Having read and taken part in this thread it seems to me that the autopilot/coupler/FMS fitted to modern helicopters has become too complicated!
The talk of which control does what function at a particular time - upper and lower modes seems to to over complicate what should be simple evolutions.
What do we want the coupler to do in the simple IFR environment of NS offshore flying?
We want it to fly:-
1. A coupled ILS down to DH where if not countermanded it will carry out a missed approach.
2. A LOC/DME approach horizontal profile where it will level at the set MDH and when commanded carry out a missed approach.
3. A VOR/DME approach horizontal profile where it will level at the set MDH and when commanded carry out a missed approach.
4. A Rig Radar approach horizontal profile where it will offset at 5deg at 1.5nm, 10deg at 1nm and if commanded at 0.75nm a 45deg turn away from the rig and climb to SA or preselected altitude.
6. A visual night approach as prescribed in the company Ops Manual
5. A system for maintaining altitude and navigating along a pre-programmed route with easy access to how much fuel there will be at each way-point and destination/diversion.
Certain safety features can also be programmed into the coupler - such as min speed for a certain type of approach.
These simple functions should be easy to program and activate from one control panel and it should be obvious what approach has been selected.
I am sure that a simpler coupler would be welcomed by NS crews but I am afraid it will never happen as the "geeks" who design these systems always want to add more and more capabilites - a bit like buying a laptop - it always has far more capabilities than you require!!
It was quite telling that DB found the S92 display confusing even though he is one of the pilots pushing more and more automation.
My view is that the coupler is there to help you fly the a/c - more accurately if required - not to take over the flying of the a/c!
HF