Originally Posted by
Chris Scott
Having studied the traces provided by the BEA of the AF A340 incident, where the third disengagement condition operated five times, I am reviewing my opinion.
Chris - the ultimate question at the end of the day is "how much hand-holding is a good idea to provide?". It's reasonable to assume that Alpha Prot and Alpha Floor as designed were in the main intended to assist a pilot who is already commanding nose-up with the stick, such that the pilot's command is followed to the best of the aircraft's ability while the aircraft remains flying. In this airprox incident we have a situation where one or both of the alpha protection modes were triggered by transient weather conditions, which were outside of the original spec.
Contrary to legend, the protections were designed to assist a pilot who, for whatever reason, has been forced to take the aircraft to the edge of the safe operating envelope - counteracting handling mistakes is and always was a secondary design consideration.
In this case we have an incident during which - for whatever reason - a protection mode has actually had a negative impact on the safety of the flight, hence the change in logic.