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Disclaimer: I don't have a real Airbus A330 at hand, nor am I a pilot.

After having crashed twice due to icing in rainy weather (not to talk about that here) with an Airbus A330 in X-Plane 12 simulator, I realized that I did not turn on anti-ice protection!

While I still trying to find a good manual, I had tried to get accustomed with the panel and its logic, realizing that when some light are off, it actually means that the underlying system is on, so at some point I had made the erroneous decision that "all lights off" is a good state for the panel.

Example where "lit" means "on" (Airbus A330 Anti-Ice

Example where "lit" means "on" (Airbus A330 Air-Flow)

Still it seems that it's easier to spot a single light that is on, rather than finding a single light that is off. The situation may be more interesting if the light, but not the underlying system fails.

Airbus A330 Over-head panel

So I wonder: Why did Airbus mix different logic models in one panel?

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  • $\begingroup$ If you cannot find a good manual for flying the A330 in flight simulators, try looking for an A320 manual instead. There are far more A320 simulations out there and the two types are very, very similar in most aspects. $\endgroup$
    – Bianfable
    Commented Jan 4 at 10:16

2 Answers 2

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The logic for illumination of buttons on the overhead panel is called the dark cockpit concept, previously also called the Forward-Facing Crew Cockpit.

It was originally developed by Airbus for the A310, which eliminated the flight engineer position of the early A300 variants and therefore had to simplify system operation for the two pilots using a simple overhead design combined with electronic monitoring and warning instruments:

Airbus improved the cockpit layout, allowing a two-pilot flight crew to operate the aircraft without the need for a flight engineer. The new concept, called the Forward-Facing Crew Cockpit [...]
This A310 “glass cockpit” used six computer-driven cathode ray tube displays to provide the captain and co-pilot with centralised flight and navigation information as well as monitoring and warning data.

(Airbus Technology Leaders (1977-1979), web.archive.org)

The general principle for the overhead panel is that when all lights are extinguished, the systems are in their normal state for flight. If you see lights, they are colour-coded to indicate any of the following:

Dark Cockpit Concept

No White Lights
System is set
Fit to fly

The state of the Lights and information provided on display units are color coded to indicate the status of the system, or the nature of the information

Airbus Overhead Lights

(ICAO/Airbus FOSAS presentation)

As the anti-ice is only selected temporarily1, it will be illuminated in blue while ON. This serves as a reminder for the crew to select it back OFF when it is no longer needed.

Note that the indications on the overhead panel are only there to catch your eye, not to give a full overview of the current system state. This is done using the ECAM:

The Electronic Centralized Aircraft Monitoring (ECAM) system is a main component of Airbus’ two-crewmember cockpit, which also takes the ”dark cockpit” and ”forward-facing crew” philosophies into account.
The purpose of the ECAM is to:

  • Display aircraft system information
  • Monitor aircraft systems
  • Indicate required flight crew actions, in most normal, abnormal and emergency situations.

(Airbus A320 FCTM - Operational Philosophy - ECAM)

Today, all Airbus aircraft share this concept for reasons of commonality, which allows pilots to transition between different models very easily:

Another standard Airbus feature is the ‘dark cockpit’ concept whereby lights only show on the overhead systems management panel to indicate where an action is required. Overall the A330neo and A350 cockpits share a similar layout.

(Airbus: A330neo cockpit - Commonality with A350 innovations)

Some other aircraft manufacturers also followed this principle, e.g. ATR (which shares a lot of avionics with Airbus), McDonnell Douglas (starting with the MD-11) and Bombardier:

Dark cockpit

The Bombardier Vision flight deck leverages a dark cockpit philosophy. Featuring push-button annunciators that remain dark in normal operation, toggle switches positioned forward for flight and knobs that are in the 12 o'clock position when in AUTO, pilots can have situational awareness at a glance and focus on flying.

(The Bombardier Vision flight deck)

Boeing still follows are more traditional design, where pushbuttons always indicate their state, even when in their normal setting, e.g. here is the window heat section of the Boeing 787:

Boeing 787 Overhead

(cropped from source)


1 Engine anti-ice should be selected ON whenever the aircraft is in icing conditions: TAT < 10°C and visible precipitation / clouds. Wing anti-ice should be selected ON when airframe icing is visible (e.g. on the black stick between the two forward cockpit windows).

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  • $\begingroup$ A great answer; I just doubt that AIrbus still uses CRT (Cathode ray tubes) (e.g. for weight and size reasons). -- A question that remains is whether the pilot sees the buttons as shown (e.g.) in i.sstatic.net/e5anw.png, or is it just for illustration showing the possible illuminations? In the view I had (in the simulator), it was not obvious whether lit would mean "ON" or "OFF". $\endgroup$
    – U. Windl
    Commented Jan 8 at 8:30
  • $\begingroup$ @U.Windl CRTs were replaced on older aircraft (source). You can see the not illuminated text on the real buttons, see e.g. this image where you can recognize the "OFF" on the buttons (source). $\endgroup$
    – Bianfable
    Commented Jan 8 at 8:39
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I think this gets into Human Factors and other usability issues, but as an interface designer as part of my job I can say how I would approach this... I don't have (and I don't think it is published) specific information on Airbus engineers thought process...

The lights indicate a "not normal" state. In the case of anti-ice, the "normal" state is anti-ice is off, so the light indicates when the anti-ice is on.

For your second picture, the Engine Bleed normal state is "ON", and "OFF" is indicated as something abnormal. Same with the pack fault, the "fault" indication is abnormal and therefore lighted.

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    $\begingroup$ Agreed, No specific knowledge on Airbus, but when we were working on upgraded onboard displays for the space shuttle back in the day, the rule was "quiet dark" - as you say, light on if attention is needed. $\endgroup$ Commented Jan 3 at 21:30
  • $\begingroup$ Well, during winter "anti-ice" may be "normal". As I said: I wasn't expecting icing when it was "just raining" (BTW: Chicago on Jan 1st, near 0:00 UTC) $\endgroup$
    – U. Windl
    Commented Jan 3 at 21:55
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    $\begingroup$ I think you misunderstand what "anti-ice" means or how airframe icing works... I've gotten airframe icing on a warm day (at ground level, at altitude it was much colder). $\endgroup$
    – Ron Beyer
    Commented Jan 3 at 21:59

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