Announcement

Collapse
No announcement yet.

Virgin Australia B738, Jan 4th 2013 Incident Report

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by MCM View Post
    Its about horses for courses - and remembering which horse you got on.
    And believing that the horse knows the way to carry the sleigh.

    Thank you.

    Comment


    • #17
      Originally posted by Evan View Post
      ...which was the result of using FLCH and apparently (though not yet confirmed) failing to set a minimum safe altitude (where VNAV should have been armed) on the MCP... ?
      They wanted to use FLCH to try correct the high and fast situation. And that's basically ok IMHO, but not how they did it.

      They should have set a target altitude, one by which if they had not established a stable approach they'd go around (say 1000ft), set FLCH, idle the throttles (or does the FLCH does it by itself as MCM explained for LVL CHG?), select Vapp on the MCP, throw everything out (gear, full flaps) and let the plane go down. If that doesn't take you to a stable approach in time, nothing will.

      If by 1000ft you haven't already establish a stable approach, which includes having changed modes to something suitable for final approach (or manual flight), you go around. If you are distracted and don't immediately go around, the plane will level-off at 1000ft and hold the selected speed.

      What is a no-no is to select some of these "pitch controls speed" modes just to kill the AP and control pitch manually with the intention to follow a vertical path, not to hold a speed (which is what the command bars of the flight director will be asking you to do). If neither the AT (because you selected a "pitch control speed" mode), the AP (because you turned it off) nor you are controlling the speed, why would you expect that the speed will remain under control?

      --- 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


      • #18
        Originally posted by Gabriel View Post
        They wanted to use FLCH to try correct the high and fast situation. And that's basically ok IMHO, but not how they did it.

        They should have set a target altitude, one by which if they had not established a stable approach they'd go around (say 1000ft), set FLCH, idle the throttles (or does the FLCH does it by itself as MCM explained for LVL CHG?), select Vapp on the MCP, throw everything out (gear, full flaps) and let the plane go down. If that doesn't take you to a stable approach in time, nothing will.

        If by 1000ft you haven't already establish a stable approach, which includes having changed modes to something suitable for final approach (or manual flight), you go around. If you are distracted and don't immediately go around, the plane will level-off at 1000ft and hold the selected speed.

        What is a no-no is to select some of these "pitch controls speed" modes just to kill the AP and control pitch manually with the intention to follow a vertical path, not to hold a speed (which is what the command bars of the flight director will be asking you to do). If neither the AT (because you selected a "pitch control speed" mode), the AP (because you turned it off) nor you are controlling the speed, why would you expect that the speed will remain under control?
        Exactamundo!

        There was something about pilots who were 'cheating' the automation by entering 0 or some very low altitude below MDA and selecting FLCH. It went something like:
        Originally posted by Professional Pilot Chat Room
        "Dude.. no dude... check it out: you just do it like this. I'm tellin ya it works like a charm. It's fuckin genius. Dude! Stop hoggin the bong!"
        The Asiana pilot manually retarded the thrust to IDLE. If you do this in FLCH and hold it there for more than 1.2 secs AT goes into IDLE HOLD and stays there until reaching the MCP altitude or transitioning to another vertical mode. And if you shut the AP down before then, AT or no AT, there it stays right down to the end (speed protection is inhibited below 100').

        "That's why you go with FLCH dude! Screw the manual! That's for losers! This way you don't have to keep holding the damned thrust levers back. So you have a free hand to pass the blunny around. It's freaking brilliant!!! "
        I would go as far as to say that it is a design flaw that Boeing allows you to do this. But I guess Boeing has always assumed all pilots are not this stupid...

        Comment


        • #19
          Gabriel - they're just different versions of the same mode, and so you don't find them on the same aeroplane. LVL CHG is the older version you see on the 737, and FLCH is on the 767, 777 and 787.

          Looking at Asiana, part of the problem comes from the way these modern aircraft are flown to touchdown with the A/T engaged even when the autopilot is disengaged as a standard policy. The Asiana crew were most likely, as Gabriel says, using FLCH for a perfectly reasonable purpose.

          When the autopilot stops doing what it is supposed to, we should disconnect and fly the aircraft and IGNORE the incorrect guidance on the instruments. To some extent they did this. However, what happened in this case, was the lack of realisation that the A/T would also not work as they had hoped because the flight mode (which they weren't even using) was one that wasn't appropriate for landing. When you're looking out the window to land, the actual mode the afds is in is largely irrelevant on most aeroplanes - except when you plan to have the A/T engaged for landing.

          I know its a bit old fashioned, but I'm still an advocate for the old Autopilot off = Autothrottle off pilot mantra.

          Comment


          • #20
            Thanks for the explanation MCM.

            Originally posted by MCM View Post
            I know its a bit old fashioned, but I'm still an advocate for the old Autopilot off = Autothrottle off pilot mantra.
            You mean "both or none"?
            Anywhere or just final approach/landing?

            Correct me if I'm wrong, but I think that on take-offs, where the AP is ALWAYS off, it's quite normal to let the AT handle the thrust.

            And it looks to me that, in any case but especially in final approach, its ok to leave the AT on when hand flying as this reduce the workload: The pilot has one fewer parameter to control (in the sense of "ajust") BUT:
            - He MUST control (in the sense of "monitor" the speed as if the AT was off.
            - It's a good practice to have your hand on the throttles to "follow" what the AT is doing and be in condition to take action at once if needed.

            But, that's from a pilot that never flew an AP or AT

            --- 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


            • #21
              Yes thats right Gabriel - both on or both off, and yes, for arrival manoeuvring and final approach. Takeoff is a different beast - the thrust is doing one thing only - giving you a set thrust level. Manoeuvring and approach the thrust goes up and down to fly a speed, but you're pitching at the same time...

              Its a somewhat outdated mantra now that the A/T systems are so good, but the idea was that when the A/T is controlling thrust, and you're manually controlling pitch, you can get a little out of sync as the two are so closely related.

              It just comes down to being more in tune with the aircraft - you have total manual control. You don't have to think about what the A/T system is doing, as you're doing it. Pitch and Power are so closely linked that it seems natural to want both. However, clearly the other way works - 777's and 737's have been doing it for years, not to mention the Airbus family. But it still seems a little unintuitive to someone who, admittedly, hasn't done it. Maybe its my turn to sound like the dinosaur.

              You are correct in that rather than actually doing it yourself, you have to be much more aware of what mode it is in and that it is actually doing what you want. No different to normal automation management really.

              Comment


              • #22
                Originally posted by MCM View Post
                Looking at Asiana, part of the problem comes from the way these modern aircraft are flown to touchdown with the A/T engaged even when the autopilot is disengaged as a standard policy. The Asiana crew were most likely, as Gabriel says, using FLCH for a perfectly reasonable purpose.
                According to the Asiana 'report', Boeing specifically states that autothrottle is to be considered an essential tool and should always be used in manual flight. This somewhat contridicts investigation reports I've read that identify the mix of manual flight and automation as a potentially hazardous regime.

                But com'on MCM, they engaged FLCH at 1,600 ft! Is there a reasonable purpose to do that? (In the 'report' they claim that this was unintentional and that neither pilot can recall doing this). I suspect that it was an unofficial practice used to cheat the automation, relying completely on the autothrottle to 'wake up' when capturing the glideslope but perhaps never before done on a non precision approach.

                Comment


                • #23
                  Yes Evan, its a brave new world .

                  I don't think it was something that crew would do to 'cheat'. If you were trying to capture the glideslope from above, its a perfectly reasonable mode to do it in (probably the preferred). It will maintain the speed you desire and pitch down, and then capture an altitude in the window if you don't get to the glideslope first. Assuming you've set a reasonable one. Its actually a good mode to use for this purpose.

                  And yes, you're right, you would normally have the glideslope mode to capture. So its not 'wrong' as such to do something like that (although by 1600ft you'd have to suspect it was starting to go wrong). When you're not doing an ILS approach, then you have to get back into an appropriate mode if you're going to use the automation, such as V/S (or VNAV which they should have been using the whole time...). But if you're planning to hand fly, it shouldn't really matter which mode you're in, because you've decided they're not giving you what you want. Unless, of course, you didn't consider that you are leaving the A/T engaged, and it won't do what you want it to...

                  The crew clearly got overloaded and pressed modes to try and do something, before realising that it wasn't going to work like that without the glideslope. Poor planning, and then panic when it started to go a bit pear shaped.

                  Comment


                  • #24
                    Originally posted by MCM View Post
                    Yes Evan, its a brave new world .

                    I don't think it was something that crew would do to 'cheat'. If you were trying to capture the glideslope from above, its a perfectly reasonable mode to do it in (probably the preferred). It will maintain the speed you desire and pitch down, and then capture an altitude in the window if you don't get to the glideslope first. Assuming you've set a reasonable one. Its actually a good mode to use for this purpose.

                    And yes, you're right, you would normally have the glideslope mode to capture. So its not 'wrong' as such to do something like that (although by 1600ft you'd have to suspect it was starting to go wrong). When you're not doing an ILS approach, then you have to get back into an appropriate mode if you're going to use the automation, such as V/S (or VNAV which they should have been using the whole time...). But if you're planning to hand fly, it shouldn't really matter which mode you're in, because you've decided they're not giving you what you want. Unless, of course, you didn't consider that you are leaving the A/T engaged, and it won't do what you want it to...

                    The crew clearly got overloaded and pressed modes to try and do something, before realising that it wasn't going to work like that without the glideslope. Poor planning, and then panic when it started to go a bit pear shaped.
                    I see. Just two things to add:

                    They selected FLCH at only 1,600 ft, well below where it should be used (correct?). This is what I mean by 'not reasonable'

                    They did not set a safe altitude in the MCP, which I suspect was an intentional practice when high on final (but typically descending to glideslope capture). A seemingly safe but in reality very dangerous practice outside the recommended operating procedures. This is what I mean by 'cheating'. Maybe I should stay 'freestyling'?

                    The 'report' also states that shortly after engaging FLCH the AP went into TOGA and this is when they chose to disconnect and handfly. The Asiana 'report' contains some plot convenience I think.

                    Comment


                    • #25
                      Originally posted by Evan View Post
                      I see. Just two things to add:

                      They selected FLCH at only 1,600 ft, well below where it should be used (correct?). This is what I mean by 'not reasonable'
                      That doesn't look very reasonable, as you say. But it's not so bad either, especially if the stable approach gate is 500ft (in your airline in VFR, which I don't know if it was the case here).

                      But what was not reasonable at all was to expect that someone or something would keep the speed, after you say "it will not be the AT, it will be the AP", and then kill the AP and not control the speed by yourself. This was either a gross misunderstanding of how the automation works, or they really set FLCH by accident and unknowingly.

                      Leaving at a side whether it was smart to select FLCH or if they used it in a smart way, there are a bunch of good practices (so say the least) that this crew did not apply:

                      1- First and foremost, if you are the pilot FLYING use the PRIMARY FLIGHT display to FLY. If you are the pilot MONITORING, what do you have to do better than monitoring the PRIMARY FLIGHT display. The famous "six pack" of instruments that you have to systematically scan in your little Tomahawk (AI, ASI, VS, ALT, DC and NAV) defaults to several indications shown together in this single instrument that, again, has the words PRIMARY and FLIGHT in its name for a good reason.
                      2- Speed control is especially important in a final approach. You know how much the pilots love to have it nailed at Vapp+2/-0 kts. And in a hand flown visual final, speed is really the only flight parameter that you have to monitor. Everything else comes from a big instrument called windshield. Heading and lateral navigation is straightforward. Especially if you have a PAPI or VASI (but even if you don't), you don't even care about altitude or VS. Follow the glide path at the right airspeed and you are at the right altitude and VS.
                      3- If you have some automation on, monitoring what it's doing is of paramount importance, especially during critical phases of flight, like a final approach and landing. Start with the FMA. You should include it in your systematic instrument scan. If these pilots unintentionally and unknowingly set FLCH at 1600ft, it's absolutely unacceptable that they didn't realize that at any time along the approach. I also wonder what the AT sector was showing in the FMA at the time (surely not "speed", I guess "idle" or similar).
                      4- The stabilized approach criteria is your friend. It was created for a good reason, which is that many unstabilized approaches ended badly. Use it. It's not only mandatory, it's healthy for your plane, your airline, your passengers and yourself.
                      5- Finally, and this is very important and, unfortunately, Airbus removed this capability form their airplanes. When you are in a critical phase of flight where keeping the flight path and energy within a narrow range is of utmost importance and any deviation must be immediately addressed, and you have some or all of the automation on, keep your hands on the controls and "follow" the automation to be aware all the time of "what is it doing now" and, if you don't like it, be ready to correct it at once. "Click click, clack clack".

                      They should have applied all 5, but had they used only one of them, any one, this accident would have very likely not happened.

                      --- 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


                      • #26
                        Originally posted by Gabriel View Post
                        That doesn't look very reasonable, as you say. But it's not so bad either, especially if the stable approach gate is 500ft (in your airline in VFR, which I don't know if it was the case here).

                        But what was not reasonable at all was to expect that someone or something would keep the speed, after you say "it will not be the AT, it will be the AP", and then kill the AP and not control the speed by yourself. This was either a gross misunderstanding of how the automation works, or they really set FLCH by accident and unknowingly.

                        Leaving at a side whether it was smart to select FLCH or if they used it in a smart way, there are a bunch of good practices (so say the least) that this crew did not apply:

                        1- First and foremost, if you are the pilot FLYING use the PRIMARY FLIGHT display to FLY. If you are the pilot MONITORING, what do you have to do better than monitoring the PRIMARY FLIGHT display. The famous "six pack" of instruments that you have to systematically scan in your little Tomahawk (AI, ASI, VS, ALT, DC and NAV) defaults to several indications shown together in this single instrument that, again, has the words PRIMARY and FLIGHT in its name for a good reason.
                        2- Speed control is especially important in a final approach. You know how much the pilots love to have it nailed at Vapp+2/-0 kts. And in a hand flown visual final, speed is really the only flight parameter that you have to monitor. Everything else comes from a big instrument called windshield. Heading and lateral navigation is straightforward. Especially if you have a PAPI or VASI (but even if you don't), you don't even care about altitude or VS. Follow the glide path at the right airspeed and you are at the right altitude and VS.
                        3- If you have some automation on, monitoring what it's doing is of paramount importance, especially during critical phases of flight, like a final approach and landing. Start with the FMA. You should include it in your systematic instrument scan. If these pilots unintentionally and unknowingly set FLCH at 1600ft, it's absolutely unacceptable that they didn't realize that at any time along the approach. I also wonder what the AT sector was showing in the FMA at the time (surely not "speed", I guess "idle" or similar).
                        4- The stabilized approach criteria is your friend. It was created for a good reason, which is that many unstabilized approaches ended badly. Use it. It's not only mandatory, it's healthy for your plane, your airline, your passengers and yourself.
                        5- Finally, and this is very important and, unfortunately, Airbus removed this capability form their airplanes. When you are in a critical phase of flight where keeping the flight path and energy within a narrow range is of utmost importance and any deviation must be immediately addressed, and you have some or all of the automation of, keep your hands on the controls and "follow" the automation to be aware all the time of "what is it doing now" and, if you don't like it, be ready to correct it at once. "Click click, clack clack".

                        They should have applied all 5, but had they used only one of them, any one, this accident would have very likely not happened.
                        Pretty good summary of their failings. What struck me about this crash and others like it, is that to my mind, in general, a pilot needs to be operating with heightened senses and be fully "in the moment" and situationally aware when in a critical phase of flight like take-off or landing. You cannot fly like these guys were flying, wholly neglecting to pay attention to critical parameters. As you mentioned, on approach to final all the way to the flare speed needs to be monitored closely, it's one of the most if not the most important variable at that phase. I just imagine what would have happened to BA 38 with pilots like these up front. Even if the autopilot/autothrottle IS handling speed and functioning properly you should STILL be monitoring airspeed vigilantly, along with the rest of the instruments feeding you important information. Commercial pilots flying heavy iron being this detached from their situation is highly disconcerting.

                        Comment


                        • #27
                          Originally posted by Gabriel View Post
                          Leaving at a side whether it was smart to select FLCH or if they used it in a smart way, there are a bunch of good practices (so say the least) that this crew did not apply:
                          Yes, of course, we all recognize that the Asiana crash was the result of not flying the airplane. I'm not trying to blame the automation in any way for that.

                          What I am getting at (in descent, not climb) is that FLCH, because it lacks the speed protection 'wake-up' function of V/S and VNAV, is particularly dangerous beyond the FAF because pilots do forget to fly the airplane and there is nothing there to defend the passengers from this phenomena. Therefore it should be somehow prohibited during that phase of flight (and is with certain operators as MCM has pointed out). Aside from that, flight crews must understand the hidden dangers of creating custom procedures that fall outside the normal SOP's, even if they seem to work every time.

                          In climb, the only inherent danger I see is a latent human factor: because FL CHG and FLCH do not require the pilot to monitor speed and adjust power as in V/S or VNAV, there may be a greater tendency to not monitor at all (complacency). Again, nothing wrong with the systems, just perhaps more emphasis on the need to closely monitor when using these less interactive modes.

                          That's my outsider perception anyway.

                          Comment


                          • #28
                            Originally posted by Evan View Post
                            What I am getting at (in descent, not climb) is that FLCH, because it lacks the speed protection ...
                            I don't understand what you mean. In these "pitch controls speed" modes speed is the king. This mode will provide better speed control and assurance than any other. It will go as far as descend when commanded to climb if that's what it takes to hold the airspeed. PROVIDED THAT YOU LET THE MODE FLY THE PLANE FOR GOD'S SAKE!

                            --- 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


                            • #29
                              Originally posted by MCM View Post
                              Just because you look at the airspeed indicator doesn't mean you would necessarily notice anything was wrong. Remember VNAV handles the speed bug most of the time, and these guys do a LOT of sectors at varying weights where you expect to see different things. As long as the speed bug was within the manoeuvre margins, you may not necessarily twig that the speed was slower than normal, particularly above about 20,000ft (as it may not really have been that much slower than normal). So, its only really in the last little while when the speed got very close to the amber band that you would have a huge cue that something wasn't right. You say your optimum climb speed might be 280kts, but it isn't that fixed. It changes a fair bit flight to flight - on the 767 by up to about 60kts.

                              Yes, absolute 100% paranoid attention should make you notice this - but it doesn't work that way in real life.
                              Tough words above...

                              And I'm not sure I'm comfortable with them...

                              I get it that the airspeed was probably fat, dumb and happy for a lot of the climb.

                              Still- shouldn't someone be watching "the basic flight instruments" on a reasonable periodic basis (contrasting to "100% paranoid attention")

                              I get the human factors and the mundane aspects and the fact that the plane ALWAYS climbs nicely up to altitude and that the Mark IV bioFMS throws an occasional hiccup....

                              But @#%!- an occasional glance at the ASI, AI, VS, Heading...

                              I'm word mincing with you...but still...
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                              Comment


                              • #30
                                Originally posted by Gabriel View Post
                                .........................................................................................................................................................................................................................................

                                They should have applied all 5, but had they used only one of them, any one, this accident would have very likely not happened.
                                1-5 sounds an awful lot like that "fundamental airmanship" BS.
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                                Comment

                                Working...
                                X