One of these is to get 5 hours of "actual or simulated instrument flying". Since our Robinson 44 is not allowed to fly in actual conditions (i.e. in clouds), this means flying "under the hood", using a gadget which restricts the pilot's view to just the instruments. This is how most instrument training and currency is done, even in airplanes, since you can't really count on clouds to be there when you need them, especially in our part of the world. Yesterday I completed my second helicopter flight under the hood, amounting to a magnificent total of 3.4 hours so far.
Foggles" which are like industrial eye protection goggles with most of the lens covered in a translucent film. Only the bottom part, corresponding roughly to the reading part of bifocal glasses, is left clear. As long as the pilot isn't actually trying to cheat, these do the job very well. In fact, it's surprisingly easy not to cheat, assuming your goal is to be trained rather than just to pass a checkride. (In the latter case, it isn't really worth trying to cheat because the examiner will notice immediately). I remember one flight, on my own in actual cloudy conditions, where I popped out of the cloud and it took me a while even to realise that I didn't have to rely on instruments.
In the helicopter, it's harder to do an adequate job of restricting vision, because the visibility is so much better. The only thing that works - and then not very well - is the decidedly steampunk Francis hood, looking like something a submarine commander should be wearing. Even so it's impossible not to see ground through the lower part of the canopy - you just have to try not to notice it.
Flying the helicopter under the hood is much harder than a plane. For a start, you can't take your hands off the controls. A plane will cheerfully fly for tens of seconds, hands off. You sometimes see a plane referred to as a good "instrument platform", meaning that it is naturally stable. My own Cessna TR182 falls into this category. The heli, on the other hand, always requires a hand on the cyclic (the up/down/sideways control corresponding to the stick or yoke in a plane). Normally it's your right hand, but you can switch hands if you need to, for example to twiddle the Garmin 430 in the usual R44 instalation. Even that is tricky - it's difficult to fly as smoothly with the "wrong" hand (I guess left-handed helicopter pilots may find the opposite, but probably not - it's all a question of habit). And you have to be constantly prepared to get a hand on the collective really fast if the engine stops, to enter autorotation in the couple of seconds you have before the aircraft simply drops out of the sky.
Flying, and especially instrument flying, involves a lot of fiddling round with bits of paper - charts, approach plates and so on. It is very difficult to refold a flimsy IFR en-route chart with just one hand. For this reason, IFR-approved helicopters have either a crew of two, or an autopilot (or both of course). But helicopter autopilots are eye-wateringly expensive - little change out of $100,000 - and anyway not available for training aircraft like the R44. So, even during an instrument checkride, the instructor (or examiner) can be used as an "autopilot".
I've done a lot of airplane instrument flying, both under the hood and in real clouds. Much of it has been partial panel, i.e. without a functioning attitude indicator, which generally mysteriously "fails" at the very start of my instrument currency flights. So much so, that I've got used to flying without using it very much - the turn coordinator and the altimeter work just as well. That absolutely does not work in the heli, at least not at first. It is so much more sensitive that the AI absolutely has to be the primary reference all the time, just like it says in the IFR manuals. It took me a little while at the start of my first flight under the hood to realise this. Once I did, my flying became a lot more stable. In an airplane, quite a casual instrument scan works fine. But in the heli you really have to be moving very quickly between all the instruments. It takes only a small distraction to suddenly find yourself in a 30 degree bank or a couple of hundred feet off altitude. This is especially a problem when tuning radios or fiddling with the GPS - you have to scan back and forth between the AI and whatever you're twiddling, making the latter just an extra part of the scan. It's hard.
Once cruise flight is mastered, or at least under control, the next thing to tackle is approaches and holds. In principle an approach is just flying, but there's a lot more to keep track of - altitudes and headings change, and there's radio work too. A general problem with instrument flying is what happens when you get overloaded. You can go very quickly from feeling comfortable to being on the edge of complete panic, not because anything has gone badly wrong but just because there is so much to keep track of. Then small things start to go wrong - altitude and heading deviations, maybe a bit of an extreme attitude - and that piles on the workload too. It takes self-discipline to take a few deep breaths and get back to focusing on basic flying, get straight and level again, go around if you have to. For some reason the hood adds to stress too - flying in actual clouds, without the hood, seems less daunting. This may be just a very basic animal reaction to not having complete vision.
The handful of approaches I've flown have worked out pretty well, all things considered. My first helicopter ILS was the long, long descent into Moffett (KNUQ). Although it's charted as a series of step-down fixes, in practice you can fly the whole thing down the glideslope, all the way from HOOKS - 20 miles out and 5500 feet above the field. It's probably the longest ILS descent in the world, 15 minutes or so of following the needles. Fixed-wing, I flew it once with everything covered up except the VOR head - everything done by making tiny corrective inputs as the needles start to drift. It's a great exercise, but I'm certainly not ready to do it in the heli just yet!
What next? I only need one more flight like this to "tick the box" for my CPL-H. A helicopter instrument rating is pretty useless, since it's unlikely that I'll ever fly one that's equipped for IFR. But there again, it might be fun to do after the CPL-H - amazingly, it only requires another 10 hours of hood time to meet the legal requirements.