Dozy
Sorry - not buying that - I've never been entirely convinced that the DFDR elevator readout doesn't take the THS position into account. I see OG has popped along - Owain, what's your take on this?
I don't think I have a "take" and I'm not sure I understand what you mean by the readout not taking the THS position into account. The elevator deflection as recorded in the DFDR is measured relative to the THS chordline, so the elevator position relative to the fuselage datum is measured elevator angle plus THS deflection.
Does that answer your point?
Or did you mean the bit about increasing NU elevator?
In which case, although I wouldn't use the same words I tend to agree with Phoenix.
Remember that in both normal and alternate laws S/S movement commands a delta g not an elevator position. Neutral S/S is in effect a command to "keep me at the 'g' I have at this moment", so if the stick remains neutral and the 'g' falls because there isn't enough lift to sustain the g at the time the stick was released the system will apply up elevator in an attempt to recover the selected level. If this persists then the THS, following the integral of elevator deflection, will also move NU.
Coming back down, so far as I can see, one would need to apply a negative g command greater than the actual (less than 1g) situation at that time before the system would actually apply ND elevator. That command would have to be held for some considerable time before the integrated elevator signal caused the THS to start moving ND.
Last edited by Owain Glyndwr; 13th Sep 2014 at 16:50.
Reason: additional comment