Originally Posted by
Ian W
It is necessary to go back to the principle of FMC/FMS and avionics design. There are pilots on board and the FMC/FMS avionics is intended to make their life simpler. There is a significant cost in coding to deal with every potential error. So the design principle is that the automatics will be coded to field the basic well understood errors however as soon as it becomes complicated, - the 'otherwise case' - in the last resort the automatics hand the bag of bolts to the crew. The crew are expected to carry out the fault finding and correction using a set of checklists and if all else fails, their own innate capabilities as pilots to recover from the 'otherwise case'.
Originally Posted by
Ian W
If the AD is considered in this light it is right along the line of the design principle. FMC cannot cope with differing angle of attack indications so passes bag of bolts to pilot. The pilots in this instance were not able to fly out of the problem. So the AD emphasizes the correct checks and operations to be used if this otherwise case occurs again. If the design principles are changed (and they are slowly changing) eventually the 'otherwise cases' the automatics cannot handle become extremely unlikely; and perhaps pilots will not be needed as the automatics will not drop out.
It is becoming clear that the avionics should hand a plane to the pilot in a stable and best possible state to fly. For each FL, this should be possible. FL should be simple to determine from multiple sources.
The focus should be to stabilise the situation and to give the pointy end the maximum time to fly the thing in the state that it is in.
Giving the thing to the pilots in a dynamic state, with a known outcome of self-destruction is madness.