lomapaseo;
Quote:
One thing that sticks with me so far is that the pilot comments on this thread seem to have a pretty good idea of what they would have done in the the loss of air-data turbulence scenario.
If my interpretation is correct then this is a pointer for searching for other factors.
PJ2;
Quote:
Yes. That is one of the reasons I wished to take some time to write this rather longish post. I think looking towards "the computers" for a cause is a rabbit trail; we will not be able to determine what happened by following it.
lomapaseo, PJ2
Thank-you for bringing the discussion back down to earth.
Will Fraser;
Quote:
I proposed early on that the interface between Otto and flying pilots is weak and in an out of balance "command" way. It is too quick and too absolute, seemingly wonderful traits, but deadly under certain circumstances. Pilots are comfortable (too much so) when things go pear and the computers make command decisions that are precipitous, and leave the ultimate pilot out of "the loop".
Imagine flying along fat and happy, and in less time than one can belch, the box cascades decisions and reports to be assimilated immediately with the a/c and its contents at risk!! Dark, turbulent, seven miles up, and the box hands two people two folders of data, to be understood and acted upon whilst the seats under your primitive "cheeks gyro" are telling you you have one half second to input a control.
The previous reports of similar loss of data flow involved less than harrowing conditions, and were successfully escaped; conclusions about those incidents are being debated even now, and you are at ease with the highly possible loss of data, panel, as, etc. to be dumped unceremoniously on the pilots laps???
This interface is the 400 kg gorilla no one seems to be discussing.
Will,
Frankly I'm getting tired of your dramatic, near hystrionic imaginings. Based on your comments you don't really seem to have much of an idea how this airplane actually works or what the situation that presents itself in the cockpit will look like or how it is dealt with by either pilot or aircraft.
I do. And it is nowhere near "
the a/c and its contents at risk!!" "
in less time than one can belch" scenario you keep trying to conjure. Now, before you come up with some "No, you don't really, you just think that based on sim exercises" type remark, let me state that I really do. This is the result of an event in the real aircraft (in this case an A320) at night in bad weather. My experience was the second (at that time, 14 years ago) ever recorded near-simultaneous dual TAT probe failure on an Airbus family aircraft (later traced to non-common failure modes with an incredibly low probability of occurence). Because it was such a rare experience it was fully investigated by Airbus even to the point of sending update telexes directly to me as the PIC involved.
The incident, which included a very similar set of failures to that which I have seen from the AF ACARS print-out other than the assumed loss of airspeed indication, did not involve the "
box cascading decisions" or "
two folders of data, to be understood and acted upon whilst the seats under your primitive "cheeks gyro" are telling you you have one half second to input a control." (do you happen to write for the Sun when you're not posting here?).
What did happen was first the loss of AP1, then of AP2 and Auto-thrust. This was followed by reversion to Alternate Law and ECAM messages related to changes and degradations in a number of other sub-systems. This occured while climbing at night through cloud with turbulence somewhere in the mid-twenties. None of the losses as they occurred caused any significant effect on how the aircraft handled, and in that sense the transition from autopilot control to manual control by the pilot was virtually seemless. The number of ECAM messages to be dealt with, though significant, did not cause "cheek gyro clenching panic" or even a great deal of confusion for the crew in terms of how to configure or operate the aircraft. The biggest challenge was that the source failure (a dual one as it turned out) was difficult to correlate to the system failures observed. This turned out to be a result of the failure message for the STBY TAT probe failure not being sufficiently unambiguous to be differentiated from the message for the CAPT TAT probe failure. Hence it was only immediately obvious that one source had failed, not two, which caused a good deal of FCOM investigation as we went along to try and match what we were observing to that which had to have failed.
Shortly after we left our departure airfield it had closed due to weather and likewise the weather had reduced all nearby airfields to CAT II conditions or lower. Given our situation we did not consider a return or diversion for landing in such conditions to be an optimal choice and hence we then flew the airplane (yes, all manual flight at high-altitude) for over an hour across the Rockies to get to a suitable diversion airfield. As the situation evolved, it was the more mundane aspects that proved a bit more challenging, the aircraft handling itself was a complete non-issue. The dual TAT probe failure locked some of the FMGC functions such as flight phase changes, adding a few tricks to how to navigate to our diversion airport and make approach preparations. When we arrived at the diversion airport the approach was conducted hand flown in alternate law with an uneventful landing in direct law once the gear was extended.
The moral of the story, Will, is that the probe faliures that have been described, and which we believe may have occurred to the AF aircraft, do not result in things going immediately and dramatically pear shaped or the aircraft making "
command decisions that are precipitous, and leave the ultimate pilot out of "the loop". They are a challenge to deal with, as they would be on any aircraft, but they do not materially affect the controlability or stability of the aircraft. Trying to cast this as "
the 400 kg gorilla no one seems to be discussing", is a venture into over-wrought hyperbole at a point where there is no information that supports how a loss of control may have occurred and whether or not it was from forces that would have caused an upset in any aircraft, modern or geriatric.
ELAC