Flight Controls
Gentlemen,
please consider these :
02:13:45 F/CTL PRIM1 FAULT
02:13:51 F/CTL SEC1 FAULT
First, this describes a simultaneous failure of PRIM1 and SEC1, which greatly reduces the likelyhood of a manual shutdown or reset.
Second, this has a fascinating consequence, which can only be found when looking carefully at the flight controls reconfiguration schematic in the FCOM: PRIM2 becomes Master of pitch, through both elevator halves and the THS (trim) because PRIM1 and SEC1 have given up.
Third, it is interesting to relate this mastery over pitch by PRIM2 with another event affecting the same computer in a strange way :
02:11:55 WRG:ADIRU1 BUS ADR1-2 TO FCPC2, HARD
(FCPC2 is PRIM2)
What the heck does this message mean ?
One interpretation is PRIM2 loses connection with ADR1 (part of ADIRU1) through a failed bus. BEA exlained it away with "PRIM2 rejects ADR1"... However, this particular failure does not seem to have anything to do with unreliable airspeed and ADR comparison, it is quite obviously an electronics connectivity issue : WRG means wiring, gentlemen. Airbusese for "warning" is WRN.
How strange is it that such an event, electr(on)ical in nature, would be simultaneous with the failed probes, which has external causes (icing) :
02:11:49 PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA), HARD
How strange is it that this PRIM2 computer would find itself in the middle of an erroneous air data situation while at the same time suffering a connection failure with one of its three sources ? How would it react in this condition ? How would it compute its flight controls commands ? Has this been tested or even considered during design ?
Comments ?