Originally Posted by
gums
No problem here with HAL until HAL starts to get in the way of what we pilots believe, actually BELIEVE, what we need to do and HAL gets in the way because HAL is programmed to PROTECT us. 'nuf there, so on....
The problem there is that in the vast majority of cases, the FCU (or as you insist on calling it, "HAL") is right. In any case you have to be doing some pretty unusual maneouvres for an airliner before any of the hard protections kick in (namely continuing to demand bank angles past 67 degrees, letting the AoA increase until approach to stall or increasing thrust or downward pitch at the overspeed limit).
INSERT: Alaska airlines THS accident not relevant here, as it was a clear mechanical problem and the crew tried everything in the book and some neat techniques until all was lost..
I wasn't saying the incidents were similar, I was using it to illustrate the different tactics the higher-ups were using to reduce costs - cutting maintenance in the '90s, and training when the FAA closed the door on dodgy maintenance practices.
The 'bus reversion sequence appears to preserve many "autopilot" functions until all else turns to worms ( old fighter pilot phrase, so excuse me). Fer chrissakes, the jet seems to be very docile and has inherent spin resistance and such. There should only be two "laws" - autopilot and manual. The Otto limits could also be the "manual" ones, but the pilot inputs would be from the pilots and not some confuser. So retain the overspeed and AoA warnings. Let the pilots fly as they wish, but don't allow HAL to keep trying to "protect" them.
You're getting autopilot functions and limits confused with FCU protections - for a start, traditional autopilot limits are set considerably more stringently than the FCU protections will allow (as far as I'm aware there's no autopilot in the world that will allow 67 degrees of bank, for example). FCU protections can also command the engines to increase thrust in the case of stall protection whether FMC (A/P) is engaged or not, which is one of the reasons why they are called "protections" rather than "limits" (I believe you asked that question earlier on?).
With all due respect, I find "confuser" as infuriating as "HAL". If I started using derogatory terms for pilots in the same manner I'd be banned before too long. I go out of my way to show respect to the pro flyers on here, and I don't think it's unfair to request a bit of common courtesy in return.
Problem with the 'bus is after A/P disconnects for whatever reason the pilot may think he/she has the "protections" that existed just a second before. Not so. The "autotrim" function still is active, and the alpha prot feature can be confused or even disabled when HAL decides that air data is unreliable.
If the A/P disconnects in almost all cases, the pilot *will* still have the protections - the protections are lost in a UAS situation when Alternate Law is triggered and latched. The protections in Alternate Law are soft protections that consist of warnings and attempts to return to S&L - unless they are overridden by pilot inputs as they appear to have been in this case.
What the pilots need is something to hang their hats on when the autopilot functions and all the layers of "protections" are invalid.
And they have it - you can't blame the systems for the apparent response of the PF, which would be wildly inappropriate in any airliner.
Many of the sfwe-illiterate pilots, and even anti-sfwe folks can provide bad inputs to the sfwe folks. I have some great war stories about the shuttle folks when NASA implemented the HUD for that beast. My roomie helped get the one you all saw a few months ago on its last landing.
Would be interested in hearing them, but I don't see where that applies here - this is not a case of the Airbus control logic being a specific example of a complex system confusing the pilots, this is a case of a really nasty overwhelming situation getting on top of a crew who were not prepared to deal with it by their trainers and empoyers, just as it was with the Stony Point 727, the BirgenAir 757 and the ColganAir Q400.
We can discuss this issue privately, or we can create a new thread.
Maybe another time, as I've got a lot on at the minute and can't follow this as much as I'd like to.
