make sure the HUD is working and then make sure the EVS isn't overpowering the non-EVS symoblogy. More about this below: Technique.


The EVS Side

Figure: HUD brightness control panel, from G450 Aircraft Operating Manual, §2B-18-10, page 6.

EVS CONT

[G450 Aircraft Operating Manual, §2B-18-10 ¶3.] The EVS CONT knob controls the contrast of the EVS video that is displayed on the combiner assembly.

[G450 Aircraft Operating Manual, §2A-34-90 ¶.D.] A separate EVS CONT knob, installed above the EVS / SYM DIM knob, is used to set the contrast of the EVS infrared image shown on the combiner screen.

The EVS contrast can do everything from make the imagery disappear to flood the screen with a field of green that makes everything impossible to see. See Technique, below, for a way around this problem.

EVS/SYM DIM

[G450 Aircraft Operating Manual, §2B-18-10 ¶3.] The EVS/SYS DIM knob adjusts the EVS video and HUD symbol brightness.

[G450 Aircraft Operating Manual, §2A-34-90 ¶.D.] In the MAN position the EVS / SYM DIM knob to the left and below the switch is turned to set light levels of the EVS raster image and the HUD flight guidance symbology. With the MAN / NORM switch in NORM, the EVS / SYM DIM knob can set the initial desired illumination level and an automatic brightness sensor on the combiner will subsequently adjust theillumination to compensate for changes in ambient light conditions.


Technique

The HUD Brightness Control Panel can seem a bit mysterious because of the interaction of the four controls and the sometimes recalcitrant nature of the HUD itself. A few pointers:


References

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