3 ms·

> - risk tolerance shrank. There's a lot of truth here and it plays out in even more ways than that. I look back through documentation of legacy systems and se

by wycy 6y ago

> - risk tolerance shrank. There's a lot of truth here and it plays out in even more ways than that. I look back through documentation of legacy systems and see so many things designed based on "engineering judgement". Sizing for that bearing? Engineering judgement. Thickness of other minor structure? Engineering judgement. Now, the load on every little thing requires a 50 page engineering calculation report with figures, charts, and tables, that takes 3 months to prepare and another month to get reviewed by everyone. The littlest things now take forever.

morei 6y ago
There's a lot of things changed since the era of 'engineering judgement'. In the 50s and 60s when 'engineering judgement' was common, it was a signal to a skilled machinist that "You have more experience with the material, so use your best guess because I don't know what the right answer is". Things have changed a lot! 1. Material quality is much higher. Which is to say that batch-to-batch variance is vastly reduced. This means that it's worth investing the effort in detailed understanding of the material because that material is more predictable. Which led to ... 2. We understand a _LOT_ more about material science. Our knowledge of materials is vastly higher, so things that used to be 'best guess' are now 'do this because it will reliably work'. e.g. Spallation and galling used to be poorly understood issues that were worked around based on personal experience and guesswork. Now we understand them very well, and any competent manufacturer will clearly explain exactly how to (eg) install their bearing in a way that prevents such issues. 3. Expertise shifted. The 'machinist' is no longer a 20-year experienced highly trained person, but a CNC operator, who probably won't be within eye-sight of the running machine. So the practice of 'increase the RPM until it chatters slightly then back off' doesn't cut it any more. The answer needs to be known up-front to go into the G-code, not 'feel'. This has led to the obvious cycle where more responsibility moved to the engineering end, which increased the demand for exact knowledge, which reduced the requirements on machinists, which led to lower skill, which further moved responsibility to engineering. So I totally get pining for the era of 'engineering judgement', but it died for a reason and it's not really likely to come back!
- wycy 6y ago
  I would've thought your first 2 items there would help increase the use of engineering judgement by reducing pitfalls previous generations encountered. Your third item is definitely a significant factor. It's not so much that I yearn for the era of engineering judgement so much as I yearn for refocusing on work that's important. Not every little decision needs to written up in professional report, circulated around through multiple drafts, signed off by 4-5 people, briefed out in slide deck form, then never read again.
  - colineartheta 6y ago
    Ok, boomer.
  - InitialLastName 6y ago
    That would be nice, but you just wait until the root cause analysis of a catastrophic failure gets traced to a backside that was inadequately obscured by "engineering judgement".
cgearhart 6y ago
A month for review? Where is this glorious Valhalla?! Navy flight certification checklist is a 2-3 column full page of densely packed names for the approval authority on all the different systems. It may take a month to circulate your proposal to those folks just to get a final list of the subset who will need to ultimately sign off. We had cases where item X was used on USAF aircraft Y, but it could not be used on Navy aircraft Z (which was the same airframe) without literally tens of millions of dollars in testing. Not because the loads on the platforms were substantially different, but because the test standards between USAF and USN were different and the approval authorities wouldn’t sign off otherwise. (See also: zero risk tolerance.)
- wycy 6y ago
  A month for review is an achievable-but-best-case scenario for projects that need to get out the door ASAP, but its not unusual for these reports to be in review for many months. I know of one project report that's been "in review" since 2015.

by wycy 6y ago

morei 6y ago

There's a lot of things changed since the era of 'engineering judgement'. In the 50s and 60s when 'engineering judgement' was common, it was a signal to a skilled machinist that "You have more experience with the material, so use your best guess because I don't know what the right answer is". Things have changed a lot! 1. Material quality is much higher. Which is to say that batch-to-batch variance is vastly reduced. This means that it's worth investing the effort in detailed understanding of the material because that material is more predictable. Which led to ... 2. We understand a _LOT_ more about material science. Our knowledge of materials is vastly higher, so things that used to be 'best guess' are now 'do this because it will reliably work'. e.g. Spallation and galling used to be poorly understood issues that were worked around based on personal experience and guesswork. Now we understand them very well, and any competent manufacturer will clearly explain exactly how to (eg) install their bearing in a way that prevents such issues. 3. Expertise shifted. The 'machinist' is no longer a 20-year experienced highly trained person, but a CNC operator, who probably won't be within eye-sight of the running machine. So the practice of 'increase the RPM until it chatters slightly then back off' doesn't cut it any more. The answer needs to be known up-front to go into the G-code, not 'feel'. This has led to the obvious cycle where more responsibility moved to the engineering end, which increased the demand for exact knowledge, which reduced the requirements on machinists, which led to lower skill, which further moved responsibility to engineering. So I totally get pining for the era of 'engineering judgement', but it died for a reason and it's not really likely to come back!

wycy 6y ago
I would've thought your first 2 items there would help increase the use of engineering judgement by reducing pitfalls previous generations encountered. Your third item is definitely a significant factor. It's not so much that I yearn for the era of engineering judgement so much as I yearn for refocusing on work that's important. Not every little decision needs to written up in professional report, circulated around through multiple drafts, signed off by 4-5 people, briefed out in slide deck form, then never read again.
- colineartheta 6y ago
  Ok, boomer.
- InitialLastName 6y ago
  That would be nice, but you just wait until the root cause analysis of a catastrophic failure gets traced to a backside that was inadequately obscured by "engineering judgement".

cgearhart 6y ago

A month for review? Where is this glorious Valhalla?! Navy flight certification checklist is a 2-3 column full page of densely packed names for the approval authority on all the different systems. It may take a month to circulate your proposal to those folks just to get a final list of the subset who will need to ultimately sign off. We had cases where item X was used on USAF aircraft Y, but it could not be used on Navy aircraft Z (which was the same airframe) without literally tens of millions of dollars in testing. Not because the loads on the platforms were substantially different, but because the test standards between USAF and USN were different and the approval authorities wouldn’t sign off otherwise. (See also: zero risk tolerance.)

wycy 6y ago
A month for review is an achievable-but-best-case scenario for projects that need to get out the door ASAP, but its not unusual for these reports to be in review for many months. I know of one project report that's been "in review" since 2015.