5 ms·

If I were an airline's insurer, I wouldn't want to gamble on the good luck lasting.

by Kye 6y ago

sandworm101 6y ago
Not luck. Design. These failures are anticipated. That they can be handled so well is testimony to the energy and regulation put into engine safety over decades. Whereas once such failures could down an airline, killing all on board, they can now be handled safely.
- BrianOnHN 6y ago
  How do you safely handle the debris falling to the ground?
  - sandworm101 6y ago
    You dont. A few pounds of engine parts is infinitely better than the previous option, many tons of airliner falling on a house.
  - wavefunction 6y ago
    @sandworm How about a third option where neither the plane nor the debris falls?
    - galangalalgol 6y ago
      I'm sure people PW is working on that, but the failure rates on commercial aircraft parts are already ridiculously low. Bad things will always happen.
      - airhead969 6y ago
        "Bad things will always happen" is a despicable shrug mentality. Bad things happen when people don't have their acts together in design, engineering, manufacturing, maintenance, and operation. The failure rates should be striving for zero, unlike the stunts Boeing has pulled on 737NG, MAX, and the 787.
        galangalalgol 6y ago
        Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common mode errors and just human fallibility to see all the possibilities mean we miss stuff. And all this is so much easier in software than in mechanical designs where redundancy sometimes just isn't doable. We shouldn't give up best practices, but we shouldn't have unreasonable expectations of them either. And not every engineering failure implies a failure in engineering process.
        galangalalgol 6y ago
        I wanted to clarify my last statement. Even when best practices are followed bad stuff happens, and that doesn't necessarily mean best practices need to change.
        airhead969 6y ago
        Of course not. Make improvements rather than knowingly shove-in bad Ducommun parts on the line or crappy MCAS. Also, hold manufacturers responsible when they take cost-shortcuts, sacrifice safety, and kill people. Boeing routinely gets a slap for doing so since it's also considered a strategic defense contractor, part of the MIC that greases palms in DC.
        airhead969 6y ago
        I never said it was feasible, you did. It must be strived for, because that's the difference between excellence and crap.
    - sandworm101 6y ago
      The risk of falling debris actually killing someone pales in comparison to the risks of it perhaps doing more damage onboard the aircraft. A loose part near/inside an engine is no longer doing its job and could cause more damage where it is. And the ground is a big place. Drop a random pin in google maps. Then zoom in to see if it is actually on someone's head. This is lottery odds territory. Objects drop from aircraft all the time, daily. It isn't generally newsworthy unless part of a larger story. And even then, only if the object is found and recognized as being from an aircraft. Small rocks also fall daily from space, probably more by weight than aircraft-related objects, yet virtually nobody ever gets hit by space rocks.
      - ClumsyPilot 6y ago
        To add to that, 100 tons of spacerocks hit eath every day. I dont think 100 tons of parts fall of airliners daily. That being said, there was a russian spacecraft that disintegrated and hit someone house, in the middle of siberia bo less. So it does happen, but its freak ecen3ts territory.
        sandworm101 6y ago
        Oh, if you are going to include manmade space-related objects there have been many deaths. Dig into how many Chinese rocket stages have landed on villages. If we include such things as "aviation" I would retract my above statements re debris. Rockets do sometimes fall on people. https://en.wikipedia.org/wiki/Intelsat_708 https://en.wikipedia.org/wiki/Intelsat_708 https://arstechnica.com/science/2019/11/china-keeps-dropping-toxic-rocket-parts-on-its-villages/ https://arstechnica.com/science/2019/11/china-keeps-dropping... "It has happened many times before, including most infamously in 1996 when a Long March 3B rocket veered off course shortly after a launch and crashed into a village. Chinese officials reported six dead from the accident, although Western sources have speculated that hundreds of Chinese citizens may have died in the accident."
        o-__-o 6y ago
        Why compare two sovereign nations with vastly different safety regulations?
- pdonis 6y ago
  > These failures are anticipated Sort of. The possibility of some types of failure is anticipated in the design of other parts of the engine. But there are also inspection procedures in place to ensure that engine parts that might fail are replaced before they fail. A report on a previous incident in Feb 2018 (referred to upthread) says that the root cause was a cracked engine fan blade that should have been detected on a previous inspection but wasn't. Failures that are supposed to be prevented by inspection and replacement of parts are not necessarily also allowed for in other parts of the design. So it's quite possible that luck is involved here as well and that a future failure of this type could have much worse consequences.
  - sandworm101 6y ago
    fan blade failures are expected. Engines are designed to contain failed blades. There is a huge test that is done whereby a blade is "failed" at full throttle. Engine dies but damage is to be contained. https://youtu.be/j973645y5AA https://youtu.be/j973645y5AA (A380 "blade off" test, rare footage of giant engine failing)
    - netsharc 6y ago
      4:37 for the content and to skip all the typical over-dramatization of these kinds of documentaries...
    - pdonis 6y ago
      > fan blade failures are expected. No, they're not. Fan blade cracks are expected; and fan blades are inspected for cracks so that the blades can be replaced before they fail. Yes, it's also true that, as a second line of defense, engine housings are designed to contain failed blades. But the overall risk of the system is calculated on the assumption that that is a second line of defense, not the only line of defense. In other words, it's calculated on the assumption that a fan blade failure in flight will not be due to a crack that could have been detected at the last inspection but wasn't. It's calculated on the assumption that a fan blade failure in flight will be due to some other root cause that nobody has ever seen before. In other words, we have second lines of defense because we don't presume that we know about all possible root causes for a given failure. We don't expect fan blades to fail, but just in case one does due to some root cause we didn't know about, we design an extra layer of protection. But what happened here is that an inspection regime designed to catch a root cause we do know about, failed to catch it. That's not within the design parameters of the system.

If I were an airline's insurer, I wouldn't want to gamble on the good luck lasting.

by Kye 6y ago

If I were an airline's insurer, I wouldn't want to gamble on the good luck lasting.

Not luck. Design. These failures are anticipated. That they can be handled so well is testimony to the energy and regulation put into engine safety over decades. Whereas once such failures could down an airline, killing all on board, they can now be handled safely.

BrianOnHN 6y ago
How do you safely handle the debris falling to the ground?
- sandworm101 6y ago
  You dont. A few pounds of engine parts is infinitely better than the previous option, many tons of airliner falling on a house.
- wavefunction 6y ago
  @sandworm How about a third option where neither the plane nor the debris falls?
  - galangalalgol 6y ago
    I'm sure people PW is working on that, but the failure rates on commercial aircraft parts are already ridiculously low. Bad things will always happen.
    - airhead969 6y ago
      "Bad things will always happen" is a despicable shrug mentality. Bad things happen when people don't have their acts together in design, engineering, manufacturing, maintenance, and operation. The failure rates should be striving for zero, unlike the stunts Boeing has pulled on 737NG, MAX, and the 787.
      - galangalalgol 6y ago
        Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common mode errors and just human fallibility to see all the possibilities mean we miss stuff. And all this is so much easier in software than in mechanical designs where redundancy sometimes just isn't doable. We shouldn't give up best practices, but we shouldn't have unreasonable expectations of them either. And not every engineering failure implies a failure in engineering process.
        galangalalgol 6y ago
        I wanted to clarify my last statement. Even when best practices are followed bad stuff happens, and that doesn't necessarily mean best practices need to change.
        airhead969 6y ago
        Of course not. Make improvements rather than knowingly shove-in bad Ducommun parts on the line or crappy MCAS. Also, hold manufacturers responsible when they take cost-shortcuts, sacrifice safety, and kill people. Boeing routinely gets a slap for doing so since it's also considered a strategic defense contractor, part of the MIC that greases palms in DC.
        airhead969 6y ago
        I never said it was feasible, you did. It must be strived for, because that's the difference between excellence and crap.
  - sandworm101 6y ago
    The risk of falling debris actually killing someone pales in comparison to the risks of it perhaps doing more damage onboard the aircraft. A loose part near/inside an engine is no longer doing its job and could cause more damage where it is. And the ground is a big place. Drop a random pin in google maps. Then zoom in to see if it is actually on someone's head. This is lottery odds territory. Objects drop from aircraft all the time, daily. It isn't generally newsworthy unless part of a larger story. And even then, only if the object is found and recognized as being from an aircraft. Small rocks also fall daily from space, probably more by weight than aircraft-related objects, yet virtually nobody ever gets hit by space rocks.
    - ClumsyPilot 6y ago
      To add to that, 100 tons of spacerocks hit eath every day. I dont think 100 tons of parts fall of airliners daily. That being said, there was a russian spacecraft that disintegrated and hit someone house, in the middle of siberia bo less. So it does happen, but its freak ecen3ts territory.
      - sandworm101 6y ago
        Oh, if you are going to include manmade space-related objects there have been many deaths. Dig into how many Chinese rocket stages have landed on villages. If we include such things as "aviation" I would retract my above statements re debris. Rockets do sometimes fall on people. https://en.wikipedia.org/wiki/Intelsat_708 https://en.wikipedia.org/wiki/Intelsat_708 https://arstechnica.com/science/2019/11/china-keeps-dropping-toxic-rocket-parts-on-its-villages/ https://arstechnica.com/science/2019/11/china-keeps-dropping... "It has happened many times before, including most infamously in 1996 when a Long March 3B rocket veered off course shortly after a launch and crashed into a village. Chinese officials reported six dead from the accident, although Western sources have speculated that hundreds of Chinese citizens may have died in the accident."
        o-__-o 6y ago
        Why compare two sovereign nations with vastly different safety regulations?
pdonis 6y ago
> These failures are anticipated Sort of. The possibility of some types of failure is anticipated in the design of other parts of the engine. But there are also inspection procedures in place to ensure that engine parts that might fail are replaced before they fail. A report on a previous incident in Feb 2018 (referred to upthread) says that the root cause was a cracked engine fan blade that should have been detected on a previous inspection but wasn't. Failures that are supposed to be prevented by inspection and replacement of parts are not necessarily also allowed for in other parts of the design. So it's quite possible that luck is involved here as well and that a future failure of this type could have much worse consequences.
- sandworm101 6y ago
  fan blade failures are expected. Engines are designed to contain failed blades. There is a huge test that is done whereby a blade is "failed" at full throttle. Engine dies but damage is to be contained. https://youtu.be/j973645y5AA https://youtu.be/j973645y5AA (A380 "blade off" test, rare footage of giant engine failing)
  - netsharc 6y ago
    4:37 for the content and to skip all the typical over-dramatization of these kinds of documentaries...
  - pdonis 6y ago
    > fan blade failures are expected. No, they're not. Fan blade cracks are expected; and fan blades are inspected for cracks so that the blades can be replaced before they fail. Yes, it's also true that, as a second line of defense, engine housings are designed to contain failed blades. But the overall risk of the system is calculated on the assumption that that is a second line of defense, not the only line of defense. In other words, it's calculated on the assumption that a fan blade failure in flight will not be due to a crack that could have been detected at the last inspection but wasn't. It's calculated on the assumption that a fan blade failure in flight will be due to some other root cause that nobody has ever seen before. In other words, we have second lines of defense because we don't presume that we know about all possible root causes for a given failure. We don't expect fan blades to fail, but just in case one does due to some root cause we didn't know about, we design an extra layer of protection. But what happened here is that an inspection regime designed to catch a root cause we do know about, failed to catch it. That's not within the design parameters of the system.