Hi Bogus,
sorry for chipping on the thread. I am flying Russian-made choppers without ILS, DME or VOR. We have only ADF stuff on-board with radio altimeter. So, we are practicing full NDB approaches, and preparing to do it everywhere according to the AIPs.
If an aerodrome issues its approach procedures, it means that everyone who wants or accidentally happens to fly in, must follow these. If this aerodrome has a terminal and/or approach radar (or radar info), which they can use for separation either in IMC, the APP can vector evy aircraft on different flight paths if necessary: for example, helos don't need to fly "full" approaches and can be inserted into the gaps between fixed wing traffic. If I have to alternate to an int'l aerodrome with a big pile of heavy traffic in IMC, I'll probably be vectored although I know and can use the NDB stuff.
But if our aerodrome has no terminal radar information, they can't ensure IFR separation. In these cases (which are far more often), every aircraft must follow the issued procedures. Either if I am with a helo or not, I must use my approach plates. These are developed for all the approach speed categories, so for helos as well. The APP can maintain separation by requiring mandatory reports over fixes, using holding patterns, altitude separation etc., so they can handle a Big Mac and a JetRanger in the same time.
And one more thing: I heard a story about a, well, fixed-wingie commander who said: who cares about helos in IMC in this airbase? They can hover over the runway and descend below the clouds to the ground... No. A simple helo (no Doppler, no GNSS) has no instrument to get into hover in IMC, and even with these stuff, it is hard to maintain your hover within the clouds. Try it with BS but turn off the HUD.
Helos also shouldn't decelerate under a specific airspeed during an IFR approach. Although they won't stall and fall down but the helo will be less stable around her axes (and unstable according to airspeed), more and more handjob :D will be necessary to maintain the attitude (and the approach path), and the loss of sensing your attitude often happens. Not a good feeling IRL... That means, in IMC, that helos have to be handled as a fixed wing stuff but with less airspeed.
Sorry again for chipping on, but I think I should write these.
Cheers!