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Thread: Pitot Tube Failure

  1. #41
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post

    And what is FDnH?
    Fat Dumb n' Happy. (AF447 was not FDnH when the airspeeds were lost).

  2. #42
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    Quote Originally Posted by Evan View Post
    Fat Dumb n' Happy. (AF447 was not FDnH when the airspeeds were lost).
    Sure, it was. At least FDnH enough not to mess with. Even if you got a good amount of bumpage happening, that's still plenty FDnH not to go pitching and pulling and Krishna only knows what else. The only "memory item" should have been to leave the airplane be and methodically and deliberately go through the ECAM.

  3. #43
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    Quote Originally Posted by Gabriel View Post

    I do recall someone (don;t remember if you or somebody else) bringing to the table the fact that the UAS procedure introduced the memory items with "If needed to stabilize the flight" or something like that.

    And what is FDnH?
    It was me, and it wasn't "if needed to stabilize flight", it's a rather more forceful "if safety of flight is impacted". The purpose of this memory item is to get you away from the ground, so you can level off and troubleshoot (which is what the memory item ends with), not to start doing things things when you're seven miles away from the ground.

  4. #44
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Sure, it was. At least FDnH enough not to mess with. Even if you got a good amount of bumpage happening, that's still plenty FDnH not to go pitching and pulling and Krishna only knows what else. The only "memory item" should have been to leave the airplane be and methodically and deliberately go through the ECAM.
    I believe that Evan refers to the fact that they had just selected a lower speed to enter the turbulent zone so the A/T had just reduced thrust. The A/T was supposed to add thrust when the selected lower sped was achieved, to keep the plane from keeping losing speed, but with the UAS the A/T disconnected and that would not happen. I remember Evan was concerned that if they didn't set climb thrust (which ironically started by taking the thrust levers OUT of the climb detent) they would stall. Not that I agree with that.

    Now Evan, googling some I found that ATLcrew is so right that official Airbus documentation explains why they added the "If the safe conduct of the flight is impacted" condition to the memory items and how they propose to train the pilots to specifically NOT apply the memory items unless the safety of the flight is impacted and how that relates to ground/obstacle clearance.

    Check the date of this document (admittedly, it is for the A320 family but I can see that the A330 UAS procedure in place when AF happened follows exactly the same structure and logic).
    http://www.smartcockpit.com/docs/Unreliable_Speed.pdf

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  5. #45
    Senior Member Gabriel's Avatar
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    I think that Jhonmicky started the fuse and ordered a large bucket of pop-corn.

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  6. #46
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    I believe that Evan refers to the fact that they had just selected a lower speed to enter the turbulent zone so the A/T had just reduced thrust. The A/T was supposed to add thrust when the selected lower sped was achieved, to keep the plane from keeping losing speed, but with the UAS the A/T disconnected and that would not happen. I remember Evan was concerned that if they didn't set climb thrust (which ironically started by taking the thrust levers OUT of the climb detent) they would stall. Not that I agree with that.
    Specifically this:

    2 h 09 min 58 - Speed handling changes from managed to selected. The selected Mach is 0.8.
    2 h 10 - Pitch attitude decreases from 1.8° to 0° in 3 seconds. In 8 seconds, the N1 commanded and the N1 change from 100% to 84%.
    2 h 10 min 05 - The A/P2 disconnects.
    2 h 10 min 08 - The FD 1 and 2 become unavailable. The A/THR disengages and the THR LK mode isactivated. The N1 are at 83 %.

    Q: Is 0-3° pitch (known values) and 83% N1 at their current weight and altitude FDnH?

    Complex modern aircraft have stealth factors. Procedures are needed to overcome them.

    Now Evan, googling some I found that ATLcrew is so right that official Airbus documentation explains why they added the "If the safe conduct of the flight is impacted" condition to the memory items and how they propose to train the pilots to specifically NOT apply the memory items unless the safety of the flight is impacted and how that relates to ground/obstacle clearance.
    I don't see that. What I see is a doc that says "If the safe conduct of the flight is impacted" is something to be "Defined During Training", It is left undefined in that document.

    However, one can extrapolate: The flowchart showing the decision tree to determine if memory items are called for involved two options:

    • Safe Conduct of the Flight Affected: Unreliable Airspeed Procedure
    • No (Safe Conduct of the Flight Not Affected): ADR Check Procedure


    The scenario it is showing for "No" is "Speed between CAPT and F/O PFD starts to diverge while in climb."

    That is NOT an "NAV ADR DISAGREE" ECAM message and a sudden loss of autoflight and reversion to alternate law caused by the simultaneous obstruction of multiple pitot tubes (an emergency at hand). That is an indication to run the ADR check procedure and to isolate a faulty unit (a problem developing). There is no indication of loss of autoflight under the NO scenario.

    Does the sudden loss of autoflight and reversion to alternate law affect the safe conduct of the flight? Absolutely!

    So, while disturbingly vague and potentially misleading, this doc seems to me to warrant the memory procedures if ""NAV ADR DISAGREE" is encountered at any altitude.

    Furthermore, the memory items continue to have separate pitch/power values for flight above FL100. So that sort of blows any theory that these memory items are only for "how that relates to ground/obstacle clearance." Wouldn't you agree?

    What did we learn from AF447? What did we learn about human factors when pilots have no memorized and practiced procedure in their head and improvise under the disorienting affects of being startled and stressed?

    Bottom line (hasn't changed): If the crew of AF447 (and every other instance of high-altitude UAS) had applied the standard memory item pitch and power values, nothing bad would have happened, whereas when left to individual pilot improvisation, anything can happen. Why do pilots (and apparently now, the industry itself) continue to resist that hard lesson and that self-evident truth?

  7. #47
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Gabriel View Post
    ATLcrew is so right
    That deserves a post all it's own.

    And he interjects his wisdom to us AND feeds homeless kittens.

    I only hope we provide some entertainment as he pops popcorn.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  8. #48
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    Quote Originally Posted by Evan View Post
    Bottom line (hasn't changed): If the crew of AF447 (and every other instance of high-altitude UAS) had applied the standard memory item pitch and power values, nothing bad would have happened, whereas when left to individual pilot improvisation, anything can happen. Why do pilots (and apparently now, the industry itself) continue to resist that hard lesson and that self-evident truth?
    Because that's the bottom line only in your mind. The memory item was not applicable in this case. You disagree, and that's fine, that's your business. The document Gabriel linked is actually from 2006 (before AF447) which is why the memory item there reads differently than it does now. Now it OPENS with "If safety of flight is impacted". Why? Because Airbus wants us to initially do NOTHING. Not improvise, not do memory items, nothing. Just breathe. Keep breathing. Call for ECAM actions. Keep breathing. If the thrust is not where you want it, match and mash. If you got no IAS, but everything else jives, keep breathing.

    I'm not paid to regurgitate memory items, I'm paid to know my airplane, which includes when NOT to use memory items. Why do you continue to resist that self-evident truth?

  9. #49
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    Quote Originally Posted by 3WE View Post
    That deserves a post all it's own.

    And he interjects his wisdom to us AND feeds homeless kittens.

    I only hope we provide some entertainment as he pops popcorn.
    A post? Hell, I'm going to print it out, frame it, and hang it on my glory wall.

  10. #50
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    Q: Is 0-3° pitch (known values) and 83% N1 at their current weight and altitude FDnH?
    A: Yes.

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
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  11. #51
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    Quote Originally Posted by Evan View Post
    Q: Is 0-3° pitch (known values) and 83% N1 at their current weight and altitude FDnH?
    Affirmative.

  12. #52
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    Quote Originally Posted by Evan View Post
    Q: Is 0-3° pitch (known values) and 83% N1 at their current weight and altitude FDnH?
    I don't have a phugoid clue.

    But based on rather limited 172 time, I would guess yes because ~80% power and relatively level attitude tend to be robust pitch and power levels.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  13. #53
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by ATLcrew View Post
    The document Gabriel linked is actually from 2006 (before AF447) which is why the memory item there reads differently than it does now. Now it OPENS with "If safety of flight is impacted".
    Actually, yes, the document is from 2006 and AF was in 2009, but this document IS the change when they added the "I the safe conduct of the flight is impacted ==> [memory items]".

    You have the old version (where you had in instruction that told you when to apply the ADR check procedure and when the UAS procedure that lacked the "If..." sentence) and the new UAS+ADR unified procedure with the "If..." sentence (in page 17).

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  14. #54
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Affirmative.
    Q: The N1 was previously at 100% Pitch was at 0° (1.8° was the FDnH value 10 secs earlier, before the selected guidance). Can an A330-200 at this weight/altitude maintain 35,000 ft with power set at 83% N1 and still fly well below alpha prot AoA?
    Q: Does the sudden loss of autoflight and reversion to alternate law impact the safe conduct of the flight?

  15. #55
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    Quote Originally Posted by Evan View Post
    Does the sudden loss of autoflight and reversion to alternate law impact the safe conduct of the flight?
    Negative.

  16. #56
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    Q: The N1 was previously at 100% Pitch was at 0° (1.8° was the FDnH value 10 secs earlier, before the selected guidance). Can an A330-200 at this weight/altitude maintain 35,000 ft with power set at 83% N1 and still fly well below alpha prot AoA?
    Who said anything about maintaining the altitude? Will 5 deg + CLB maintain the altitude?

    Leave the throttle alone, keep the pitch, and you will be fine.
    Or try to keep the altitude if you want. If you do that and you need increasing pitch to keep it, you need to add more thrust. It is written in the UAS PROCEDURE!

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  17. #57
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    Quote Originally Posted by Evan View Post
    Q: The N1 was previously at 100% Pitch was at 0° (1.8° was the FDnH value 10 secs earlier, before the selected guidance). Can an A330-200 at this weight/altitude maintain 35,000 ft with power set at 83% N1 and still fly well below alpha prot AoA?
    I don't know (I'm thinking it should), but if not, you match and mash and put the nose back where it was. It's not hard, really.

  18. #58
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    I don't know (I'm thinking it should), but if not, you match and mash and put the nose back where it was. It's not hard, really.
    But is that your definition of FDnH?

  19. #59
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    Quote Originally Posted by Evan View Post
    But is that your definition of FDnH?
    Affirmative. Even if we're in a gentle descent, that's still FDnH.

  20. #60
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Who said anything about maintaining the altitude? Will 5 deg + CLB maintain the altitude?

    Leave the throttle alone, keep the pitch, and you will be fine.
    Or try to keep the altitude if you want. If you do that and you need increasing pitch to keep it, you need to add more thrust. It is written in the UAS PROCEDURE!
    Let me be more specific: Can an A330-200 at this weight/altitude with power set at 83% N1 not descend and still fly well below alpha prot AoA?

    We always lose context with these arguments. So let me remind you of the context:

    Pierre Bonin, PF, was clearly concerned about the weather situation and the altitude prior to the event. He repeatedly asked the captain about RECMAX and indicated that he wanted to climb above the weather. The Captain did not give him an answer before retiring. He continued to mention this with the relief FO who replaced the previous one in the left seat. He wanted to climb. HE DEFINITELY DID NOT WANT TO DESCEND. When the event happened, due to the role of Mach in calculating altitude, the altimeter began to display a negative rate, a descent. He reacted by adding pitch, but overcontrolled, probably due to a lack of experience hand-flying at high altitude where manual inputs are amplified (and he was also contending with on onset of roll at that moment). Add to this his now urgent desire to climb over the storm (RECMAX was about FL380). And now add to that the fact that the N1 is locked at 83%.

    That's the context.

    Now imagine that he didn't continuously pull up into a stall, but rather leveled out, with FDnH pitch, intent on NOT DESCENDING and with a desire to then climb steadily to FL370 (instead of following the memory procedure and CRM/QRH procedure).

    Is that not a bit unsafe? Or should I say, is that not more dangerous than following the procedure?

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