From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!feeder.eternal-september.org!news.dns-netz.com!news.freedyn.net!newsreader4.netcologne.de!news.netcologne.de!peer02.ams1!peer.ams1.xlned.com!news.xlned.com!peer02.am4!peer.am4.highwinds-media.com!peer01.iad!feed-me.highwinds-media.com!news.highwinds-media.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!buffer1.nntp.dca1.giganews.com!buffer2.nntp.dca1.giganews.com!news.giganews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 18 Apr 2019 11:39:40 -0500 From: Dennis Lee Bieber Newsgroups: comp.lang.ada Subject: Re: Boeing 737 and 737 MAX software Date: Thu, 18 Apr 2019 12:39:41 -0400 Organization: IISS Elusive Unicorn Message-ID: References: <8736mwi257.fsf@nightsong.com> <2590d3d8-5f91-4f59-897e-e0c9b7e1b5ca@googlegroups.com> <5f483f72-9213-4c63-b3f9-7150fc4e455f@googlegroups.com> <03d33940-85e9-4fc9-9f2b-2b43f2cfd6af@googlegroups.com> <47a71ba7-38cb-426b-8dad-564f08afbcb2@googlegroups.com> User-Agent: ForteAgent/8.00.32.1272 X-No-Archive: YES MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Usenet-Provider: http://www.giganews.com X-Trace: sv3-u6bLPC0hOzl9pLJH3xFMX4UrHX3slUqUWnsvIsQ+2IJQNxi3xd0l7yLq3ck9fgo6Ph6ccKPXUr1ZDWF!tATsxOTvVpes3cxtj6XrJGMnXKGzDuah7ztaxWYvmYZ8BGkx8fx3N99sy3kvC5ocIbVJ43V5 X-Complaints-To: abuse@giganews.com X-DMCA-Notifications: http://www.giganews.com/info/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 X-Original-Bytes: 3229 X-Received-Bytes: 3512 X-Received-Body-CRC: 4111358836 Xref: reader01.eternal-september.org comp.lang.ada:56159 Date: 2019-04-18T12:39:41-04:00 List-Id: On Thu, 18 Apr 2019 06:53:10 -0700 (PDT), tranngocduong@gmail.com declaimed the following: > >a) Ada was used but programmers have chosen a wrong (too relaxed) subtype, or other language was used and programmers failed to code whatever equivalent to raising and handling a CONSTRAINT_ERROR. Simply: software bug. > The common action on any exception is to log it (in flash memory) and /restart/ the FMS software. Restarting likely includes synchronizing with the second FMS -- but after such a synchronization, aircraft control would have been given to the primary FMS; which likely would have almost immediately produced an exception and.... repeat until the pilots manually switch control to the second FMS processor. >b) Contrary to general belief, the software was not programmed with multiple redundant computation. Simply: process failure. > >I chose to believe a). It is most likely a variant of B. MCAS was supposed to nudge the aircraft attitude when it sensed a potential stall condition from just AoA (airflow angle against the wings) with no concern for air speed; pre-existing air speed computations were not changed by the addition of MCAS (couldn't have been if MCAS can be manually disabled in flight). Without the (formerly optional) hardware, this becomes a single sensor matter -- and one which can not be detected as faulty (while each FMS may have had its own sensor, during a disagreement, the primary FMS likely pushes /its/ computed aircraft state to the secondary FMS which is supposed to start computations from those values; probably diverging again until the next sync interval -- get enough of these divergences and the secondary might be the one to shut down; the FMS displays might show "SINGLE FMS" mode]) -- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com