HelmetFire - a couple of questions:
Do the operators flying single pilot NVG carry out landings to unrecced LS or do they fly HLS to HLS and just use the goggles for terrain clearance and lookout?
If they are carrying out landings to unrecced sites do they use white light (nightsun or equivalent) to recce for wires and is the crewman on NVG as well?
For a visibility estimate do you work on the observed Met vis or do you try and judge 5000m (or 3000m) visually on goggles?
If you encounter a large shower (CB for example) and the vis comes below 5000m, is a climb to LSALT the best option? I only ask this because according to your rules I wouldn't have been able to complete a hospital transfer the other night - although we were at 500' agl, the vis came down regularly to 1000 - 1500m and with large showers and forecast CB activity, an instrument abort to safety alt wasn't an option.
If the met vis is below 5000m is it automatically a nogo?
The light levels graph may not take into account cultural lighting but it still gives you a good idea of what the real light levels are going to be when you get away from the built up areas - for us working over the sea and in fairly rural areas of the UK it is a much better guide than visibility.