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  • (Bloomberg) -- The pilots of AirAsia Bhd. Flight 8501 cut power to a critical computer system that normally prevents planes from going out of control shortly before it plunged into the Java Sea, two people with knowledge of the investigation said.
    I would treat this as shady information. It doesn't explain the pitch-up order as the FAC's only control yaw. It would only explain the loss of stall protections.

    It's strange that they would use the CB when there are pushbuttons right there on the overhead. I suppose one possible theory is that the flight was dispatched with one FAC inop and perhaps the system won't allow the remaining one to be shut down using the PB. But I doubt that as this is not an essential flight control system.

    If this turns out to be true I think it will only be a layer in the cheese: first the loss of AoA protections, then, for an unrelated reason, the loss of autoflight (possible UAS) and bad airmanship + lack of procedure/CRM leading to a stall, left roll excursion and failure to recover. The flight can be dispatched with one FAC inop and can be safely flown in alternate law with both FAC's inop. If this were not true, the MMEL would not allow dispatch with a single FAC.

    I also find it amusing that these press articles state the loss of protections leaves the crew having to fly 'manually'. Of course, the loss of autopilot leaves the crew to fly manually and protections are only valuable in manual flight. Loss of protections only leaves the crew having to fly manually without doing something unthinkably wrong.

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    • Indications that the guy's were pulling circuit breakers? That makes it a bit scary in it's parallels to 2001 Space Oddesy and having to shut HAL down!

      In contrast to AF-pulling up the whole time- I think the AF guys at least sort of gently eased into their climb, where this looks like more of a WHAM-HARD-LEFT-HARD-UP-AT-THE-SAME-TIME...something OTHER THAN a procedurally-trained human would seem to have initiated the control inputs...they are typically a bit gentle.

      Will we hear the words, "But I've been pushing over the whole time." and "What's it doing now?"?

      By the way, we need to modify our CRM procedures: What's a CB? I big nasty cloud that likes to eat airplanes or something that turns off electricity?
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

      Comment


      • Originally posted by 3WE View Post
        Indications that the guy's were pulling circuit breakers? That makes it a bit scary in it's parallels to 2001 Space Oddesy and having to shut HAL down!
        Scary and stupid. In the case of HAL9000, the only way to shut him down was to pull memory modules (I'm having a geek moment). There was no off switch.

        That is NOT the case with the A320 FAC's and there is no FCOM procedure for pulling CB's in flight serving the FAC's. This is because there are already overhead pushbutton switches to do this. These switches are indicated in the QRH procedure for FAC 1 (2) FAILURE and FAC 1 + 2 FAILURE.

        It is VERY IMPORTANT to use these switches for the following reason: Each FAC has separate channels for each of its functions (yaw damping, rudder trim, rudder travel limit, rudder position awareness, speed limitation computations, PFD speed indications, etc.) When the pushbutton is used, the flight control channels of the FAC are deactivated but the SPEED ENVELOPE FUNCTIONS REMAIN ACTIVE. That means you still have envelope protections and all the airspeed guidance displayed on the PFD's.

        When you deactivate them via the CB's you lose all of this. That means no AoA protections, no stall or overspeed indications on the speed tape, no green dot, no trend arrow, no yellow band or barberpole. Really, truly stupid move.

        I know for a fact that when you pull both FAC breakers you also lose autopilot and autothrust. This is also true when you select both pushbuttons to off. Shutting down a single FAC does not affect autoflight however if the other is still engaged.

        The overhead CB panel has only breakers for FAC1. The breakers for FAC2 are on the M lane which is on a separate panel in the rear of the cockpit. I think this is because pulling FAC2 is a ground maintenance move, while pulling FAC1 is seen as a extreme but possible scenario in flight (where FAC2, if available, takes over). Someone has to get out of their seat to pull FAC2. However, if the plane was dispatched with FAC2 already pulled (on the MEL), then pulling the FAC1 CB's would result in all of these lost systems and indications.

        But again, that is what the pushbuttons are there for. Pulling a CB in flight should ONLY be done if an electrical short is suspected. If the system is behaving erratically the procedure is to use the pushbuttons off and then on again. (only systems that do not have a pushbutton are reset with the CB's).

        So if in fact the rumor is true that these guys shut down both FAC's with the breakers (or the remaining one with the breaker) it is pure pilot improv error and contrary to procedure for a some very good reasons.

        If in fact the rumor is true we would also know they lost: autoflight, normal law, speed protections, speed guidance on the PFD including barberpole, yaw damping and RTL and turn coordination. They would still have PFD speed indications and stickshaker/stall warnings however.

        Attachment: Overhead pushbuttons for flight control systems.

        Comment


        • Originally posted by Evan View Post
          Scary and stupid. In the case of HAL9000, the only way to shut him down was to pull memory modules (I'm having a geek moment). There was no off switch.

          Additional acronym-laden verbiage.
          As I recall, they had to open the pod bay doors to freeze HAL.

          With respect to the additional verbiage, I really look forward to the final report here

          The thought of an electronic plane going WHAM and doing a "full" pull up, or a hydraulic plane going WHAM full right rudder on short final, or even suddenly screaming stall at 2000 on a late night in a snowstorm, and the time one has to react...in some of these instances it's disturbing and I have great sympathy.

          Conversely, if it's JUST a bunch of warnings at flight level...ATL mentioned that one guy who said, "First do nothing", and the old fundamental joke to light a cigarette.

          ...where some of your reactions ARE trained responses, and then they don't work...Oh crap, what's next...what's the term, "startle factor" but when things keep getting worse fast...
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

          Comment


          • More and more and more this sounds like a badly trained crew with poor airmanship skills being permitted to sit in the worst two seats imagineable.
            If it 'ain't broken........ Don't try to mend it !

            Comment


            • Originally posted by brianw999 View Post
              More and more and more this sounds like a badly trained crew with poor airmanship skills being permitted to sit in the worst two seats imagineable.
              Amen to that. I'm hoping these are just rumors.

              Comment


              • Originally posted by brianw999 View Post
                More and more and more this sounds like a badly trained crew with poor airmanship skills being permitted to sit in the worst two seats imagineable.
                The seats right next to the only toilet on an Easyjet late night flight back from Prague, filled with stag-night-attendees? Been there...

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                • Are the flight hours hours for the pilot and co-pilot of Air Asia 8501 in the average range, or unusual in any way?

                  The co-pilot, with 2,247 hours of flying experience, was at the controls and talking to controllers while the captain, who had 20,537 hours, was monitoring, said Mardjono Siswosuwarno, the lead investigator of the crash. The account was the first description of the last moments of the flight.

                  Comment


                  • This crash reminds of something that was a contributing factor to this A320 crash. (also dramatized here). Essentially when the Airbus reverts to full manual, just pushing the stick forward isn't sufficient to (quickly?) drop the nose. A trim wheel must also be manually adjusted as well; something easy to overlook in a panic situation if the pilots not ready for it.

                    Comment


                    • Originally posted by srw View Post
                      This crash reminds of something that was a contributing factor to this A320 crash. (also dramatized here)...
                      Dramatized to say the least... In the first depiction of the crash, they don't even mention that the crew was doing an intentional low-speed alpha floor test. I have a big problem with this series and their laughable plywood cockpits and plywood understanding of these events (not to mention the little things: notice the plane has reversers deployed on 'takeoff' roll and the Hudson River crash plane has an MD-80-ish windscreen.)

                      But more importantly, notice that the PFD has no speed bugs, no yellow band or barberpole. The real crash aircraft had these clearly displayed and they were quite obviously in the wrong place due to the AoA vane issue. Vs was well below the speed that the airplane could possibly fly at. That's a red flag, especially on a test flight. The crew should have noticed that (basic airmanship).

                      They are also wrong about why the pitch trim needed to be used manually. When the A320 reaches an extreme AoA, well beyond approach-to-stall, the control law becomes Abnormal Attitude Law. In most respects this is like Alternate Law but the pitch trim is frozen at the present state. This crew let the situation decay far too long until the pitch trim was full nose up and then the control law froze it there. There was also another factor involved. In trying to recover, the pilot commanded full thrust. This added thrust-pitch coupling to the problem. The pitch trim being frozen nose-up and the thrust coupling combined to cancel out the pilot's elevator inputs. Unless pitch trim was moved manually or thrust reduced, nothing was going to bring the nose down but gravity.

                      And, icing on the cake, they are wrong about the AoA probes being there to indicate the angle of the aircraft. They are only there to enter angle-of-attack data into the computers. Attitude is determined by the IR system gyros.

                      Perhaps most significantly missing from this dramatization, the center system AoA probe was not frozen and is responsible for the stall warnings that DID work. The pilot got stall warning. Funny, it doesn't happen on the video leaving him to wonder why this 'crazy' airplane is in trouble.

                      The bottom line here is that this was maintenance negligence combined with poor procedural discipline, poor airmanship and a weak understanding of the aircraft's essential control law reversions. There was never anything wrong with the aircraft aside from that.

                      And yes, it could have happened again, but these rumors about pulled FAC circuit breakers suggest another kind of foolishness.

                      Comment


                      • Originally posted by Evan View Post
                        these rumors about pulled FAC circuit breakers suggest another kind of foolishness.
                        Some sources insist the CB part is only rumors, lost in translation. They crew may have manipulated only the overhead FAC switches. And of course, the preliminary report is not going to be made public.

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                        • Pilot left his seat at time of loss of control.

                          SINGAPORE/JAKARTA/PARIS (Reuters) - The captain of the AirAsia jet that crashed into the sea in December was out of his seat conducting an unusual procedure when his co-pilot apparently lost control, and by the time he returned it was too late to save the plane, two people familiar with the investigation said.

                          Details emerging of the final moments of Flight QZ8501 are likely to focus attention partly on maintenance, procedures and training, though Indonesian officials have not ruled out any cause and stress it is too early to draw firm conclusions.

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                          • Originally posted by Evan View Post
                            The pilot got stickshaker warning.
                            Uh?

                            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                            --- Defend what you say with arguments, not by imposing your credentials ---

                            Comment


                            • Originally posted by Gabriel View Post
                              Uh?
                              Sorry, stall warning, what's the difference? I've been reading too many of these things lately. Too many stalls.

                              Between 15 h 44 min 30 and 15 h 45 min 05, the stabiliser moved from -4.4° to -11.2° corresponding to the electric pitch-up stop. It stayed in this position until the end of the recording. At 15 h 45 min 05, the aeroplane was at 2,910 ft altitude and a speed of 99 kt. Pitch angle was 18.6 degrees. The stall warning sounded. In the second that followed, the thrust control levers were moved to TO/GA.

                              Comment


                              • Originally posted by Jpmkam View Post
                                Pilot left his seat at time of loss of control.
                                FAC2, M18, M19, on the bulkhead breaker panel. That would explain it.*

                                *Massive speculation

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