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  • #91
    Originally posted by Gabriel View Post

    The odd ones (1st, 3rd...) are "upside up", i.e. the 90 hz signal is stronger than the 150 hz signal above the slope (and vice versa), and the ILS instrument reacts normally (the needle goes down when the plane is above the slope and vice versa).

    The even ones (2nd, 4th...) are "upside down" (inverted), with the 150 hz being dominant above the slope, so the indication in the plane is reversed.
    Uh yeah... this is where it gets tricky. There are five different types of glideslope antenna systems in use today. Three of them are imaging-type antennas. With those systems, the 6° and 12° false glideslopes are 'null' and the 9° one is always INVERTED. The other two operate as you described. I think you are correct that in this accident, we are dealing with non-imaging type antennas, so the 9° would NOT be inverted and thus the command after passing through would be 'fly down'.

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    • #92
      Originally posted by 3WE View Post
      The magenta line needs to start working vertically...
      It already does on the newest displays
      Attached Files

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      • #93
        Originally posted by Evan View Post
        It already does on the newest displays
        I was meaning on 'all aircraft', not just 'the newest displays'...and synthetic vision where you simply fly 'visually' through boxes... effortless SA and confirmation for the approach profile, unlike this AND the NZ bunch on your other thread.
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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        • #94
          It seems like with a system that has GPS and an airport database with the right info, this should be almost a non-issue.

          The GPS knows where the plane is in 3 dimensions, and the airport database can know where the runway threshold is, including its elevation. That's assuming of course you've correctly programmed it with the destination airport and runway.

          With that info, it's easy to compute the descent angle required to reach the threshold from the aircraft's current position. If the GS indication is centered and the descent angle isn't 3 degrees (or whatever's correct for that runway), it could display a warning. Something similar could be done with the localizer if localizers are prone to similar issues.

          I'd certainly expect any system capable of displaying an image like Evan posted to be able to do that.
          Be alert! America needs more lerts.

          Eric Law

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          • #95
            An EGPWS should have been able to prevent this accident too. After all it was a CFIT.

            --- 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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            • #96
              Originally posted by elaw View Post
              ...It seems like with a system that has GPS and an airport database with the right info, this should be almost a non-issue...
              Brief predominately serious moment for 3BS:

              Two primary issues stand in the way:

              1) Certification- yeah sure, it would be 'nothing' to add this sort of technology- and that's what I'm talking about...10-year old MSFS could provide a half decent, totally fake picture of reality WITH BOXES FOR YOU TO FLY THROUGH!...but what if the computer system hiccups? Liability, cumbersome government regulators, the public's disdain for mistakes and 1a) Unforseen circumstances???

              2) $. Because of #1, it would cost $...lots of $...and, like it or not, old, used, lower-tech aircraft are pretty darn important to aviation. I was surprised to see 'old fashioned' instruments on the MD-88 I rode this week...I sort of assumed (as is a major fault of mine) that almost all passenger jets in the US had gone glass- The cargo industry REALLY likes old planes...I still see ITS-Mobiles flying about Graceland International Airport.

              ...and I haven't become Evan...I still think Airmanship and fundamentals are important...but the old fashioned cryptic ness of ADF needles and ILS needles and doing some quick height-distance math when an I-pad can show you what you'd see in CAVU conditions...

              Which is better for a quick check of all-important SA?

              As Evan will rant (with some validity)...it's all about the $$

              And ATL, et al. will counter rant with equally valid: Stats say we are really really really really really really really safe with our systems as they are now, don't fix what isn't broke...(Gabe's EGPWS reference noted.)

              [/serious]I restate from another thread, I hope that safety officials are taking note!
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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              • #97
                Originally posted by Gabriel View Post
                An EGPWS should have been able to prevent this accident too. After all it was a CFIT.
                I guess, since they were always over the field when in ground proximity, and TAWS doesn't know which end of the runway you are landing on, the alerts would be inhibited in landing configuration.

                ILS is a pretty antiquated system but also probably proven reliable because of its analog simplicity. There are layers of protection against failure, including back-up amplifiers and nearby sensors that detect any signal anomalies. When those sensors detect a problem, they alert ATC and switch to the back-up amplifiers, and if the back-ups fail they shut the system down. The only way you are going to get into these erroneous situations is if maintenance or testing work is being done, maintenance procedures are not followed and the flight crew is not monitoring altitude and distance. That's a lot of cheese to pass through. You can avoid false glideslope by always catching the glideslope from below and remaining vigilant about altitude and distance. What's that thing that comes between AVIATE and COMMUNICATE again?

                I favor an internal guidance safeguard like EGWPS for 3D positional awareness. Maybe in the future we will have an infrared terrain-mapping version of radalt comparing itself to a 3D terrain database.

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                • #98
                  Originally posted by Evan View Post
                  Today, we have radar mapping synthetic vision and 3D terrain databases.
                  Fixed.

                  ...just not in all planes, especially older cargo planes.

                  ...I still like the idea of checking your altitude at "the outer marker" and VSI afterwards...maybe even the old ILS signals are a good confirmation of what the synthetic glideslope is showing you. (Primary secondary inversion kind of thing)...
                  Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                  • #99
                    Originally posted by Evan View Post
                    I guess, since they were always over the field when in ground proximity, and TAWS doesn't know which end of the runway you are landing on, the alerts would be inhibited in landing configuration.
                    I would be very disappointed if that was the case. I don't understand the workings of the EGPWS as well as the GPWS, but one of the main difference between the them is the "look ahead" feature. And "ahead" requires heading information. I would expect, for example, that while descending across certain altitude at one specific coordinate and one specific descent rate, whether the EGPWS triggers a "terrain ahead" warning will depend on whether I am heading towards the mountain or away of it

                    I favor an internal guidance safeguard like EGWPS for 3D positional awareness. Maybe in the future we will have an infrared terrain-mapping version of radalt comparing itself to a 3D terrain database.
                    Almost every new Cessna C-172 comes out of the factory with Synthetic Vision (SVT) where you can actually see ahead the terrain, runway and obstructions (except inconsistent obstructions like deer or trucks). EVS (enhanced vision system, using an IR camera that can look through the fog and clouds and smoke and depicting the image directly on the PFD, together with the pitch information and sometimes together with the SVT) is also already available for small GA airplanes. To be fair, at least SVT is available on most new airliners coming out of the factory too.






                    What's that thing that comes between AVIATE and COMMUNICATE again?
                    NAVIGATE, but that's an emergency procedure

                    --- 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
                      I would be very disappointed if that was the case. I don't understand the workings of the EGPWS as well as the GPWS, but one of the main difference between the them is the "look ahead" feature. And "ahead" requires heading information. I would expect, for example, that while descending across certain altitude at one specific coordinate and one specific descent rate, whether the EGPWS triggers a "terrain ahead" warning will depend on whether I am heading towards the mountain or away of it.
                      Fair, but there are certain areas of that terrain database, namely in direct proximity to airfields, on both sides of the extended centreline where very low altitude flight will naturally occur, where EGPWS (and TAWS) MUST be inhibited. It you are outside of this area and approaching terrain threats, the system can of course sense the course you are on, but I doubt that it sounds a terrain warning in the area just beyond the overrun where this plane came down. I expect that this area is designated as an 'inhibit' zone. Might be wrong about that...

                      Anyway, in this case the warnings would have needed to occur over the runway. I highly doubt EGPWS gives altitude alerts because you are too far past the TDZ. That would be cool if it did though.

                      Comment


                      • Originally posted by Evan View Post
                        Fair, but there are certain areas of that terrain database, namely in direct proximity to airfields, on both sides of the extended centreline where very low altitude flight will naturally occur, where EGPWS (and TAWS) MUST be inhibited.
                        The GPWS (and even more the EGPWS) are trend monitors, not static ones. They don't check where you are and how high, but also how much you are descending or climbing and (ofr the E version) where you are heading to. For example, if immediately after take off and while still above the runway you start to descend, the GPS (even without the E) will start to say "don't sink".

                        So yes, very low altitude flight will naturally occur in the zone where the plane crashed (or where the alert would be triggered), but not in that combination of vertical speed and heading. The system can easily detect that with the current trend I will end up touching a couple miles past the runway threshold that would be consistent with the heading. Even more, I know that there is a "long landing" alert in some planes, but I don't know if it is part of the EGPWS.

                        Anyway, in this case the warnings would have needed to occur over the runway. I highly doubt EGPWS gives altitude alerts because you are too far past the TDZ. That would be cool if it did though.
                        I would expect it to do. If you say "too far past the TDZ" then it sounds mild. But we can also say "aiming to a point that is nowhere close to a valid TDZ".

                        --- 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
                          ...Almost every new Cessna C-172 comes out of the factory with Synthetic Vision (SVT) where you can actually see ahead the terrain, runway and obstructions (except inconsistent obstructions like deer or trucks). EVS (enhanced vision system, using an IR camera that can look through the fog and clouds and smoke and depicting the image directly on the PFD, together with the pitch information and sometimes together with the SVT)...
                          WOW...

                          What happened to the six-pack which lost suction so much that- when practicing IFR skills, it was probably a good idea to try to not use the AI at all and hope that the crazy swinging backup heading indicator would get you to better weather...

                          ...and here "we" are calling for similar systems in big shiny jets!
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                          Comment


                          • Originally posted by Gabriel View Post
                            The GPWS (and even more the EGPWS) are trend monitors, not static ones. They don't check where you are and how high, but also how much you are descending or climbing and (ofr the E version) where you are heading to. For example, if immediately after take off and while still above the runway you start to descend, the GPS (even without the E) will start to say "don't sink".

                            So yes, very low altitude flight will naturally occur in the zone where the plane crashed (or where the alert would be triggered), but not in that combination of vertical speed and heading. The system can easily detect that with the current trend I will end up touching a couple miles past the runway threshold that would be consistent with the heading. Even more, I know that there is a "long landing" alert in some planes, but I don't know if it is part of the EGPWS.


                            I would expect it to do. If you say "too far past the TDZ" then it sounds mild. But we can also say "aiming to a point that is nowhere close to a valid TDZ".
                            Well, apparently it didn't, and it's safe to say that this 2003-build 747 had EGPWS (TAWS) installed. As you say, the principal difference between GPWS and EGPWS if the look-ahead feature, and GPWS is inhibited in landing configuration, so I'm assuming EGPWS is also inhibited in landing configuration UNLESS something in the terrain database presents a look-ahead threat based on the trending path of the aircraft. I'm further assuming that there is nothing threatening in the terrain database between the two opposing glidepaths of the runway. If EGPWS has something like a 'long-landing' feature, I think it would have gone off here and it sure doesn't look like that was the case...

                            I'm pretty sure that if you are descending onto any part of the runway in landing configuration, without excessive closure rate, EGPWS isn't going to bother you. Feel free to prove me wrong though.

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                            • Originally posted by 3WE View Post
                              ...and here "we" are calling for similar systems in big shiny jets!
                              Not necessary, due to the flawless airmanship that all airline pilots must certainly possess. Like envelope protections, it would just be another insult.

                              Comment


                              • Originally posted by Evan View Post
                                ***Like envelope protections, it would just be another insult.***
                                Methinks almost all big shiny jets have stall warnings and stick shakers and pushers and overspeed warnings, and not too many of them had their wings ripped off, nor am I aware of pilots being insulted by said envelope protections.

                                I think the complaints are mostly the Airbus-mega-vanilla-computer that makes it behave like a not_airplane, until the computer decides to hell with it, it is an airplane after all...(Acknowledging that one making normal mundane operations can try to ignore that feature and have some fun boring holes in the sky or trees just beyond the show area)...

                                ...Still, why no envelope protection for rudders that can be slammed stop to stop by very low input forces and very low input movements?

                                As to whether you might actually momentarily need an 80-degreee bank or 60 degree pull up...indeed, that's debatable.

                                Now, as to doing something to help with situational awareness...why not. Even with a big accurate HUD of an artificial-but-accurate terrain picture, it's still probably a good idea to nail the ILS and your speeds...lest you come up short like Asiana on a sunny evening or run long like Southwest et al.

                                Systems that provide safety checks: Good. Systems that replace pilot skill: Old timers utter the phrase "Puppy Mill"
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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