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Southwest 737-300 Emergency Landing After Fuselage Tears Open

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  • #16
    Highkeas, perhaps one of the channels between the ceiling/fuselage?

    Like an "H" channel.
    Live, from a grassy knoll somewhere near you.

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    • #17
      I have never been in an emergency descent, but I'm sure it will scare the pants off most people, especially since they probably haven't been told that the descent is controlled, the pilots being occupied with other things...

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      • #18
        There are ways to do an emergency descent with the passengers barely noticing, and it's not necessarily to do it very smooth and slowly. It could differ a bit regarding the use of speedbrakes, but ir's more or less likie this:

        - Roll normally to 30 deg of bank.
        - Don't pull up to hold the altitude. Instead, keep 1 G and the nose will go down. As long as the plane is banked and you keep 1 G the vertical speed (sink rate) will keep increasing simply because it takes more than 1 G to keep a constant vertical speed in a turn.
        - As the speed starts to build, reduce thrust and push down to keep 1 G (otherwise with the greater speed the plane will pitch up itself).
        - Once the throttles are at idle, keep doing the same. Use the speedbrakes to avoid overspeeding.
        - Once the speedbrakes are fully extended and the speed is nearly at max allowable speed (Vmo/Mmo), roll back to level normally.

        This maneuver achieved three things:
        It put the plane in an emergency descent quickly.
        It turned the plane away of the airway, there could be other planes flying below you.
        It was all done at 1G all the time. The only thing that the passengers will feel is comparable to be steady on a down slope (if you put a ball on the floor of the plane, it will roll forward).

        --- 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 ---

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        • #19
          I don't think with a gash in the airframe/fuselage that kind of maneuver with g's is advisable.
          Live, from a grassy knoll somewhere near you.

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          • #20
            Originally posted by guamainiac View Post
            I don't think with a gash in the airframe/fuselage that kind of maneuver with g's is advisable.
            With g's???????

            How do you manage to understand exactly the opposite of what's written?
            Please do re-read my post.

            --- 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 ---

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            • #21
              I did.
              Live, from a grassy knoll somewhere near you.

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              • #22
                Originally posted by guamainiac View Post
                I did.
                And?

                --- 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 ---

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                • #23
                  I understand it Gabriel. If you're in the front seat you know you have a decompression, but you don't know why. Wouldn't you want to slow the airplane in case the cause is structural and just pull spoilers? I would think you could get a pretty high sink rate that way.

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                  • #24
                    Originally posted by Deadstick View Post
                    I understand it Gabriel. If you're in the front seat you know you have a decompression, but you don't know why. Wouldn't you want to slow the airplane in case the cause is structural and just pull spoilers? I would think you could get a pretty high sink rate that way.
                    Ok, you're right.

                    Now that you've said it, I remember having seen an emergency descent procedure that called for diving at Vmo/Mmo, unless a structural failure was suspected in which case the current speed was to be kept.

                    However, that doesn't change the core of the previous sequence.

                    What's most uncomfortable (and scaring and vomit-inducing) for the passengers is changes in the vertical acceleration, particularly to be exposed to accelerations below 1G (were you feel lighter), not to mention zero G (weightless) or negative Gs (hanging from the seat belt).

                    So the question is, how does one change from zero fpm to -5000 fpm as quickly as possible but without exposing the passengers to significantly less than 1G?

                    For example, if you push down to 0.75 Gs, which is already a quite uncomfortable, it takes some 10 seconds. Surely these will be some unforgettable 10 seconds for your passengers.

                    Another alternative is to keep the load factor at 1G but to direct the lift somewhere else than upwards.

                    If you roll 45° and keep 1G, only 70% of the lift is pointing upwards, so the effect in vertical speed is like being at 0.7Gs, and it'll take less than 9 seconds to reach -5000fpm. While the time is about the same as before, your passengers felt 1G all the time and never learnt that you were entering a dive.

                    The speed can be managed as you like by, as it tends to increase due to the dive, reducing throttles and extending spoilers as needed to keep any desired speed, be in Vmo/Mmo or the original speed.. When you reached the point where the throttles are where you want them, the speedbrakes are where you want them, and the speed is where you want it, you roll back to wings level and keep descending at the vertical speed attained so far.

                    And as said, normally the procedure is to turn away from the airway as yous tart the descent, then call ATC and inform them. You are not supposed to "ask permission" because you are in an emergency and need to go down now, the ATC has to put conflicting traffic out of your way, but you help by turning away. So this maneuver has the good side effect of having that turn built-in.

                    --- 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 ---

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                    • #25
                      I was ridding on a Kitty Hawk's DC-9 cargo airplane as mechanic long time ago, on their "jump seat" and we experienced a rapid decompression, the cargo door broke some seals, and the first thing you experience is a "pop-out" in your ears, a violent one, and a painful one....I guess this is the first indication of a rapid decompression if anyone want to know....the next thing is the cockpit's pressure altimeter dropping 1,000 ft/minute...
                      A Former Airdisaster.Com Forum (senior member)....

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                      • #26
                        Originally posted by Gabriel View Post
                        Ok, you're right.

                        Now that you've said it, I remember having seen an emergency descent procedure that called for diving at Vmo/Mmo, unless a structural failure was suspected in which case the current speed was to be kept.
                        Isn't explosive decompression reason enough to always suspect structural failure?

                        What's most uncomfortable (and scaring and vomit-inducing) for the passengers is changes in the vertical acceleration, particularly to be exposed to accelerations below 1G (were you feel lighter), not to mention zero G (weightless) or negative Gs (hanging from the seat belt).
                        Perhaps most vomit inducing, but if I were in a plane that suddenly decompressed AND went into an endless 45° roll, I would be plenty scared. I prefer the level wings and high rate of descent.

                        And as said, normally the procedure is to turn away from the airway as yous tart the descent, then call ATC and inform them. You are not supposed to "ask permission" because you are in an emergency and need to go down now, the ATC has to put conflicting traffic out of your way, but you help by turning away. So this maneuver has the good side effect of having that turn built-in.
                        Are you certain of this? I would expect ATC to want to know exactly what heading you are on and divert other traffic. Since the doctrine is aviate, navigate, communicate, there may be some delay in getting that information across once you depart from your previous heading.

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                        • #27
                          Originally posted by Gabriel View Post
                          There are ways to do an emergency descent with the passengers barely noticing, and it's not necessarily to do it very smooth and slowly. It could differ a bit regarding the use of speedbrakes, but ir's more or less likie this:

                          - Roll normally to 30 deg of bank.
                          - Don't pull up to hold the altitude. Instead, keep 1 G and the nose will go down. As long as the plane is banked and you keep 1 G the vertical speed (sink rate) will keep increasing simply because it takes more than 1 G to keep a constant vertical speed in a turn.
                          - As the speed starts to build, reduce thrust and push down to keep 1 G (otherwise with the greater speed the plane will pitch up itself).
                          - Once the throttles are at idle, keep doing the same. Use the speedbrakes to avoid overspeeding.
                          - Once the speedbrakes are fully extended and the speed is nearly at max allowable speed (Vmo/Mmo), roll back to level normally.
                          Why not 45deg of bank?

                          Why not idle the engines right away?

                          Why not extend the spoilers right away?

                          Comment


                          • #28
                            From a Time.com article:

                            The tear along a riveted "lap joint" shows evidence of extensive cracking that hadn't been discovered during routine maintenance before Friday's harrowing flight — and probably wouldn't have been unless mechanics had specifically looked for it, officials said.
                            Ok, not by mechanics, but would it have been found by inspectors specifically looking for it...

                            NTSB board member Robert Sumwalt said Sunday that the rip was a foot wide, and that it started along a joint where two sections of the 737's skin are riveted together. An examination showed extensive pre-existing damage along the entire tear. But Sumwalt noted that the extensive cracking, known in the industry as "multi-site damage," could not have been spotted during routine maintenance.
                            Again, not by routine maintenance: by scheduled inspection. How can something like this evade inspection...

                            The NTSB could issue urgent recommendations for inspections on other 737s if investigators decide there is a problem that has been overlooked. The type of riveted joint involved is not normally subjected to extensive checks for wear or fatigue.
                            Oh, hmmm... well, this is a difficult one, whether or not to recommend inspecting this part of the aircraft. I mean, why should they...

                            Federal records show cracks were found and repaired a year ago in the frame of the same Southwest plane.
                            Yeah, ok, maybe there is a problem that has been overlooked, but we best mull that over for a while before acting hastily and requiring that ALL of the metal subject to fatigue be included in the metal fatigue inspection...

                            An Associated Press review of Federal Aviation Administration records of maintenance problems for the 15-year-old plane showed that a March 2010 inspection found 10 instances of cracking in the aircraft frame, which is part of the fuselage, and another 11 instances of cracked stringer clips, which help hold the plane's skin on. The records show the cracking was either repaired or the damaged parts replaced.
                            Alright, so unless all of this fatigue occurred within one year of service, there obviously was a problem that had been overlooked. But how...

                            Southwest officials said the Arizona plane had undergone all inspections required by the FAA.
                            Aha. Always the same answer. Not required...

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                            • #29
                              I agree you might want turn make a turn away from traffic below during a rapid descent, but I'm not so sure a 45 degree bank angle would be a great idea. Again, I'm worried (if I'm in the front seat) about some kind of structural failure and I want to get low and slow. I'm very interested in MCM's take on this.

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                              • #30
                                Originally posted by Evan View Post
                                From a Time.com article:



                                Ok, not by mechanics, but would it have been found by inspectors specifically looking for it...


                                If I recall from a previous discussion on metal fatigue, inspections are not the ideal solution in preventing problems on an aging fleet. While the technology for detecting fatigue at the molecular level is improving, it still tends to be the case that you detect nothing, you detect nothing, you detect nothing... then bam, a crack, unless you are undertaking costly and time-consuming procedures. Instead, again IIRC, most airlines try to estimate the life expectancy (in terms of metal fatigue) of the aircraft by number of cycles, and phase them out well in advance of that point. In the case of Southwest, the skins on the 737-300's are being replaced over time, and the aircraft themselves are being phased out. The message, therefore, might not be that they need to improve their inspection process, which may or may not be effective in preventing future occurrences, but that they need to accelerate the process of replacing the skins, and ultimately, the fleet. Maybe this will hold true for all airlines with these particular aircraft.

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