Alaska Airlines' door-dropping flight was missing bolts
- Reference: 1707291247
- News link: https://www.theregister.co.uk/2024/02/07/alaska_airlines_doordropping_flight_lost_cvr/
- Source link:
Seven passengers and one flight attendant suffered minor injuries during the January 5 incident, when a Boeing 737-9 Max bound for Ontario, California, experienced a rapid decompression when the door plug - a structure installed in place of an optional emergency door – fell out. The bolts connecting the door plug to the Mid Exit Door plug (MED plug) were missing, it has subsequently been shown.
All 177 passengers and crew on board de-planed safely.
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Boeing's reputation, however, took a battering as it represented yet another example of the aerospace giant getting it wrong on safety and quality control.
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However the preliminary investigation [4]report issued on Tuesday by the US National Transportation Safety Board (NTSB), stops short of assigning blame for the incident.
The document observes that cabin pressure control system functioned as designed, and that airplane maintenance logs showed entries "indicating that a pressure controller light had illuminated on three previous flights." So the plane performed as intended.
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The report also considers the state of the blown-out door plug, which was recovered in the backyard of a private residence and analyzed at the NTSB's Maintenance Laboratory. That examination found the door "departed the airplane" due to four bolts designed to hold it in place not being present.
"Overall, the observed damage patterns and absence of contact damage or deformation around holes associated with the vertical movement arrestor bolts and upper guide track bolts in the upper guide fittings, hinge fittings, and recovered aft lower hinge guide fitting indicate that the four bolts that prevent upward movement of the MED plug were missing before the MED plug moved upward off the stop pads," the report states.
It appears the bolts went missing before the flight took off. The report indicates they were removed after the creation of a work order to fix five damaged rivets at the edge of the door frame. The rivet repair was performed by employees of contractor Spirit AeroSystems, the MED plug maker, on September 19 last year. According to a photo exchanged by Boeing team members who were discussing interior renovation that would follow the rivet fix, there were no bolts visible in three locations at that point.
[6]Boeing goes boing: 757 loses a wheel while taxiing down the runway
[7]United Airlines' patience with Boeing is maxed out after repeated safety issues
[8]Travel app Kayak offers Boeing 737 Max 9 filter after that door plug drama
[9]Perfect timing... US Navy throws Boeing $103M to update its sub recon jets
The report also noted that the Cockpit Voice Recorder (CVR) on the Boeing 737-9 MAX didn’t retain recordings of pilot chatter during the incident, because it’s only required to store two hours of audio before overwriting itself. It’s possible to override that limit, but nobody appears to have bothered.
"The CVR circuit breaker had not been manually deactivated after the airplane landed following the accident in time to preserve the accident flight recording," the report reveals, noting that the Flight Data Recorder did document the period when the door plug "departed."
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The NTSB’s report doesn’t mention data recovery efforts to retrieve the overwritten audio, which IRTR finds odd as the org [11]knows that modern CVRs use digital storage media. Our experience with data recovery services suggests it’s possible to recover info that’s been overwritten, even on reformatted drives.
The NTSB is continuing to look into Boeing's manufacturing process and associated records.
On January 25 Boeing issued a message to aircraft operators with revised guidance for inspecting 737-9 MAX aircraft with MED plugs. Earlier this week, Boeing announced that it expects to have to delay aircraft delivery to customers in order to [12]rework about 50 aircraft fuselages due to poorly drilled rivet holes.
In [13]a statement issued in conjunction with the NTSB report, Boeing president and CEO Dave Calhoun conceded, "Whatever final conclusions are reached, Boeing is accountable for what happened. An event like this must not happen on an airplane that leaves our factory. We simply must do better for our customers and their passengers. We are implementing a comprehensive plan to strengthen quality and the confidence of our stakeholders. It will take significant, demonstrated action and transparency at every turn – and that is where we are squarely focused."
A month after the incident, Boeing's stock is down about 18 percent. ®
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[4] https://www.ntsb.gov/investigations/Pages/DCA24MA063.aspx
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[6] https://www.theregister.com/2024/01/24/boeing_757_wheel_failure/
[7] https://www.theregister.com/2024/01/23/united_boeing_737/
[8] https://www.theregister.com/2024/01/22/travelers_takes_kayaks_filter_function/
[9] https://www.theregister.com/2024/01/18/us_navy_boeing_upgrade/
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[11] https://www.ntsb.gov/news/Pages/cvr_fdr.aspx#:~:text=The%20older%20analog%20units%20use,aircraft%2C%20usually%20the%20tail%20section.
[12] https://www.theregister.com/2024/02/05/aircraft_rivet_hole_issues_cause/
[13] https://www.boeing.com/737-9-updates#updates
[14] https://whitepapers.theregister.com/
Hey! Bob! ....
.... [1]have you got the torque wrench?
[1] https://www.youtube.com/watch?v=VEQriHQpJFQ
Re: So by failing ....
Would your torque wrench be a [1]"reliable" nut runner ?
[1] https://www.nozominetworks.com/blog/vulnerabilities-on-bosch-rexroth-nutrunners
Major major cock-up
I've worked on flightlines before, any decent QA would be literally screaming about FOD (Foreign Object Debris) risk. They've removed 4 bolts. Those bolts should have been placed somewhere very safe, and very visible, and then at the end of the maintenance, someone should have been asking some very big questions, about why the f%&k are there 4 bolts still sitting here.
You also would NEVER throw old bolts directly in the Bin, UNLESS there was 4 new shiny bolts standing there ready to be inserted. It is just not done, because it is so easy for exactly whats happened here to happen. Bolts go in bin. A while later, someone asks did you put back those bolts, someone else thinking of another part of the job, says of course. And there you have it, a plane released for service, without any locking bolts.
What you can say is that the initial design engineers did a pretty fantastic job, the plane flew multiple times without the locking bolts, triggered the pressure loss light (3 times!), but didnt lose the door in any of those occasions. Yes it finally did come out, but I still find it unbelievable that you can have a pressure loss light come on 3 times, and not pull the plane out of service for inspection. After the first time, you'd make sure that it's not a faulty sensor, after the second time, you'd make sure you can identify where the sensor is triggering. After the third time, you bloody well take the plane out of service and investigate!
Cock-ups all round on this one! What QA should have been doing in this case ----->
Re: Major major cock-up
It's unclear though where the work was done. A work order was raised, but by whom? Boeing or Spirit? Where was the work done? Whose employees removed the bolts prior to doing the work?
If all this was done at Spirit by their employees then everything should have been tracked and new bolts fitted as they also manufacture the entire fuselage sections so it should have been known about and inspected afterwards.
If there were things being done by both Boeing and Spirit employees in that same area then there was obviously a massive breakdown in communication between them but the final post-work inspection again should have ensured everything was in order. Either way, this indicates a huge QA issue here for both companies.
As for the rivet holes, these should have been picked up during manufacture and fixed at the time: There is absolutely no excuse for anything like this to ever make it into a production aircraft.
Re: Major major cock-up
When you repair something, and you do it right, you'll always get some spare screws and other parts at the end of the process.
Re: Major major cock-up
That's because you haven't done it right.
The word you're looking for is hubris.
Re: Major major cock-up
I think he's making an oblique reference to the DIY experience of ending up with more bits than you started with. I think we may all have experienced this at home, but in a workshop, it should set off red lights. In The Meaning of Liff (Douglas Adams and John Lloyd) said that This issue seems to be unrelated to the plug loss. See http://www.b737.org.uk/pressurisation.htm AFAIU the warning light indicated the control system had a fault, and the alternate system (successfully) took over: at no time until the plug came off the aircraft, was the pressurisation incorrect (I'm speculating, but if the warning light was as a result of a leak making the pressurisation system unable to "keep up", the alternate system would have immediately failed in the same way). We'll have a much more detailed explanation in the final report, but that's at least a few months away.
"poorly drilled rivet holes"
Okay, I have one question now : Boeing, do you still know how to make planes ?
Because it sure seems not.
Re: "poorly drilled rivet holes"
Boeing decided a while ago that making planes wasn't their business. So they spun-off the part of the business that did the core manufacturing and it became Spirit AeroSystems. I think the idea was that Spirit would make parts for other companies. But I believe Spirit get most of their business from Boeing and Boeing only buy from Spirit. (Basically, if one company fails, they both fail)
I'm sure some clever MBA can explain why this separation is a good thing. Being a lowly engineer, it's beyond my capacity to understand these complex business/financial topics.
Re: "poorly drilled rivet holes"
A couple of reasons for the spin-off: new contracts with the new company can help reduce future pension liabilities; new contracts can mean lower starting wages for new employers; keeps the plebs workers further from decision-making. But I think the main reason would be to mask capital costs as operational expenditure, thus "freeing up" capital either for acquisitions or gifts to investors.
Re: "poorly drilled rivet holes"
Think a few days ago someone at Spirit AeroSystems flagged poorly riveted holes on a few planes currently in assembly. So it's interesting to read this interim report knowing this has been raised recently. Almost as if they knew it would be something that would be coming out.
What's more concerning for me is that the CVR wasn't saved by the pilots. At one end of the scale it screams poor pilot training. At the other, it feels they may have had to hide something (or felt they had to).
I would be interested to read why the CVR wasn't retained like it should've been.
Re: "poorly drilled rivet holes"
I find it even more interesting why in this day and age of "infinite storage", 2 hours is considered sufficient recording time before being overwritten at all.
Re: "poorly drilled rivet holes"
I read somewhere that it's an FAA ruling and not constrained to the capacity of the device.
I think in Europe they're 25 hours, and the European aviation people ask for the full 25 hours to be kept.
This is what happens when you replace a skilled worker with an unskilled worker holding a photocopy of a work-procedure. To a bean counter they both look he same, but the results are always that the unskilled worker misses or doesn’t understand his mistakes.
Naively I would have thought that a plug in a pressurised aircraft would have been shaped so that it can never move outward being effectively wedge shaped so that pressure only increases the sealing force.
That way the worst that happen would be the plug falls into the cabin when the plane is unpressurised (and in theory on the ground)
It's a good point; but I think the plug sits in an opening designed for an emergency exit door. It would be bonkers to have to certify two versions of the fuselage with a different frame structure at this location, so the plug is very likely to be compatible with the way the emergency exit door is attached to the aircraft.
I read somewhere that emergency doors are designed with this kind of protection by design, but the plugs are an option (not offered by Airbus) which allows even more seats to be squeezed in.
MBAs despise the kind of overengineering that became standard in the airline industry precisely to save lives: the engineer must assume there is a risk he hasn't thought of; the MBA wants a to be able to price risks in order to determine which are acceptable.
It (sort of, without the "wedge" part) is designed that way. When pressurised, the main forces operating on the plug are the aircraft internal pressure pushing the door against the frame (specifically through structures called "stop pads", presumably because they "stop" it departing the aircraft). This stops the plug moving out but (other than from friction) does nothing to stop it moving up , so if the plug moves up to an extent that the stop pads are no longer matching up, it's on its way. This upward movement is how it would be removed during checks/maintenance and is prevented by the bolts (which in this case were missing). Others alluded to this, but the reason emergency exits (and therefore also other-things-designed-to-go-in-the-same-hole) aren't simple plugs is because the new thinking is to throw them out the aircraft by the person opening it, rather than being pulled in and placed on seats, dropped on the floor, etc., possibly causing obstruction.
None of this is a problem if you put the bolts where they're meant to go.
"the plane performed as intended"
At least they're honest then...
Recover of overwritten data
Modern CVRs use FLASH for the storage, so any overwrite would require a block erase of the underlying storage cells and recovery would not be possible.
Door opened for civil suits
Responsibility hasn't yet officially been apportioned but the statement by the CEO makes this almost a formality. It wouldn't surprise me to see civil suits, which is how America disciplines its companies in lieu of effective regulation, coming on this, and the C-suite might have to worry about ones from investors who will have a good case to make about the company trashing their investment.
So by failing ....
.... to screw (I mean bolt) it up they screwed it up!
--------> Mines the one with the torque wrench in the pocket!