26 ms·

How operating one type of plane makes recovering from disruption harder? I'd expect it to make it easier - you can replace any crew with any other crew, and any

by smsm42 5y ago

How operating one type of plane makes recovering from disruption harder? I'd expect it to make it easier - you can replace any crew with any other crew, and any plane with any other plane. Same with secondary airports - I am not sure how it makes recovery harder. Distributed systems are usually more robust against disruption that centralized ones - if you can't fly in an out of the hub, then all your flights in that hub's vicinity are grounded, but if you just lost one secondary airport, there might be another close by. So I'm not sure I am convinced those particular qualities are detrimental to robustness, at least without a convincing argument.

bobthepanda 5y ago
well, as an example, when the 737MAX was grounded, many airlines had already started taking delivery of them and were operating them. Southwest was the largest recipient at that time. Southwest had plenty of older 737s as well, but the new MAX planes both fly farther and have more seats, so while the grounding was in effect Southwest was essentially paying to keep the things on the ground while scrambling to reconfigure their flight network, and it affected them the most.
- hef19898 5y ago
  Single AC fleets mean an airline has somewhat of a single point of failure. If the issue at hand is caused by that point of failure, sure recovery will be harder. In most other cases it makes it actually easier, at least on paper. No need to get crews to certain planes, just a crew to a plane, as every crew is certified on any plane.
  - bobthepanda 5y ago
    The utilization rate is so high that specific planes and crew are needed in specific times and places. If plane going from A -> B is late it cannot become flight B -> C. If crew for this plane are stuck in the ground long enough, they have to wait til the next day to fly as they‘re only allowed to be awake and work for so long.
  - WalterBright 5y ago
    And people wonder why Boeing made such an effort to not need different pilot training for the MAX.
    - hef19898 5y ago
      I wondered always why people wondered. Airbus went to great length to make cross-certification of pilots possible for that very reason.
      - ethanbond 5y ago
        Nobody is wondering anything. Advantages are obvious. They were wondering why you’d prioritize that over the aircraft’s ability to stay in the air.
        deleted 5y ago
        [deleted]
        WalterBright 5y ago
        I've followed many 737MAX threads on HN, and they sure did dismiss this issue. It was always "why didn't they design a whole new airplane from the ground up". > why you’d prioritize that over the aircraft’s ability to stay in the air. This is an egregious misunderstanding. There was nothing wrong with the purpose of the the MCAS system nor the concept of it. What went wrong was its failure to follow the dual path design, and do a proper failure analysis of its design. There was a further problem with some pilots not understanding how to deal with stab trim runaway. These problems have since been corrected, and MCAS is still on the 737MAX.
        ethanbond 5y ago
        IIRC a few 737MAXs fell out of the sky. Clearly there being nothing wrong with the purpose nor concept of MCAS wasn't sufficient to keep the airplane from crashing.
        5y ago
paulclinger 5y ago
Maybe it's the same effect as happens with monoculture (https://en.wikipedia.org/wiki/Monoculture#Risks https://en.wikipedia.org/wiki/Monoculture#Risks): more efficient, but more fragile/risky?
ethbr0 5y ago
> Distributed systems are usually more robust against disruption that centralized ones Distributed systems can also be more complex to re-converge after a major disruption. I'd imagine it's non-trivial to re-plan a network, given equipment and crew limitations. And as context, we're talking about 24 hours later, now?
- bobthepanda 5y ago
  Yeah. Part of Southwest‘s high utilization rate is their ability to turn around planes and crew quickly. In the event of widespread disruption, planes will not make it to their next airport to become a different flight, nor will their crew. Crew can also only be awake and working for a limit of time, so if the disruption causes a crew to go over that limit they are not going out until the next day, etc. With cloud computing, it‘s a bit different because which host you‘re using in a region doesn‘t really matter, but for airline a specific plane with specific people need to be in a specific time and place.
  - smsm42 5y ago
    But not using the same plane would not make it any better, neither would using a hub - that's my point. This is a common problem, but the properties outlined in the parent post which are supposedly specific to SW do not make the problem worse.

by smsm42 5y ago

bobthepanda 5y ago

well, as an example, when the 737MAX was grounded, many airlines had already started taking delivery of them and were operating them. Southwest was the largest recipient at that time. Southwest had plenty of older 737s as well, but the new MAX planes both fly farther and have more seats, so while the grounding was in effect Southwest was essentially paying to keep the things on the ground while scrambling to reconfigure their flight network, and it affected them the most.

hef19898 5y ago
Single AC fleets mean an airline has somewhat of a single point of failure. If the issue at hand is caused by that point of failure, sure recovery will be harder. In most other cases it makes it actually easier, at least on paper. No need to get crews to certain planes, just a crew to a plane, as every crew is certified on any plane.
- bobthepanda 5y ago
  The utilization rate is so high that specific planes and crew are needed in specific times and places. If plane going from A -> B is late it cannot become flight B -> C. If crew for this plane are stuck in the ground long enough, they have to wait til the next day to fly as they‘re only allowed to be awake and work for so long.
- WalterBright 5y ago
  And people wonder why Boeing made such an effort to not need different pilot training for the MAX.
  - hef19898 5y ago
    I wondered always why people wondered. Airbus went to great length to make cross-certification of pilots possible for that very reason.
    - ethanbond 5y ago
      Nobody is wondering anything. Advantages are obvious. They were wondering why you’d prioritize that over the aircraft’s ability to stay in the air.
      - deleted 5y ago
        [deleted]
      - WalterBright 5y ago
        I've followed many 737MAX threads on HN, and they sure did dismiss this issue. It was always "why didn't they design a whole new airplane from the ground up". > why you’d prioritize that over the aircraft’s ability to stay in the air. This is an egregious misunderstanding. There was nothing wrong with the purpose of the the MCAS system nor the concept of it. What went wrong was its failure to follow the dual path design, and do a proper failure analysis of its design. There was a further problem with some pilots not understanding how to deal with stab trim runaway. These problems have since been corrected, and MCAS is still on the 737MAX.
        ethanbond 5y ago
        IIRC a few 737MAXs fell out of the sky. Clearly there being nothing wrong with the purpose nor concept of MCAS wasn't sufficient to keep the airplane from crashing.
        5y ago

paulclinger 5y ago

Maybe it's the same effect as happens with monoculture (https://en.wikipedia.org/wiki/Monoculture#Risks https://en.wikipedia.org/wiki/Monoculture#Risks): more efficient, but more fragile/risky?

ethbr0 5y ago

> Distributed systems are usually more robust against disruption that centralized ones Distributed systems can also be more complex to re-converge after a major disruption. I'd imagine it's non-trivial to re-plan a network, given equipment and crew limitations. And as context, we're talking about 24 hours later, now?

bobthepanda 5y ago
Yeah. Part of Southwest‘s high utilization rate is their ability to turn around planes and crew quickly. In the event of widespread disruption, planes will not make it to their next airport to become a different flight, nor will their crew. Crew can also only be awake and working for a limit of time, so if the disruption causes a crew to go over that limit they are not going out until the next day, etc. With cloud computing, it‘s a bit different because which host you‘re using in a region doesn‘t really matter, but for airline a specific plane with specific people need to be in a specific time and place.
- smsm42 5y ago
  But not using the same plane would not make it any better, neither would using a hub - that's my point. This is a common problem, but the properties outlined in the parent post which are supposedly specific to SW do not make the problem worse.