Originally Posted by
deSitter
BOAC above presented a report from Der Spiegel that a certain Prof. Huettig had re-created the incident in the simulator - the THS went up and stayed there - curtains. This seems to me to be the smoking gun in this crash.
The simulator is not the aircraft - given that it seems that they were in a situation that had not even been encountered in test flying, so no data with which to program the simulator. There are no details as to the specific actions Prof. Huettig performed, or how they correlate to the actual actions as they were performed in the flight deck.
I find it quite ironic that you of all people, who considers software so unreliable and so many of the people who create software to be... What was it? I believe the word was "dolts" (no offence taken,
sir...) would be willing to put his whole weight behind a "smoking gun" derived from a computer simulation that was based on incomplete data.
Originally Posted by
Graybeard
Does anybody understand the rationale for two sets of control laws between Normal and Direct? It seems to make systems management take precedence over aviating.
It's simple really - past the dry engineering language it boils down to the fact that Alt1 has protections, Alt 2 (effectively) does not. If I were a pilot, I would be very wary of relying on any of the remaining protections in Alt Law to back me up, doubly so in a situation when there's an obvious data capture issue (or in aviation terms, unreliable instrument readings).
Originally Posted by
Lonewolf_50
As yet, no evidence that the AH's embodied in the glass cockpit displays (for basic flying instruments I note above to Clandestino) were other than functioning per spec.
Correct.
Originally Posted by
bearfoil
I'm writing with some very old notes, I may traipse back a couple years, the notes are not mine, apologies. My understanding is the pilots were without any reliable instrumentation re: AoA. If one is committed to, and experiencing stable cruise flight, attitude is critical when things go bump? Pitch is in there?
AoA information and functioning AH/AI/ADI (whichever you want to call it) are not one and the same thing, bear. On modern aircraft (talking about anything post 757/767), attitude information is provided from a redundant pair of electronic gyro boxes known as an AHRS. Attitude information does not rely on either AoA vanes or Pitot/Static sensors.
I refer you again to the Birgenair accident where the aircraft (a 757) was effectively in the same situation, though it was a case of the captain's blocked pitot tube being hooked up to the FMS (autopilot), thus inadvertently creating a single point of failure rather than all pitots being blocked. In fact by programming the FCU to detect multiple pitot failure and kick the autopilot out upon detection, Airbus actually created a safer design. The Birgenair 757's FMS actually tried to fly the aircraft on the bad information, pitching the aircraft up to an extreme AoA, and it was only that extreme AoA that caused the FMS to switch out. If I recall correctly (and please, anyone, correct me if I'm wrong) Boeing later retrofitted the 757 and 767 fleet to enable selection of pitot/static data to the FMS, so that a failure on one side would not be catastrophic.
In that case, the all the ADIs (powered by AHRS) were functioning perfectly, and the relief F/O repeatedly called out "ADI!" on the way down, pointing out that the aircraft was in an extreme nose-high attitude (the other F/O, who had a working ASI repeatedly called out that they were stalling) - all the way down to the ocean. The pilot in that case, as I've said before - no low-hour newbie, but an experienced ex-Air Force jockey appeared to be so overwhelmed that he failed to check the ADI in front of him that was telling him he was nose-high, even as his F/Os were emphatically telling him what to look at.
Originally Posted by
bearfoil
The Plane rolling right meant that a/p had been trimming out a chronic and trending condition, both Right wing heavy, and NOSE HEAVY. ... Perhaps?
Bear, you've got to be careful how you phrase this stuff. A newcomer to this thread would think that what you're presenting is a known fact rather than a theory posited by a single poster that is based on no evidence whatsoever.
BOAC, If the context wasn't so serious, I'd be willing to wager with you that what comes out of this will prove all this talk of software and laws to be something of a red herring. We've seen two 757s go down due to pitot/static failure and their controls were not software-driven.
That said, if what some posters are saying about inadequate training in use of the manual trim wheel is true, then it's a major problem, but it's not a software problem. Ultimately, even if you're in Normal Law and you don't like what the trim is doing you can grab that wheel and set it manually.
I know that the increased presence of computers in the flight deck is an emotive issue for pilots, but I can assure you that from the perspective of this software engineer, and, I'd be willing to wager even more - every software engineer who worked on the FBW aircraft that are flying today - we are on your side. We are trying to make your job easier. The systems we built were specified and designed from requirements put forward in the main by pilots. We are not intending to replace you. If your employers are saying that the technology effectively reduces you to systems monitors - and that hand-flying is discouraged - then they are abusing what we gave them, and as PJ2 says, you *must* fight them on it for the sake of every person who boards your aircraft. That was not the intent, and I hope never will be in my lifetime.