The debate continues...
Sorry about the tone of the text, but I have to get this out quickly, sorry for not being around for a while!
I repeat again, if I am a CAT I equipped aircraft, I do not have the capability of making an automatic approach and landing. I want to have a go at seeing the lights. You have no power to stop me from making the approach. I am only regulated by the IRVR limits. So, if the cloud ceiling is 150 feet, I might, or might not see the lights. If it is 1/8 at 200 feet, I probably will see the lights. If I lose visual reference below DH, I go around.
If it is low cloud, and you start to apply LVP separations (note, I have assumed that you have completed all of the safeguarding functions on the ground), then you are reducing the movement rate. I have had many discussions with operators over the years and they will fly hooked up autopilot approaches and manually monitor the landings, ready to take over. I have worked with many technical pilots who specialise in Low Vis Operations for their airlines over the years, and they all express the same opinion.
For a busy airport, it makes more commercial sense to push and to have the odd go-around, than it does to space everyone out. Fine in the old Trident only days. Now 90% plus are CAT II equipped at most airports. Therefore, if you drop the operational rate from say 48 an hour to 30 an hour, it begins to hurt and quickly.
Primary causal factors: interesting expression, should have died in 1990. Unfortunately, we still go off down that line in aviation so we are only 16 years behind the drag curve there. Primary cause, and the other considerations like contributory, are the sole emotional opinion of the investigation team. They are not risk based, probability based or assessed against any fixed criteria. Try Jim Reason's Swiss cheese model, where does Jim say, ah well, here is a thick piece of cheese with some wholes so that must be primary cause. The cheese model, as was developed (and unfortunately, I can actually claim to be there at the time!) was an event sequence showing how the defence in depth failed. Interestingly enough, the sequence of events actually reverses half way along the cheese wheels. It is usually the initiating event, then the failure to correct (which goes with time progression towards the accident) and then you jump backwards to the precurser latent failures.
You find when you sit down and think about it, that all events were necessary, so all are important. If Greek ATC had passed the departure time to the system, so the controllers knew that AeroLloyd 1135 was going to come into the sector, then the second controller would not have gone to bed. Was that a primary cause? Accident investigators in Australia have a different classification system and do not use primary cause, but they have been running along the Reason model for years.
I will get back on more detail on all of the points, sorry, but I have to dash.
PS I enjoy debate and do not take offence. Those who know me personally will know that! I am more than willing to continue this debate on-board, via PM or even over the phone (and the odd personal visit has been known). All I really give a monkeys about is safety, so fire away!