Announcement

Collapse
No announcement yet.

Tenerif .... MUMBAI!

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by Evan View Post

    Here, I’ll give you some shades of grey:

    Departing aircraft rejects. Auto brakes. Rapid deceleration. Arriving aircraft touching down is not aware of this. Situational awareness delay. Then reaction time. Then the reverser/ground spoilers/brakes malfunction. The following occurs over a span of seconds.

    shade a) Arriving aircraft attempts to stop but collides with the rejecting aircraft. Bad outcome.

    shade b) Arriving aircraft attempts to get airborne again. Tenerife. Bad outcome.

    shade c) Arriving aircraft manages to steer off the runway at damaging speed. Maybe only losing some gear and an engine in the process, Or maybe only slicing into the departing aircraft with one fuel-laden wing. Best outcome.

    This scenario requires two factors. Most fatal accident do. Swiss cheese.

    What the FAA seems to understand and you cannot is that all of these outcomes are possible when two aircraft are on the same runway in a high-energy state. And I’m not even getting into jetwash in the flare.

    I had a flight into JFK break-off last minute in severe VMC because the pilot didn’t like the separation. The traffic ahead had landed but had not cleared the runway. That’s a pilot from a strong safety culture. I wish they were all like that.
    To be fair, and while I still would not like it, if the European regulation allows the aircraft that landed ahead or the one that is taking off ahead to be on the runway if they are at least 2500m from the landing threshold, that would be an ample margin to make an outcome like the ones you describe above extremely unlikely. These are the layers of Swiss cheese:

    0- 2500m is enough landing distance for most normal landings with moderate braking. I mean if you remove 1000 of the 2500m due twice-longer-than-normal flare, a deceleration of just 0.2G which is less than 4 kts/sec (a moderate deceleration, Autobrakes 2 in the 737) would let you to go from 150kts to 0 in the remaining 1500m. Note that I am combining an abnormally high landing speed, an abnormally long touchdown, and a normal but very moderate braking. That combo is a pretty thick slice of cheese. And you still have several more:
    1- Assuming that the plane flew at that landing speed from the threshold to the touchdown point, the whole threshold to touchdown to stopping point journey would take 52 seconds. The plane ahead will most likely not be 2500m down the runway, the same spot that it was 52 seconds ago when the landing plane crossed the threshold.
    2- The pilots will not just sit there looking the other plane static on the runway estimating that it will be tight or worse if they leave Autobrakes 2, and leave Autobrakes 2 being along the ride for the crash.
    3- Even if any evasive maneuver is needed a the last moment because the layers #0, 1, 2 and 3 all failed, it would be a low speed event, maybe with an airplane stuck in the mud at worst. Not your "best outcome" above.

    And I want to think that there are provisions in place such as if you have an overweight landing, a flapless landing, or a very high density altitude conditions, where you need a greater landing speed and greater stopping distance (layer #0 at risk), these operations would not be performed.

    So why I still don't like it? It still has the crystal ball thing. It is easy to watch the video and see hoe long down the runway the plane landing / departing ahead was on the runway when the landing plane crossed the threshold. But it is very difficult to predict where it will be when you are clearing the landing airplane for landing. Now, withholding the landing clearance until the conditions are met (rather than clearing a plane for landing when another one is cleared or about to be cleared to land or take off in front of them on the same runway) would eliminate the crystal ball thing, rendering an accident almost impossible.

    --- 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


    • #17
      Originally posted by Evan View Post
      I had a flight into JFK break-off last minute in severe VMC because the pilot didn’t like the separation. The traffic ahead had landed but had not cleared the runway. That is a pilot from a strong safety culture. I wish they were all like that.
      Good for you.

      I’ve survived two airliner traffic go-arounds in severe VMC
      One airliner traffic go-around in IMC
      One missed approach in a regional turboprop
      DONE one 172 go around when a departing dude apparently wasn’t listening to Unicom
      TOLD another tower I was making a 360 because he had me and a Dash-8 aiming at each other on intersecting runways.
      And watched and listened to plenty of successful squeeze plays AND less successful go arounds at Flyover in the TWA/Ozark glory days. One night at STL, a pilot pulled into position and then did something to the radio. The tower cleared them three times, finally saying immediate takeoff and then asked the landing plane to switch runways, to which they said “it’s too late now”. There was a good verbal jab when the plane in position checked in.

      Spare us the attitude that you were blessed with one of the “few”, safety-minded, not_cowboy pilots. The system and people are pretty damn good, even though ATC sometimes gets folks too close. Pilots land or go around from squeeze plays and the passengers don’t did died every day.

      I’m more worried about gross brain farts on intersecting runways and taxiways than an admittedly-spectacular, VMC squeeze-play or Gabieee’s long paragraphs of what-ifs.
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

      Comment


      • #18
        Originally posted by Gabriel View Post
        Assuming that the plane flew at that landing speed from the threshold to the touchdown point, the whole threshold to touchdown to stopping point journey would take 52 seconds.
        And this is what gets me... Assuming that each plane landing or rolling on takeoff needs that runway to itself for less than a minute, what are they doing piling on like this? Is it really too impractical to enforce a 'sterile runway' rule?

        An outcome like the ones you describe above extremely unlikely
        Like Tenerife, you mean? Or soooo many other bad outcomes. One in a million is a lot of fatality. The entire reason I am so interested in aviation safety is that it actually works so well, despite enormous risks, and retains integrity when the rest of the human experiment is racing down the drain of corruption and lassitude. And it works because it does often consider extremely unlikely risks unacceptable. The philosophy seems to be asking 'why do that' as much as 'why not do that'.

        An arriving plane and a departing plane sharing a runway.
        Why not do that? Because extremely unlikely risks are introduced.
        Why do that? .... (I've got nothing)

        Comment


        • #19
          Originally posted by Gabriel View Post

          Note that, while 6000ft is more or less 2000m, that distance can be used in lieu of "the other aircraft has crossed the runway end". Not in lieu of "the other aircraft has departed".
          The original article says the arriving aircraft crossed the threshold 22 seconds after the departing aircraft had begun its takeoff roll. The two aircraft were just 1670ft, or 500m, apart at closest approach, at which time the departing aircraft had not yet rotated. At rotation, the separation was just a few feet greater. The landing aircraft touched down 3 seconds later.

          Comment


          • #20
            Originally posted by Evan View Post
            Why not do that? Because extremely unlikely risks are introduced.
            Why do that? .... (I've got nothing)
            That's simply an unrealistic POV to think that you can avoid even "extremely unlikely risks".
            If you want to achieve that, you have to cancel basically all airline ops.
            Double engine failure on two engined airliner have happened, all engine failures on four engined airliners as well. etc.
            Don't you think that e.g. the CAA hasn't considered every imaginable case (and most likely a lot more you haven't thought of) before approving the LHR & LGW procedures and it's pro and cons? E.g. you disregarded the risks of go-around related accidents, which is by an very large margin higher than your assumed reverser/ground spoilers/brakes malfunction. (Btw. I don't know what reverse thrust has to do in this scenario)

            Comment


            • #21
              Originally posted by bstolle View Post

              ***You can't be so naive to assume that e.g. the CAA hasn't considered every imaginable case (and most likely a lot more you haven't thought of) before approving the LHR & LGW procedures and it's pro and cons.***
              Many years ago, ATL said this. Not exactly, but the concept. It’s a very important statement.

              I enjoy discussing aviation as an outsider and appreciate when you, Bobby, ATL and others share reality.

              We outsiders are all guilty of providing overly-simple, free advice to the aviation industry…hopefully, I think twice and am not_overly bold when I do…but then again, my nickname is 3BS.

              Evan, however…
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

              Comment


              • #22
                Originally posted by bstolle View Post
                That's simply an unrealistic POV to think that you can avoid even "extremely unlikely risks".
                If you want to achieve that, you have to cancel basically all airline ops.
                You’ve addressed the why not but not the why. If you need to have planes going around to avoid this scenario, you have a major problem with your air traffic control. Spacing arrivals at least 90 seconds apart does not equate with “cancel all airline ops” (you’re starting to sound like 3WE).

                (Btw. I don't know what reverse thrust has to do in this scenario)
                Longer stopping distance…?

                And you must factor in human error. The FAA does. There is situational awareness, the time it takes or if it doesn’t happen at all. That can be a lot of runway. There is float, landing further down the runway. There is reaction time, which the FAA factors into stopping distance as an average, expected time. Then, and perhaps most importantly, there is stress and time compression related error. A pilot might touch down, realize the airplane ahead has rejected and choose to go-around. I know it’s the wrong move but check your aviation accident history and you will see a lot of wrong moves made by very experienced pilots under sudden urgent situations. Human factors. You do not want to create an environment that can lead to human error and accidents.

                Now, can you tell me why spacing arrivals and departures at least a minute apart is “cancel all airline ops”?

                Comment


                • #23
                  Originally posted by 3WE View Post

                  Many years ago, ATL said this. Not exactly, but the concept. It’s a very important statement.

                  I enjoy discussing aviation as an outsider and appreciate when you, Bobby, ATL and others share reality.

                  We outsiders are all guilty of providing overly-simple, free advice to the aviation industry…hopefully, I think twice and am not_overly bold when I do…but then again, my nickname is 3BS.

                  Evan, however…
                  Evan, however, is a passenger, a passenger inside, very much an insider and very much what the industry is all about. I’m not giving advice. I’m discussing what might make being a passenger safer or more risky. And so is the FAA. As an insider yourself, I would think you would share those concerns.

                  Comment


                  • #24
                    Originally posted by Evan View Post
                    Longer stopping distance?

                    And you must factor in human error. The FAA does.
                    Reverse thrust is not included in performance calculations on a dry runway.

                    The FAA does and the CAA not? You seriously believe that?

                    Comment


                    • #25
                      Originally posted by Evan View Post

                      Evan, however, is a passenger, a passenger inside, very much an insider and very much what the industry is all about. I’m not giving advice. I’m discussing what might make being a passenger safer or more risky. And so is the FAA. As an insider yourself, I would think you would share those concerns.
                      Bravo!

                      And let me repeat: Intersecting runway brain farts (and the Austin thing) are bad news.

                      Severe-VMC squeeze plays happen every day. You and I have 3 between us: JFK, IAH, STL. #4 was at CLT where someone botched up the 20-mile final in solid rain. We didn’t died.

                      OK, I guess this is a naughty video and the controller SHOULD have sent the dude around and THE DUDE HIMSELF should have gone around…But, since you want to discuss things, one plane doing measured pull ups and fighting underslung engines and somatogravic illusions may lose sight of the departing plane AND outside of Cessna 1X2 aircraft, there ain’t many rear-view mirrors in the departing planes.

                      I disagree that the industry needs to change its ways over stuff like this. Just fire some executives.
                      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

                        Bravo!

                        And let me repeat: Intersecting runway brain farts (and the Austin thing) are bad news.

                        Severe-VMC squeeze plays happen every day. You and I have 3 between us: JFK, IAH, STL. #4 was at CLT where someone botched up the 20-mile final in solid rain. We didn’t died.

                        OK, I guess this is a naughty video and the controller SHOULD have sent the dude around and THE DUDE HIMSELF should have gone around…But, since you want to discuss things, one plane doing measured pull ups and fighting underslung engines and somatogravic illusions may lose sight of the departing plane AND outside of Cessna 1X2 aircraft, there ain’t many rear-view mirrors in the departing planes.

                        I disagree that the industry needs to change its ways over stuff like this. Just fire some executives.
                        The separation incident I experienced happened at what I estimate to be decision height, and the pilot abruptly turned off the runway heading and back out over the bay. I don't see a considerable risk with go-arounds at that point. Actually, I think that's why they call it decision height...

                        Originally posted by bstolle
                        Reverse thrust is not included in performance calculations on a dry runway.
                        I'm not even going to get into that. Pick another failure that affects stopping distance. The point is that they do happen. ​Runway overruns happen. And I'm pretty confident that 100% of them are unintentional. So combine runway overrun with rejected takeoff. The point is, you can't combine them if only one airplane is on the runway at any given time.

                        Comment


                        • #27
                          Originally posted by Evan View Post
                          The separation incident I experienced happened at what I estimate to be decision height, and the pilot abruptly turned off the runway heading and back out over the bay. I don't see a considerable risk with go-arounds at that point.Actually, I think that's why they call it decision height...

                          Pick another failure that affects stopping distance.​
                          Runway overruns happen.
                          FYI a go around never starts with a turn and there is no DH in VMC.
                          Maybe it's a languafe thing, but I don't know why you assume that DA/DH has anything to do with go around safety/risk".
                          I's almost funny that you apparently didn't notice that you just confirned that landing is the safer option than going around according to your own definition.
                          Land after = extremely unlikely risk
                          Go around = no considerable risk

                          Just out of curiosity, please point me to a case of a complete loss of braking and while you are searching, for an overrun in VMC on a dry >10000ft runway.

                          Comment


                          • #28
                            Originally posted by bstolle View Post
                            FYI a go around never starts with a turn and there is no DH in VMC.
                            I’m referring to the missed approach point, the MAP. Do you have a Jeppesen chart for JFK’s VOR approach to 13 L/R? You will see that the procedure is a turn at or beyond the MAP.

                            Who said anything about runway length? The issue here is stopping distance between aircraft sharing the same runway when one lands and the other rejects (or one performs a last-second go-around and the other takes off). The runway can be 100,000ft and they might still collide. I only brought up overruns to point out that these errors and failure do occur, and are not 'extremely unlikely', which could cause such a collision.

                            Comment


                            • #29
                              Originally posted by Evan View Post

                              ***The separation incident I experienced***
                              Please stop comparing your incident to this video. For all four of our collective, personal go-arounds, I am sure the pilots were monitoring things (including electronic wizardry) and probably made rather black and white decisions with minimal judgement. Ok, we’re at 2.0 miles, let’s go around. You know, USA-style.

                              I will now return to the fascinating discussion between you and Bernt regarding an overhaul of international regulations and procedures. I’m sure the industry is taking note.

                              I long for the olden days of spotting locations and traffic at STL where you had 50:50 odds of seeing a go around if you gave it a couple of hours.
                              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
                                I am sure
                                Well, that settles it then.

                                Comment

                                Working...
                                X