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Luxair DH8D "aborted" takeoff

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  • #16
    This is a possible explanation, perhaps more likely than everything discussed here so far: PREMATURE GEAR RETRACTION

    This can happen due to a too early gear-up command, or because the gear lever was up on ground, with the airplane weight directly or indirectly keeping it locked down, but when the wight on wheels is reduced during rotation, the gear goes up.


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    • #17
      Originally posted by Gabriel View Post
      This is a possible explanation, perhaps more likely than everything discussed here so far: PREMATURE GEAR RETRACTION

      This can happen due to a too early gear-up command, or because the gear lever was up on ground, with the airplane weight directly or indirectly keeping it locked down, but when the wight on wheels is reduced during rotation, the gear goes up.
      Interesting...

      But the crew would have had to ignore the gear unsafe lights during preflight and the fact that the amber handle light was on before takeoff...

      And there is a lever lock that must be tripped to move the lever up, so it couldn't have been done by accident.

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      • #18
        Originally posted by Evan View Post
        Interesting...

        But the crew would have had to ignore the gear unsafe lights during preflight and the fact that the amber handle light was on before takeoff...

        And there is a lever lock that must be tripped to move the lever up, so it couldn't have been done by accident.
        Things like that have happened. But even then you still have the "commanded premature" version.

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        • #19
          On Nov 17th 2015 the airline reported in a press conference, that the first officer had retracted the landing gear too early before the captain aborted takeoff causing the aircraft to settle on its belly without landing gear. The captain as well as cabin crew acted well in the course of the occurrence, the first officer however was suspended.
          http://avherald.com/h?article=48d1e3ae&opt=0

          Stil not clear if the captain aborted late (after rotation) because of the smoke and the FO was already retracting the gear or if the FO retracted the gear too early, the plane settled on its belly, the captain aborted the take-off and that caused the smoke.

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          • #20
            Originally posted by Gabriel View Post
            http://avherald.com/h?article=48d1e3ae&opt=0

            Stil not clear if the captain aborted late (after rotation) because of the smoke and the FO was already retracting the gear or if the FO retracted the gear too early, the plane settled on its belly, the captain aborted the take-off and that caused the smoke.
            Well, the rotation must have happened or the ground sensor would prevent the gear retraction. The mains might have still been on the ground though. Can't imagine an FO dumb enough to do that. Isn't it SOP to get above v2 before touching the gear or flaps?

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            • #21
              Originally posted by Evan View Post
              Isn't it SOP to get above v2 before touching the gear or flaps?
              Not that I know. Positive climb ==> Gear up.

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              • #22
                Originally posted by Gabriel View Post
                Not that I know. Positive climb ==> Gear up.
                But isn't that the point of calling v2? Once you reach v2, you will have positive climb above screen height even if you lose an engine, thus there is no longer any reason to go back down (unless you're on fire and there's a nice patch of runway left). Time to bring up the gear. (Flap retraction would be further on, I realize.)

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                • #23
                  With all engines running a twin is accelerating more than twice as fast as with one engine gone. You will achieve V2 much faster, probably well before the 35ft mark, maybe even before lift-off. So it's not a good idea to use V2 as a trigger to raise the gear. The "positive climb" is not as soon as the VSI moves either. The simple act of rotation (i.e. changing the AoA) can cause small variation in the static pressure ports that, while will have a minimal effect on the absolute change (i.e. indicated altitude), it's said change can happen at a rate fast enough to cause a very real (but false) indication in the VSI. Generally the criteria is that the VSI is positive and either stable or smoothly increasing and the altitude is clearly increasing too. If the FO raised the gear at V2 or as soon as the VSI moved, the plane could have been still rotating but still with a lift even slightly less than the weight, the difference being the wight-on-wheels, as long as there are wheels to bear this weight. If not, it's weight-on-belly. So perhaps it is not that the pilot "decided" to abort. Not at least sooner than the scraping sound.

                  And even when I understand your point and your scenario, you'll have to admit that the alternate option is ever more weird. The pilot starts to abort and then the FO raises the gear???? Why would the gear even retract (or the lever move) if the strut switch is still in "compressed"?

                  In any event, very strange situation.

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                  • #24
                    Originally posted by Gabriel View Post

                    And even when I understand your point and your scenario, you'll have to admit that the alternate option is ever more weird. The pilot starts to abort and then the FO raises the gear???? Why would the gear even retract (or the lever move) if the strut switch is still in "compressed"?
                    AFAIK, if the plane is in rotation, the switch is on the nose gear, so main gear would be unlocked (flight mode) at that point and would retract. Idiot-proof only goes so far.

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                    • #25
                      Idiot-proofing is impossible because idiots are too creative.

                      --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
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