Boeing finds debris left in new 737 MAXes, now in storage

By Scott Hamilton


Feb. 18, 2020, © Leeham News: Boeing recently discovered some of its stored 737 MAXes have foreign objects in the fuel tanks.

The entire fleet of 400+ newly produced but undelivered MAXes is being inspected.

Foreign objects, called foreign object debris (FOD) in aviation parlance, consist of tools or rags. FOD has been found in the fuel tanks of some MAXes. MAXes are stored at four locations in Washington State and in San Antonio (TX).

It’s unlikely that the FOD inspections will delay recertification or testing of the MAX.

FAA informed

The FAA was informed by Boeing.

It takes up to three days to inspect each airplane, LNA is told. Fuel must be drained and vapors dissipated before the fuel tanks can be opened.

It’s unclear what other areas of the airplane must be inspected.

Reuters last week reported that the certification flights for the MAX may not happen until “April or later.” Boeing hoped to stage the certification flight this month or next. Boeing would not confirm this timeline today to LNA, saying only that the flights will happen “soon.”

Quality Control issues

The FOD in the MAXes are unrelated to the technical issues that grounded the airplane for almost a year. As such, no connection to the MAX’s grounding, accidents or investigations should be made other than it’s just one more issue discovered that now must be rectified.

FOD in the airplanes is a quality control issue on the assembly line. QC is a problem that exists on other airplane programs at Boeing.

The US Air Force halted deliveries of the KC-46A tanker twice because FOD was discovered on the newly produced airplanes at the Everett (WA) wide-body factory. FOD issues on the 787s produced at the Charleston (SC) factory were detailed last year in a report by the Charleston Post and Courier.

The MAX is produced at the Renton (WA) factory.

There are strict protocols to avoid FOD in the final assembly process. Boeing is investigating to determine how the FOD into the MAX occurred.

Boeing’s message to employees

Mark Jenks, the VP and GM of the 737 Program, sent this message to employees today:


During these challenging times, our customers and the flying public are counting on us to do our best work each and every day. That’s why we’re taking action after a range of Foreign Object Debris (FOD) was recently found in the fuel tanks of several 737 MAX airplanes in storage.

FOD is absolutely unacceptable. One escape is one too many. With your help and focus, we will eliminate FOD from our production system.

We’ve already held a series of stand down meetings in Renton with teammates on the factory floor to share a new process for stopping FOD. This process includes:

      • Updated instructions and required checklists for teammates working in the fuel cell areas.
      • Additional verifications including inspections, audits and checks into our tank closure process to ensure there is zero FOD within the fuel tanks.
      • New signage added in these work areas to help remind teammates of the appropriate steps to take.

The success of this initiative is dependent on you. We need our entire team to make this a priority. Thank you for your commitment to put safety, quality and integrity into everything we do.


46 Comments on “Boeing finds debris left in new 737 MAXes, now in storage

  1. Seems like this should be simple to fix, but I bet it’s not. A surgery takes hours and involves about 300 “tools”. Despite long standing efforts and strict protocols items being left behind is still a problem.

    Building an aircraft takes days to months and I can’t image how many tools and other items enter the aircraft and need to be retrieved. Some FOD seems inevitable.

    • You think leaving FOD in fuel tanks “seems inevitable”? It’s just indicitive of very poor QC and manufacturing processess.

      Boeing’s CEO just had to remind his team to not leave their stuff behind in the planes they’re building. It’s not like this is the first time recently.

      • Not that it is acceptable but it is more common than you seem to believe. I must admit that FOD in the fuel tanks is a much more sensitive issue than certain FOD items left lying in the lower fuselage.

      • Well rags in the fuel tanks seems like a particularly egregious and dangerous example. But yes I think some level of FOD is almost inevitable. And addressing it should follow a risk based approach. Where is FOD most dangerous and work hardest to prevent it there.

        Some surgeries are now adding rfid tags to all items, scalpels, sponges etc. They get checked out and need to be check back in before closing. But that is probably not practical on an assembly line.

    • Name one reason why this should be “inevitable?” Can you drive away in your car if you have left the keys on your desk? You’re gonna sit in the parking lot and wait for a tow because this was obviously inevitable? It’s not like each worker is burdened with thousands of tools. And it’s not like they can’t count and take out what they brought in. The only reason this happens is workers pushed too hard, workers otherwise out to “get” the company passive-aggressively or lazy workers. The first two things can be fixed and the third can be fired. We really don’t need to make excuses. At this rate, what is inevitable is another one of these planes crashing. They need serious oversight or to be shut down.

  2. What type of FOD? Rags, wrenches, insulation off of wiring, lunch boxes? How did they notice the FOD? Was it visible, or did it make a noise, or cause fuel flow problems, or contaminate fuel samples? Are there magnetic pickups as cars have in oil pans?

    • What type of FOD and where is a very important question going forward, and I should think that the likes of EASA are now very interested in that aspect too.

      It’s been clear for some time that Boeing has a FOD / QC pandemic across pretty much their entire operation which has not been effectively addressed in, what, decades? Certified aircraft result from certified designs and certified manufacturing. The latter should feature a process that ensures that the rate of FOD incidents tails off.

      That’s clearly not happening in Boeing, which is why I describe it as a pandemic. They haven’t got effective anti-FOD processes in place across the company. Given the amount of time this has been going on for, it’s probable that Boeing doesn’t know what such a process looks like. And if they’ve not got that process in place, what else aren’t they doing properly?

      [It’s likely that a proper anti-FOD process includes feedback all the way to the design process, to have assembly orders that simply provide fewer opportunities for FOD in the first place. That’s hard to do if the design is effectively unchanged since the 1960s…]

      Thus these incidents raise fundamental questions about Boeing’s fitness to manufacture aircraft. I’m wondering just how much more patience the EASA and other world regulators have with the FAA / Boeing on the issue of FOD, and the implications arising from these continuing FOD incidents.

      We’ve seen a number of Boeing customer across the globe decide for themselves that the aircraft they’ve been delivered are not fit to fly, and have sent them back. How long does that have to go on for before EASA / CAAC / etc *have* to intervene at a regulatory level when it’s clear that the FAA hasn’t been doing so effectively on everyone’s behalf?

      One immediate point is that if Boeing can’t be trusted to keep a tight control on FOD, and they’ve got wiring bundles in the MAX (and NG?) spaced too closely which they’re proposing to not fix, what is it about that situation that encourages one to conclude that any of the existing MAXs can ever be fit to fly?

      As the what sort of FOD it is, perhaps we can draw some conclusions from what they’re now doing. If they’re now having to inspect the entire stored fleet, as the article seems to suggest, that seems like it’s not tools. If it were tools then you’d think that it would be possible to identify what tools had gone unaccounted for and when, and what aircraft they’d then be likely to be inside of. I suppose I ought to say that I’d be shocked if they had no way to account for tools, but then again perhaps I wouldn’t be.

      If it’s manufacturing debris (rags, swarf, etc), that’s a whole other issue. We know from other reports that some Boeing production staff have been less than diligent with swarf from drilling, etc. If they’ve gone and found swarf in fuel filters (I can imagine these are being looked at as part of the pre-RTS checks), then that sounds really bad. If they’re leaving swarf inside fuel tanks, where else might one find swarf? On top of wiring bundles for example? Similarly rags; an oily rag lodged on top of wiring may in time degrade the insulation (the oil might).

      And if its non-production related items (lunch boxes, MP3 players, or whatever), that’s just as horrific to contemplate. Can you imagine in 10 years time a Lithium Ion battery in an abandoned music player eventually failing, catching fire, etc?

      I’d really like to know what airline fleet buyers feel when they take delivery of a new Boeing these days. Do they have them thoroughly inspected by their own techs? Do they take a chance? How do the pilots of these new aircraft feel? Apprehensive? Do service techs simply clean it up as and when they find it, leaving the rest of the company in the dark? Is this problem a widely known but dirty little secret across the entire industry?

      The whole issue of FOD in Boeing sends shivers down my spine. For balance I ought to be as concerned about Airbus, except that one hears very few stories about Airbus and FOD. Certainly a web search turns up far fewer stories about FOD at Airbus than at Boeing.

      • “”I’d really like to know what airline fleet buyers feel when they take delivery of a new Boeing these days. Do they have them thoroughly inspected by their own techs?””

        One Middle East airline inspected their new 787 and found lots of debris and didn’t want 787 from Charleston for some time. They also found a chewing gum covering a hole in a wall close to a door.
        FAA announced an AD that new aircraft need to be free of debris. Boeing agreed but nothing changed. FAA checked again and debris was still found.
        When I read this I wondered about the 500 787 already flying and the FAA didn’t care about … think of this when you fly on a 787 next time.

        • LH as an example seems to do “heavy neck breathing” during production of their frames.
          About the same I see with maritime production.

          Future owner and the involved cert authorities have representatives around the yard and all over the new ship.

          Same for repairs/refurbish: Class representatives follow the work ( and on occasion demand rework or change of process ).

    • Most likely small metal/composite (cuttings with adhering drilling fluids) residues from drilling, still no good.
      One would assume they would flush the tanks and verify in fine filters after manufacturing that all residues are gone.
      They do that in many industries (even in nuclear powerplants they find alot at final flush after summer repairs)

      • Agree with you. I thought there would be a “final inspection” before closing the tanks, as they are both difficult to access and very sensitive areas.
        Am surprised there is no such “final” inspection, or it is not a very good one.

      • If you in a manufacturing process create shavings, other contaminations you are expected to have a plan how to remove those. ( I’ve seen in XFW that fuselage segments
        are moved apart after circumference drilling, cleaned out and then fit together for fastener application.)

  3. Thé issue of BOEING’s quality control leaves a lot to be desired, since the Air Force Tankers debris found in their delivered aircrafts presented imminent danger to the aircrafts and flying Staff. It was all about “Hurry Up & Cash-In”🤑

  4. Not quite enough detail, but I am not forgiving. People were paid to inspect these fuel tanks during production and it can’t be that hard to spot FOD because they have managed to spot it now. Why were Boeing even looking at finished aircraft? Bad publicity, but it would have been far worse if the FAA had spotted it as the fleet is returned to service.

    • What Mark Jenks said is true enough. However, it is too easy to discuss FOD in abstract terms. I recently retired from a division of BGS. I witnessed how cost cutting resulted in key people not being replaced. The end result was fatigue, and in some instances, lower morale. There is considerable anecdotal evidence that this occurred across the enterprise, including BCA.

    • Clearly some of the staff don’t think that the entire employment package (targets, pay, job security, pension, workplace processes, etc) are sufficient for them to inspect the fuel tanks. If that’s what some staff are thinking, what Boeing thinks they’ve paid for is irrelevant.

      In the Toyota production system, there aren’t really any production targets, job security is guaranteed by admitting to mistakes (not concealing them, and indeed the company management effectively takes the responsibility for having created the conditions in which a mistake was made), workplace processes evolve very quickly with staff actively encouraged to raise problems (and its management’s responsibility to respond positively), and pay / pension packages are pitched to encourage a high rate of staff retention. This sounds like more or less the complete opposite of Boeing.

    • Probably they found residues in fuel system during filter checks after delivery flights to Boeing storage. Hence any FOD in the tanks float around and are pumped thru filters towards the Engines.

  5. Airplanes parked up for extended periods are subject to periodic maintenance. Depending on where these planes are parked up could be the reason for fuel tank contamination. Hot/ Humid areas can make fuel tanks subject to fungal contamination which in turn cause fuel tank corrosion (Under Wing Corrosion). A substance called biobar can be mixed with fuel to retard this condition but inspection of tanks is necessary before putting Aircraft back into service

    • The memo talks about “tank closure process” and “eliminating FOD from the production process “. This sounds absolutely damming.

    • I’ve yet to see weather conditions severe enough to produce a tool. We’ll see, but I’m pretty sure this is serious FOD, not some substance produced by extenuating circumstance. This is stuff that should have been spotted. They have procedures which obviously were not followed.

  6. Of course the FOD problem had zip to do with Boeing getting rid of a few thousand Q/C types as announced several months ago.

    There is simply to much walking FOD in the offices and Corporate chairs

    • Just checking – these people weren’t replaced by some sort of infalible auto-robot inspector droid? No? Thought not.

      I wonder if they were fired because they were slowing down production rates?

      At a time when quality is being examined all over Boeing’s entire operations, firing Q/C staff sounds like a dumb move…

      • ” At a time when quality is being examined all over Boeing’s entire operations, firing Q/C staff sounds like a dumb move…”

        But it looks great on the Chicago power poInt presentation since it reduces factory floor costs and labor.

        Thus we save a dollar no matter the cost (in another department- not mine )

  7. This is what happens when a company de-unionises to take advantage of repressive “right-to-work” laws solely to cut costs. Add in some tax breaks offered by desperate states and this is what you get. No excuses. Pay people properly, and have adequate staff levels and training.

    • “de-unionised”
      that would apply to Charleston but not to Renton, right?

      Unions or not the US native existing workplace environment is toxic. Unions appear as dysfunctional as management.

      Foreign entities seem to have insignificant workplace issues. More in “right to work” states than in a unionized environment. ( back to unions dysfunctional 🙂

  8. Rsal43
    February 18, 2020
    What a sham to read that. but that indicates the level of negligent which is currently available among BA employees.
    There may be a lot of reasons behind that:
    – Lack of well trained labor.
    – Lack of good communication between labors and their supervision
    – Labors are quite overloaded or not trained well.
    – Lack of well trained supervision.
    – Lack of good quality control persons / inspectors.
    – Bad of labor moral.
    – Bad management.
    – Bad work conditions
    In general labors sometimes make mistakes intentionally if they are not satisfied for different reasons related with their work, site conditions, bad supervision.. etc.
    Hope Boeing will be able to sort this problem soon.
    Problems are easily generated but takes hours and hours to be sorted beside their impact on cost.

  9. I’m somewhat curious on how they found these FODs. I wouldn’t expect that someone is crawling through fuel tanks randomly, no?
    Nevertheless, another shocking revelation, that really makes you wonder what is going on at Boeing.

    • If you were confident that you had done the job properly, why would you be looking? Perhaps it arrived at the filters.

      • rule #1:
        never shall the person working a job also check for conformance of said job.

        self certification is the beginning of the end.
        ( look in any of the domains this was introduced as “much more efficient. We know what we are doing” )

  10. Just wondering if Boeing is seeing this as a quality issue or are they suspecting other issues in play (hate to say it, but could it possibly that someone is doing this intentionally?)?

    Having said that, I imagine there is a certain, almost inevitable case of “familiarity breeds contempt” here. I know I was always very careful whenever going on an aircraft in the line, but then I did not do so on anything like a regular basis. Imagine working on an aircraft day in and day out, with all the associated tools, equipment, packaging etc. always on hand and even the occasional snack. I could well believe that things can be left behind, especially if there is no final walk through.

    Strange that this is something that has only started over the last few years. I wonder if Boeing is looking into what might have changed to cause this to become an issue?

  11. It was int he last year that Boeing ‘replaced’ 900 QC inspectors, anyone surprised then that we are seeing issues.

    • with mvp mechanics, and from my view as
      QA for a boeing supplier…. they don’t get enough training and too many don’t give a flying F#$(.
      ive never seen one lose an MVP cert for generating tags/pickups or shoddy work.
      it USED to be about quality but seems like it went full on quantity in the last few years

  12. Hello.

    This is not a sales pitch.

    I work for a company that makes a vacuum fuel drain system called a SealVac (or referred to by mechanics as a “fuel bowser”). This is a ground service cart specifically designed to quickly vacuum residual fuel from aircraft fuel tanks. The alternative is gravity draining into pails or drums. Boeing has purchased several of these carts from us over the years, but typically only has one or two per manufacturing site (however, Everett has maybe 6).
    After reading your story here, and the subsequent Seattle Times article, my thought was “Boeing is going to wish they purchased a lot more SealVacs!”
    Unfortunately, even if they called today, there is about an 8 week lead time…

  13. This is somewhat like the pickle fork issue, in that only some aircraft are affected, but all aircraft must be inspected.

    The inspection can be done by draining the tank, doing a nitrogen purge to inert below flammability limits, and doing a remote optical inspection. The tank doesn’t need to be opened if it’s clean.

    The FAA has passed FOD rules but they are for airports and runways, as well as for associated aircraft maintenance. However the industry associations have developed guidelines for manufacturing FOD prevention and Boeing subscribes to them, along with all suppliers.

    As Mark Jenks indicated, these are QC escapes and they shouldn’t happen. They should be isolatable to specific teams at Boeing, and I’m sure those teams are under scrutiny right now. I’m sure additional checks have been added as well.

    One of the frustrations of FOD is that they are so easily prevented, and are basically a matter of carelessness.

  14. Count me astonished if there’s no rule in the FAA’s (or anyone else’s) books about how the manufacture of aircraft should ensure that there’s no debris left behind.

    Afterall, an aircraft design doesn’t incorporate debris too, so an aircraft stuffed full of it *by definition* isn’t built according to the certified design. The 787 one receives full of junk isn’t the 787 that the FAA certified.

    If there is no explicit rule, perhaps it’s high time there is one.

  15. this would seem emblematic of the replacement of Boeing’s 50+ year safety and innovation culture with the Muilenberg-Mc Donnell “shareholder value” culture

    • The pre-merger Boeing wasn’t that much different to their peers.
      Boeing has apparently always been a producer with a highly productive “folk lore” PR department, inventing much less than what that established folk lore would suggest.

      Effectively they excelled at avoiding the traps showcased by their competitors. With all those aides having been absorbed or heaving left the market no further “testing the waters” is available.
      Last straw seems to have been Airbus: copy the product, copy the processes but the Cargo Cultish replication couldn’t be made to work as expected.

  16. “Team,
    During these challenging times, our customers and the flying public are counting on us to do our best work each and every day.”

    It is always down slope where more work needs to be done. all the mirrors shrouded. 🙂
    ( topic is “doing overtime” :-)) )

  17. I just can’t believe how something as basic as FOD in the fuel tanks is allowed to happen ?

    Words fail me…

    Do we have any idea what the FOD consists of, what are the chances of fuel starvation leading to both engines quitting on climb out from a major city ?

    What on earth is going on at Boeing at the moment ? What’s next ?

  18. On the wiring issue, the entire certification process seems to me to be encapsulated in this quote from:

    “Whatever decision it ultimately makes, he said, “The FAA better have a strong case.””

    Remind me again who is the airframer, and who is the regulator ?

    I really don’t see why the regulator has to have a strong case for the regulations, the regulations have been established for a good reason.

    It’s the airframer that wants to ignore those regulations, surely in any sane world, the airframer would have to prove to the regulator why it would be safe to go against the regulations ?

    Also in the same article:
    “He noted that 2011, a year when Boeing certified two new airplanes, saw a spike in discoveries of designs failing to comply with requirements, with 98 non-compliances found in the 787 Dreamliner and 24 non-compliances in the 747-8 jumbo jet.”

    Does anyone know where documentation of such non-compliances can be found, also documentation of non-compliances for Airbus aircraft ?

    • JakDak, the dilemma on the wiring issue is that the same regulations that expanded the scope of the wiring analysis, also introduced rules for analysis of wiring modifications. This recognizes that modifying wiring also carries risks.

      At present the MAX has safe wiring, as evidenced by the NG performance. It can be made statistically safer by modification, but the modifications have to ensure that no new risks are introduced. So the FAA will need to allow for both these risks in their decision. That was the point of the article.

      In the comment period of the 2007-2009 regulation change, Boeing asked about applicability to existing designs. The FAA gave a layered answer:

      1. No expectation of modifying existing aircraft.

      2. For in-production aircraft holding a previous TC, STC or ATC, if those TC’s predated the subchapter on EWIS, there was no expectation of change. If TC’s were issued after the EWIS subchapter, the FAA would decide on a case-by-case basis.

      3. For new aircraft with originating TC’s, full compliance was expected.

      For the NG, the first part of #2 above would hold. For the MAX, the second part of #2 should have held, but Boeing did not ask for a decision, they reused the NG wiring design in the belief that it was still compliant.

      Even if Boeing had asked for a decision on the MAX wiring, there was a chance the FAA would have left it alone. But they should have asked, and not asking was another failure on Boeing’s part.

      Another change in the 2007-2009 regulations, was that previously, safety experience with an existing or similar design could be used in establishing a safe design. Now, all wiring designs have to undergo the same evaluation process, including modifications. This was a recognition that EWIS is becoming very complex, such that even small changes may introduce risks.

      Boeing may have been thinking in terms of the pre-2009 regulations when considering the MAX around the time of the change, such that they did what they had always done before, using an earlier known-safe design. Note that doesn’t excuse them, they still should have aware of the change and followed the rules.

      • Rob,

        I get all that, I think in terms of a single catastrophic failure, possibly even the NG wiring may not have met existing regulations at the time ? Hindsight is a wonderful thing.

        So we’re down to statistics, and yes, so far we haven’t had an issue with an NG down due to wiring issues. But that’s the thing, if your chances are 1 in 10,000,000 for instance, after you’ve had a number of safe flights, you’re just getting closer to that 1 time !

        The MAX’s that will be back in the air soon, and produced for the next 5 or so years will still be flying in 20 years, perhaps more, perhaps time for that 1 in x catastrophic event to occur.

        I guess what I was saying, is that at this point Boeing doesn’t have the luxury of saying we followed regulations. If there is another accident, however remote the chance, it may well be the straw that breaks the camel’s back.

        If Boeing had passed it by the FAA during MAX certification, I agree they’d be better off. The thing is that they didn’t, and now if anything happens, the perception may well be that Boeing managed to get the FAA to relax regulations that are there for a good reason. (Assuming that the FAA / EASA / CAAC etc. don’t require the wiring to change).

        There are enough potential holes in the Swiss cheese, just waiting to line up, it’s prudent to reduce the number of such holes.

      • By the way, I hope that Airbus is being very pro-active, and has put a team together to go through their own aircraft looking for any possible slip-ups. I would expect Airbus to be randomly checking newly assembled A320s for any signs of FOD in the fuel tanks now as well.

        There were indications that Airbus did have a look at their horizontal stabiliser control in light of the MAX disasters, and have a software modification planned. Airbus restricted the COG envelope with an Aircraft Flight Manual Temporary Revision, I have myself recently been moved from the last few rows of an A320 to the front of the aircraft just before departure from the gate. The last few rows were left empty for the entire flight.

      • Regulations will always advance and move forward, to achieve safer operation. That does not imply the older regulations were unsafe. The MAX is now undergoing an evaluation by the regulators, so it will have been scrutinized and passed before RTS.

        Your argument applies equally to the NG, which were still manufactured up to a short time ago. Yet there is no concern that they have safety holes waiting to line up. That’s not a correct view, it’s a projection of the statistically possible to the inherently present. Just as with the other views of the MAX as being inherently unstable or inherently unsafe.

        One change that occurred in the rules for EWIS was that all EWIS had to be involved in the analysis, not just the listed essential systems as before. This vastly expanded the number of possible combinations for fault paths.

        The FAA recognized this and said that design should move to qualitative methods rather than quantitative. Designers need to review for specific combinations rather than examine the relationship of every wire to every other wire. Then resolve the potential combinations in the design. If that was not possible, then quantitative results could be used to demonstrate safety of the combination.

        So the quantitative analysis is what Boeing did, and is now being reviewed by the regulators. I’m sure they will do their own separate confirming analysis, so we will have to see what they say. Boeing has said they will make any requested changes.

  19. I don’t understand why shareholders and corporate executives don’t understand that vicious devaluation of labor and laborers results in demoralization. Directives and slogans do not cut it. I work for a sector that has some of the most liberal labor policies imaginable. But discourses of efficiency, effectiveness and excellence are taking their toll. The CEO makes seven times as much as I do, and has no vision and no apparent energy. He is a master of slogans and pep talk though. The Board is pushing the CEO to make us more productive, disregarding our professionalism and expertise. We do our jobs well because we love them — and I’ve been doing mine happily for more than 20 years. But I am losing control over my “product” in a field where I once had a high degree of independence. There is a mentality of profits in a not-for-profit sector that is squeezing me and my colleagues. And we have become demoralized. What do corporations think would be the effect of radical income inequality, outsourcing, draconian gutting of union contracts, insecurity, layoffs to increase profits, crappy pension plans, and a religious obsession with stock value?

    To me, lack of quality control not only indicates an absence of proper procedures and doesn’t just point to lazy or sabotaging workers; it indicates a pathological culture and a demoralized work force. They don’t care. And firing them will replace them with other workers who don’t care. Slogans won’t make it better. The corporate attitude needs to change and become one of better and more equally sharing the wealth while valuing the workers and their input. The contemporary neo-liberal model for American corporations isn’t working — and Boeing is the poster child.

  20. I’m not surprised that Ethiopia is not ready with a final accident report yet.
    There’s not much left to physically examine easily. Trying to determine if it was a bird
    strike or something else that caused the Left AoA vane to stick up at 75 degrees until just
    a few seconds towards the end of the flight. When the pitch attitude finally went negative
    at the end of the flight, the Left AoA vane seemed to have woken up and began to display
    correct values, as the stick shaker stopped for a few seconds according to the preliminary report tracings. The AoA vane seemed to have gone from 75 to 70 degrees earlier on in the flight when the pitch attitude dipped below zero also. What this actually means will take some research.

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