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Old 11th Apr 2019, 16:21
  #3870 (permalink)  
bill fly
 
Join Date: Feb 2015
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Originally Posted by alf5071h
L39 Guy,

“… sadly this all points to …”
… the persistence, the difficulty in avoiding hindsight, prejudging, assuming; -

How would a crew know that stick-shake just after lift off is erroneous. How is the accuracy of AoA established, of attitude, or at that instant, speed, until the accuracy of these is confirmed all that remains is assumption.
Whatever is argued, the correct AoA cannot be determined even with an EFIS display - which one is correct.
The on-side airspeed will be inaccurate because AoA is used in pressure error correction. Similarly the EFIS low speed awareness - based on AoA, perhaps adding to a belief that stick shake is valid.
Add distractions of Speed and Altitude Disagree alerts, and Feel Diff Press, together with the surprise of an unexpected event, or even higher stick force due to Feel Diff, then all available thinking ability is required to manage what exists.
In time, crosschecking speed, attitude, ‘feel’ (experience) might judge otherwise.

Assumptions such as “… it cannot be a bona fide stall but an erroneous indication” can be just as hazardous as an abnormal technical situation.
And thus any conclusion based on such assumption fails because of false reasoning.

Back to the links in Ethiopian airliner down in Africa - background reading.


Well, you can have that problem on all aeroplanes which have an AoA dependent stall warning system. And there are a lot of those certified.
bill fly is offline