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Old 27th May 2011, 16:49
  #105 (permalink)  
Svarin
 
Join Date: Jun 2009
Location: Earth
Posts: 79
Manual pitch trim (3)

takata wrote :

Right, of course: it is like having a "direct law" with only manual THS trim available, with a message poping up and saying "Manual pitch trim only"... WTF!!! I won't ever use this [email protected] or I'll be fired! Your position doesn't make sense: it is not "per-design", it is not "forbidden": it is always better not to have to use it (like being in normal law instead of direct)... up to the point that you need it! Now, how training is performed is a different issue.
Regarding manual pitch trim, the design and associated training is thus :

Normal law : auto-trim. Dont touch it or fail the test and get fired. 99.9999% of the time for airline pilots. Protections have ultimate authority on control surfaces (hard protections). Eliminated at the start of the accident event sequence.

Alternate law (1 & 2) : auto-trim, which means dont touch it either. No specific PFD, ECAM, whatever, indication regarding manual pitch trim. Rarely trained for. Some protections remain, with a less assertive authority (soft protections). According to factual report, this was how the airplane flew its last minutes. Requires at least one working PRIM.

Direct law : PFD amber warning USE MAN PITCH TRIM. Similar to conventional airplane, direct stick position to control surface position. According to factual information, this law was not triggered. No protection. Rarely if ever trained for, except initial training towards type rating (box-ticking mentality). Requires at least one working SEC.

Mechanical backup : PFD red warning MAN PITCH TRIM ONLY. Basically, sidestick becomes useless. Remaining only manual pitch trim wheel and mechanical rudder, which could give you a reasonable fighting chance depending on actual circumstances. According to factual information, not triggered. Trained once, upon type rating training process (box-ticking mentality). Main condition is all five FCCs lost (3 PRIMs, 2 SECs, all off. Did not happen.)

For the sake of almost completeness :
Other laws : abnormal attitude law, flare law, ground law, ground/air blending laws... These (apart from abnormal attitudes) are quiet transitions, appear every day, and would be perhaps considered subsets of Normal law. No cockpit indication that these sub-laws are triggered. Conditions that activate them can be found in the FCOM. Probably irrelevant to our current matter, apart perhaps from abnormal law but this was not reported.

Assuming that such a significant event as any additional flight law change would have been reported by BEA. Subject to revision as more information becomes available.

Last edited by Svarin; 27th May 2011 at 16:50. Reason: added "no protection" to Direct law
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