I believe there is a reason behind a particular design especially in aviation. I wanted to know how A320 cockpit was designed ?. For example: Why is RCDR, EMER ELEC PANEL is on the left side of the OVHD panel (is it because the Captain has priority/authority to perform these actions ?)

How are the buttons designed? for example: Image source: Internet

As you can see Cargo smoke fwd compartment has only indications and it is not really a button whereas if you see ventilation panel OVRD is enclosed in square box. What does it exactly indicate ?.

I am interested in knowing the thought process went into design engineer for the reason behind this development.

Any references to external document would be highly appreciated!

  • 1
    $\begingroup$ Kind of surprised the words Feng Shui weren't used.... $\endgroup$
    – CGCampbell
    Commented Feb 6, 2023 at 11:23

2 Answers 2


I'm not specialized in Airbus, but here is a general answer for a part of your question:

The logic in cargo smoke panel is such, that the black button is an indicator. If smoke is detected by both sensors, the"SMOKE" text will illuminate. Crew will then verify the alarm, and co-pilot will lift the red latch and activate the fire bottle by pressing the button under the latch. The button on the right will then verify the fire bottle discharge by illuminating the "DISCH" text.

This video will explain how the CARGO SMOKE panel works.

The logic here is to separate visually and physically the indications and operating of a critical system. This will mitigate the possibility of mistakes, which is of great importance, since (as DeltaLima pointed out in the comments) the discharging of a fire bottle is not reversible, you only have one chance / bottle.

The ventilation system is not (as) critical from safety point of view, hence indication and operating can be integrated. Under normal condition, which is "AUTO" the button is not illuminated. Pilot can shut of the system by pushing the button which will then illuminate the "OVRD" text. If the system detects a fault, obviously the "FAULT" text will illuminate.

As for the placement of separate panels, they are generally placed such that they form logical groups and they are as close as possible to the crew member that is usually supposed to operate them.

  • 3
    $\begingroup$ You may want to emphasize the irreversible nature of the discharge button. Once pressed, the content of the single bottle of fire extinguishing agent is fully released into either the forward or aft cargo bay. Unlike the blower en extractor fans, which can be switched on and off without further consequences, the fire bottle discharge is a one-shot operatation which cannot be undone. If the wrong bay is selected, or the button is accidentally pressed, there is no way to correct that mistake. Hence a red guard latch to offer protection against accidental activation. $\endgroup$
    – DeltaLima
    Commented Feb 6, 2023 at 12:18

I'm not into cockpit design so here is just a (partly) educated guess for the main layout.

If you do "boot" the plane from Dark-Start up of the plane you have to check, if all white "off" lights are unlit before taxi.

So the design of e. g. the Fuel Pump buttons includes only a white "off" lamp and not an "on" indicator. enter image description here

On the other side e. g. the APU Master button only has a blue "on" indicator.

enter image description here

The Fuelspumps should be activated before Taxi, the APU is not required to be turned off when taxiing.

So the button design of these simplifies the procedures and makes overseeing the activated functions or functions that still have to be enabled easier.


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