Crab
You are operating IMC below MSA when conducting a rig radar approach. It happens everyday on the North Sea by commercial aircraft flown by two pilots with a forward looking radar. OK, the mimima is .75nm for obvious reasons and the MDA is deck height plus 50' but this is a CAA approved approach both flown as a pattern or alternatively straight-in. Letting down to radar contacts IMC below MSA by civilian SAR operators is also approved by the CAA. When a company applies for its approvals a CAA ops inspector flies with the operator, inspects the Ops Manuals and makes sure that the correct training is in place before an EXEMPTION is granted. This exemption will also state that the operator is exempt the 500' rule etc. whilst conducting training. It will also state the exemptions involved for training power requirements. For example, the S61 rules are significantly different to the L2 due to the power available and the way the system deals with power loss.
I hope this answers your question. In terms of operating in congested parts of our seas and waterways, a 360 radar would be handy. However, there are parts of the North Sea that are still very congested and we manage to let down to rigs and vessels with the radar we have. Please remember that civilian operators are letting down to dive vessels etc. everyday to carry out public transport ops - it isn't just rigs and the sole domain of the military. If you saw what goes on in the North Sea during the winter it would open your eyes a little - it did mine
