Originally Posted by
TTex600
Can you confirm that the AF447 crew could have held the trim wheel and stopped the trim from its run to nose up limits?
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Can anyone confirm what would happen if a pilot, on a test flight of course, just held the trim wheel?
From an earlier post by A33Zab:
Originally Posted by A33Zab, thread 4, post 327
"An override mechanism, which is installed in the PTA (Pitch Trim Actuator),
makes sure that the mechanical control through the trim wheels cancels the electrical control.
When a manual command is made with the trim wheels, the override
mechanism gives priority over the electrical command from the FCPCs.
It mechanically disconnects the PTAoutput from the mechanical input(via
electro-magnetic clutch) and also operates the overriding detection
switches which in turn signal the FCPC's to stop any electrical command
from the FCPC's."
Why weren't they aware of the continuous trim motion?
They should have been - continuous trim motion in the FBW Airbus design is a given in Normal and Alternate laws.
Why no "trim in motion" claxon, or other indication?
Because the trim is more-or-less constantly in motion, it would quickly become a nuisance. A warning that the trim is exceeding a certain value, on the other hand, would be a viable proposition.