post 3061 - RetiredF4
Quote:
And if the full forward stick does not lead to the desired reaction, feed in manual trim.
Quote Ventus
What good would that do ? If "the system" wants 1g, if you trim the THS nose down, won't it just keep feeding in up elevator to counter you, until it is finally full up ? By that stage you will have far more THS nose down trim than is healthy. Might you then be in a worse place than from whence you came ?
ventus45 is offline
The system wants, what is demanded by the SS position. Therfore the positioning of the SS to nose down is the first priority. If that works, than fine, but if it does not work fast enough, than the trim most probably is already all the way up.
If we look back to the documented stall accidents we know, that most crews were reluctant to do that in an appropriate way. The ND input was not present at all, was not far enough nose down, not long enough down or accompanied by noseup inputs averaging in an overall nose up input. This inapropriate SS handling may command a loadfactor value greater than the one present while descending in a stalled attitude. The consequence is that the flight computers may drive the elevators and in turn the THS trim to full nose up position.
As long as the elevators are nose up from neutral, the trim will not move
afaik despite the SS nose down position. As the certification requirement is -1 and +2.5g, I assume that a full nose down SS input would not deliver more than 0 G (i could not find a reference with the applicable loadfactor demands in relation to the SS position). A controlled manual trim input would assist the SS input and not counter it.
In A320 series the THS trim might have stopped depending on the law reconfiguration, and it might only be available in mechanical mode.
But is there time for error and try?
As I said before, follow the procedure, which says under step 2.b
" Nose down pitch trim .......as needed.