Originally Posted by AZR
I'm not sure Direct law is always the best fail mode
The laws and protections on the Airbus are very much dependant on the reliability of the numerous probes and sensors. Airbus has opted to keep as much as automation as possible depending of the circumstances. My proposition would be different : As soon there is a doubt on any data, first advise, second degrade to the basic.
That way, any Airbus simulator training would invariably lead to direct law with manual trim in case of manual flight and the crews would be used to that known and unambiguous state.
In Perpignan, the only reliable AoA data was
silently discarded by the system, the crew proceeded with the test at an unreasonable low altitude, but knowing what we know now on AF447, nothing positively indicates that the test would have ended differently if the crew had tested at the minimum recommended altitude …
The simple and logic thing would have been to merely advise the crew of the loss of certainty regarding the data : AOA DISCREPANCY
My bet is that the crew would not have proceeded with the test at all as the test was specifically based on the accuracy of the AoA readings.
And why not reverse to direct law with still the capability for the AP ?
Many airliners fly around that way, is it a problem ?
Lets keep the magic of the Airbus when everything is known at 100% not lower.