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Runway Incursion at Shanghai Hongqiao Airport

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  • Runway Incursion at Shanghai Hongqiao Airport

    http://avherald.com/h?article=49f37b96&opt=2048

    Surprised no one brought this one up

  • #2
    Hmm... looks like in this case, pulling up relentlessly saved the day.
    Be alert! America needs more lerts.

    Eric Law

    Comment


    • #3
      Originally posted by elaw View Post
      Hmm... looks like in this case, pulling up relentlessly saved the day.
      In an Airbus in normal law, pulling back relentlessly on the sidestick will not result in a relentless pull-up simply because HAL won't follow your commands.

      --- 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


      • #4
        Originally posted by Gabriel View Post
        In an Airbus in normal law, pulling back relentlessly on the sidestick will not result in a relentless pull-up simply because HAL won't follow your commands.
        It could result in momentarilly exceeding alpha max though. Protections reduce the chance of this but do not eliminate the possibility. For one thing, you are in direct law on the take-off roll until you enter flight mode, at which point alpha-protect is equal to alpha-max for the first five seconds. If you pull up agressively full aft stick while in ground mode at Vr you will first get the full 2G envelope limit in pitch (reduced from 2.5G because the flaps are out) before alpha protect limits elevator deflection in the air. In an emergency manuever I can see this leading to an AoA exceeding stall at least momentarilly. The two critical bits of caveat you will find in the FCOM are 'sidestick moved gently to full aft' and 'reduced possibility of exceeding'. FBW protections control elevator deflection, not physical momentum. I wouldn't put blind faith in it, but then again, there's no procedure for leaping over crossing traffic on takeoff and it's probably best to momentarilly exceed alpha max at that point anyway. I would also get the gear up directly after liftoff.

        Comment


        • #5
          Originally posted by Evan View Post
          It could result in momentarilly exceeding alpha max though. Protections reduce the chance of this but do not eliminate the possibility. For one thing, you are in direct law on the take-off roll until you enter flight mode, at which point alpha-protect is equal to alpha-max for the first five seconds. If you pull up agressively full aft stick while in ground mode at Vr you will first get the full 2G envelope limit in pitch (reduced from 2.5G because the flaps are out) before alpha protect limits elevator deflection in the air. In an emergency manuever I can see this leading to an AoA exceeding stall at least momentarilly. The two critical bits of caveat you will find in the FCOM are 'sidestick moved gently to full aft' and 'reduced possibility of exceeding'. FBW protections control elevator deflection, not physical momentum. I wouldn't put blind faith in it, but then again, there's no procedure for leaping over crossing traffic on takeoff and it's probably best to momentarilly exceed alpha max at that point anyway. I would also get the gear up directly after liftoff.
          But doesn't the logic include a tail-strike protection too? If so, because in the A320 the tail strike happens before stall, the airplane will lift off first and then alpha prot will kick in without ever stalling.

          --- 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


          • #6
            Originally posted by Gabriel View Post
            But doesn't the logic include a tail-strike protection too? If so, because in the A320 the tail strike happens before stall, the airplane will lift off first and then alpha prot will kick in without ever stalling.
            Where did you read that? No, you can freely drag the tail to your heart's content. That's how they calculate Vmu during certification. The rest of your post I don't follow.

            Comment


            • #7
              Originally posted by Evan View Post
              Where did you read that? No, you can freely drag the tail to your heart's content. That's how they calculate Vmu during certification. The rest of your post I don't follow.
              Hmmm.... I wonder how Airbus determines the stall speed during certification. They can't because the normal law won't allow them to stall.

              I am not saying that there is a tail strike protection. I seem to remember having read about it somewhere, but I can be wrong.
              Now, your Vmu certification argument is ridiculous.

              The rest of my post... What happens if you pull up hard a bit below Vr in an A320?
              If the tail strike protection exists, then the pitch will be limited first by the tail strike protection, then the plane will become airborne, the plane enters flight mode, alpha-protect is equal to alpha-max for the first five seconds (which is less than Alpha critical/stall) and the plane doesn't stall.
              If the tail strike protection doesn't exist, then you have first a tail strike (which happens at less than the critical AoA), then the plane becomes airborne, the plane enters flight mode, alpha-protect is equal to alpha-max for the first five seconds (which is less than Alpha critical/stall) and the plane doesn't stall (which, in any event, is jot what happened since there was no tail strike).

              And did you note that I was replying to a humorous comment?
              Hmm... looks like in this case, pulling up relentlessly saved the day.


              The answer to this could be:
              - They didn't pull up relentlessly because if they had there had been a tail strike (which didn't exist)... or...
              - That's ok in the A320; you can pull up relentlessly because HAL will take care of tail strikes and stalls.

              --- 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


              • #8
                Originally posted by Gabriel View Post
                Hmmm.... I wonder how Airbus determines the stall speed during certification. They can't because the normal law won't allow them to stall.

                I am not saying that there is a tail strike protection. I seem to remember having read about it somewhere, but I can be wrong.
                Now, your Vmu certification argument is ridiculous.

                The rest of my post... What happens if you pull up hard a bit below Vr in an A320?
                If the tail strike protection exists, then the pitch will be limited first by the tail strike protection, then the plane will become airborne, the plane enters flight mode, alpha-protect is equal to alpha-max for the first five seconds (which is less than Alpha critical/stall) and the plane doesn't stall.
                If the tail strike protection doesn't exist, then you have first a tail strike (which happens at less than the critical AoA), then the plane becomes airborne, the plane enters flight mode, alpha-protect is equal to alpha-max for the first five seconds (which is less than Alpha critical/stall) and the plane doesn't stall (which, in any event, is jot what happened since there was no tail strike).

                And did you note that I was replying to a humorous comment?
                Hmm... looks like in this case, pulling up relentlessly saved the day.


                The answer to this could be:
                - They didn't pull up relentlessly because if they had there had been a tail strike (which didn't exist)... or...
                - That's ok in the A320; you can pull up relentlessly because HAL will take care of tail strikes and stalls.

                I see your point. Around Vmu, in direct law, the tail and the runway are likely to be your alpha protection on a geometrically-limited aircraft. There was no mention of a tail strike here and the rotation was initiated at 130kts, which is the low side of Vmu for the aircraft. So I assume that they didn't just pull up relentlessly.

                But the thing I was pointing out is that momentum is going to possibly win over alpha protect, at least momentarilly, if you pull full aft too abruptly once you are flying. You are commanding alpha max with those underslung engines at TOGA. I bet you can make it past CL max, lose precious height, maybe drop a wing into somebody else's fin... It's not always OK to trust HAL and just yank the stick back. I hope pilots understand that. Again, all the AB lit says "gently".

                And no, the A320 isn't protected by logic from tail strike. I think the longer A340's have some form of protection in the form of a PFD indication (Maybe I'm wrong about that one). The B777 offers it though. In that case the PFC's are limiting elevator without giving feedback to the control columns (talk about HAL!) It would seem very unsafe to me to actually limit pitch below tailstrike at that critical point. Isn't the whole idea of minimum unstick speed to accommodate emergency situations like this? Better to strike the tail on the runway than on somebody else's business class section, eh?

                Comment


                • #9
                  Originally posted by Evan View Post
                  Isn't the whole idea of minimum unstick speed to accommodate emergency situations like this?
                  Hmmm, no. Sorry.

                  Vmu (minimum unstick) is the minimum speed at which the plane can possibly lift off the ground and continue the take-off. It is one of the many "engineering speed" (not available to the pilot) used to determine other "pilot speeds" (the ones in the manuals).

                  In particular, it establishes a lower bound for Vr. Vr must be such that, if the rotation is started exactly at Vr at the maximum practicable pitch rate (i.e. relentless pull up), the plane will lift off the runway at a speed that is not less than a prescribed factor above Vmu (the factor varies between 1.04 and 1.10 depending on whether you are in the "all engines operative" or "critical engine inop" whether the Vmu attitude is limited by the geometry of the plane or not).

                  So a relentless pull up at Vr may lead to a tail strike and/or a stall but nor before the plane lifted off.

                  In short, you need to demonstrate the minimum safe lift-off speed first, and then demonstrate that actual lift off will happen with at least a prescribed margin above that minimum safe speed.

                  --- 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


                  • #10
                    The A320 family offers no tailstrike protection as such. Rather, the airplane starts screaming "PITCH! PITCH! PITCH!" when approaching limits, which vary by model. The system monitors both the actual pitch angle and the rate of change thereof. As a result, it's somewhat jumpy. Both times I've had it activate, there was no problem either with pitch itself or the rate of change. In fact, both times were on landing, one of them long AFTER touchdown, when the airplane was pitching DOWN.

                    Computers, I tell ya...

                    Comment


                    • #11
                      Originally posted by ATLcrew View Post
                      [...]

                      Computers, I tell ya...
                      Yes. What are they good for, if not saving lifes! Let me againg quote this flight:
                      Two German pilots failed during an A320 flight.

                      Probably, the CEO of my favourite airline is tired to read comments about another A320 flight. And since he published where he began in the LH company, he gains 110% of my respect (of before 100%). Captain Spohr knows how to use that a/c.

                      So, what went wrong during G1 flight 888T?

                      Since I have watched flight G1 888T on TV, I doubt that computers are able to make flights safer. Or, as my father (*1945) would've said,
                      a computer can't be more intelligent than the person who sits infront of it!

                      PS: If a computer tells me how to fly, I don't trust this computer.

                      Even the point in time when the flight computer in an Airbus says, no, I don't like to continue the flight,
                      is not fix!

                      I've never understood why young aviation enthusiasts prefer Airbus. Although they don't know how to handle a 100% computerized aircraft like an Airbus, if the Airbus flight computer says:
                      oha. this is too difficult. all flight computers are switched off!

                      When is an airbus still a safe aircraft? ONLY, when there are men who are able to spontaneously take over when the Airbus flight computer exits.
                      That's what airlines are good for, amongst others,
                      The Gold Member in the 747 club, 50 years since the first LH 747.
                      And constantly advanced, 744 and 748 /w upper and lower EICAS.
                      Aviation enthusiast, since more than 35 years with home airport EDDL.

                      Comment


                      • #12
                        Computers who try to set up laws. Is this Terminator Part III?

                        Damn, I thought I'd know how to use computers since ... 1985. Fortunately, the movie ended with the reign of

                        the humans!

                        Btw, #777 must be a good number.

                        PS: And Dredd (2012) is a good movie. Not all FSK 18 movies are bad due to a lack of a story...
                        Computers have ALWAYS tended to be misused. Not only since that movie: 'This is the doorman computer of block # 297846. No human being is able to enter that block during the next 72 hours due to technical difficulties.'

                        This is what we all want.
                        Last edited by LH-B744; 2016-10-22, 04:07. Reason: Computer failure.
                        That's what airlines are good for, amongst others,
                        The Gold Member in the 747 club, 50 years since the first LH 747.
                        And constantly advanced, 744 and 748 /w upper and lower EICAS.
                        Aviation enthusiast, since more than 35 years with home airport EDDL.

                        Comment


                        • #13
                          Originally posted by hongmng View Post
                          http://avherald.com/h?article=49f37b96&opt=2048

                          Surprised no one brought this one up
                          Hi, hong. After all what I've said about Airbus laws, which should especially be used by Airbus pilots to avoid accidents, it seems like this happening ended without
                          1 casualty
                          and, more important, without
                          1 fatality.

                          This is why I joined this platform, and this is the reason why I like aviation. Not everybody is a hero like Captain Sullenberger. But
                          we safe lifes if it comes hard.

                          PS: Hongqiao is not (yet) a frequently used airport for major European airlines. Do you like to change that?
                          Last edited by LH-B744; 2016-10-22, 04:36. Reason: Hongqiao?
                          That's what airlines are good for, amongst others,
                          The Gold Member in the 747 club, 50 years since the first LH 747.
                          And constantly advanced, 744 and 748 /w upper and lower EICAS.
                          Aviation enthusiast, since more than 35 years with home airport EDDL.

                          Comment


                          • #14
                            Originally posted by LH-B744 View Post
                            if the Airbus flight computer says: oha. this is too difficult. all flight computers are switched off!
                            Every commercial aircraft operating in RVSM airspace is flown by a computer most of the time. It's called autopilot. And yes, if things get too difficult it switches off. That happens in an A320. That happens in a 737. That hapens in your beloved 747. FBW itself is just a means of translating pilot commands into flight surface movements and FBW has never failed due to computers switching off. Traditional cable-control has failed a number of times. So what will it take to earn your trust?

                            It's almost funny how ignorant everyone on aviation forums are about FBW. They spout this kind of nonsense as if legions of aerospace engineers are just complete idiots. If you knew how much redundancy Airbus had to build into the A320 to get it certified, how paranoid the regulators were and how over three decades that redundancy has never been needed to it's full extent you might begin to understand how counter-productive all this scarebus chatter is.

                            Comment


                            • #15
                              Originally posted by Evan View Post

                              It's almost funny how ignorant everyone on aviation forums are about FBW. They spout this kind of nonsense as if legions of aerospace engineers are just complete idiots. If you knew how much redundancy Airbus had to build into the A320 to get it certified, how paranoid the regulators were and how over three decades that redundancy has never been needed to it's full extent you might begin to understand how counter-productive all this scarebus chatter is.
                              How easily we see ignorance in others...

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