"5. Improve constantly and forever the system of production and service, to improve quality and productivity, and thus constantly decrease costs." - Edwards Deming
https://en.wikipedia.org/wiki/W._Edwards_Deming
This does make version and revision management and service harder, but that you can manage with software and its worth the cost.
However, what you say is partially true, its not all positive. If you endlessly make the same car with very little change you can also hit very high quality and reliability. That is why sometimes cars like Jeep look good in quality rankings.
Overall however, I think there is good reason for iteratively interdicting changes.
What you're saying is true, with one important distinction we may disagree on:
>"but that you can manage with software"
This is a take that seems accurate on it's surface but belies a lot of additional problems. Leaning on software for improving reliability can be a dangerous path. It's tempting because it's cheap and easy to iterate on. Software doesn't wear out like mechanical components. But software makes reliability pretty tough when you constantly iterate because it tends to fail at interfaces. Not only do the number of these interfaces tend to grow exponentially, they are notoriously difficult to test fully. Nancy Leveson has some good articles that demonstrate this distinction.
Since this thread is about aerospace, you can see where software failure caused catastrophic failures by lulling engineers into complacency about how it can enhance reliability. Ariane V, to Falcon, to CST-100 all have examples of how software can not fulfill its promises to increase reliability and often it does the opposite. Don't confuse the ability to move a design change faster with an inherent ability to make things more reliable.
>"but that you can manage with software"
This is a take that seems accurate on it's surface but belies a lot of additional problems. Leaning on software for improving reliability can be a dangerous path. It's tempting because it's cheap and easy to iterate on. Software doesn't wear out like mechanical components. But software makes reliability pretty tough when you constantly iterate because it tends to fail at interfaces. Not only do the number of these interfaces tend to grow exponentially, they are notoriously difficult to test fully. Nancy Leveson has some good articles that demonstrate this distinction.
A automotive example from my own experience is a comparison with mechanical vs. electrical robots used in the stamping process of body panels. Plant managers like electrical retrofits because they held the promise of being much cheaper to build and modify. But they needed near-constant tweaking of the control system. The number of interfaces causes a lot more failure modes and impacts the reliability. By contrast, a mechanical system is, by it's nature, constrained by mechanical linkages. Once the mechanical system is tuned and working, it works for a long time. Gradually the parts wear, but they tend to be much easier to predict and troubleshoot.
Since this thread is about aerospace, you can see where software failure caused catastrophic failures by lulling engineers into complacency about how software can enhance reliability. From Ariane V, to Falcon, to CST-100 all have examples of how software did not fulfill its promises to increase reliability and often it does the opposite. Don't confuse the ability to move a design change faster with an inherent ability to make things more reliable.
What I mean by 'manage with software' is that each car has an exact description of what hardware is in it. Meaning what revision of every part. Tesla has some advantage because they manage the process end to end, knowing exactly what vehicle was sold to what costumer and the control the service center and write the diagnostic software so the service center should know exactly what car they are working on and what potential problems each revision of the software has.
In the 70s when Deming advocated for this such extensive version tracking would likely be much harder.
The software management issue I was talking about was a different animal. Take the Ariane V; the idea was the could iterate faster if they leveraged software reuse. Since it was previously verified software, they didn't think it needed much testing. But the new rocket design exceeded the assumptions in the previous iteration and the vehicle was lost. There's a lot of instances where software allows you to iterate faster, but you have to very careful about the baked in assumptions.
But that brings ups up a specific example of where Tesla has struggled. They used to keep HUGE backstocks of excess inventory (I believe they have since tamed this) which is a classic manufacturing mistake. So if you have any production mistakes or improvements in the part, you have to scrap or just cycle through the entire inventory until the improvements show up in the car.
This is why Just-In-Time is such an important concept in manufacturing. You can iterate constantly. Meanwhile, Tesla would crank out huge batches of identical fenders and doors and mirrors to maximise efficiency (economies of scale) but then struggle with part fits and panel gaps.
Tesla has since dealt with a lot of this when they went through their production hell period. But a lot of what they had to do was re-learn things like Lean Manufacturing and JIT.
Yes Tesla had to re-learn a lot about manufacturing. They certainty didn't start out being good. But by now they are doing pretty well.
This actually undermines your point to a certain extent. Tesla is great at iterating but that often comes at a cost to quality. It is very hard to manage reliability when parts and suppliers are constantly churning.
"Older models typically fare better in reliability, as companies tend to make tweaks and redesigns to solve known problems, while sticking with the same parts and suppliers.
But Tesla deviates from this approach, Fisher explained. “At almost random times during the year Tesla will switch major components, suppliers or sensors and other units. The more you change, the greater the chances you’re going to have some problems.” [1]
[1] https://www.cnbc.com/2021/11/18/consumer-reports-2021-auto-r...