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Thread: Moscow Passenger Plane Catches Fire, Crash-Lands in Cornfield.

  1. #21
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    Quote Originally Posted by Evan View Post
    I've since read that they leveled off at 750' but there is no confirmation of their height when the actual bird strikes occurred, so it is possible that the gear was still down at that point. Question to you: Can the gear be retracted with the #1 engine at or below idle? Is the PTU on your planes automatically inhibited below 1500ft (this was a recommended retrofit, not a requirement)?
    As to the first, I imagine it can be, because the EDP produces 3000psi all the way down to 3% N2. As to the second, I'm not aware of our birds having that modification, at least not that I have seen, but I'll ask.

  2. #22
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    As to the first, I imagine it can be, because the EDP produces 3000psi all the way down to 3% N2. As to the second, I'm not aware of our birds having that modification, at least not that I have seen, but I'll ask.
    The concern was that a green system failure at takeoff would result in the PTU running constantly to supply power from the yellow system, which would then overheat, but, as the overheat ECAM warning is inhibited below 1500ft, the crew would remain unaware, take no action, and the yellow system would also fail. I think this actually occurred. The mod was to inhibit the PTU below 1500ft. Anyway, if the EDP on #1 is able to retract the gear after losing power, this is of no relevance to the thread.

  3. #23
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    Quote Originally Posted by Evan View Post
    The concern was that a green system failure at takeoff would result in the PTU running constantly to supply power from the yellow system, which would then overheat, but, as the overheat ECAM warning is inhibited below 1500ft, the crew would remain unaware, take no action, and the yellow system would also fail. I think this actually occurred. The mod was to inhibit the PTU below 1500ft. Anyway, if the EDP on #1 is able to retract the gear after losing power, this is of no relevance to the thread.
    Ah! I AM familiar with that issue. Pending verification from my Fleet Chief, it appears our 320s and 321s DO have the mod, while our 319s (except for our two newest ones) do not. I conclude that based on the fact that only those older 319s are subject to OEB-47 1.0 with which you are familiar, I'm sure.

  4. #24
    Senior Member Gabriel's Avatar
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    We are not familiar with OEB-47 1.0 but we are familiar with MOD 34236 + 35879 / SB 29-1115 and MOD 35938 / SB 29-1126.

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  5. #25
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Ah! I AM familiar with that issue. Pending verification from my Fleet Chief, it appears our 320s and 321s DO have the mod, while our 319s (except for our two newest ones) do not. I conclude that based on the fact that only those older 319s are subject to OEB-47 1.0 with which you are familiar, I'm sure.
    I'm confused by that. The issue was resolved by altering the PTU activation logic, not by altering ECAM (as airbus adheres to the philosophy of preventing non-critical distractions at low altitude). Isn't OEB-47 1.0 a deviation from HYD ENG PUMP LO PR and HYD RSVR OVHT? What was the OEB procedure in the QRH?

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    Quote Originally Posted by Evan View Post
    I'm confused by that.
    Which part?

  7. #27
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    PTU ECAM Isn't OEB-47 1.0 a deviation from HYD ENG PUMP LO PR and HYD RSVR OVHT? What was the OEB procedure in the QRH?
    And yet, people sometimes forget that aggressive pull ups can cause stalls and anti-skid systems function when you need top-performance braking.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  8. #28
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Which part?
    I mean, I'm confused by how you come to that conclusion. OEB's are procedural changes but this issue didn't involve a procedural change. Do you mean that aircraft with the PTU mod wouldn't be subject to OEB-47 1.0 because the mod removed the possibility of these two ECAM messages occurring together? Again, I don't know what was actually contained in OEB-47 1.0, I just know the criteria. I also don't understand how your older 319's are protected from this scenario. I'm genuinely curious.

  9. #29
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    Quote Originally Posted by Evan View Post
    I mean, I'm confused by how you come to that conclusion. OEB's are procedural changes but this issue didn't involve a procedural change. Do you mean that aircraft with the PTU mod wouldn't be subject to OEB-47 1.0 because the mod removed the possibility of these two ECAM messages occurring together? Again, I don't know what was actually contained in OEB-47 1.0, I just know the criteria. I also don't understand how your older 319's are protected from this scenario. I'm genuinely curious.
    Our older 319s are NOT protected from this scenario because they do NOT have the mod (as yet, more on that in a second). The OEB tells us to DISREGARD the Y RSVR OVRHT ECAM procedure that tells us to turn the Y ENG PUMP OFF (and thus lose the Y system). Instead, we are to keep the pump on, but turn the PTU off. This is also the case if we get the G RSVR OVHT ECAM following a Y system failure. The ECAM says to turn the G ENG PUMP OFF, but we are to not do that, and, again, are to turn the PTU off instead. Keep in mind that all of this applies only if G or Y systems were lost due to fluid leak, not due to pump failure.

    Per my Fleet Chief, all 320 family aircraft from about msn 4177 have the mod and are thus not subject to the issue. Eventually, all of our birds will have the mod as well.

    Hope this helps.

  10. #30
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    The OEB tells us to DISREGARD the Y RSVR OVRHT ECAM procedure that tells us to turn the Y ENG PUMP OFF (and thus lose the Y system). Instead, we are to keep the pump on, but turn the PTU off. This is also the case if we get the G RSVR OVHT ECAM following a Y system failure. The ECAM says to turn the G ENG PUMP OFF, but we are to not do that, and, again, are to turn the PTU off instead.
    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.

  11. #31
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    Quote 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.

  12. #32
    Senior Member Gabriel's Avatar
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    Wow, that almost looks like communication!

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  13. #33
    Senior Member Evan's Avatar
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    Quote 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.

  14. #34
    Senior Member Gabriel's Avatar
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    Quote 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.

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  15. #35
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    Quote 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.

  16. #36
    Senior Member Evan's Avatar
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    Quote 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.

  17. #37
    Senior Member Evan's Avatar
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    Quote 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.

  18. #38
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    Quote 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.

  19. #39
    Senior Member 3WE's Avatar
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    Quote 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.

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