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> They are complex machines, but they typically have so many redundancies But Boeing reduced redundancies, presumably to cut costs. The 737 MAX planes that cra

> They are complex machines, but they typically have so many redundancies But Boeing reduced redundancies, presumably to cut costs. The 737 MAX planes that crashed only had one AoA sensor. Where else did they cut costs? Where else did they reduce redundancies? The public trust has been lost. Boeing needs to design a new plane from scratch, this time let engineers design the plane without interference from accountants.

schlauerfox 3y ago
This is VERY bad engineering practice, you throw away knowns for unknowns. A blue sky design isn't a fix. Especially if your corporate culture has the wrong leadership. First year engineers take engineering economics for a reason. Money is always an object.
- breadwinner 3y ago
  Is there never a case where it is cheaper + better to start over? I think sometimes there is. The design of 737 MAX was flawed from the get-go. They made the engines bigger because bigger engines run hotter and burn less fuel. Ordinarily this would require the fuselage to be raised as well, so that the bigger engine can fit under the wing. Instead they changed the position of the engine. Instead of being hung under the wing, as in earlier models, the engines have been moved forward and upward, potentially leading to an aerodynamic stall under certain circumstances. Instead of going back to the drawing board and getting the airframe hardware right, Boeing relied on something called the ‘Maneuvering Characteristics Augmentation System,’ or MCAS. [1] It's just poor design. If software fails, then any plane should be designed to have a neutral center of gravity in order to give the crew the greatest amount of time to recover from the loss. [1] https://spectrum.ieee.org/how-the-boeing-737-max-disaster-looks-to-a-software-developer https://spectrum.ieee.org/how-the-boeing-737-max-disaster-lo...
  - Retric 3y ago
    Never is a loaded word. It’s almost impossible for a completely fresh design to be safer on day one. There’s so many different ways to fuck up many of them are counterintuitive because nobody ever considers if someone could install this backwards until someone does. 20+ years of debugging written with people’s lives tests just about everything in a way engineers never really think about
    - breadwinner 3y ago
      The difference here is that 737 MAX has a flaw (forward positioning of the engine) that cannot be fixed as a "bug".
      - Retric 3y ago
        You can definitely treat it as a design flaw and fix it without impacting most systems. Designers need to make radical changes before cockpit windows would need to be updated. That specific example may not seem like much but there’s a lot of safety critical engineering that goes into such things and yet design flaws where still uncovered.
        breadwinner 3y ago
        Sure you can bring over the "good parts" of the old plane, but if this design flaw is fixed then it is essentially a new plane. They will no longer be able to pretend it is the same as the old 737s (and that's what got them into trouble).
        Retric 3y ago
        When you say “parts” it’s really complex systems. The 737 family of aircraft has gone through many revisions over 50+ years at this point. The original 737-100 was 61,994 lbs empty and the 737-900ER was more than 50% heavier at 98,495 before they started calling them MAX. The 900ER was in many ways a radically different aircraft but got there through a long list of incremental changes leveraging the past. That’s not to say new designs can’t be quite safe. The much newer A320 family are some of the safest aircraft flying with only 38 hull losses and 1505 fatalities, but do not mistake good design for inevitability.
- burnte 3y ago
  Yes. A place design that's 70 years old has had THOUSANDS of bugs fixed. I'd rather fly on a new 737 than an "all new 797 or A390". Side note: I know there isn't a 797 or A390 yet, that was the intent of the statement, a future unknown plane.
  - Reason077 3y ago
    All-new aircraft designs are only certified to fly after many years of rigorous analysis and testing. It was Boeing's desire to avoid the full expensive certification process, by claiming that the MAX was just a minor update to an existing design, which led to two catastrophic crashes in the space of a few months. On the other hand, no 787 or A380 has ever had a crash or incident that resulted in a passenger fatality or hull loss. This LATAM flight is probably the most serious incident that has ever happened on a 787 in almost 10 years of service, with over 1100 aircraft active.
    - stouset 3y ago
      > On the other hand, no 787 or A380 has ever had a crash or incident that resulted in a passenger fatality or hull loss. There have been nearly 10x as many 737s built as 787s and A380s combined. Given the date of first flight (1967 vs. 2009 and 2203, respectively) it is safe to say they have been flown for significantly more than 10x the total flight hours. Probably at least 20x but I’m pulling that number out of thin air. The data is certainly promising but it’s probably a little too soon to be too confident in relative safety comparisons. For one, we don’t have nearly as much data on those newer airframes as they age.
      - rob74 3y ago
        There are two recent accidents that show how much new airplane designs (and better safety measures) have improved survivability of accidents: Emirates Flight 521 (https://en.wikipedia.org/wiki/Emirates_Flight_521 https://en.wikipedia.org/wiki/Emirates_Flight_521), a Boeing 777 that crashed in Dubai in 2016, where all 300 people on board survived (although un unfortunate firefighter lost his life); and the A350 that collided with another airplane while landing at Tokio Haneda airport in January this year - if you look at the burnt out airplane (https://en.wikipedia.org/wiki/2024_Haneda_Airport_runway_collision#/media/File:Japan_Airlines_516_JA13XJ_wreckage.jpg https://en.wikipedia.org/wiki/2024_Haneda_Airport_runway_col...), it's hard to believe that all 379 people on board made it out alive...
cesarb 3y ago
> The 737 MAX planes that crashed only had one AoA sensor. IIRC, it had two, but each of the computers only used the sensor on its side; which was OK for the original (pre-MAX) design because of they way these sensors were originally used by it.
Reason077 3y ago
The 737 MAX, like all 737s, always had two AoA sensors. The problem was that Boeing engineers wrote software for the 737 MAX which could make critical flight control inputs based on the data from one sensor only. And didn't really tell pilots about it. The fix, amongst other mitigations, was to have the MCAS software cross-check inputs from both AoA sensors.
- uuddlrlrbaba 3y ago
  Still, when two sensors disagree how do you determine which sensor is correct? Really 3+ are needed
  - DrFalkyn 3y ago
    Ask the pilot ?
    - shiroiushi 3y ago
      Can't do that: the pilot can't be allowed to control, or even know about MCAS, because that would affect Boeing's ability to claim the plane is "just another" 737 and that the pilots don't need retraining. Giving the pilot the ability to control MCAS means the pilots all need retraining.
      - anticensor 3y ago
        They already received training on MCAS once they got 737 MAXes, albeit a short superficial one (1 hour of lecture&1 hour of simulator training iirc). Hence "cannot be allowed to know" does not apply anymore.
        shiroiushi 3y ago
        Yeah, and that's wrong. It should apply. Pilots should not be allowed to know, because that means this is a different plane than the one they were rated for. And so, since the plane can't be flown safely without proper training, the planes should not get the same type rating as the old 737, and either 1) they should just be demolished, or 2) they should be considered an entirely different plane, with all the training requirements that entails. The regulators completely failed here, and by allowing this are showing they're corrupt.

schlauerfox 3y ago

This is VERY bad engineering practice, you throw away knowns for unknowns. A blue sky design isn't a fix. Especially if your corporate culture has the wrong leadership. First year engineers take engineering economics for a reason. Money is always an object.

breadwinner 3y ago
Is there never a case where it is cheaper + better to start over? I think sometimes there is. The design of 737 MAX was flawed from the get-go. They made the engines bigger because bigger engines run hotter and burn less fuel. Ordinarily this would require the fuselage to be raised as well, so that the bigger engine can fit under the wing. Instead they changed the position of the engine. Instead of being hung under the wing, as in earlier models, the engines have been moved forward and upward, potentially leading to an aerodynamic stall under certain circumstances. Instead of going back to the drawing board and getting the airframe hardware right, Boeing relied on something called the ‘Maneuvering Characteristics Augmentation System,’ or MCAS. [1] It's just poor design. If software fails, then any plane should be designed to have a neutral center of gravity in order to give the crew the greatest amount of time to recover from the loss. [1] https://spectrum.ieee.org/how-the-boeing-737-max-disaster-looks-to-a-software-developer https://spectrum.ieee.org/how-the-boeing-737-max-disaster-lo...
- Retric 3y ago
  Never is a loaded word. It’s almost impossible for a completely fresh design to be safer on day one. There’s so many different ways to fuck up many of them are counterintuitive because nobody ever considers if someone could install this backwards until someone does. 20+ years of debugging written with people’s lives tests just about everything in a way engineers never really think about
  - breadwinner 3y ago
    The difference here is that 737 MAX has a flaw (forward positioning of the engine) that cannot be fixed as a "bug".
    - Retric 3y ago
      You can definitely treat it as a design flaw and fix it without impacting most systems. Designers need to make radical changes before cockpit windows would need to be updated. That specific example may not seem like much but there’s a lot of safety critical engineering that goes into such things and yet design flaws where still uncovered.
      - breadwinner 3y ago
        Sure you can bring over the "good parts" of the old plane, but if this design flaw is fixed then it is essentially a new plane. They will no longer be able to pretend it is the same as the old 737s (and that's what got them into trouble).
        Retric 3y ago
        When you say “parts” it’s really complex systems. The 737 family of aircraft has gone through many revisions over 50+ years at this point. The original 737-100 was 61,994 lbs empty and the 737-900ER was more than 50% heavier at 98,495 before they started calling them MAX. The 900ER was in many ways a radically different aircraft but got there through a long list of incremental changes leveraging the past. That’s not to say new designs can’t be quite safe. The much newer A320 family are some of the safest aircraft flying with only 38 hull losses and 1505 fatalities, but do not mistake good design for inevitability.
burnte 3y ago
Yes. A place design that's 70 years old has had THOUSANDS of bugs fixed. I'd rather fly on a new 737 than an "all new 797 or A390". Side note: I know there isn't a 797 or A390 yet, that was the intent of the statement, a future unknown plane.
- Reason077 3y ago
  All-new aircraft designs are only certified to fly after many years of rigorous analysis and testing. It was Boeing's desire to avoid the full expensive certification process, by claiming that the MAX was just a minor update to an existing design, which led to two catastrophic crashes in the space of a few months. On the other hand, no 787 or A380 has ever had a crash or incident that resulted in a passenger fatality or hull loss. This LATAM flight is probably the most serious incident that has ever happened on a 787 in almost 10 years of service, with over 1100 aircraft active.
  - stouset 3y ago
    > On the other hand, no 787 or A380 has ever had a crash or incident that resulted in a passenger fatality or hull loss. There have been nearly 10x as many 737s built as 787s and A380s combined. Given the date of first flight (1967 vs. 2009 and 2203, respectively) it is safe to say they have been flown for significantly more than 10x the total flight hours. Probably at least 20x but I’m pulling that number out of thin air. The data is certainly promising but it’s probably a little too soon to be too confident in relative safety comparisons. For one, we don’t have nearly as much data on those newer airframes as they age.
    - rob74 3y ago
      There are two recent accidents that show how much new airplane designs (and better safety measures) have improved survivability of accidents: Emirates Flight 521 (https://en.wikipedia.org/wiki/Emirates_Flight_521 https://en.wikipedia.org/wiki/Emirates_Flight_521), a Boeing 777 that crashed in Dubai in 2016, where all 300 people on board survived (although un unfortunate firefighter lost his life); and the A350 that collided with another airplane while landing at Tokio Haneda airport in January this year - if you look at the burnt out airplane (https://en.wikipedia.org/wiki/2024_Haneda_Airport_runway_collision#/media/File:Japan_Airlines_516_JA13XJ_wreckage.jpg https://en.wikipedia.org/wiki/2024_Haneda_Airport_runway_col...), it's hard to believe that all 379 people on board made it out alive...

cesarb 3y ago

> The 737 MAX planes that crashed only had one AoA sensor. IIRC, it had two, but each of the computers only used the sensor on its side; which was OK for the original (pre-MAX) design because of they way these sensors were originally used by it.

Reason077 3y ago

The 737 MAX, like all 737s, always had two AoA sensors. The problem was that Boeing engineers wrote software for the 737 MAX which could make critical flight control inputs based on the data from one sensor only. And didn't really tell pilots about it. The fix, amongst other mitigations, was to have the MCAS software cross-check inputs from both AoA sensors.

uuddlrlrbaba 3y ago
Still, when two sensors disagree how do you determine which sensor is correct? Really 3+ are needed
- DrFalkyn 3y ago
  Ask the pilot ?
  - shiroiushi 3y ago
    Can't do that: the pilot can't be allowed to control, or even know about MCAS, because that would affect Boeing's ability to claim the plane is "just another" 737 and that the pilots don't need retraining. Giving the pilot the ability to control MCAS means the pilots all need retraining.
    - anticensor 3y ago
      They already received training on MCAS once they got 737 MAXes, albeit a short superficial one (1 hour of lecture&1 hour of simulator training iirc). Hence "cannot be allowed to know" does not apply anymore.
      - shiroiushi 3y ago
        Yeah, and that's wrong. It should apply. Pilots should not be allowed to know, because that means this is a different plane than the one they were rated for. And so, since the plane can't be flown safely without proper training, the planes should not get the same type rating as the old 737, and either 1) they should just be demolished, or 2) they should be considered an entirely different plane, with all the training requirements that entails. The regulators completely failed here, and by allowing this are showing they're corrupt.