Selects range for displayed navigation data and WXR — Page 289, Lesson 346

I want to walk you through the EFIS control panel and the EHSI display presentation. We're looking at the heart of how a multi-crew cockpit displays navigation data and weather radar. Let's start with the control panel functions. The first item is the range selector — it selects the range for displayed navigation data and for the WXR, the weather radar. This is your zoom control for the map. Next is the MODE SELECTOR. This selects the display appropriate to the mode required. You have four choices: VOR, ILS, MAP, and PLAN. Each one changes what the EHSI shows you. Then we have the BRT, or BRIGHTNESS control. This is a dual knob. The outer knob sets the main display brightness. The inner knob sets the WXR display brightness — that's the weather radar display brightness. So you can dim the radar independently from the rest of the screen. Now the MAP switches. These are used in MAP mode. When you select them, they cause their placarded data to be displayed on the EHSI. The placards are: NAV AID (navigation aid), ARPT (airport), RTE DATA (route data), and WPT (waypoints). Each switch toggles that layer of information on the map. Next is EXP ARC. This selects VOR or ILS mode to show an Expanded Arc — that's the partial compass presentation rather than the full rose. Finally, the WXR switch. When pushed in, WXR data is displayed during all modes except PLAN, or when the VOR/ILS mode is selected to present the FULL compass rose. So weather radar is suppressed in plan view and in the full compass presentation. Now let's move to the EHSI display itself. The EHSI presents a selectable, dynamic colour display of flight progress and a plan view orientation. There are four principal display modes selectable on the EFIS control panel: VOR, ILS, MAP, and PLAN. Of these, VOR and ILS can be displayed as full or expanded compass displays. The orientation of the displays may be Magnetic or True, Track or Heading, as selected. Let me walk you through the Full VOR Mode in detail. With a VOR frequency selected, the EHSI displays a full compass rose with the VOR source in the lower left and the frequency in the lower right. Course selection is displayed by the magenta course needle, the tip pointing to the selected course — in the example, 150 degrees. Course deviation is shown by the traditional deviation bar moving across a two dot left and two dot right scale. A TO/FROM pointer is shown in addition to the TO/FROM annunciation. DME distance is displayed in the top left corner. Current heading is shown in the window and by the lubber line at the top of the compass rose — in the example, 130 degrees. The current selection is Magnetic Heading, as shown either side of the window. Current track is shown by the white triangle on the inside edge of the compass rose. Selected heading is shown by the magenta heading "bug" on the outer scale of the compass rose. Wind speed and direction are shown in the lower left corner, orientated to the display selection — Heading or Track, Magnetic or True. And importantly, weather radar displays are not available in Full VOR mode. Now let me cover the system symbols — the colour coding you'll see on the display. The Active Waypoint is shown in Magenta — that's the waypoint the aircraft is currently navigating to. The Inactive Waypoint is shown in White — a navigation point making up the selected active route. Airports are shown in Cyan. An Off Route Waypoint is also Cyan. Tuned Navaids are shown in Green. An Unused Navaid is Cyan. And Wind Direction is shown in White, with respect to map display orientation and compass reference — the symbol shown in white against the black of the screen. Let me show you the physical layout. shows the multi-crew EFIS units and signal interfacing. shows the EFIS control panel itself. And shows the Boeing EADI with Decision Height selected on the ADI control panel. So to tie it together: the control panel gives you mode selection, range, brightness, map data layers, and weather radar control. The EHSI then presents that data in colour-coded form, with the full VOR mode giving you a complete picture of navigation — course, deviation, TO/FROM, DME, heading, track, selected heading, and wind — but no weather radar.