11 ms·

Unexpected cracking found on critical Boeing 737 Next Generation part

221 points by erentz 7y ago

alan5 7y ago
> Engineers design pickle forks to last the lifetime of the plane, more than 90,000 landings and takeoffs, a term known as "flight cycles" in the aviation industry, without developing cracks. That number made me do a double take. Seems planes never stay on the ground for very long.
- godzillabrennus 7y ago
  Time is money. Hopefully autonomous vehicles used on demand see many more hours on the road than our personal vehicles.
- ReptileMan 7y ago
  They literally stay only the turn around time in commercial aviation in busy operations. At least that is the goal. And of course maintenence and repair. And an airframe is used over decades. Add some serious safety factor and you are up there at 90000. But since the 737 max grounding, NGs have seen more usage. So bad news for Boeing. And heaven forbid another grounding - there will literally be not enough physical planes to fly in the skies.
  - quickthrower2 7y ago
    > there will literally be not enough physical planes to fly in the skies. It'd be interesting - flight prices go up and people realise they didn't need to fly as much as they thought they did?
    - ReptileMan 7y ago
      This is one of the questions I want to see answered in stimulation not in real life. There is a lot of discretionary flying, but there are place whose connection to the world is plane. You will also have route cancelations. And there will be social costs along the economical as well. All in all unpleasant situation. It will be good to have someone that understands airplanes to comment on how severe the issue is and possible remedies. The media have incentive to drum up the issues with boeing and be a tad sensationalist. From what I understood it will require disassembly of quite a big chunk of the airplane. So it will be expensive and worse slow.
      - sverhagen 7y ago
        >There is a lot of discretionary flying, but there are place whose connection to the world is plane. Are you talking about far away towns in, say, Alaska? Those may not be the kind of planes for which we're discussion scarcity, but alas. Me and my colleagues were flown for training from Oregon to one of our offices in California, this week. So was the trainer. There's still a lot of room to optimize the need for air travel.
        elif 7y ago
        The Galapagos comes to mind. The entire economy is premised upon commercial jets landing there hourly. Puerto Rico, Bahamas, etc. Even Continental but remote tourism-driven places like Costa Rica. I think the price response to a shortage of planes would be super-linear, given that those who fly regularly are not representative of the average economic means. Prices would more than double.
        lutorm 7y ago
        Hawaii...
        elif 7y ago
        To a degree but Hawaii has shipping ports and a more diverse economy.
- tus88 7y ago
  One flight a day for 90,000 flights is 246 years. You are right.
  - phire 7y ago
    Sometimes they fly routes that are only 30min long. With a 30min turnaround, that could mean a flight every hour. If they kept one plane flying round trips all day, they might fit 16 flights into a day and theoretically burn through the 90,000 cycles in under 16 years.
    - acjohnson55 7y ago
      Are there examples of routes like this you know of where a 737 is used?
      - markdown 7y ago
        There are routes like this, but none with anywhere near the ridiculous schedules (16 flights per day) suggested.
        JorgeGT 7y ago
        The Madrid-Barcelona "air shuttle" by Iberia has up to 26 flights a day in each direction https://www.iberia.com/es/news-updates/relaunched-the-air-shuttle/ https://www.iberia.com/es/news-updates/relaunched-the-air-sh... but they use more than one plane. Still, a lot of cycles! In the peak hours there can be a plane leaving each 15 min. You don't need to book a specific one, just a ticket for the shuttle service and then you just turn up at any time.
      - moandcompany 7y ago
        LAX-LAS, LAX-SJC, LAX-OAK for example. Not quite 30minute flights but approaching there at ~40min and ~50min. Southwest airlines for example exclusively flies a fleet of 737-type variants. Cadence for some of these flights can be over 10x daily, in each direction. The total fleet can see 4k+ flights per day.
- axaxs 7y ago
  Not an aerospace engineer, but this seems like a weird way to measure airplane life. A transpacific plane could have 1/10 the cycles but equal airtime, and one would think that the stresses of flight are worth considering. Wonder why it's not measured in hours, like say, tractors, or miles flown. Do we measure any other engined vehicle this way?
  - Obi_Juan_Kenobi 7y ago
    A cycle involves pressurizing the cabin relative to the atmosphere approaching flight altitude, and then depressurizing during the descent. The pressure differential may not seem like much, 6-10 psi in most cases, but the cabins are quite large, so these forces become substantial. Advanced airframes like the composite 787 use that extra strength, in large part, to lower cabin altitude (i.e. keep higher pressure) because it has such a substantial effect on passenger comfort. Cycles is absolutely the best way to consider airliner lifespan because that is the most significant stress on the airframe.
    - axaxs 7y ago
      Thank you!
  - agurk 7y ago
    There are a variety of ways that age of something can be measured with two common examples in everyday life being people and cars commonly measured in years and kms/miles respectively. The metric chosen is one that adds value for understanding the impact. Aeroplanes and their components do have a lot of different ways of having their ages measured, depending upon what one cares about. Engines are a good example of something where the hours spent running is usually the most salient. For fusalages, as we're talking about here, pressurisation cycles is actually very important in pressurised airframes. This is because it is the main source of material fatigue which is a major cause of issues - usually in the form of cracks. This was discovered the hard way with the de Havilland Comet[0]. Smaller non-pressurised planes are normally measured in total flight hours, but the effect of repeatedly pressuring and depressuring is so great that it's the biggest factor that will affect the life of the bigger airframes. [0] https://en.wikipedia.org/wiki/De_Havilland_Comet#Accidents_and_incidents https://en.wikipedia.org/wiki/De_Havilland_Comet#Accidents_a...
- flexer2 7y ago
  Planes are extremely expensive pieces of machinery and you don't make money if you're not flying passengers with them. I'd be more surprised if they weren't in the air as many hours as possible.
9nGQluzmnq3M 7y ago
For context, the 737 NG is previous iteration of the 737 (before the MAX) and among the most popular aircraft ever built, with over 7000 in service. Grounding this would absolutely cripple the airline industry. However, the NG also has an excellent safety record, and 35000 cycles is equivalent to 5 flights (takeoff & landing) every day for 10 years. So while this may lead to extra checks on older aircraft, it's highly unlikely to cause a MAX-style global grounding.
- samstave 7y ago
  What is the actual safety record of the B-52, which i subjectively consider to be the safest machine in history. How would the B-52 match up against modern commercial airliners? (Does anyone, other than boeing, even track this stat?) The calc would be something along the lines of; Date-of-design -> completion, testing, commissioning, hours in flight - accidents, crashes,pilot error, time in service, fuselage age, etc... I am subjectively of the opinion that the B-52 is the greatest aircraft ever made.
  - ethagknight 7y ago
    Tell me more of this b-53 safety record
  - ceejayoz 7y ago
    http://www.airsafe.com/events/models/rate_mod.htm http://www.airsafe.com/events/models/rate_mod.htm indicates 79 fatal 737 incidents with about a quarter billion flights under their belt. https://www.globalsecurity.org/wmd/systems/b-52-safety.htm https://www.globalsecurity.org/wmd/systems/b-52-safety.htm indicates 76 B-52s destroyed in accidents across 7.5 million flight hours. They're not perfectly comparable sets of numbers, but the B-52s look substantially riskier on a per-hour basis.
    - samstave 7y ago
      Thank you for this! 76 machines destroyed, carrying (obstensibly) nukes.. from 7.5mm flight miles == .00001% risk of failure. Did I do the math correctly? With ZERO nuke detonations... And a flight carcass of nearly 70 years old now???
tobib 7y ago
A lot of text providing very little information.
kjar 7y ago
I’m not flying anymore. Between the GHG annual personal emissions and the stunning staggering massively deadly failures of rushed Boeing product launches. Finally I will note the whole damn process is dehumanizing and terrible.
- heavyset_go 7y ago
  The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety. If Boeing can't escape the perverse incentives that tempt every company, then what company can and why are we relying on this economic model to drive such a high stakes industry?
  - SomeOldThrow 7y ago
    Relying on profit-motivated companies to consistently provide value at safety critical levels seems short sighted.
    - inimino 7y ago
      That's why we rely on regulation and oversight for safety, and profit motive and competition to provide value.
      - SomeOldThrow 7y ago
        Sure, it definitely works great.
  - txcwpalpha 7y ago
    >The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety. I don't see why that's "the worst part". Flying is the safest mode of travel, and among airliners the 737NG is one of the safest planes in aviation history. The fact that cracks have been discovered doesn't change that, and the routine inspections which have discovered these cracks and will lead to them being fixed is precisely the reason why these aircraft, and the aviation industry as a whole, are so incredibly safe.
hansthehorse 7y ago
There is a 9 year old documentary on two Boing whistleblowers describing cracking probability on the 737ng. It's an hour long: https://www.youtube.com/watch?v=IaWdEtANi-0 https://www.youtube.com/watch?v=IaWdEtANi-0
- alexis_fr 7y ago
  Extremely interesting. Especially, around 19-21 minutes, we find the same problem as on 737 Max: Boeing has the delegated authority from the FAA to certify their own processes and parts. I’m never flying Boeing again. They were hammering crucial parts to fit, provoking crackling; redrilling holes when the hole was 3 inches apart, endangering the whole structural integrity; painting it all green and sending that to production. The documentary is about the circles of the airframe structure, not about the wing forks of today’s article, so that makes one new type of botched work from Boeing.
  - peteretep 7y ago
    > I’m never flying Boeing again I suspect you were intending this to be obvious hyperbole, but also this will be very difficult if you’re flying at all regularly. While you can have a look at the equipment the airline thinks it’ll be flying at booking time, there’s no guarantees about which plane will actually show up, and the airline isn’t going to refund your ticket because they decided to swap out their A350 for their 787 for operational reasons.
    - kzrdude 7y ago
      All this plane talk makes me curious, if there are any airlines that tell you ahead of time what planes they are using for a route? I guess they'd now be even less inclined to tell.
      - cloudwalking 7y ago
        I'm usually flying Alaska or United or Southwest, but yes, they do tell you which plane.
deleted 7y ago
[deleted]
newnewpdro 7y ago
If a part's made of aluminum and undergoes cyclic stress, even staying within its instantaneous modulus of elasticity, it will eventually crack. Note the aluminum curve in the graph here [0], it never levels off horizontally. My understanding is this effectively means the modulus of elasticity for aluminum parts is forever diminishing. Aluminum is a metal that's "work hardened", it's basically becoming increasingly brittle the more cyclic stress it experiences. I'd been told in the past that commercial planes are regularly X-rayed for cracks as part of their maintenance, because of their extensive use of aluminum. None of this should be a surprise except that it's supposedly "unexpected" in the pickle fork. These vehicles have always been high maintenance machines, in order for them to be safe all the structural aluminum must be regularly inspected for cracks, the cracks should be expected and parts replaced as needed. [0] https://en.wikipedia.org/wiki/Fatigue_limit https://en.wikipedia.org/wiki/Fatigue_limit Edit: Out of curiosity I did some digging for photos of this part and more information, this thread delivers some insightful links and citations: https://www.pprune.org/rumours-news/625886-737ngs-have-cracked-pickle-forks-after-finding-several-jets.html https://www.pprune.org/rumours-news/625886-737ngs-have-crack...
- dredmorbius 7y ago
  AFAIU, ultrasound is far more typically used than x-rays, as the acoustic properties of fractured castings are more distinctive than their xradiographs. Apparently induction testing is also used (likely on a similar basis to ultrasound: properties deviate sharply from norm/spec).
- corbani 7y ago
  The modulus of elasticity of aluminum does not change with cycling (or basically with anything else but big temperature differences). Fatigue is a damage accumulation process, that does not show in the most obvious properties, like modulus or strength. The aviation regulations changed a long time ago from requiring to avoid cracks to requiring to have structures that can operate with cracks long enough to for them to be detected, as is exactly the case here. Of course nobody design planes to crack, but the regulations reflect the realization that completely avoiding cracks is impossible ...
m0zg 7y ago
>> We're told this is very much an ongoing investigation, and that it's unclear whether or not this is a widespread issue. TL;DR: a crack in a critical part was found in one plane during a routine inspection. But you wouldn't know that unless you read all the way to the middle of the article. This is a non-story engineered to create outrage and clicks.
- kube-system 7y ago
  > Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found.
  - m0zg 7y ago
    How many? Could be as few as 2. Out of thousands.
    - kube-system 7y ago
      Really, the only thing we know is that it's not a single plane.... which is the cause for concern. 2/7000 is not a very low incidence rate as far as safety concerns go. Many cars are recalled for far less severe issues with orders of magnitude lower incidence rates.
    - simion314 7y ago
      It is clearly not all planes were disassembled and checked, from what I read it is not a routine check so it will take a while until all planes are checked. So yeah they may have found only 2 more planes with cracks because they only checked 2 more planes that were already disassembled.
- oplav 7y ago
  >> Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found. Looks to be more than just one plane.
nutcracker46 7y ago
Stick a pickle fork in Boeing; it is cooked.
anon91831837 7y ago
Unsurprising given the 2010 Al Jazeera revelations of the Boeing-Ducommun conspiracy and cover-up: critical structural elements that were supposed to be CNC machined by Ducommun were crudely made by hand and Boeing managers ordered them installed into 737 NG (-600, -700, -800, -900) anyhow. And then when a blue-ribbon panel of Boeing employees went to find out what happened, their findings were buried and no corrective action was taken. 737 NG's are flying around with substandard critical structural components like spars and the areas around doors, leading to several fuselage breakups on hard landings and runway overruns, which has killed at least several passengers to date. In past similar incidents, aircraft fuselages survived intact. There's a very real possibility that one or more 737 NG's may breakup in heavy turbulence, hard landings and runway overruns at any time, and Boeing knows about it, but has done nothing to remedy it. https://youtu.be/IaWdEtANi-0 https://youtu.be/IaWdEtANi-0
- dehrmann 7y ago
  > leading to several fuselage breakups [citation needed]. It's what AJ is positing, but it's presented like a correlation, I don't think investigators called that out an a cause of the breakups, and it's been 10 years since that was made and this doesn't seem to be a major problem. One thing I read suggested that the fuselage is strongest at the wing, so the break happens away from that section. That, and hard landing is an understatement; One landed short of the runway, another overshot it, and one dropped onto it. https://commons.wikimedia.org/w/index.php?title=File%3AAnimation_-_Turkish_Airlines_crashed_during_approach%2C_Boeing_737-800_-_Dutch_Safety_Board.webm https://commons.wikimedia.org/w/index.php?title=File%3AAnima... (4:55)
v8engine 7y ago
For those curious about how this part looks, Boeing Pickle Fork graphic illustration: https://www.pprune.org/rumours-news/625886-737ngs-have-cracked-pickle-forks-after-finding-several-jets.html#post10581606 https://www.pprune.org/rumours-news/625886-737ngs-have-crack...
basicplus2 7y ago
<A ‘pickle fork’ is the part that connects the fuselage with wings to manage stress and torque loading on the structure> See link for pictures of design http://newsinflight.com/2019/09/28/boeing-workers-found-new-cracks-on-boeing-737ng-not-max/ http://newsinflight.com/2019/09/28/boeing-workers-found-new-...
TestPilot 7y ago
Zero mention as to where the part was manufactured... I was surprised to find that a lot of information is found online. However, there's no specific mention of "pickle fork" here: http://www.airframer.com/aircraft_detail.html?model=B737#Airframe%20Assemblies http://www.airframer.com/aircraft_detail.html?model=B737#Air... I'm not an engineer, but it looks like Magellan Aerospace Kitchener (ON, Canada) built Wing Components and Spirit Aerosystems (Wichita, Kansas, USA) built Wing Spars and the Front Fuselage. Could have been either one of those. My guess is it's Spirit as it's mentioned in the notes they build 75% of the airframe in total.

221 points by erentz 7y ago

> Engineers design pickle forks to last the lifetime of the plane, more than 90,000 landings and takeoffs, a term known as "flight cycles" in the aviation industry, without developing cracks. That number made me do a double take. Seems planes never stay on the ground for very long.

godzillabrennus 7y ago
Time is money. Hopefully autonomous vehicles used on demand see many more hours on the road than our personal vehicles.
ReptileMan 7y ago
They literally stay only the turn around time in commercial aviation in busy operations. At least that is the goal. And of course maintenence and repair. And an airframe is used over decades. Add some serious safety factor and you are up there at 90000. But since the 737 max grounding, NGs have seen more usage. So bad news for Boeing. And heaven forbid another grounding - there will literally be not enough physical planes to fly in the skies.
- quickthrower2 7y ago
  > there will literally be not enough physical planes to fly in the skies. It'd be interesting - flight prices go up and people realise they didn't need to fly as much as they thought they did?
  - ReptileMan 7y ago
    This is one of the questions I want to see answered in stimulation not in real life. There is a lot of discretionary flying, but there are place whose connection to the world is plane. You will also have route cancelations. And there will be social costs along the economical as well. All in all unpleasant situation. It will be good to have someone that understands airplanes to comment on how severe the issue is and possible remedies. The media have incentive to drum up the issues with boeing and be a tad sensationalist. From what I understood it will require disassembly of quite a big chunk of the airplane. So it will be expensive and worse slow.
    - sverhagen 7y ago
      >There is a lot of discretionary flying, but there are place whose connection to the world is plane. Are you talking about far away towns in, say, Alaska? Those may not be the kind of planes for which we're discussion scarcity, but alas. Me and my colleagues were flown for training from Oregon to one of our offices in California, this week. So was the trainer. There's still a lot of room to optimize the need for air travel.
      - elif 7y ago
        The Galapagos comes to mind. The entire economy is premised upon commercial jets landing there hourly. Puerto Rico, Bahamas, etc. Even Continental but remote tourism-driven places like Costa Rica. I think the price response to a shortage of planes would be super-linear, given that those who fly regularly are not representative of the average economic means. Prices would more than double.
        lutorm 7y ago
        Hawaii...
        elif 7y ago
        To a degree but Hawaii has shipping ports and a more diverse economy.
tus88 7y ago
One flight a day for 90,000 flights is 246 years. You are right.
- phire 7y ago
  Sometimes they fly routes that are only 30min long. With a 30min turnaround, that could mean a flight every hour. If they kept one plane flying round trips all day, they might fit 16 flights into a day and theoretically burn through the 90,000 cycles in under 16 years.
  - acjohnson55 7y ago
    Are there examples of routes like this you know of where a 737 is used?
    - markdown 7y ago
      There are routes like this, but none with anywhere near the ridiculous schedules (16 flights per day) suggested.
      - JorgeGT 7y ago
        The Madrid-Barcelona "air shuttle" by Iberia has up to 26 flights a day in each direction https://www.iberia.com/es/news-updates/relaunched-the-air-shuttle/ https://www.iberia.com/es/news-updates/relaunched-the-air-sh... but they use more than one plane. Still, a lot of cycles! In the peak hours there can be a plane leaving each 15 min. You don't need to book a specific one, just a ticket for the shuttle service and then you just turn up at any time.
    - moandcompany 7y ago
      LAX-LAS, LAX-SJC, LAX-OAK for example. Not quite 30minute flights but approaching there at ~40min and ~50min. Southwest airlines for example exclusively flies a fleet of 737-type variants. Cadence for some of these flights can be over 10x daily, in each direction. The total fleet can see 4k+ flights per day.
axaxs 7y ago
Not an aerospace engineer, but this seems like a weird way to measure airplane life. A transpacific plane could have 1/10 the cycles but equal airtime, and one would think that the stresses of flight are worth considering. Wonder why it's not measured in hours, like say, tractors, or miles flown. Do we measure any other engined vehicle this way?
- Obi_Juan_Kenobi 7y ago
  A cycle involves pressurizing the cabin relative to the atmosphere approaching flight altitude, and then depressurizing during the descent. The pressure differential may not seem like much, 6-10 psi in most cases, but the cabins are quite large, so these forces become substantial. Advanced airframes like the composite 787 use that extra strength, in large part, to lower cabin altitude (i.e. keep higher pressure) because it has such a substantial effect on passenger comfort. Cycles is absolutely the best way to consider airliner lifespan because that is the most significant stress on the airframe.
  - axaxs 7y ago
    Thank you!
- agurk 7y ago
  There are a variety of ways that age of something can be measured with two common examples in everyday life being people and cars commonly measured in years and kms/miles respectively. The metric chosen is one that adds value for understanding the impact. Aeroplanes and their components do have a lot of different ways of having their ages measured, depending upon what one cares about. Engines are a good example of something where the hours spent running is usually the most salient. For fusalages, as we're talking about here, pressurisation cycles is actually very important in pressurised airframes. This is because it is the main source of material fatigue which is a major cause of issues - usually in the form of cracks. This was discovered the hard way with the de Havilland Comet[0]. Smaller non-pressurised planes are normally measured in total flight hours, but the effect of repeatedly pressuring and depressuring is so great that it's the biggest factor that will affect the life of the bigger airframes. [0] https://en.wikipedia.org/wiki/De_Havilland_Comet#Accidents_and_incidents https://en.wikipedia.org/wiki/De_Havilland_Comet#Accidents_a...
flexer2 7y ago
Planes are extremely expensive pieces of machinery and you don't make money if you're not flying passengers with them. I'd be more surprised if they weren't in the air as many hours as possible.

9nGQluzmnq3M 7y ago

For context, the 737 NG is previous iteration of the 737 (before the MAX) and among the most popular aircraft ever built, with over 7000 in service. Grounding this would absolutely cripple the airline industry. However, the NG also has an excellent safety record, and 35000 cycles is equivalent to 5 flights (takeoff & landing) every day for 10 years. So while this may lead to extra checks on older aircraft, it's highly unlikely to cause a MAX-style global grounding.

samstave 7y ago
What is the actual safety record of the B-52, which i subjectively consider to be the safest machine in history. How would the B-52 match up against modern commercial airliners? (Does anyone, other than boeing, even track this stat?) The calc would be something along the lines of; Date-of-design -> completion, testing, commissioning, hours in flight - accidents, crashes,pilot error, time in service, fuselage age, etc... I am subjectively of the opinion that the B-52 is the greatest aircraft ever made.
- ethagknight 7y ago
  Tell me more of this b-53 safety record
- ceejayoz 7y ago
  http://www.airsafe.com/events/models/rate_mod.htm http://www.airsafe.com/events/models/rate_mod.htm indicates 79 fatal 737 incidents with about a quarter billion flights under their belt. https://www.globalsecurity.org/wmd/systems/b-52-safety.htm https://www.globalsecurity.org/wmd/systems/b-52-safety.htm indicates 76 B-52s destroyed in accidents across 7.5 million flight hours. They're not perfectly comparable sets of numbers, but the B-52s look substantially riskier on a per-hour basis.
  - samstave 7y ago
    Thank you for this! 76 machines destroyed, carrying (obstensibly) nukes.. from 7.5mm flight miles == .00001% risk of failure. Did I do the math correctly? With ZERO nuke detonations... And a flight carcass of nearly 70 years old now???

tobib 7y ago

A lot of text providing very little information.

kjar 7y ago

I’m not flying anymore. Between the GHG annual personal emissions and the stunning staggering massively deadly failures of rushed Boeing product launches. Finally I will note the whole damn process is dehumanizing and terrible.

heavyset_go 7y ago
The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety. If Boeing can't escape the perverse incentives that tempt every company, then what company can and why are we relying on this economic model to drive such a high stakes industry?
- SomeOldThrow 7y ago
  Relying on profit-motivated companies to consistently provide value at safety critical levels seems short sighted.
  - inimino 7y ago
    That's why we rely on regulation and oversight for safety, and profit motive and competition to provide value.
    - SomeOldThrow 7y ago
      Sure, it definitely works great.
- txcwpalpha 7y ago
  >The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety. I don't see why that's "the worst part". Flying is the safest mode of travel, and among airliners the 737NG is one of the safest planes in aviation history. The fact that cracks have been discovered doesn't change that, and the routine inspections which have discovered these cracks and will lead to them being fixed is precisely the reason why these aircraft, and the aviation industry as a whole, are so incredibly safe.

hansthehorse 7y ago

There is a 9 year old documentary on two Boing whistleblowers describing cracking probability on the 737ng. It's an hour long: https://www.youtube.com/watch?v=IaWdEtANi-0 https://www.youtube.com/watch?v=IaWdEtANi-0

alexis_fr 7y ago
Extremely interesting. Especially, around 19-21 minutes, we find the same problem as on 737 Max: Boeing has the delegated authority from the FAA to certify their own processes and parts. I’m never flying Boeing again. They were hammering crucial parts to fit, provoking crackling; redrilling holes when the hole was 3 inches apart, endangering the whole structural integrity; painting it all green and sending that to production. The documentary is about the circles of the airframe structure, not about the wing forks of today’s article, so that makes one new type of botched work from Boeing.
- peteretep 7y ago
  > I’m never flying Boeing again I suspect you were intending this to be obvious hyperbole, but also this will be very difficult if you’re flying at all regularly. While you can have a look at the equipment the airline thinks it’ll be flying at booking time, there’s no guarantees about which plane will actually show up, and the airline isn’t going to refund your ticket because they decided to swap out their A350 for their 787 for operational reasons.
  - kzrdude 7y ago
    All this plane talk makes me curious, if there are any airlines that tell you ahead of time what planes they are using for a route? I guess they'd now be even less inclined to tell.
    - cloudwalking 7y ago
      I'm usually flying Alaska or United or Southwest, but yes, they do tell you which plane.

deleted 7y ago

[deleted]

newnewpdro 7y ago

If a part's made of aluminum and undergoes cyclic stress, even staying within its instantaneous modulus of elasticity, it will eventually crack. Note the aluminum curve in the graph here [0], it never levels off horizontally. My understanding is this effectively means the modulus of elasticity for aluminum parts is forever diminishing. Aluminum is a metal that's "work hardened", it's basically becoming increasingly brittle the more cyclic stress it experiences. I'd been told in the past that commercial planes are regularly X-rayed for cracks as part of their maintenance, because of their extensive use of aluminum. None of this should be a surprise except that it's supposedly "unexpected" in the pickle fork. These vehicles have always been high maintenance machines, in order for them to be safe all the structural aluminum must be regularly inspected for cracks, the cracks should be expected and parts replaced as needed. [0] https://en.wikipedia.org/wiki/Fatigue_limit https://en.wikipedia.org/wiki/Fatigue_limit Edit: Out of curiosity I did some digging for photos of this part and more information, this thread delivers some insightful links and citations: https://www.pprune.org/rumours-news/625886-737ngs-have-cracked-pickle-forks-after-finding-several-jets.html https://www.pprune.org/rumours-news/625886-737ngs-have-crack...

dredmorbius 7y ago
AFAIU, ultrasound is far more typically used than x-rays, as the acoustic properties of fractured castings are more distinctive than their xradiographs. Apparently induction testing is also used (likely on a similar basis to ultrasound: properties deviate sharply from norm/spec).
corbani 7y ago
The modulus of elasticity of aluminum does not change with cycling (or basically with anything else but big temperature differences). Fatigue is a damage accumulation process, that does not show in the most obvious properties, like modulus or strength. The aviation regulations changed a long time ago from requiring to avoid cracks to requiring to have structures that can operate with cracks long enough to for them to be detected, as is exactly the case here. Of course nobody design planes to crack, but the regulations reflect the realization that completely avoiding cracks is impossible ...

m0zg 7y ago

>> We're told this is very much an ongoing investigation, and that it's unclear whether or not this is a widespread issue. TL;DR: a crack in a critical part was found in one plane during a routine inspection. But you wouldn't know that unless you read all the way to the middle of the article. This is a non-story engineered to create outrage and clicks.

kube-system 7y ago
> Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found.
- m0zg 7y ago
  How many? Could be as few as 2. Out of thousands.
  - kube-system 7y ago
    Really, the only thing we know is that it's not a single plane.... which is the cause for concern. 2/7000 is not a very low incidence rate as far as safety concerns go. Many cars are recalled for far less severe issues with orders of magnitude lower incidence rates.
  - simion314 7y ago
    It is clearly not all planes were disassembled and checked, from what I read it is not a routine check so it will take a while until all planes are checked. So yeah they may have found only 2 more planes with cracks because they only checked 2 more planes that were already disassembled.
oplav 7y ago
>> Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found. Looks to be more than just one plane.

nutcracker46 7y ago

Stick a pickle fork in Boeing; it is cooked.

anon91831837 7y ago

Unsurprising given the 2010 Al Jazeera revelations of the Boeing-Ducommun conspiracy and cover-up: critical structural elements that were supposed to be CNC machined by Ducommun were crudely made by hand and Boeing managers ordered them installed into 737 NG (-600, -700, -800, -900) anyhow. And then when a blue-ribbon panel of Boeing employees went to find out what happened, their findings were buried and no corrective action was taken. 737 NG's are flying around with substandard critical structural components like spars and the areas around doors, leading to several fuselage breakups on hard landings and runway overruns, which has killed at least several passengers to date. In past similar incidents, aircraft fuselages survived intact. There's a very real possibility that one or more 737 NG's may breakup in heavy turbulence, hard landings and runway overruns at any time, and Boeing knows about it, but has done nothing to remedy it. https://youtu.be/IaWdEtANi-0 https://youtu.be/IaWdEtANi-0

dehrmann 7y ago
> leading to several fuselage breakups [citation needed]. It's what AJ is positing, but it's presented like a correlation, I don't think investigators called that out an a cause of the breakups, and it's been 10 years since that was made and this doesn't seem to be a major problem. One thing I read suggested that the fuselage is strongest at the wing, so the break happens away from that section. That, and hard landing is an understatement; One landed short of the runway, another overshot it, and one dropped onto it. https://commons.wikimedia.org/w/index.php?title=File%3AAnimation_-_Turkish_Airlines_crashed_during_approach%2C_Boeing_737-800_-_Dutch_Safety_Board.webm https://commons.wikimedia.org/w/index.php?title=File%3AAnima... (4:55)

v8engine 7y ago

For those curious about how this part looks, Boeing Pickle Fork graphic illustration: https://www.pprune.org/rumours-news/625886-737ngs-have-cracked-pickle-forks-after-finding-several-jets.html#post10581606 https://www.pprune.org/rumours-news/625886-737ngs-have-crack...

basicplus2 7y ago

<A ‘pickle fork’ is the part that connects the fuselage with wings to manage stress and torque loading on the structure> See link for pictures of design http://newsinflight.com/2019/09/28/boeing-workers-found-new-cracks-on-boeing-737ng-not-max/ http://newsinflight.com/2019/09/28/boeing-workers-found-new-...

TestPilot 7y ago

Zero mention as to where the part was manufactured... I was surprised to find that a lot of information is found online. However, there's no specific mention of "pickle fork" here: http://www.airframer.com/aircraft_detail.html?model=B737#Airframe%20Assemblies http://www.airframer.com/aircraft_detail.html?model=B737#Air... I'm not an engineer, but it looks like Magellan Aerospace Kitchener (ON, Canada) built Wing Components and Spirit Aerosystems (Wichita, Kansas, USA) built Wing Spars and the Front Fuselage. Could have been either one of those. My guess is it's Spirit as it's mentioned in the notes they build 75% of the airframe in total.