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  • #16
    Originally posted by TeeVee View Post
    yeah, maybe. but they don't quite work so well, do they?
    How would an O2 alarm be any different? O2 concentration is a known factor of cabin altitude. Regardless of which measurement triggers it, either the alert works or it doesn't.

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    • #17
      Originally posted by TeeVee View Post
      seems to me we are long overdue to have O2 sensors onboard which can detect a low O2 situation long before the humans start passing out and can warn them of same.
      Ok, you and Evan are bickering over word choice.

      Yeah, we ALREADY have various sensors, but I think that your point is that we continue to occasionally crash a plane, and shouldn't there be something that we could fix easily, some sort of ADDITIONAL thing with no over ride, safety backup, something?

      Yeah, we crashed a whole 737 load of folks, and a few times a year, a private plane fails to check in and flies off into the gulf...we SHOULD do something, OR ban all airplanes!
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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      • #18
        Originally posted by 3WE View Post
        Yeah, we ALREADY have various sensors, but I think that your point is that we continue to occasionally crash a plane, and shouldn't there be something that we could fix easily, some sort of ADDITIONAL thing with no over ride...
        3WE, I think your account has been hacked by someone who thinks systems are better than pilots. Helios 522 did trigger the cabin altitude warning, but the crew dismissed it as a nuisance warning, the same crew that failed to pre-flight check the pressurization switch prior to takeoff.

        So, since no alarm would work there, what do we do, ban all pilots? A system that prevents the aircraft from continuing a climb without pressurization or above a given cabin altitude would be alright by me, as long as it has triple modular redundancy...

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        • #19
          Originally posted by elaw View Post
          On a related note: not that they're a big segment of the market, but there are unpressurized light planes that can fly at altitudes where you can get hypoxia. Nether a cabin altitude warning or O2 sensor would work in those planes.
          For that you have the simple blood oximeter. Which by the way will work for all kind of hypoxia, pressurized or not.

          --- 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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          • #20
            Absolutely true! But one has to possess the device, it has to be working (no dead battery etc.), and most importantly it has to be used... just like pressurization controls.
            Be alert! America needs more lerts.

            Eric Law

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            • #21
              Originally posted by Evan View Post
              3WE, I think your account has been hacked by someone who thinks systems are better than pilots. Helios 522 did trigger the cabin altitude warning, but the crew dismissed it as a nuisance warning, the same crew that failed to pre-flight check the pressurization switch prior to takeoff.
              I do not want to get overly philosophical over the Helios deal, mental processing, confirmation bias or occasional gross stupidity...

              I acknowledge that hypoxia is a tough one as it apparently starts with strong feelings of well being along with greatly reduced SA...

              How does the airplane say, it truly ISN'T pressurized in here and the pilot hear the message?

              And somewhat like TOPMS, there's generally a fair amount of time where you are "pressurizing only for comfort" when a discrepancy should be "easy" to pick out. Yes, we should fix this or demand regulations, oversight and physical punishment.

              I'm sure more training is a great suggestion so pilots efficiently and confidently address problems...until they efficiently and confidently address them incorrectly.

              In the entertainment business, they rehearse very hard, but also have the line, "if you screw up, screw up big!"
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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              • #22
                That said, leveraging the same alarm sound (an intermittent too-too-too) for 2 different purposes on the same airplane doesn't seem like the brightest idea.
                Yes, the pilot should know that the take-off config warning works only on the ground and that the same alarm sound is used for the cabin altitude alarm when not on the ground.

                But an upgrade to an alarm that SAYS "Spoilers" or "Trim" or "Flaps" or 'Brakes" or "Cabin altitude" doesn't seem to be too complicated or unreasonable.

                And that said, we also have cases where the pilot absolutely knew that there was a cabin altitude issue and prioritized other tasks over punting his mask on, and passed out.
                There was an emblematic case. The cabin altitude warning goes off. The senior captain just positions the mask partially on his face but starts to troubleshoot and passes out. The senior flight engineer puts his mask but then takes it out to assist the captain and passes out. The flight attendant comes to the rescue with portable O2 and attempts to share it with the affected flight crew and, you guessed it, passes out. The very junior FO puts his masks on as soon as the cabin altitude warning goes off and executes an emergency descent, thus saving the other 3 senior clowns and the rest of the passengers and crew.

                --- 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
                  Originally posted by Gabriel View Post
                  That said, leveraging the same alarm sound (an intermittent too-too-too) for 2 different purposes on the same airplane doesn't seem like the brightest idea.
                  Yes, the pilot should know that the take-off config warning works only on the ground and that the same alarm sound is used for the cabin altitude alarm when not on the ground.

                  But an upgrade to an alarm that SAYS "Spoilers" or "Trim" or "Flaps" or 'Brakes" or "Cabin altitude" doesn't seem to be too complicated or unreasonable.

                  And that said, we also have cases where the pilot absolutely knew that there was a cabin altitude issue and prioritized other tasks over punting his mask on, and passed out.
                  There was an emblematic case. The cabin altitude warning goes off. The senior captain just positions the mask partially on his face but starts to troubleshoot and passes out. The senior flight engineer puts his mask but then takes it out to assist the captain and passes out. The flight attendant comes to the rescue with portable O2 and attempts to share it with the affected flight crew and, you guessed it, passes out. The very junior FO puts his masks on as soon as the cabin altitude warning goes off and executes an emergency descent, thus saving the other 3 senior clowns and the rest of the passengers and crew.
                  I'm 100% for synthetic voice alerts over ding dongs (On the 737CL it's a "horn" actually, you know the one). Helios was a 737, so not only primitive aural alerts, also no ECAM. But the central concern in your story there is pilots who clearly don't understand the rapid onset nature of hypoxia. Masks firmly fitted as the very first action should be drilled into every pilots head the way it is done to us passengers. Perhaps the FA should do the same routine in the cockpit before every flight and also show them where the whistle is on their life vests.

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                  • #24
                    Originally posted by Evan View Post
                    I'm 100% for synthetic voice alerts over ding dongs (On the 737CL it's a "horn" actually, you know the one).
                    I think that it is the same in all 737s. Call it a horn if you want. It is an intermittent "toot toot" very similar to the "busy" tone in the landline telephones.

                    Like this one (this is the take-off configuration alarm in the LAPA accident, a 737-200, but it is the same alarm than the cabin altitude and I believe the same in the CL and all other 737s.)

                    https://youtu.be/pku8UZlaYSE?t=1830

                    This is what the Helios pilot heard during the climb after passing 10000 ft. They had a few minutes of useful consciousness with that alarm sounding and them not reacting to a cabin altitude issue.

                    --- 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


                    • #25
                      Was there, or was there not a red blinking light that said 'cabin altitude'? Right next to Engine 3, a little hot?

                      Being predominately serious- isn't there a hierarchy of blinking lights in a prominent position in the cockpit...Super serious kill-you crap, serious go land the plane crap, important & pay real close attention, not deadly, but you better address it, and it ain't right, but don't do anything stupid.
                      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                      Comment


                      • #26
                        Originally posted by 3WE View Post
                        Was there, or was there not a red blinking light that said 'cabin altitude'? Right next to Engine 3, a little hot?
                        Depends on the aircraft of course, but on the Helios 737-300, the initial warning was only a horn (and the overhead gauge and the green lighted overhead indication that the outflow valve was open in manual mode). After the findings of the crash, warning lights were added to distinguish a cabin altitude warning from a takeoff configuration warning.

                        However, at about 17,000ft, before hypoxia set in and when the passenger masks automatically deploy, there was a master caution light and an 'overhead' light on the glareshield. The 'overhead' light directs pilots to find the source of the problem on the overhead panel, where the green manual indication should have been noticed (as it is never otherwise seen in flight).

                        The human factors involved (including a little gem known as 'expectation bias") overwhelmed these alerts. Better ones are needed, but for cabin altitude, not blood oygen levels.
                        Attached Files

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                        • #27
                          On the NG:
                          Attached Files

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                          • #28
                            Originally posted by Evan View Post
                            However, at about 17,000ft, before hypoxia set in and when the passenger masks automatically deploy, there was a master caution light and an 'overhead' light on the glareshield. The 'overhead' light directs pilots to find the source of the problem on the overhead panel, where the green manual indication should have been noticed (as it is never otherwise seen in flight).
                            Hmmm, some things I beleive are not exactly accurate in that sentence, which would make your point even stronger:
                            - I believe the masks deploy (and deployed) at 14,000ft, not 17,000. That would be yet another full minute of useful consciousness.
                            - The master caution light is accompanied by an aural alarm.
                            - I think that, other than the outflow valave manual green light, there is a specific amber warning light for the pax O2 masks released.
                            - And I think that there is a recording played for the pax automatically when the masks are released, with instructions to put them one immediately and how to do it, which can also be heard in the cockpit.

                            --- 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


                            • #29
                              Originally posted by Evan View Post
                              the overhead gauge and the green lighted overhead indication that the outflow valve was open in manual mode). After the findings of the crash, warning lights were added to distinguish a cabin altitude warning from a takeoff configuration warning.

                              However, at about 17,000ft, before hypoxia set in and when the passenger masks automatically deploy, there was a master caution light and an 'overhead' light on the glareshield. The 'overhead' light directs pilots to find the source of the problem on the overhead panel, where the green manual indication should have been noticed (as it is never otherwise seen in flight)..

                              Ummm….yuck....Green = good.

                              Pilots deal with malfunctions DAILY....One little screw up and (expectation bias, if you want to call it that, whatever, just more $20 terminology for "insidious").

                              All the damn lights and gauges and blinking lights and you are telling me about green lights, not red ones.

                              https://www.youtube.com/watch?v=WtlBZx0yV_M
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                              Comment


                              • #30
                                Originally posted by 3WE View Post
                                Ummm….yuck....Green = good.

                                Pilots deal with malfunctions DAILY....One little screw up and (expectation bias, if you want to call it that, whatever, just more $20 terminology for "insidious").

                                All the damn lights and gauges and blinking lights and you are telling me about green lights, not red ones.

                                https://www.youtube.com/watch?v=WtlBZx0yV_M
                                You had the maintenance crew that left the outflow valve in a on-standard configuration, you had the green light, you had the cabin preparation checklist that was skipped (or at least this step was), you have the intermittent tone warning that was sounding for several minutes of useful consciousness, you have the AMBER AND CHIME master caution in front of each pilot, plus the "overhead" AMBER light that directs you to look for the problem on the overhead panel, you have (I think) the amber light of the O2 masks released, and the recording playing the instructions (and possibly some screams)...

                                There was ample room to prevent this accident.

                                That said, there was a warning sound that was shared between 2 different situations and was just a sound not a speaking alarm. That could have helped.

                                --- 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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