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787 nose gear retraction while parked

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  • 787 nose gear retraction while parked

    Certainly the 787 has logic to prevent this. Something overcame it. I vaguely remember how this occurred on another airliner because the LG lever was left in the UP position and then, at some point, a CB was pulled that powered the downlock or WOW logic, causing the gear to retract. Or something like that...

    This 787 was being used for freight alone. I'm wondering if, during the unloading process, the weight distribution could have become so aft that the NLG shock absorbers extended to their flight position with the LG lever left in the up position, and voila...

    https://www.bbc.com/news/uk-england-london-57524179

  • #2
    Weight on wheels sensors to unlock gear retraction sequence are normally taken from main gear. The only WOW logic I'm familiar with for nose gear is for NLG steering as per any aircraft I was endorsed on. Landing gear selector left in the raised position?

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    • #3
      I'm familiar with one flight deck effect message on the B787 that requires you to apply hydraulic pressure and then cycle the gear handle in the steps to clear the message. The procedure clearly states landing gear downlock pins must be installed before the gear handle is cycled. I am not endorsed on the 787 but I was assisting in carrying out the steps in this reset. I will suspect this is what happened and no where in the linked article or the links in there to two other incidents that the landing gear handle was "left in the raised" selection.

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      • #4
        Originally posted by baldwin8 View Post
        I'm familiar with one flight deck effect message on the B787 that requires you to apply hydraulic pressure and then cycle the gear handle in the steps to clear the message. The procedure clearly states landing gear downlock pins must be installed before the gear handle is cycled. I am not endorsed on the 787 but I was assisting in carrying out the steps in this reset. I will suspect this is what happened and no where in the linked article or the links in there to two other incidents that the landing gear handle was "left in the raised" selection.
        That's interesting, and of course, the WOW sensors are on the MLG so forget that imbalance theory.
        There is a CCTV video on YouTube of an A320 NLG retraction occurring on the ground. I don't know much about the 787 but the A320 gear lever is normally locked in the down position by the LGCIU logic when on the ground. So, in that instance, something must have defeated with that logic. Perhaps a CB was left open when they were performing a similar test to the one you describe.

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        • #5
          Originally posted by Evan View Post
          I don't know much about the 787 but the A320 gear lever is normally locked in the down position by the LGCIU logic when on the ground. So, in that instance, something must have defeated with that logic. Perhaps a CB was left open when they were performing a similar test to the one you describe.
          Here is a B-787 Landing gear panel. Note LOCK OVRD button next to handle. Pressing it will override the safety lock. I doubt a CB was left open. I suspect the nose gear pin was not installed correctly, trust me, I've seen it happen.

          Click image for larger version

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          • #6
            Evan

            Here is what has been released pertaining to this thread. As having to install the nose safety pin myself on occasion, yes it can be confusing where to install.

            https://simpleflying.com/what-caused...se-last-month/

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            • #7
              Originally posted by baldwin8 View Post
              Evan

              Here is what has been released pertaining to this thread. As having to install the nose safety pin myself on occasion, yes it can be confusing where to install.

              https://simpleflying.com/what-caused...se-last-month/
              Can the design be changed and/or an insert be installed by Boeing during manufacturing to firmly prevent this confusion in the future?
              Uh, yeah... Boeing seems to be suffering from a lack of vision lately with regard to potential human error.

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              • #8
                Interestingly, it appears that this is not the first time an incident of this nature has occurred. The AAIB states that in 2018, another Boeing 787 experienced a retraction of the nose landing gear while the aircraft was on the ground. The cause was found to be an incorrect insertion of the NLG downlock pin.

                As a result of this previous event, Boeing published a service bulletin instructing operators to “install an insert into the NLG lock link apex pin inner bore.” Doing so would prevent the NLG downlock pin from being inserted into the apex pin bore instead of the adjacent NLG downlock pin hole.

                This procedure was mandated by an FAA Airworthiness Directive (AD) published on January 16th, 2020. However, it looks like authorities considered this to be less than urgent, providing a compliance time of 36 months (three years) from the publication date. In the case of G-ZBJB, an insert had not been installed.
                On one hand, the issue is not so severe as to make an Emergency AD that requires immediate rectification. The probability of occurrence is low and the severity is relatively low too. It will not cause a deadly crash (but it could cause a deadly crush).

                On the other hand.... come on guys, how many 787s are out there? Make a batch of 3D-printed plastic inserts that click in place. The whole AD procedure would take just 1 hour, 59 minutes of which would be paperwork and going to the mailbox to grab the insert.

                --- 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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