Worst possible news for Boeing

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September 24th, 2019 at 3:45:35 AM permalink
AcesAndEights
Member since: Oct 24, 2012
Threads: 5
Posts: 286
Quote: Pacomartin
Some new very disturbing details have emerged about the MCAS design. The original design was due to some wind tunnel tests in 2012 and the MCAS required both a bad angle of attack reading and high G forces. Command was limited to 0.6 degrees from trimmed position.

A separate problem appeared in 2016 that did not involve high G forces. So MCAS was modified and the high G force requirement was removed, command was changed to be limited to 2.5 degrees from trimmed position.

The decision to remove the high G force requirement should have (at the very least) meant that both AoA sensors should have been used. It seems that the AoA sensors were destroyed by bird strikes.

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Early in the process of selling the MAX, according to two people familiar with the discussions, Boeing promised to give Southwest Airlines a substantial rebate for every plane if the MAX required simulator training. One former MAX worker, said the rebate reported to him by managers was $1 million per plane, a figure another Boeing employee indicated is roughly accurate.c

I did a quick google and didn't see any recent news, could you share from where you sourced that quote?
"You think I'm joking." -EvenBob
September 27th, 2019 at 8:09:58 PM permalink
Fleastiff
Member since: Oct 27, 2012
Threads: 57
Posts: 7296
recent rave review of the neo released on youtube.
the Electric Neo motorized glider
September 27th, 2019 at 8:18:49 PM permalink
Fleastiff
Member since: Oct 27, 2012
Threads: 57
Posts: 7296
Boeing to no longer be permitted to rely on well-trained test pilots. Reaction times and computer interface time to be determined by pilots of ordinary skills and training.
September 28th, 2019 at 2:04:04 AM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 934
Posts: 10988
Quote: AcesAndEights
I did a quick google and didn't see any recent news, could you share from where you sourced that quote?


https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/
By recent I mean in the last three months

While most of the stories about the MAX have focused on the "disagree light" between the two AoA sensors, I thought it was far more significant that for four years the design required both a poor AoA reading and high G force. I have only read about the G force requirement (that was removed) in this one article.

While it seems perfectly sensible that a bird strike could destroy an AoA sensor, and it is incredibly poor design to have the lives of the entire passenger list dependent on a single sensor - it is much harder to have a sensor misread high G forces. Plus the odds of the G force sensor and the AoA sensor failing at the same time are minimal.


I did find this one paragraph too brief in discussing the "other problem".
Quote: The Seattle Times

About a third of the way through flight testing in 2016, as first reported by The Seattle Times in March, Boeing made substantial changes to MCAS. The flight-test pilots had found another problem: The same lack of smooth stick forces was also occurring in certain low-speed flight conditions. To cover that issue too, engineers decided to expand the scope and power of MCAS.
...
Because there are no excessive G-forces at low speed, the engineers removed the G-force factor as a trigger.


The March article was not much more helpful.
https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/
October 7th, 2019 at 8:58:37 PM permalink
Fleastiff
Member since: Oct 27, 2012
Threads: 57
Posts: 7296
Southwest's pilot union sues Boeing for lost wages due to their rush to sell an unsafe product in an unjust and misleading manner.

Damages alleged at over 100 million dollars as all those planes were either totally grounded or awaiting maintenance and therefore pilots lost both normal wages as well as overtime and flight time for their logbooks and pension program.
October 25th, 2019 at 6:23:21 AM permalink
Fleastiff
Member since: Oct 27, 2012
Threads: 57
Posts: 7296
Grounding costs over one billion dollars.

Indonesia releases report distributing blame but emphasizing Boeing's design assumptions, lack of oversight and making Angle Of Attack Sensor Disagreement Resolution only available as an added option.

Admits to imprecise communication between crew and maintenance personnel.
October 25th, 2019 at 3:27:31 PM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 934
Posts: 10988
Quote: Fleastiff
making Angle Of Attack Sensor Disagreement Resolution only available as an added option.


That conclusion was an easy one to make.
October 25th, 2019 at 4:59:05 PM permalink
Fleastiff
Member since: Oct 27, 2012
Threads: 57
Posts: 7296
Quote: Pacomartin
That conclusion was an easy one to make.
yes. Worse perhaps was burying that option inside a package, so it was less obvious as a hazard.

To a salesman it was a get in fly it situation using existing personnel. To an engineer it was bigger, heavier and more powerful, particularly during certain phases of flight wherein the computer would do what it thought right even if that data came from only one AOA sensor.
October 29th, 2019 at 6:42:04 PM permalink
petroglyph
Member since: Aug 3, 2014
Threads: 22
Posts: 4280
Everyone gets thrown from the plane to maintain altitude
October 29th, 2019 at 10:51:17 PM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 934
Posts: 10988


Interesting story on QF7. It's interesting to hear one about an Airbus jet where they had redundant Angle of Attck sensors.

The aircraft was fitted with three air data inertial reference units (ADIRU) to provide redundancy for fault tolerance, and the Flight Control Primary Computers (FCPC) used the three independent Angle of Attack (AOA) values to check their consistency. In the usual case, when all three AOA values were valid and consistent, the average value of AOA 1 and AOA 2 was used by the FCPCs for their computations. If either AOA 1 or AOA 2 significantly deviated from the other two values, the FCPCs used a memorised value for 1.2 seconds. The FCPC algorithm was very effective, but it could not correctly manage a scenario where there were multiple spikes in either AOA 1 or AOA 2 that were 1.2 seconds apart.
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