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  • #31
    Originally posted by Evan View Post
    Aha. Now I get it. Also, out of curiousity, do your planes have the OEB reminder function on ECAM. That is a free-of-charge, optional retrofit (an optional feature from SB 31-1264) so I'm curious as to how successful it has been.

    They do.

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    • #32
      Wow, that almost looks like communication!

      --- 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


      • #33
        Originally posted by Gabriel View Post
        Wow, that almost looks like communication!
        To put this non-acronymically, when there is a system failure, the order in troubleshooting is normally ECAM, then QRH. Airbus engineers will occasionally issue temporary updates to procedures that should override the current ECAM procedures. They do this by issuing OEB's (Operational Engineering Bulletins) that are added to the QRH. The OEB procedure replaces the ECAM procedure and pilots are expected to review and be aware of the QRH OEB's during preflight. Some OEB's affect airworthiness; these are red. Others are considered less vital; these are white. The entire scheme rests on the crew being aware of the OEB and proficiently executing it despite the displayed ECAM procedure, and white ones would potentially get less attention during cockpit preparation. Not ideal. The procedure ATL and I are discussing, which prevents a dual hydraulic failure, was a white OEB. An example of a red OEB would be OEB 48, issued to deal with the possibility of multiple frozen AoA probes being considered valid and causing alpha prot to both put the aircraft into a progressively steeper dive and prevent recovery, as happened here: http://avherald.com/h?article=47d74074. OEB 48 instructed pilots to recognize the situation and regain control by degrading to normal law, by switching off two ADR's. In a situation like that, there is no time for error and very little time to get to the procedure. This one should be memorized. Or at least referenced on ECAM as soon as possible.

        Around 2007, I think, Airbus began offering an optional OEB reminder function that does appear on the ECAM. Essentially, the ECAM reminder informs the crew that an OEB exists and that they should refer to the QRH before the ECAM (reversing the normal order) The message REFER TO QRH PROC appears either on the upper alert display, on the lower status display or on both, depending on the nature of the OEB. Now there is a defense against pilots neglecting to review the OEB's preflight. But that function, AFAIK, is still optional.

        So, in the event of a loss of the green hydraulic system immediately after takeoff, the scenario I brought up here, the green system would lose pressure and the pressure differential would cause the PTU between the yellow system and the green system to automatically activate, but the PTU is not designed to power the green system for an extended period like this, it's just there to supplement transient drops in pressure, and running it for any length of time will overheat the yellow system as well. Now you've lost both engine-driven systems and all you have left is the blue system for flight control. Not a great situation. So, in this scenario, the PTU must be deactivated asap, but, since Airbus defers ECAM caution messages below 1500' to avoid distractions, the pilots will most likely not be aware of the situation until both systems fail. The solution Airbus came up with is to inhibit activation of the PTU below 1500', as a recommended modification. So now, if the green system fails below 1500', it just fails, while the yellow system remains healthy. Thus, no gear retraction, which uses the green system (if the gear is still down).

        Now, if I have this right, ATL could deduce that his company A319's did not yet have this modification by the fact that they had the OEB requiring the crew to shut down the PTU's manually, meaning they are not inhibited below 1500', meaning they don't yet have the mod.

        The only likely scenarios I can imagine for this happening just after takeoff are a plumbing failure in the gear retract mechanism, a badly-timed failure of the #1 EDP or a loss of the #1 engine, which is why I brought it into this. The fact that the gear was up suggests either that the engine was affected after the gear was up or the engine was still running at a speed adequate to power the gear retraction (interestingly, the QRH I have indicates that gear retraction is also not possible with a yellow + blue failure. I'm not clear as to why).

        So, ATL, do I have that right? Or please correct me on this.

        Comment


        • #34
          Originally posted by Evan View Post
          To put this non-acronymically, ECAM QRH OEB AoA ADR PTU EDP
          Just joking, I am not as an acronym-phobic guy like our aggie friend.

          Sorry for misleading you. I do know about the issue of the G+Y hydro systems failing in cascade, the PTU, the PTU logic change, and the OEB + ECAM's OEB reminder for when such change is not in place. I got the MOD 34236 + 35879 / SB 29-1115 and MOD 35938 / SB 29-1126 stuff from somewhere after all, didn't I? (and it was not from my butt but from an issue of Airbus's Safety First magazine).

          When I said "that almost looks like communication" I wasn't being sarcastic (or perhaps I was, in a different way). I meant that you and ATL were communicating in a way very much unlike what we saw in the pitot tube thread, a way that really resembles communication.

          --- 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


          • #35
            Originally posted by Evan View Post

            So, in the event of a loss of the green hydraulic system immediately after takeoff, the scenario I brought up here, the green system would lose pressure and the pressure differential would cause the PTU between the yellow system and the green system to automatically activate, but the PTU is not designed to power the green system for an extended period like this, it's just there to supplement transient drops in pressure, and running it for any length of time will overheat the yellow system as well. Now you've lost both engine-driven systems and all you have left is the blue system for flight control. Not a great situation. So, in this scenario, the PTU must be deactivated asap, but, since Airbus defers ECAM caution messages below 1500' to avoid distractions, the pilots will most likely not be aware of the situation until both systems fail. The solution Airbus came up with is to inhibit activation of the PTU below 1500', as a recommended modification. So now, if the green system fails below 1500', it just fails, while the yellow system remains healthy. Thus, no gear retraction, which uses the green system (if the gear is still down).


            So, ATL, do I have that right? Or please correct me on this.
            You're close, but you missed the key point of this only being an issue if the hydraulic failure is due to loss of fluid. The PTU can power the green system all day and all night if there is no fluid loss. The scenario in the OEB happens because the PTU is trying to pump fluid that is not there, and THAT is what causes it to overheat very quickly. If we lose ENG1 or EDP1, the PTU will power the Green side no problem at all if there is no fluid loss. The same is the case with the yellow system. So, we can lose ENG2, EDP2 AND Y ELEC PUMP 2, and STILL not lose the yellow system as long as there is no fluid loss. With the modded airplanes, we will lose the Green system until we cross 1,500 feet and the PTU picks it back up, so it doesn't JUST fail. Again, assuming there was no fluid loss.

            Comment


            • #36
              Originally posted by ATLcrew View Post
              You're close, but you missed the key point of this only being an issue if the hydraulic failure is due to loss of fluid. The PTU can power the green system all day and all night if there is no fluid loss. The scenario in the OEB happens because the PTU is trying to pump fluid that is not there, and THAT is what causes it to overheat very quickly. If we lose ENG1 or EDP1, the PTU will power the Green side no problem at all if there is no fluid loss. The same is the case with the yellow system. So, we can lose ENG2, EDP2 AND Y ELEC PUMP 2, and STILL not lose the yellow system as long as there is no fluid loss. With the modded airplanes, we will lose the Green system until we cross 1,500 feet and the PTU picks it back up, so it doesn't JUST fail. Again, assuming there was no fluid loss.
              I see. HYD G SYS LO PS caution doesn't distinguish whether the LO PS is due to pump failure or fluid loss. Maybe it should read LO FL and inhibit the PTU whenever that condiition is present. It seems to me that the logic could distinguish between the two.

              Also, do you know why the QRH procedure for HYD B + Y SYS LO PS indicates no gear retraction? I'm wondering if it is because G can't operate the gear and the PTU simultaneously.

              Comment


              • #37
                Originally posted by Gabriel View Post
                Just joking, I am not as an acronym-phobic guy like our aggie friend.
                I know. That wasn't directly at you. I shouldn't have 'replied with quote' there.

                Comment


                • #38
                  Originally posted by Evan View Post

                  Also, do you know why the QRH procedure for HYD B + Y SYS LO PS indicates no gear retraction? I'm wondering if it is because G can't operate the gear and the PTU simultaneously.
                  Ours doesn't indicate that, it indicates gear EXTENSION gravity only "to preserve system integrity", retraction is not mentioned at all. I don't know if it's necessarily because of the PTU or just because to minimize load on the system in general.

                  Comment


                  • #39
                    Originally posted by Gabriel View Post
                    Just joking, I am not as an acronym-phobic guy like our aggie friend.
                    Razzing of my disdain for acronyms is acknowledged.

                    However, may I cite a recent post of the International Super Genius Pilot of the Millennium, where he suggested that pilots might read more, study more and learn more if aircraft information manuals were written better and more clearly. (Not a quote, but I think that was the essence.)

                    Somehow, I think they (not we) can write better than "OEB + ECAM's OEB reminder for when such change is not in place. I got the MOD 34236 + 35879 / SB 29-1115 and MOD 35938 / SB 29-1126" and "NAV ADR DISAGREE ECAM83% N1 alpha prot AoA RECMAX THRUST RED ALT WTF".

                    And may I re re re re re re re re re re re re re re re re re repeat that at the puppy mill, some pilots might focus very hard on memorizing that important stuff to the detriment of other important stuff like: relentless pull ups have a moderately strong correlation to stalls. They then go on to adequately demonstrate the required knowledge on the competency checklist for whatever rating, and then go and do a very good job of flying us around, except for those seemingly unbelievable, rare-but-somewhat-repeated crash incidents.

                    I don't know that RPUHAMSCTS is really helping the learning process for the flawed human mind.
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                    Comment


                    • #40
                      My VHS VCR doesn't get MTV. Is that a problem?
                      Be alert! America needs more lerts.

                      Eric Law

                      Comment


                      • #41
                        Originally posted by elaw View Post
                        My VHS VCR doesn't get MTV. Is that a problem?
                        No, because MTV sucks.

                        Comment


                        • #42
                          Originally posted by elaw View Post
                          My VHS VCR doesn't get MTV. Is that a problem?
                          Originally posted by ATL
                          No, because MTV sucks.
                          Dude...you have not lived until you have a DVR.

                          Indeed, MTV sucks...sadly VH1 is not much better.

                          Let's not forget CNN, ESPN, ABC, CBS, NBC, TWC, HBO, TMC, TCM...
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                          Comment


                          • #43
                            Originally posted by 3WE View Post
                            Razzing of my disdain for acronyms is acknowledged.

                            However, may I cite a recent post of the ISGPM, where he suggested that pilots might read more, study more and learn more if AFM's were written better and more clearly.

                            And may I RPT that at the PPYML, some pilots might focus very hard on memorizing that important stuff to the detriment of other important stuff like: RPUs have a moderately strong correlation to stalls. They then go on to adequately demonstrate the RN on the COMCHK for whatever rating, and then go and do a VGJ of FUA, except for those SURBSRCI's.

                            I don't know that RPUHAMSCTS is really helping the learning process for the FHM.
                            FXD

                            Comment


                            • #44
                              Originally posted by Evan View Post
                              FXD
                              Please note: ISGPOTM

                              (I know, it deviates from normal, fundamental procedure, BUT, that's how it's traditionally been done on aviation fora and we have to be type specific).

                              TISGPOTM is also acceptable- the copyright for TOSU has not yet been ruled upon.
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                              Comment


                              • #45
                                Originally posted by 3WE View Post
                                Please note: ISGPOTM

                                (I know, it deviates from normal, fundamental procedure, BUT, that's how it's traditionally been done on aviation fora and we have to be type specific).

                                TISGPOTM is also acceptable- the copyright for TOSU has not yet been ruled upon.
                                Noted.

                                Comment

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