Electronic Flight Information System (EFIS) — Page 287, Lesson 289

Let's start with the two display modes, because they set the stage for everything else on the Electronic Flight Information System — the EFIS. First, the map mode. This is the mode you'll use most in normal flight. It shows the navigational information you've selected on the control panel, and it is heading orientated. That means the top of the screen is always the direction the aircraft's nose is pointing — the map rotates as you turn, so what's ahead of you is always at the top. You can see this in the figure: the heading is up, and the route, waypoints, and distances are drawn relative to that heading. Now the plan mode. This is the opposite in one key way: it is orientated to true north. So the top of the screen is always north, regardless of which way the aircraft is pointing. The information displayed at the top of the screen is the same as in the map mode — same data, just a different orientation. The plan mode lets you review the planned route using the FMC/CDU LEGS page. The FMC is the Flight Management Computer, and the CDU is the Control Display Unit — that's the keypad and screen you use to talk to the FMC. The LEGS page is where the route legs are listed. When you use that page, the display will be centred using it — so the route you're reviewing is brought to the middle of the screen. Now let's move to the EHSI colour coding. EHSI stands for Electronic Horizontal Situation Indicator — that's the display that shows you the horizontal picture: heading, route, and navigation. The colour coding on it is to the ICAO standard, which is also the standard adopted by EASA. And EASA's CS-25 — that's the certification specification for large aeroplanes — recommends this colour presentation. Let me walk you through the display features and their colours. Warnings are Red. Flight envelopes and system limits are also Red. Cautions and abnormal sources are Amber/Yellow. Earth — the ground on the display — is Tan/Brown. Engaged modes are Green. Sky is Cyan/Blue. The ILS deviation pointer — that's the localiser and glideslope deviation indicator — is Magenta. And the flight director bar is Magenta/Green. Then there are specified display features that should be allocated colours from one of the following colour sets. In Colour Set 1: Fixed reference symbols are White. Current data and values are White. Armed modes are White. Selected data and values are Green. Selected heading is Magenta. And the active route or flight plan is Magenta. There's an important note about that magenta: it's intended to be associated with those analogue parameters that constitute 'fly to' or 'keep centred' type information. So magenta isn't just a pretty colour — it's a signal to you, the pilot, that this is something you actively fly towards or keep centred, like a heading bug or the ILS pointer. Finally, let's look at how precipitation and turbulence are coded. Precipitation is coded by rainfall rate in millimetres per hour. From 0 to 1 mm/h it's Black. From 1 to 4 mm/h it's Green. From 4 to 12 mm/h it's Amber/Yellow. From 12 to 50 mm/h it's Red. And above 50 mm/h it's Magenta. So the heavier the rain, the more intense the colour — black for light, up to magenta for extreme. Turbulence is coded White or Magenta. So the whole system is built on a consistent colour language: red for warnings and limits, amber for cautions, green for engaged modes and moderate precipitation, magenta for fly-to information and extreme precipitation, white for fixed and current data, and tan and cyan for earth and sky. Once you know that language, you can read the display at a glance.