Go Ahead, Try And Argue Facts….

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You’ll fail, but I would love to see this debate such as it is.

Let’s start: Boeing.  An aircraft “door” (really a plug, but in a place where it can be a plug or a door) flies off in flight. Looking at the images posted by the passengers on social media and which got out basically immediately it is clear that at least two, and perhaps as many as four, bolts, nuts and cotters or safety wire were missing.  This is really not in much dispute and wasn’t as soon as the door was found and not structurally “folded” — and the airframe portion where it is installed appears to be undamaged so we know that did not fail either. The frame of the door drops over two pins on the frame of the fuselage at the top on each side, the bottom two hinge points are vertical posts, the hinges are still there (so the bottom attachments to the hull are intact) and so are the pins on the side.  Once over the pins a bolt is inserted from the rear with a nut and a cotter pin or safety wire on the front, so the bolt cannot back out — but with that bolt in there it is impossible for the plug to rise vertically and clear the pins because the bolt blocks it from moving, and thus it cannot come off.  It may also be the case (not sure without being able to personally view the assembly) that the two retaining bolts on the bottom going through the pins on the hinge assemblies also prohibit vertical movement (in which case its four bolts, nuts and cotters that have to be missing.) Even if the torque on those four bolts is incorrect if the cotters or safety wires are installed there is no way for them to back off.

I like this design; it requires four separate ****-ups to come apart in flight and it appears that is exactly what happened. That is either wild-eyed gross-incompetence or deliberate, but whichever it is doesn’t matter because there are supposed to be cross-checks and sign-offs by both the original person who does the work and someone who checks it.  

So how did it happen in the case of Alaska Air?  At least two and perhaps four bolts, nuts and their safety wiring or cotter pin were left off when the plug was installed onto the frame of the aircraft.  What’s worse is that United, when inspecting their similar aircraft after the first incident, has reported loose bolts on the lower hinge assemblies and some photos of those have circulated. Again everything has a torque spec in anything important on an aircraft (or in a car for that matter) and in an aircraft someone has to install it to specification and then it has to pass inspection, with both the person who did the installing and inspecting signing off on it.  Obviously the inspecting is not happening and the installing is not being done competently which is not one failure it is two failures, sequentially, in the same place.

What happens when you start firing people who are skilled (and expensive) and replace them with people who are less-skilled (and cheaper)?  This! (read more)