Originally Posted by
HazelNuts39
Dozy,
For practical purposes, the difference escapes me. Perhaps you should say that the PRIM's, having rejected the three ADR's, cannot define alpha-prot?
That's one technical explanation (aside from replacing "alpha-prot" with "alpha max"). But the issue from an engineering standpoint is that the flight surface limits are not defined within the system that controls them, but imposed by a second system from outside (hence the G-clamp analogy). In Alt 2 that second system as a whole is considered failed and therefore inhibited.
This design decision was made based on the hypothesis that the pilot should have full authority across every flight control surface if the reliability of data was doubtful, and ironically this is a position that every Airbus sceptic would normally agree with.
What makes this situation doubly ironic for me is that if Airbus had slapped a limit on autotrim in alternate law and that limit had prevented a recovery in another incident, the same people who are currently lambasting the autotrim design for unquestioningly following the PICs inputs would be lambasting Airbus for preventing a recovery by limiting autotrim authority.