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Circuit Breaker Incidents / F.A.O.: Graham2001

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  • Circuit Breaker Incidents / F.A.O.: Graham2001

    I misspoke: Valuejet (not AirFlorida) at Nashville.



    I THINK Evan is aware of this one (then again, given the lack of computers, maybe not.)

    On this one, I'll say Indeed and agree with his over-used "improvisation-with-a-lack-of-systems-knowledge" declarations...it seems that these pilots were trying to trick the planes systems just a bit, not realizing it would pop the spoilers.

    Also of interest is the "go around". Perhaps not a called go-around, but instead a big bounce and unintended resumption of flight.

    And, I think this one is more of a genuine NEAR TOTAL AIR DISASTER, in contrast with some other declarations.

    Ironingly, I know a passenger from this flight.

    Enjoy

    -3BS
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  • #2
    This was also a classic case of "all the words matter". Although the company AOM stated that the CB's must be reset during taxi, the words "during taxi" were left out of the QRH. The crew weren't completely improvising here. They were following the QRH as well.

    The golden rule, however, with any FCC-equipped aircraft, is NEVER reset a CB in flight UNLESS specifically directed to do so.

    This is a grey area accident.

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    • #3
      Originally posted by Evan View Post
      This was also a classic case of "all the words matter". Although the company AOM stated that the CB's must be reset during taxi, the words "during taxi" were left out of the QRH. The crew weren't completely improvising here. They were following the QRH as well.

      The golden rule, however, with any FCC-equipped aircraft, is NEVER reset a CB in flight UNLESS specifically directed to do so.

      This is a grey area accident.
      I'd prefer training to sure as hell just about never ever pull a pressurization circuit breaker on short final...it will pop the spoilers. I like that better than "reset the circuit breaker during taxi".
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

      Comment


      • #4
        Or how about this wild-and-crazy idea: don't design the airplane such that messing with a c/b for a system that is completely separate from the plane's flight controls causes a disruption of the flight controls?
        Be alert! America needs more lerts.

        Eric Law

        Comment


        • #5
          Originally posted by elaw View Post
          Or how about this wild-and-crazy idea: don't design the airplane such that messing with a c/b for a system that is completely separate from the plane's flight controls causes a disruption of the flight controls?
          I'm sure the Engineers designed that using the best science... just like the infallible FCOM procedures for UAS, including 4-minute holds.
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

          Comment


          • #6
            Originally posted by elaw View Post
            Or how about this wild-and-crazy idea: don't design the airplane such that messing with a c/b for a system that is completely separate from the plane's flight controls causes a disruption of the flight controls?
            The CB's were for the air/ground sensors. They are absolutely a part of the flight controls.

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            • #7
              Originally posted by Evan View Post
              The CB's were for the air/ground sensors. They are absolutely a part of the flight controls.
              Again, a design choice. They could have had the pressurization and spoiler systems each have their own sensors. Or, design the system such that the spoilers don't activate when the sensors are powered down.
              Be alert! America needs more lerts.

              Eric Law

              Comment


              • #8
                Originally posted by elaw View Post
                Again, a design choice. They could have had the pressurization and spoiler systems each have their own sensors. Or, design the system such that the spoilers don't activate when the sensors are powered down.
                LIke every modern aircraft using an FCC, it has a system to detect and select ground and air modes. When you arm the spoilers, you do this so that they automatically deploy on the ground. In order for this to happen, the aircraft needs to know when it is on the ground and therefore there is a system using mechanical sensors in the landing gear (nose gear on the MD) that accomplishes this.

                In this case the sensor was mechanically stuck in ground mode. Since the aircraft thought it was still on the ground, they couldn't retract flaps with the throttles advanced without getting a configuration warning. The only was to silence the warning was to power off the sensor system via the CB's. This is ok because the QRH instructs them to do so. No big deal.

                However, resetting them in flight was a big mistake because by doing so they once again entered ground mode in flight. Bingo, the armed ground spoilers deployed as designed. In flight. In retrospect, I'm sure these guys felt pretty stupid abut that, but the QRH doesn't include the words "during taxi" so under pressure it is an understandable mistake.

                Understandable that is, unless you are taught the golden rule about NEVER resetting CB's in flight unless you are specifically directed to do so. They should have at least contacted the company maintenance before improvising like that.

                This is not a design issue. It's a piloting issue (and a ground maintenance oversight to begin with).

                Comment


                • #9
                  Originally posted by Evan View Post
                  ...This is not a design issue...
                  There's multiple design issues here.

                  Eric was right...a procedure to fix the pressurization, also operates the spoilers. There could have been separate circuit breakers. Pretty easy to do as opposed to mixing super duper critical things with only mildly sorta critical things.

                  ALSO, and much bigger... don't power interruptions 'just happen sometimes' when we shove electrons down wires? It blew up a 747 fuel tank (so you say), I'm thinking it wouldn't be too hard for the ground contact wires to break...

                  ...why not design the thing so power raises the spoilers instead of power interruption raising them?
                  Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                  Comment


                  • #10
                    Originally posted by 3WE View Post
                    .......

                    ...why not design the thing so power raises the spoilers instead of power interruption raising them?
                    Good idea. A bit like heavy goods truck compressed air braking systems. If the compressed air system fails, the brakes automatically come on.
                    If it 'ain't broken........ Don't try to mend it !

                    Comment


                    • #11
                      Originally posted by 3WE View Post
                      Eric was right...an improvisation to fix the pressurization, also operates the spoilers.
                      FIxed.

                      Originally posted by 3WE View Post
                      ...why not design the thing so power raises the spoilers instead of power interruption raising them?
                      That is exactly what happened here.

                      I've already explained it. The CB is NOT a pressurization CB or a SPoilers CB, it is a air/ground relay CB. You cannot have a seperate air/ground relay for every system that depends on one of these modes. That would be idiotic. Instead you have a crew that understands that systems have cascading effects on other systems and therefore a flight-control CB should NEVER be reset in flight unless you are aware of EVERY consequence involved.

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