Originally Posted by HN39
I don't see the relevance of (1) and (2) for the AF447 scenario.
You are the one asking the ''difference in stickforce vs stick angle'' I just provide the exemple.
Originally Posted by HN39
IMO 1/5 of the full SS deflection demands a certain level of 'g' and the FCS will provide that irrespective of the THS position, as long it it doesn't need more than full elevator.
How will you get that certain level of 'g' if the autotrim does not cooperate but by pulling more on the stick ?
No autotrim and it won't be 1/5 but anything up to full stick deflection in the target pursuit.
The BEA is not saying anything different except that for those 2 key paragraphs they avoid mentioning the word
autotrim and they should have added to the end of the second one :
"It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall
and the aggravation of the stall."
Originally Posted by Final Report P187 en
When there are no protections left, the aeroplane no longer possesses positive longitudinal static stability even on approach to stall. This absence specifically results in the fact that it is not necessary to make or increase a nose-up input to compensate for a loss of speed while maintaining aeroplane altitude. This behaviour, even if it may appear contrary to some provisions in the basic regulations, was judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material. Indeed, the presence of flight envelope protections makes neutral longitudinal static stability acceptable.
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.