takata;
This aircraft control should not have been compromised by this event alone, meaning, an adequate crew reaction (or without reaction at all. In some other cases, they just did nothing until A/S anomalies ended by themselves).
Exactly. The aircraft was stable before the loss and any change in that state would require input, (crew, aircraft weather); if none, stable flight would remain, requiring only minor adjustments until the event passed, as shown by the previous events. The aircraft wasn't "out of control", and there was no need for the pilots to "control" the aircraft...as with any abnormality, there was the need to respond as per training, in this case, to ensure that everything
remained the same, within the bounds of possibly-turbulent flight. A loss of airspeed data does not cause a loss of control.
For a number of reasons, I concur with your comments regarding the crew break. It makes sense to infer that the RP was in the left seat, as P2.
oldengmkr;
I was wondering when or if this AAIB report would surface again and had been considering the events and responses described for some time. The link to the Report was first posted by
delta092b on the second thread (of four, this being the fourth "major" thread) on June 5th, 2009,
post #239, four days after the accident.
The report as quoted above, states: "
Ten seconds after the autopilot disengaged, the corrected or phase-advanced angle of attack (a computed parameter which is not recorded but can be calculated by Airbus Industrie from the DFDR data) reached the 'alpha prot' value. This angle of attack excursion beyond alpha protcaused a change in the pitch flight control law from normal law (NZ law) to angle of attack protection law (AoA law). "
To keep any response to a reasonable length, the CAoC or "Corrected Angle of Attack", (I hadn't seen the term "phase - advanced" in my research), is calculated by the ADIRS; it may or may not be recorded. AoA is certainly recorded; I have accessed it and monitored it in turbulence using the ACMS-Parameter Alpha Call-up mode, available in the MCDUs.
Among other uses, it is used by the SFCC [Slat-Flap Control Computer] as part of an anti-retraction mode which is based upon CAoA, (nominally, 7.5deg) and <148kts CAS) if I recall.
The outcome for the A340 is dramatic: 6000fpm up, a loss of 65kts or so and a climb of over 4000ft.
We must bear two things in mind, (notwithstanding the crew's surprise and concern in re the A330 800ft or so above them!) - a) For this to obtain for AF 447,
the aircraft would have to be in Nz Law before the other events occurred, and b) as per the Report, full forward stick would return the aircraft to Nz Law (from Angle of Attack Law).
What I don't see explained in the report is why the AoA Law was triggered. Was it Mach-related or low-speed related? Was it turbulence-related, and if so, what was the AoA and what were the exact circumstances (re Mach number) that exacerbated the event and possibly opened the door for subsequent factors to trigger the AoA Law? I don't think this was just a case of "Mach buffet".
We do have the evidence which shows a very high vertical impact force. A number of theories are "in play" so to speak as to the loss of control, including some which contemplate a controlled descent followed by loss of control lower down. Possibly - nothing we know verifies this or a LOC near cruise vice lower down - We can only infer but not conclude.
One item I have considered is the UAS QRH checklist, which can, I think, be misinterpreted. Examining flight crew training manuals explains the correct way to handle the memory drills and subsequent read-do checklist but I think this notion should be examined if only to dismiss it.
gums;
Just waiting and reading. There is really nothing to say at this point.
There will be time enough for robust debates after the data is read and some general hints at what happened are provided. The discussions will be interesting when a 3rd Interim Report is released in due course, (which I would expect to include the maps, an outline of the way of LOC, some flight data examination and comparisons with the ACARS series).
HN39;
I was unable to locate "Appendix B". If the report has something to contribute to an understanding of the AFS especially the reconfiguration of flight laws from Nz to AlphaProt Law, I'm sure what there is in this report will be available and its relevance hopefully established. There are some primary differences in that event: For an AlphaProt Law response, the aircraft must be in Nz Law as the response (HIGH AoA and PITCH ATT) wouldn't be available in either Pitch Alternate law.
As we are aware, the AD that was released on December 22, 2010 states, "
However, in some cases, the autopilot orders may be inappropriate, such as possible abrupt pitch command.
In order to prevent such event which may, under specific circumstances, constitute an unsafe condition, this AD requires an amendment of the Flight Manual to ensure that flight crews apply the appropriate operational procedure." The AD does not mention those "specific circumstances", nor do we know to what event(s) the characterization of "abrupt" refers, if any.
Perhaps the dots are still too far apart to see viable connections but this event and the one to which I refer above concerning the UAS QRH Drill, are possible areas to focus upon along with weather.