Originally Posted by xcitation
@Takata
Do you recall the posts that AF did not install all of the available backup steam guages option on this a/c?
As far as I can remember, this was all about the optional BUSS (Back Up Speed System) not installed on AF fleet. Hence, this is not related to inertial references or standby gauges. In this regard, AF opted for optional ISIS as a backup instrument display.
Originally Posted by xcitation
The report does not explicitly state attitude failure. However it does not state that attitude indactions were all displayed faithfully. FDR did not record speed on right PFD, so maybe not the attitude.
Actually, the BEA report #2 explicitly ruled out
attitude failure:
Fact/findings:
None of the messages present in the CFR indicate loss of displays or inertial information (attitudes) This fact was not challenged by further findings, including CVR and DFDR readings. What the BEA is stating in the last note as being the current pitch angle, at certain time, is comming directly from the same source used by the pilots. Even if ADIRU 2 (F/O's source) is not recorded, the way the system monitors the attitude sources (IR references) is ruling out that it could be at any time in error with the other sources recorded (ADIRU 1 & 3).
Originally Posted by xcitation
The BEA report does show errors on both ADIRU and ISIS. Having read some other incidents I recall that Airbus can give bogus stall warnings and PFD degradation under certain ADIRU failures (those 2 Airbus incidents near the Australian radar station?). IMHO the scant BEA reports do not eliminate the possibility of a degraded attitude indicator on the right PFD.
The BEA reports, as well as the fault sequence analysis, is showing that no attitude degradation of the PFD and ISIS ever occured during this flight.
PFD and ISIS are displaying a lot of informations, each linked with various functions. The faulty functions recorded in the ACARS CFRs (current flight report) is showing faults unrelated with aircraft
attitude.
- ISIS failure: what faulted was the Speed/Mach function; specifically (now with further avail. data), it is showing that
static pressure was at one point higher than total pressure (pitot/static probe 3 related fault); this happened between 0211:00 and 0211:59 (at this point, aircraft had already reached its top climb, 38,000 ft, and was certainly stalling).
- ADRIRs failure: the one reported by IR parts of the 3 ADIRUS is also related to probe issues: it is pointing that either values of pressure altitude, barometric vertical speed and true airspeed were invalid on the three ADRs (possibly all three cited values were wrong). As above, this happened between 0211:00 and 0211:59, same remarks.
Beside, Quantas issues with a faulty ADIRU was also unrelated to IR faults.
Originally Posted by xcitation
The list of 7 reasons are purely speculative.
Right, but basic speculations should be based on the whole dataset, not discarding a single information or pushing wilde interpretations of automatized systems which are basically highly predictibles (because they have been built to behave like that, this is a very deterministic process, unlike crew actions).
Originally Posted by xcitation
Probably a better title is "possible contributing factors to a general nose up/stick back". I was struggling with imagining the crew spending nearly 4 minutes looking at the +15 deg pitch and giving it generally stick back - sometimes to the stops. Which scenario(s) would you envisage to explain this?
When one reads many other reports (in whatever context) about human behavior in stressful circumstances, this is not very hard to catch up that a wrong initial analysis may surely lead one to sustained wrong acts. Here "the Crew" is a too strong term as for explaining the first sequence until reaching max altitude. This lasted no more than 40-50 seconds, Captain was in his bunk and PNF was certainly very busy with systems checks rather than monitoring exactly what the PF was actually doing, not even talking about him making some cool headed instrument scans.