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  • Originally posted by Black Ram View Post
    I think the acars message was about change in the pressure difference inside and outside the cabin, a rapid equalization consistent with the rapid descent. It's all about the cabin vertical speed. I don't think there was a message regarding loss of cabin pressure.
    Nor did the masks deploy. I'm afraid the passengers were likely awake and aware.

    Comment


    • Originally posted by KurtMc View Post

      From the quoted quote:
      .............Given a wings level impact, with high vertical and relatively low horizontal velocities,...............

      I have not seen any indication of vertical velocity at impact in any BEA report. The BEA June1, 2009, report states
      "the airplane had likely struck the surface of the water in level flight with a high rate of vertical acceleration"fficeffice" />>>

      Vertical velocity and vertical acceleration should not be confused; acceleration relates to the rate of change of velocity and very high accelerations occur with relatively low velocity if the acceleration occurs over a very short distance.

      My prediction is that vertical velocity was low (tens of ft/sec) relative to the horizontal velocity just prior to impact.

      Comment


      • Originally posted by Evan View Post
        Am I wrong?
        Often

        Listen, he is assuming that the plane stalled because it lost speed. He doesn't say what happened with the pitch, neither with the altitude, leading to the stall. It could be that they held altitude or that they held pitch. Both things require pilot ACTION, because otherwise the airplane, left alone once in alternate law, would have just held the AoA, as any regular airplane would. If the speed goes down and you want to hold the pitch, you have to add increasing amounts of nose-up elevator. If the speed goes down and you want to hold the altitude, you have to add even more nose-up elevator than before. In this last case you WILL stall, and don't tell me that these type of things (the pilots fixating in one parameter while overlooking others) don't happen because they do.

        I agree with you that holding the pitch while loosing speed would hardly lead to a stall, surely not initially, and probably never. Say that you hold 2~4° of pitch while loosing speed. The plane will start to descend. By when the trajectory of the plane reaches a descent slope of say 5° the component of the weight in the direction of the flight equals to some 9% of the airplane weight, enough to provide enough "thrust" to hold the airspeed (stop slowing down) even with the engines idled. The AoA by then is 7~9° (5 + 2~4). Not enough to stall.

        Now, I don't see anywhere the Scientific American column suggest that this is was what happened (that they lost speed and held the pitch). And that's what I'm objecting from you.

        --- 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


        • Originally posted by Highkeas View Post
          I have not seen any indication of vertical velocity at impact in any BEA report. The BEA June1, 2009, report states
          "the airplane had likely struck the surface of the water in level flight with a high rate of vertical acceleration"fficeffice" />>>

          Vertical velocity and vertical acceleration should not be confused; acceleration relates to the rate of change of velocity and very high accelerations occur with relatively low velocity if the acceleration occurs over a very short distance.

          My prediction is that vertical velocity was low (tens of ft/sec) relative to the horizontal velocity just prior to impact.
          Time out here- I am thinking that before the crash, there was some evidence (perhaps injuries to the folks they recovered) indicating a largely vertical "pancaking" into the water.

          And, now, at the bottom of the sea, we have a whole bunch of the airplane in a very small debris field (also indicates lesser horizontal speed).

          Ok, I recognize that we are both using all sorts of relative comparrisons and wiggle words, but, I seem to recall a comment regarding compression fractures to spinal areas, that would suggest that the vertical speed was pretty high and the vertical deceleration when it hit the water was pretty severe.
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

          Comment


          • Originally posted by MCM View Post
            One thing to consider is that in an Airbus aircraft, with the lack of a "feel" sense for where the controls are located..."
            I don't understand that.

            And what would happen if the temperature suddenly increased by say 20 degrees C as this weather pattern was entered? Would that result in a smooth controlled descent if it wasn't immediately recognised and a descent commenced? If you were suddenly a few thousand feet above your maximum altitude for that weight/temperature combination...
            The plane, in alternate law and the A/P off, with no pilot intervention, would just hold the AoA (or oscillate about the AoA of equilibrium for the trim/elevator position, which was the one that was there when the laws degraded to alternate and the A/P disconnected). So yes, I'd expect a fairly smooth descent (I would not call it "controlled" unless the crew is intentionally letting the plane go by itself, which wouldn't be a bad idea by the way). The plane stalling and falling off the sky? This type of things require pilot intervention (human, like the "lets four'oh'one it, dude" CRJ crew, or auto, like Turkish). Airplanes just don't stall for themselves, even if the speed suddenly becomes slower than the 1G stall speed (the plane left alone will put itself in a less than 1G flight, will hold the AoA, and won't stall). Someone or something must be pulling up.

            ... and you got some gusts/turbulence increasing your load factor...
            Add enough gusts/turbulence and anything is possible.

            --- 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


            • Originally posted by Gabriel View Post
              he is assuming that the plane stalled because it lost speed.
              Stalls happen when you go too slow.
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

              Comment


              • Originally posted by Evan View Post
                But I'm having trouble understanding how the slow side of the coffin corner(ish) regime can result in a stall if the pilots know better than to try to hold altitude with significant pitch inputs without having airspeed data or stall warnings to guide them.
                Given that "if", it can't result in a stall.

                There is a case, however, beyond the coffin corner, where you can be between a rock and a hard point.

                You can't reach "beyond the coffin corner", but "beyond the coffin corner" can reach you.

                Say that you are flying at your service ceiling with an OAT of 60°C below zero, and at a speed that is at the same time close to stall and close to the critical Mach. Say that somehow you suddenly enter a zone of 20° above zero (maybe a mass of warm air brought from below). The pressure won't change much, but the density will be reduced by the (273-60)/(273+20)=0.72 factor. While your TAS will be initially the same, your IAS would have dropped probably well below your stall speed. Yet, the plane will not stall for itself. The AoA is initially the same than before, but the lift is reduced by a 0.72 factor. The plane, left alone (assuming no intervention on the control surfaces by anyone and anything) departs 1G flight and starts an accelerated descent of 0.72Gs. Initially the pitch is the same, so the AoA stars to increase, both in the wing and the tail, which causes a nose-down pitching moment and the pitch stars to reduce. The plane never stalls or, if it does, it's a transient stall of which it recovers for itself. The problem now is that, in the descent, the speed starts to increase (both the IAS and the TAS). It could happen that you reach the critical Mach before you can stop gaining speed because the speed is still below the 1G stall.

                That would be an extreme case, I've never heard of something that this actually happening, and I very much doubt that that's what happened to this AF flight.

                --- 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


                • Originally posted by 3WE View Post
                  Stalls happen when you go too slow.
                  Stalls happen (and not happen) at any airspeed.

                  --- 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


                  • Nor did the masks deploy. I'm afraid the passengers were likely awake and aware.
                    It could have been very horrific. However, given the severe turbulence, they may not have been aware they were crashing. But then they would have felt the rapid change in altitude with their ears? My guess is there was horror, panic, things bouncing around - it was probably just a very bad case of turbulence for the passengers, with a sense of not being in control - and then suddenly they hit the water and it was all over. Chances are, the passengers weren't aware of the problems with the airspeed readings and the subsequent loss of automation, or any of the issues that caused the crash; it wasn't like there was a fire on board, or parts falling off their airplane. Still, there must have been some chaos in the cabin.

                    Comment


                    • Originally posted by Gabriel View Post
                      Often
                      But not in in this case and you know it. When a respected scientific publication describes something like aerodynamic stall, without mentioning caveats like emergent warm air masses, turbulence or pilot error in raising pitch to hold altitude, it is inaccurate and misleading. That is what I'm objecting to. Because this conveniently titled phenomena called "coffin corner" has been trumped up by every journalist trying to get print out of this, and in the process both coffin corner and stall have been misleadingly represented.

                      Yes, they might have stalled by trying to hold altitude via pitch while losing airspeed, but that in itself is left to speculation and it's a completely different issue. The topic would then be "why do pilot continue to stall aircraft by exceeding AoA" (see your own thread on this question a ways back), not some concrete statement like "flying too slow near coffin corner and the plane will stall", which is incorrect. And yes, I do understand that under the circumstances it would be easy for these pilots to make such an error in pitch that would lead to stall, but again, that's speculation and these article are presenting unconditional facts. Fly too slow and you stall: Untrue.

                      I simply would like the so-called professionals writing these things to get their aerodynamic facts straight BEFORE adding any speculation as to what might have gone wrong.

                      Considering the collective experience of the crew, and the quality of training within Air France, I would be very surprised to learn that the crew was not giving AoA a high priority. I still seriously wonder if the stealth nature of the Airbus A/THR didn't play a contributing factor, and I've read a few testimonials from Airbus pilots where this is mentioned as a disconcerting aspect of the design.

                      Comment


                      • Originally posted by Black Ram View Post
                        I. Chances are, the passengers weren't aware of the problems with the airspeed readings and the subsequent loss of automation, or any of the issues that caused the crash; it wasn't like there was a fire on board, or parts falling off their airplane. Still, there must have been some chaos in the cabin.
                        What about the people like me who play with the in flight progress screen on the IFE. It shows speed and altitude. I am not sure what these systems get their data from but am sure it made for some worrying viewing.

                        I usually have it one when i am not watching a movie or if i am reading a book.

                        Comment


                        • Originally posted by TeeVee View Post
                          Joe H: where exactly did you get your medical training from? the body dies but the heart keeps pumping for a few minutes? gases in the tissue explode as the body is raised?

                          here are a couple of problems.

                          1: impact great enough to essentially shatter the aircraft most likely killed all on board "instantly" which includes their hearts. rapid deceleration found in high speed collisions tends to separate internal body parts and cause aortic tears, brain stem separation etc etc. recall that the bodies are strapped to the seats, which are bolted to the airplane which came to a rapid stop, while the internal organs are essentially suspended and continue to travel forward, at least until they tear, leading to death in seconds not minutes.
                          My medical training ? the UK NHS, form 1980 to 1994 - Including - as well as Paramedic qualifications,ACLS, PHTLS, ATLS, PALS and again, instructor qualifications. Also C21 / D32 etc.

                          why do you think the seats are still bolted to the aircraft, some may be, some may not be, the 30 bodies on the surface were in relatively good condition although we have no autposy data. Even with a broken neck and spinal damage the heart can still carry on pumping - obviously if one has severe tearing trauma then a beeldout will occur. As you may know, the heart has many survival mechanisms, It can continue to operate in the event of LOSS of cns stimulation for a short period. I think it is fair to say most would be 'dead' as per not going to wake up, 'dead' as per everything stopped within a few minutes' or 'dead' as per ripped apart internally, but that all depends on direct decelleration, blunt trauma etc which neither you now I know until the results of the autopsies are released. IMpact, tumbling of parts, seats and bodies dispersed, forces redistributed, who knows, we will see - HOWEVER !!!! It is also not really relavent to the compression of gasses as you will see. read on -

                          2. once the heart and lungs stop the gas exchange in the body stops.
                          Almost instantly yes, but not instantly, once the diastolic pressure falls low enough and exchange pressures equalise THEN tissue gas exchange stops. However, you cannot say that the heart AND lungs stopped instantaneously, the lungs could be in a non functioning state, however, the heart can continue until it is no longer possible to maintain it's pumping function.
                          3. anyone who has taken a real scuba course will remember Boyle's law and the law of partial pressures. assuming you held your breath from the point of entry into the water (which is the case here since everyone died at the surface or was already dead at impact), although gases in the blood at the surface remain dissolved in the blood their concentrations in the tissue remain the same as depth increases, since no new gas is being introduced. if no new gases are introduced your "exploding" bodies theory fails. now you may think that the small volume of air in the lungs at impact could theoretically become dissolved into the tissue by shear force, but i think that is error. the immense pressure of the water during the descent would have collapsed any airspaces within the body. releasing the air into the surrounding water rather than force it into dissolving into the bodies' tissues.

                          ok morning rant over!
                          Glad you got your rant over, now, no new gasses NEED to be added, In a diving scenario, one assumes that the tissues are in the same state once they return to the surface as they were when they left it, take a free diver for instance. ALL blood vessels will contract, although the liquid is to all intents non compressible, the gasses within are compressible. Or are you saying (wrongly) that the gasses in the blood and tissues are not in gaseous form ? - they ARE.. again, so read on..
                          Now, the total level of gasses in the blood and tissues will be the same on the surface as at the seabed, however the space they occupy will be smaller. You would, of course, be aware of the combined gas laws as well as old boyle, but the basis is the same, deeper more pressure - less space occupied, colder, less space occupied. and yes, seeing that you like to collect qualifications, I was also a diver, indeed held diving instructional qualifications with the SAA, I also wrote the original oxygen therapy course for the SAA, but hey.... anyways, thats an aside....
                          Now your theory goes pear shaped good sir.
                          We now have a complete body at a depth and temperature that the gasses are super compressed and occupy a tiny percentage of the space that they did on the surface ? - are you with me so far - ?
                          IF one brought the body up immediately, then it would return intact. However, these bodyies have lost the elasticity if you like of the tissues, and the blood is no longer liquid, the tissues are no longer flexible, a good analogy that has been used is the mumified state. However, they STILL contain the original volume of now compressed gasses. They are not released necessarily into the surrounding water as the pressures are higher outside than in during the decent in the water, and will eventually equalise - hence no pressure differential on the seabed, just a change in volume.
                          When you raise them, the gasses expand back to their original, but against a non elastic or pliable medium, the now mumified tissues - so on expansion of the gasses - what do you think happens to the mumified tissues. ? it will shatter in effect. The diving analogy you quote does not apply as there is no space or flexibility for the compressed gasses to expand back to surface pressure and volume.
                          If you took a full plastic bottle of lemonade for example, submerged it to 20,000 feet, then it would be compressed, its would deform as the dissolved gasses within it were compressed, where a full plastic bottle of water would not. Now, on bringing it back to the surface, the bottle would regain it's original shape.... the lemonade bottle though, if a chemical change occured (the mumification analogy), the fluid in the bottle would change state to a more solid form, but the gasses within are still compressed as is the container., If one now brings that back to the surface, It will disintegrate as the container (the tissues etc) has also changed form from a semi elastic deformable / reformable stucture to a fragile structure.
                          If you need any more info, please ask.

                          wow some here do like asking for qualifications dont they
                          You also asked in your next post about how many bodies I have seen in certain circumstances etc, what is this ? my dad is bigger than your dad ? - or - Let's drop our shorts and compare sizes ? the answer is, more than enough thankyou !.

                          I hope that makes it simple enough for you

                          Once you have that clear in your head, we can move on to more of the survivablity aspects of 103, 800 etc etc prior to impact, Loss of consciousness at altitude in a decompression scenario, regaining of such consciousness as height is rapidly lost etc etc, but one step at a time.

                          Have a nice day.
                          Oh !, and, by the way, can you please post YOUR CV, or at least the parts that allow YOU to openly question MY experience or qualifications, and, I would like it in as much detail as you keep asking for. You seem to be the one wanting a pissing match lol.. - rather than a 'discussion'

                          Comment


                          • What about the people like me who play with the in flight progress screen on the IFE. It shows speed and altitude. I am not sure what these systems get their data from but am sure it made for some worrying viewing.
                            Maybe some did see the worrying picture. I don't know how much the speed would have meant, as it is ground speed, but the altitude....

                            Comment


                            • Originally posted by MCM View Post
                              One thing to consider is that in an Airbus aircraft, with the lack of a "feel" sense for where the controls are located..."


                              Originally posted by Gabriel View Post
                              I don't understand that.
                              I think he is referring to the sidestick for of control that Airbus use.

                              As the Sidestick is not a feedback device, the pilot will not have the traditional feel for the controls as a pilot in a Boeing.
                              Boeing's Control Yokes always move in direct proportion to the flight control and vice versa. So Autopilot engaged or hand flying the controls always move so the pilot has a direct visual and tactile feel for the aircrafts controls

                              Airbus's sidestick does not move and control inputs do not necessarily translate to the same degree of movement of the control surface. There is no tactile feel and visual indication is on a screen.

                              Even with 787 though fly by wire, the control column will move like a traditional column via servo motors, Embraer do the same with the E jets.

                              Comment


                              • Originally posted by Joe H View Post
                                My medical training ?...
                                .................
                                ..................
                                .................
                                .................

                                You seem to be the one wanting a pissing match lol.. - rather than a 'discussion'
                                There's an awful lot of speculation going on about what went on with the aircraft with us having relatively little data.

                                When that speculation goes beyond the elusive middle ground, it is customary to suggest that we chill out and wait for the final report.
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                                Comment

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