Originally Posted by
bobrun
Wasn't there more failures than those related to the air data?
Loss of pitot tubes or ADRs wouldn't explained the failures of PRIM1 and SEC1 flight control computers. It wouldn't cause the aircraft to lose pressure either.
Also, the failures were reported by the CMS computer over 2-3 mins, but that doesn't mean they happened over that period of time.
The search function is a wonderful thing.
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Originally Posted by
captainflame
From a pilot prospective and arguably by just looking at the failures on the list:
2- One ADR failure is NOT consistant with flags on PFDs. (airbus eliminates 1 erroneous data source if 2 others are the same, transparently to the pilots)
BUT
Two ADR failures is ! and the ECAM message would read:
3- NAV ADR DISAGREE ! which we find in the list.
4- which in turns get the Airbus to revert to ALT LAW without protections (overspeed, and alpha)
5- autopilots, ATHR, NAV TCAS and F/CTL RUDDER TRVL LIM are associated inop items.
6- F/CTL computers (Prim 1 and SEC 1) could then be reset, and recovered (or not) (they receive wrong data from ADRs)
We're left with the STBY probe, feeding directly (no ADR) the ISIS (self contained stby instrument). Which also seems to report faulty info !!
Near Max rec ceiling, the operational airspeed margin on a jet is quite narrow. easy to go to overspeed, or a stall (no protection), especially in very turbulent conditions.
Flight manually assured using good old techniques of "Pitch and Power", in the QRH for "unreliable airspeed"
7- last message on list : ADVISORY pertaining to Air cond/pressurisation MODE Fault, seems to be linked to cab descent rate (unable to cope with a high VS descent to maintain required DIFF pressure !)
The F/CTL computers will report faults if they get enough bad air data info. The only message which doesn't seem to be directly air data driven is the last one - which may be a result of the aircraft having at that stage departed controlled flight. Or could yet be a strange air data driven one, if the cabin pressure controller is being confused by very strange air data.
And someone familiar with ACARS has mentioned that it takes the system fractions of a second to process a message and transmit it, so we can be reasonably sure that the timings are ROUGHLY correct, at least in terms of the to-the-miute timings.