From: Paul Rubin <no.email@nospam.invalid>
Subject: Re: Boeing 737 and 737 MAX software
Date: Thu, 18 Apr 2019 13:20:29 -0700
Date: 2019-04-18T13:20:29-07:00 [thread overview]
Message-ID: <87ftqfhxpu.fsf@nightsong.com> (raw)
In-Reply-To: ghrifuFssqbU1@mid.individual.net
Niklas Holsti <niklas.holsti@tidorum.invalid> writes:
> On the issue of Ada subtypes, it seems to me that if the SW
> specification, design and coding considers sensor faults (as it of
> course should), the normal approach for such critical SW
One of the criticisms of the decisions leading to the MCAS software is
that the software is certified only at DO-178B level C, defined as
software whose consequences are (https://en.wikipedia.org/wiki/DO-178B):
Major – Failure is significant, but has a lesser impact than a
Hazardous failure (for example, leads to passenger discomfort rather
than injuries) or significantly increases crew workload (safety
related)
This is instead of level A (catastrophic, the whole plane can be lost),
or level B (hazardous, people can be injured). The rationale was that
at worst MCAS going wrong would change the nose pitch by a few degrees
and then the pilot could fix it. They didn't consider the possibility
of it activating over and over again, tilting a few more degrees each
time.
Since the software was treated as level C, its development and
certification process was less rigorous than what it would have gotten
at a more critical level.
Certifying and developing this system at level C instead of level A was
itself obviously some kind of process failure. I believe finding out
how that happened is one of the investigation's objectives.
next prev parent reply other threads:[~2019-04-18 20:20 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 21:16 Boeing 737 and 737 MAX software Paul Rubin
2019-04-06 1:16 ` Jere
2019-04-06 19:05 ` Paul Rubin
2019-04-18 22:04 ` Paul Rubin
2019-04-19 9:13 ` tranngocduong
2019-04-06 17:30 ` Dennis Lee Bieber
2019-04-06 18:45 ` Niklas Holsti
2019-06-28 23:45 ` Paul Rubin
2019-06-29 2:52 ` Dennis Lee Bieber
2019-06-29 3:38 ` Paul Rubin
2019-06-29 16:29 ` Dennis Lee Bieber
2019-08-07 6:06 ` robin.vowels
2019-11-08 1:12 ` Paul Rubin
2019-11-08 15:32 ` Dennis Lee Bieber
2019-11-18 11:16 ` robin.vowels
2019-11-18 15:32 ` Optikos
2019-04-12 7:46 ` tranngocduong
2019-04-12 22:15 ` Dennis Lee Bieber
2019-04-17 17:27 ` Maciej Sobczak
2019-04-18 9:45 ` tranngocduong
2019-04-18 12:44 ` Maciej Sobczak
2019-04-18 13:53 ` tranngocduong
2019-04-18 15:13 ` Niklas Holsti
2019-04-18 16:21 ` tranngocduong
2019-04-18 18:20 ` Niklas Holsti
2019-04-20 0:29 ` tranngocduong
2019-04-18 20:36 ` Randy Brukardt
2019-04-18 20:51 ` Paul Rubin
2019-04-18 20:20 ` Paul Rubin [this message]
2019-04-18 16:39 ` Dennis Lee Bieber
2019-04-19 2:39 ` Dennis Lee Bieber
2019-04-22 19:36 ` Norman Worth
2019-04-28 18:27 ` russ lyttle
2019-04-18 13:50 ` Simon Wright
2019-04-18 15:07 ` tranngocduong
2019-05-05 14:29 ` robin.vowels
2019-05-06 13:54 ` robin.vowels
2019-05-06 15:12 ` Dennis Lee Bieber
2019-08-07 5:51 ` robin.vowels
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