I have no intention of speculating of the possible cause/s of this tragic accident, but I would like to ask a question that relates to the Airbus radar.
Several posters have mentioned that it is possible to have the radar "dimmed" and that this may not be noticed by the crew.
What I don't understand is how it is possible to select, test, tilt and operate the radar if it is dimmed to an extent that it prevents seeing any image or returns. Surely, in order to start any kind of scan using the radar, the image must be visible so that tilt and intensity scans can be seen and set up for the phase of flight.
Radar is not simply something that you switch on in the hope that significant returns will pop up - the display must be seen to even test and start using it - unless Airbus have some fancy system that I have not yet come accross.
Can Airbus pilots please explain the "dimming" problem that several have mentioned
Clive you're quite right. To try to give you an idea of how it works (or doesn't) In front is your ND - Nav Display, which is to the side of the PFD - Primary Flight Display, which contains horizon, altitude, speed, mode annunciators (FMAs) etc. On the ND you can toggle between overlays of weather, of GPWS terrain data, or nothing.
The dimming function doesn't refer to the operation of the weather radar itself, it simply changes the brightness of the selected overlay on your ND. So if you have is pointed right down, and turned to full brightness you be presented with a huge swathe of primary colours, mainly red. Much like the contrast of brightness on your TV you can then adjust the brightness of that colour to what is the most comfortable or least distracting. The actual functions of the weather radar itself are as I'm sure you can imagine, controlled on the weather radar panel elsewhere.
In my own experience I have found the weather radar on my Airbus fallible. A day or two before the Air France accident I flew through an area of numberous isolated CBs. All well defined in daylight in an otherwise clear blue sky and easy to spot and count by eye. Try as I might, scanning up and down with the radar for my own amusement, by my reckoning only 50% produced a return. When it did come, it was very good but for some reason others produced not a sausage. Not a problem on a day like that, but it gave me pause for thought should the same scenario be repeated with the addition of turbulence, night and embedded CBs. I do not think that a weather radar need be inoperative in order for you to fly into something.