Southwest, 737s, and Holes: What Happened and What Now?

737, Accidents/Incidents, Southwest

I’m sure a lot of you have been wondering why I haven’t written about the Southwest 737 that had a big hole open up inflight last week. It was big news for sure, but I just didn’t know enough beyond the basic information to make a post worthwhile. Southwest is still not saying much at all, but I was able to piece some things together from other sources to get a better idea of what’s actually going on. It all starts with a lap joint.

Lap Joint Problems on 737s

What Happened
Last week, a Southwest 737-300 airplane was flying from Phoenix to Sacramento when a hole opened up in the roof. The airplane lost pressurization (of course) but the pilots were able to land the airplane in Yuma and everyone was fine. You may have heard people talk about how the airplane plunged after the hole appeared, but that was on purpose.

When an airplane loses pressurization at altitude, you can’t breathe. And that’s a problem. There are oxygen masks but those don’t have an endless supply of oxygen in them. So anytime this happens, the pilots are trained to go into a steep descent until they get to around the 10,000 foot mark where the air is breathable. It may seem like you’re plunging, but it’s all part of the plan.

Once on the ground, it was easy to see that this was no small hole. It happened in the crown of the airplane along a lap joint. That’s a horizontal line where two pieces of the skin come together and are fastened to each other. As you can imagine, this area is cause for concern regarding fatigue because joints are the weakest points in a structure.

Tear Straps
The part that’s really concerning here isn’t the tear itself so much as it is the size of the tear. See, on all these airplanes, they install what are called tear straps. The aircraft of particular concern are the 737-300, -400, and -500s, collectively called 737 Classics. Next Generation (or “NG”) airplanes make up the bulk of the 737s you’re likely to fly, including all of the ones that American and Delta operate. Those had a different design and are newer so they aren’t impacted by this. I’m sure, however, that the FAA and Boeing will be watching this closely.

But back to the Classic airplanes. On the older models, these tear straps were placed every 10 inches horizontally along that lap joint. In 1993, a change was made that resulted in the straps being needed only every 20 inches. These tear straps are meant to stop any crack from spreading further. In other words, even if a hole opened up, it should never go further than 10 or 20 inches depending upon the airplane because the tear strap will stop it.

As you may have seen, this went for feet, not inches, and that means that the tear straps were breached. That is not good. So, Boeing, the FAA, and the airlines are diving in to try to figure out what exactly happened here. But for now, they are simply mandating inspections for cracks so that this never even becomes an issue. Why weren’t these being inspected before? That’s a different story.

Shouldn’t These Have Been Inspected?
For the older 737 Classic models that were built before 1993, there were directives issued that required inspections (using technology, not visual) for aircraft with more than 45,000 cycles. That was eventually lowered to only 35,000 cycles. One cycle is one takeoff and landing. This metric is used because that’s a good measure of how much stress is put on the airframe going through the pressurization process.

At US Airways media day yesterday, that airline confirmed that all of its 737s fall into this category, and they’ve been doing the inspections since the FAA mandated them early last decade. More than half of Southwest’s 737-300s fall into this category, so presumably the airline has been conducting these checks as required. But it didn’t use this as a standard 737-300 maintenance procedure for the full fleet. On those airplanes built after the 1993 manufacturing change, none of these non-visual inspections were done, because they didn’t have to be done.

With hindsight, that’s too bad, because had Southwest inspected all of its 737-300s, it would have found the cracks. The airplane that opened up a hole had more than 39,000 cycles. But the newer manufacturing process wasn’t expected to have problems this early on in the life of the airplane. In fact, Boeing thought that 60,000 cycles would have been a good conservative number for an inspection. Now, the FAA has mandated checks on these newer airplanes starting at 30,000 cycles.

So as you can see, there’s a lot up in the air. Nobody knows why cracks are showing up on these airplanes so early in life, but stepped up inspections will make sure that they are safe to fly regardless. Now the investigation can focus on why this is happening.

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51 comments on “Southwest, 737s, and Holes: What Happened and What Now?

  1. This is definitely not a good thing, but looking at this from the positive side, there was a failure, and the plane still landed safely.

    Although, I wonder if this’ll push any orders toward Airbus? Its small, but Boeing jets of this vintage have had a rash of these incidents lately…

  2. I wonder if this will speed up SWA’a 700NG orders going forward? Just from PR standpoint, I think they might like to get past the 300 era sooner rather than later.

  3. I’m just wondering why the inspection threshold wasn’t lowered the last time WN had a depressurization incident on a 737-300 in July of 2009.

    1. That is a great question. The airplane in that incident was N387SW and it had 42,500 cycles at the time. (See the accident report.) It was built in 1994 so it would have been under the newer manufacturing process. At the time, the FAA put out an Airworthiness Directive that simply required the airlines to conduct visual inspections of that area to make sure there were no cracking. No idea if these two incidents are related (though we’ll find out eventually), but at the time they clearly didn’t think this was enough of a problem to bother doing the more sophisicated inspections on a regular basis. It could be that the FAA and Boeing end up looking very bad if these are related.

  4. It’s like everything else in life, things just aren’t made like they used to be. And nothing they test in a lab will ever give the same results as normal everyday use of a product to know if something will last a certain time or not.

    Kind of funny but this weekend the Liberty Foundation will be at my local airport and you can take rides in a B-17 fortress or P-40 war plane (if you have a fat wallet to pay the price). I wonder how many people will feel completely safe in a 60 year old plane compared to getting on a 15-20 year old ‘modern’ plane right now. Even the UA airbus event in MSY is on peoples minds.

  5. Last fall an Al Jazeera investigative show did a full program on two Boeing whisleblowers, who around 99-01 brought to attention the quality and workmanship of the supplier that produced the “bear straps” parts for the 734NG. Allegedly many of the parts didn’t fit to exact specifications, but not rejected as on-conforming, and as one interviewed said flat out made the plane non-airworthy.

    I thought it was very well done, not sensationalistic, and both sides well represented.

    1. This is very interesting, but just to be clear, these are unrelated issues. The problem on the Southwest 737 is an issue with the skin. The issues brought up by Al Jazeera are about the frame, so the parts that the skin attaches to. Also, that’s about the next generation 737s while the Southwest issue is with older 737 Classics.

      Doesn’t take anything away from the story itself – just wanted to clarify.

      1. If Boeing knew of problems and they didn’t address them or share them with the appropriate agencies, they’d end up being criminally negligible, something that they’re not stupid enough to do.

        Air travel is the safest its been. In the past accidents like this resulted in deaths, instead, we have some scared passengers and a plane that is out of commission. Not a bad deal..

        1. Are you serious? Have you watched the video above? Of course Boeing knew about the problem….how obvious does it have to be????

          Sorry man…I totally disagree with you. Safety in flight is a smokescreen. The margin of safety is very very small in reality.

          The US government has protected many companies in the past….Halliburton, etc…protecting Boeing is paramount…screw people.

          1. I haven’t watched the video, but I read the article. Yes there are problems with parts. I never expect anything to be perfect.

            The fact is the number of fatalities per passenger on airliners are the lowest of any form of travel. Its likely more dangerous to walk across the street, and it definitely is more dangerous to go driving than to fly in an airliner.

          2. That’s a ridiculous thing to say “there are problems with parts.”….not with structural components you don’t….NEVER. Not on aircraft.

            These critical components were fitted on these aircraft with full knowledge and understanding of parties involved and the government completely was in bed with Boeing and looked the other way. It’s as simple as that.

            The number of fatalities in flying may be low but per accident, the fatalities are extremely high. You will not survive most likely.

            All the more reason to bring Boeing to justice about this….the margin of error is too small and the false feeling of security due to lack of accidents is wrong.

            Not sure why you’re so protective of them….very odd.

          3. Agreed, that the number a fatalities per accident are higher with aircraft, thus why emphasis is placed on not having any accidents.

            Simply we don’t have the full story on this. Lots of really smart people spend time engineering airplanes. I know a 789 engineer who has spent four years working to develop a 30 page document of the fatigue related to a single system on the plane. They’re very through in their investigation and engineering.

            I’m not an airplane engineer, but I realize that people who are experts in their field deal with a great deal of complexity that when viewed from the outside can appear that they’re making an unprincipled decision.

            Until you’ve walked a mile in their shoes I recommend giving them a reasonable degree of leniency.

  6. I am rather disappointed in article that you sent out. The way I interpreted it is Southwest did not do a good job of inspection. Please see the article below and the one at the following link. I think you owe your readers more than just speculation or opinion. You did work for an airline at one time.
    Boeing didn’t expect 737 cracks so soon

    Reader wonders why we’re not reporting much on Southwest Airlines’ maintenance problems
    By Terry Maxon/Reporter

    1. I would say that your interpretation is wrong, or at least premature. If you read the Maxon article that you reprinted without his permission (I have removed it and put a link there instead), he in no way faults Southwest for inspection issues because he hasn’t seen facts that suggest that’s the problem.

      The MSNBC article does try to pin something on Southwest for not catching the cracking, but we don’t know the details of what happened there yet. There was no requirement to do deeper inspections on this part of the airplane, so Southwest isn’t out of compliance there. But should they have done further inspections after discovering some other cracking? It’s too early to know exactly what happened. So I will refrain from just throwing around very dangerous blame there until we know more from the investigation.

  7. Has this ever been a problem with DC-9, MD-80, 88, 90 series planes? They do a lot of cycles also but have never heard of that happening to them.

    1. Metal fatigue is a concern for any airplane made from . . . metal, but I don’t recall there being any high profile problems with Douglas airplanes. That doesn’t mean metal fatigue isn’t an issue. It just means that they adequately dealt with the problem before it became an incident. (Anyone else know of any metal fatigue incidents those birds?)

      In general, those Douglas airplanes were built like tanks. They can fly forever. (And at Delta, they do.)

  8. Don’t count on the FAA to do anything…even with the NTSB’s recommendations. The FAA runs on the philosophy of “Tombstone Technology.” Things are done after the fact and then it’s too late.

    But airlines needn’t worry. The bean counters at airlines have already figured out the hit airlines will take if an accident occurs. Airlines are OK with a certain amount of accidents/deaths for an airline’s operation. It’s all calculated in the cost of operation. Insurance takes care of the rest.

    They penny pinch until the last moment or beyond and understand FULLY the risks associated with such methods of business operation. Maximize profit, minimize costs…that’s the name of the game.

    This is especially true for budget US carriers…which is pretty much all the US airlines.

    I personally try to avoid US carriers like the plague…I can’t stand how they are run, operated, and have very little trust in them.

    My wife and I are planning on going to Hawaii in August and unfortunately we have to take a US carrier…ended up booking with United. Not looking forward to it.

    1. The FAA and the NTSB have disagreed for years, that isn’t news.

      Airlines don’t like accidents. Accidents can and have brought down airlines. PanAm would likely still be flying if it wasn’t for flight 103.

      Armond, which airline would you prefer to be flying? And if you really wanted to I’m sure you could get to Hawaii by not flying on a US carrier. If you’re in the US you could go via Vancouver, BC, Canada or even via London England without flying a US carrier.

      1. Nicholas:

        Airlines don’t like accidents…but there operational methods take these incidences into account monetarily. They are taking a gamble in terms of surviving the fallout of “bad press” but it’s clear they are willing to do it. There a many FAA/NTSB directives to make changes on aircraft (many of them “voluntary”) of which airlines do not spend the money to do…clearly stated by the former FAA inspector at 41-42 minutes of the video above.

        I’m actually flying from Los Angeles…too late…we booked it!!!! Shit!

        It’s very very clear that the government, the FAA, and the airlines are, for the most part, in bed with each other and with the aircraft manufacturers.

        The government will go to the ends of the earth to protect its military contractors and military war machine….and this is an exemplary case to that.

        1. Armond,
          A question for you, when booking your flight from LA to Hawaii, did you pick the cheapest flight? If so you’re contributing to exactly what you are complaining about.

          1. Nicholas….

            I believe you should really think about what you’re saying…do I seem like a person who would pick the cheapest flight given how little faith I have these firms?????

            Unless absolutely necessary, I ALWAYS choose a direct flight…which are always the most expensive. Our trip to Hawaii is no exception. We booked a direct flight non-stop and paid up the yazoo for it.

          2. I choose my words carefully, thank you very much.

            But of the direct flights, did you choose the cheapest ticket price? Why not pay more? That would allow the airline to spend more on maintenance. (and yes, their other costs and profits.)

            If you still chose the cheapest ticket price you’re contributing to the cost pressures in this industry, and have little right to state what you have stated.

            You still haven’t answered my question, given any airline in the world, which airline would you prefer to fly?

          3. What on earth are you talking about? No I do think you really should choose your words more carefully…

            I booked the deal as a package and the ticket cost was included in the deal but the deal cost ALOT more for direct flights. Whether it was the cheapest or not I can’t say but was at least 50% more than multiple stops.

            Stop being a strawman…you know damned well nonstop flights are much more expensive….telling me that I chose the “cheapest” nonstop flight is stupid frankly. Sorry.

            And to answer your question…Singapore, Emirates, and Air Tahiti Nui are the airlines that I would fly.

            Any questions???

          4. No Armond, I’m making the point that even people who state that they care about safety won’t pay for it. If you were given the option to pay two times your air fare price, to fly on a plane that’s maintenance, construction, and operational standards were certified by an independent authority (say Underwriters Laboratories or a similar outfit) would you? Probably not, I’ll admit that I wouldn’t and most passengers wouldn’t. Cost pressures are the rule in this industry. Thats just the way it is.

            I took a brief peek at Singapore Airlines, Emirates, and Air Tahiti Nui’s accident and incident records. I’m not impressed, it appears that they’ve had incidents of exceptionally poor crew decisions within the past fifteen years.

            I’d rather have a plane flown by an expert crew even with poor structural parts. Smart people can overcome problems with equipment, well designed equipment can never overcome problems created by human error.

          5. Nicholas,

            Using me as an example is ridiculous…I’ve paid premium for my ticket and you making an issue out of it is just plain lame. Use someone else who pays $49 for a ticket as an example…not me who paid premium for a non-stop flight when most would take 1-2 stops to Hawaii.

            I personally would pay extra for safety and always have. I have avoided air travel within the US as much as possible and when I do fly overseas, I pay premium for zero stops and pick my planes accordingly. Do you? Apparently not.

            If you want to make stupid excuses for the industry go ahead. You seem rather comfortable playing Russian Roulette with your own life…I’m not. Unfortunately you have a very fatalistic view on your own existence Nicholas.

            Singapore Airlines and Emirates are ranked at the top of the airline industry. You not being impressed is irrelevant. Their reputation and safety records speak for themselves. Singapore Airline is one of the safest in the world…SilkAir…the airline subsidiary has had most of the incidents such as the SilkAir 737 crash, 744 crash in TPE, 744 tail strike in AKL, and 772 runway incursion in BKK.

            I find it amazing that you overlook what Boeing has done with the 737NG.

            The fact that you would rather fly a structurally unsafe aircraft seriously places a big question mark on your level of judgement…I frankly find it absolutely absurd.

          6. We’ll have to agree to disagree.

            Although the odds of dying from Russian Roulette are at best 1 in 6. The odds of dying in an airplane crash are 1 in 9 million. I’ll take my odds at flying, thank you very much.

          7. You can disagree all you want…but the fact remains that Boeing is involved in a coverup and flying in an aircraft that has structural problems reduces your great odds enormously.

            Making silly comments about the odds of dying playing RR may be funny to you but ignorance is bliss and you never think it’ll happen to you.

            Happy flying in those substandard 737’s!

  9. No you’ll just have to worry about unrecoverable rudder deflections, fuselages ripping open, and constant over-running of runways….and all this in production aircraft with people like you on board!

    And you really don’t understand the difference between a software glitch in pre-production aircraft and a KNOWN and purposefully covered up structural flaw in a production aircraft do you. As they say once more…ignorance truly is bliss…and we wonder why corporations get away with murder.

    Happy flying!

  10. I’ll remember to tag my sarcasm as such for you in the future. That being said, I still don’t understand your views. But at the moment I don’t care to, as I’ve already expended enough keystrokes on this topic..

    1. I fail to understand your lack of understanding about the seriousness in the matter.

      Any sane person would never have views like yours about blatant safety violations in aviation. I have no idea what angle you have in all this but frankly telling someone you would be OK flying a structurally compromised aircraft whose manufacturing processes have been flawed and illegally covered up is INSANE.

      I agree..I too have wasted too many keystrokes on this…it’s clear it’s simply not getting through to you and either you have a vested interest in the matter somehow or your judgement is extremely poor. But it doesn’t matter which really.

          1. Sure sure…you win.

            Do some research and get back to us…till then…you have no clue…at least about 737 safety.

            Have a great night! Oh and you’re a WINNER….DUH.

  11. I have absolutely no idea why I’m going to insert myself into this back and forth, but, I just thought I would clarify some facts here.

    “There a many FAA/NTSB directives to make changes on aircraft (many of them “voluntary”) of which airlines do not spend the money to do.”

    If it’s a real safety issue, the FAA won’t make it voluntary. (If you disagree, I’d like to see links to the directives you’re referring to that were safety issues but were not complied with.)

    “Use someone else who pays $49 for a ticket as an example…not me who paid premium for a non-stop flight when most would take 1-2 stops to Hawaii.”

    Flying nonstop is one of the few things that people will pay a premium for, so you are not alone in this by any stretch. Many, many people pay extra to fly nonstop and it’s the only reason the legacy airlines can make hubs work.

    “Singapore Airline is one of the safest in the world…SilkAir…the airline subsidiary has had most of the incidents such as the SilkAir 737 crash, 744 crash in TPE, 744 tail strike in AKL, and 772 runway incursion in BKK.”

    The 737 crash in 1997 was the only SilkAir accident. That airline only operates short haul airplanes, so the 747 in Taipei, the 747 in Auckland, and anything else involving a widebody is from Singapore Airlines directly.

    “No you’ll just have to worry about unrecoverable rudder deflections, fuselages ripping open, and constant over-running of runways”

    The rudder deflections and fuselage issues have not occurred on the 737NG but rather on Classic airplanes. The rudder issues have been fixed and I don’t recall hearing about an issue with that in ages. The fuselage issues are quite concerning but have nothing to do with the 737NG chord issue. As for runway overruns, that is a not an aircraft issue. Which specific runway overruns do you think are due to the 737 itself?

    “737NGs have been flying for quite some time, they haven’t crashed. . . . They’ve never crashed??? LOL…ok….you win. Now I know you really have no clue.”

    They have crashed but there hasn’t been a single accident related to the chord manufacturing issue above. In fact, any accident related to a structural issue is rare. I believe the China Airlines 737 in Taipei was related to a structural issue, but nobody was hurt on that and an emergency directive was issued to fix the problem.

    1. They have crashed but there hasn’t been a single accident related to the chord manufacturing issue above. In fact, any accident related to a structural issue is rare. I believe the China Airlines 737 in Taipei was related to a structural issue, but nobody was hurt on that and an emergency directive was issued to fix the problem.,/i>

      Rubbish….3 aircraft have broken up in the same exact locations where the chords and straps were located….identical failures. It was and still is a cover up.

      It took 2 fatal accidents (perhaps even more) as far as rudder deflection goes before anything was really looked into. There were also hundreds of pilot testimonies of uncontrolled rudder deflections that were thankfully recoverable but almost. Much these reports went unheeded by airlines and Boeing a like….with the FAA sitting with its hands crossed deciding on how not to damage Boeing’s business.

      You miss the point entirely…which is that the problems are ignored until it’s too late. The break up of fuselages should not have happened….that’s the point.

      The FAA has a completely piss-poor record of acting and has been in bed with big airlines and manufacturers for a very very long time.

      Southwest’s problems with it’s aircraft and lack of safety checks has been on-going (on the books) for at least 3 years….no one knows actually how long they’ve been cutting corners…probably for years before.

      As for FAA directives and blatant failures and hiding of problems:

      “U.S. Senator Patty Murray (D-Wash.) scolded the FAA at hearing Thursday on airplane inspections and passenger safety, saying “We need an FAA that actually fixes problems as they are found rather than one that rushes into a public relations campaign to assure everyone that there isn’t a problem.”


      You get the picture…ignore…ignore…ignore. Intentionally.

      Now…bring on the excuses….I agree with you though..I have no idea why you are inserting yourself in this argument about SAFETY versus blatant lying and cozying up of the FAA/Boeing.

      I’m not sure what you’re even arguing about…it’s truly pointless. But continue your ambulance chasing I suppose. Excuses to the rescue!

      1. There’s no reason to be an ass, though clearly you’re very good at it. Comments are automatically moderated when multiple links are included because that’s usually spam. Believe me, I have no interest in wasting my time specifically moderating you.

        No accident has occurred because of chord failure. That’s it. The Southwest incidents have pointed to problems with lap joints and stringers. Does this point to potential concerns about Southwest? Absolutely. And there’s no question that this needs a deeper look. And does it point to concerns about Boeing? Sure. I never argued against that. The FAA? You know it. The agency is generally in a more reactive mode. But I’m not talking about any of that here.

        My only point was to clarify some of the points which were incorrectly presented as facts. I have no interest in arguing with you but just making sure that others who read this aren’t misled by incorrect information. Stick to the facts and I won’t bother responding again.

  12. The only asses here are you and Nicholas….you’re talking about peoples’ safety as if it’s no big deal. Disgusting viewpoint.

    Stick to the facts?? You’ve completely ignored what’s going…who the hell do you work for???? The FAA??? Boeing???

    Give me a break…what YOU are completely overlooking is the FACT that the FAA has for decades been in bed with the manufacturers and you’re too busy looking at the microscopic issues and not looking at the bigger picture.

    It’s flown right over your head….pun intended.

    Please..YOU get your facts straight and realize how large this issue is…don’t be a strawman like the other guy.

    I’m done here…it’s quite obvious your view is one of “whatever.” Appalling when it comes to air safety. No wonder the FAA is in such a corrupt state.

    1. I’ve sat on responding to this comment for several hours. So I’m going to respond to one and only one specific statement “you’re talking about peoples’ safety as if it’s no big deal.” I take great offense that you would even insinuate this, let alone state it outright. Human life is important. It is one of the reasons why I have spent my own time and money (while unemployed even.) to ensure that I am certified in First Aid and CPR. I want to be prepared to do my best to deliver this emergency care if I need to.

      My final thought on this. There is a great book by Mark Eberhart, “Why Things Break: Understanding the World By the Way It Comes Apart”, where he documents a shift over the past thirty years of viewpoint that failure is inevitable and should understood, and prevented as much as possible, with the understanding that is is inevitable, to the viewpoint that failure should never happen, and any failure is unacceptable. I believe that Boeing, Airbus, other airliner manufacturers, the FAA, the JAA, and other air travel regulators, have accessed the risks of flying and minimized them to the benefit of all air travelers. I am willing to put my faith in them. It is not blind faith, I recognize that they are not perfect, and that they will fail, but I firmly believe it is not misplaced faith.

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