Air France Jet Missing Off Brazil Coast

[MrRiplEy[H]]

What caused the wrongfull speed reading?

Nothing is certain but the plane reported weird readings and the sensor has a history of ice induced malfunctions. Shortly after that automatic system notices reported system malfunction after another (plane breaking up in air?).

[RTHolmes]

Wouldn't the GPS give ground speed instead? The satellite doesn't know what the winds are does it?

sry yes ground speed, presumably the instruments also give an indication of ground speed calculated from IAS?

[Golfer]

The failure of one air data system, air data computer or smartprobe (or whatever Airbus calls them) wouldn't bring down the airplane.  On an airplane as sophisticated as the A330 you likely would have an air data miscompare message which very likely would disengage the autopilot leaving the standby systems (which are independent of the main ADCs) giving reliable information.  The autopilot disengaging in that situation would leave the airplane flying in its previously trimmed condition and present no challenge to the flight crew to resume hand flying.  They would also know it failed because they would have the aural autopilot disengage warning playing until they silenced it.  If there is a miscompare I imagine the 330 would tell you which has failed but troubleshooting shouldn't prove to be a difficult task to determine the failed system.

Even with no airspeed information the airplane will still fly.  Leaving the thrust levers where they were, keeping the pitch attitude where it needs to be to maintain level-ish flight and using your still working navigation systems would add workload but not present undue risk to those on board.  We don't know anything about this accident and the facts we do have can present in several different ways.  I'll keep waiting for more facts.

[F111]

here's a question?

over land, all commercial flights like this are on radar all the time. is there radar that far out?

They were beyond radar range.  No radar contact.

[MrRiplEy[H]]

The failure of one air data system, air data computer or smartprobe (or whatever Airbus calls them) wouldn't bring down the airplane.  On an airplane as sophisticated as the A330 you likely would have an air data miscompare message which very likely would disengage the autopilot leaving the standby systems (which are independent of the main ADCs) giving reliable information.  The autopilot disengaging in that situation would leave the airplane flying in its previously trimmed condition and present no challenge to the flight crew to resume hand flying.  They would also know it failed because they would have the aural autopilot disengage warning playing until they silenced it.  If there is a miscompare I imagine the 330 would tell you which has failed but troubleshooting shouldn't prove to be a difficult task to determine the failed system.

Even with no airspeed information the airplane will still fly.  Leaving the thrust levers where they were, keeping the pitch attitude where it needs to be to maintain level-ish flight and using your still working navigation systems would add workload but not present undue risk to those on board.  We don't know anything about this accident and the facts we do have can present in several different ways.  I'll keep waiting for more facts.

Probably the systems are more advanced nowadays but I remember seeing several cases in aircraft crash investigation series where false readings and no visibility caused the crew to rollercoast 10k up and down almost hitting the ground at lowest points. Aircraft was giving the crew two readings and they didn't know which to believe. Eventually they crashed just because they had no ground contact and misread the airspeed.

[Golfer]

Such would not be the case of the airplane in question.  It's a very low time/low cycle airplane delivered in 2005.

I cannot imagine it being delivered without systems as I described.  New off the line Embraers and even my 10 year old airplane have such systems in place.  The data of all systems will be compared and if they exceed the tolerances you will receive a miscompare.  Your options then become to switch to the good system, typically regaining control of the autopilot when doing so or if for some reason both main systems dropped offline at the same time (not even a 1x10^9 chance for that) you'll have standby instruments running on their own independent air sources which on a 330 are located left center of the instrument panel adjacent to the captain side PFD.

Even if a complete ADC failure were to occur where you flew through a giant film of jello clogging all of the air data probes the airplane wouldn't fall out of the sky.  This would be losing ADC/ADS 1, ADC/ADS 2 and the Standby instruments (note: This doesn't happen) resulting in no airspeed/altitude indications.  During cruise time the loss of airspeed and altitude indication would provide little more than an annoyance to a crew.  Your navigation systems are still operating and prudence would dictate offsetting course as you will not know your exact altitude. You'll still have attitude control, control of the engines and surfaces and lots of time to find your way to good weather to make a landing in visual conditions.  This would be greatly aided with an AoA (Angle of Attack) indication which are options (not standard) on Boeings and I would expect not standard on Airbus given their levels of electronic integration. 

[Eagler]

even if its discovered to be a bomb, another reason will be generated to avoid panic as this economy can not stomach the thought