Originally Posted by
Vessbot
Bombardier modified the C* (C-star) FBW design control system to be speed-stable,
This is what's also in use by the 777 and 787. C*U
Before even hinting that C*U might be a solution to AF447, one should consider what it becomes when U (ie. speed) is unknown...
787 is, I believe, slightly different in that if speed is unavailable it calculates a synthetic airspeed from AOA and other data both for display and use in the control laws. This might have been developed with an eye on the vulnerability of C*U to loss of U.
C*U hasn't been without its problems though:
https://www.flightglobal.com/news/ar...d-data-423735/
https://www.atsb.gov.au/media/577302...-149-final.pdf
Pitot icing, plane's computers can't cope, yet again (even with the synthetic airspeed).
to quote the second link:
In response to a previous, similar event on another B787-8, the FAA published an airworthiness directive warning flight crew not to make large abrupt magnitude flight control inputs in response to
unrealistic drops in airspeed.
Boeing also revised the flight control software to limit the rate of elevator feel reduction with drops in airspeed. This will specifically allow the column to stay at a higher feel force to mitigate large and abrupt unintentional pitch inputs.
So, C*U is not quite the fix-all some seem to think it is.
Another salient quote from that report:
In this case, the crew showed a high level of professionalism in response to a weather related event. The crew demonstrated high levels of communication and coordination, promptly applied checklists and procedures.
And therein, I submit, lies the crucial difference between making it home and ending up at the bottom of the ocean.