Re: [OT] “Raise the nose, HAL.” “I’m sorry, Dave, I’m afraid I can’t do that.”

[Walter Bright]

On 4/21/2019 1:45 PM, Paolo Invernizzi wrote:
> We will see the reports of the investigation process, but it seems really 
> probable that it was the MCAS that crashed the planes, and it seems plausible that:
> - there's no check from redundancy input coming from the left sensor
> - there's no check from other inputs too
> - there's no a second "unit" running to check for output differences.

Yes, and all that is correctable with software changes.


> Walter, you are an engineer, but I'm a manager, so I believe that cost saving 
> _could_ be a cause, and a major one.
> 
> For example, the quote you have made about "one airplane that all their pilots 
> can fly" is related to airlines, not airplane builder, and that's a basic rule 
> in organisation to be more efficient.

It's both a cost saving and a safety improvement. There's a very good reason why 
cars have the brake on the left and the gas on the right and this is standardized.


> I'm not interested in the specific case. What I'm wondering is if software is 
> still not so under the lens of regulation as hardware of mechanical engineering 
> in general, so that's a "trend" in shifting "weight" from traditional 
> engineering to software engineering, and that's starting to be a problem.

There's been constant upheaval in aircraft systems since the very beginning. 
There's not really any such thing as "traditional". For example, the switch from 
cable operated surfaces to hydraulic boost to fully powered surfaces. The pilot 
moving the surfaces directly was abandoned with the 747, for obvious reasons.

It's important to realize that the MCAS problems were not due to bugs in the 
software implementation. It was bugs in the design specification. The spec seems 
to contradict principles of aircraft design which Boeing holds dear, and I 
cannot explain how such a design got approved. Cost savings do not explain it at 
all.