Just last week, I was in a small, light-turbine helicopter giving a checkout to
a rather low-time pilot who'd never flown the type before. Although the wind
was fairly calm, he was having a LOT of trouble acheiving a stabilized hover.
He was wrestling with the controls in a manner that made me think that the
hydraulics had perhaps failed. I mean, he was WORKING!
Finally, out of sympathy, I took over, gave him a break and said "Watch this." I brought the ship to a 3-foot hover, then removed my hand from the collective and put it on my left knee. Thus, I hovered all around the area we were using, making gentle pedal turns while the ship maintained a perfectly nice hover. Did the hover-height vary? A little. Sometimes it would be four feet, sometimes two. It never did sag all the way to the ground, nor did it balloon to an unsafe altitude. The guy in the other seat was astounded.
This: When you make an "adjustment" of a control - especially the collective- it effects all the other ones. Even if you only make a tiny movement of the collective, it WILL require a change in the tail rotor pitch to compensate for the change in torque. That change in tail rotor pitch (i.e. thrust) WILL require a change in lateral cyclic to compensate for the lateral drift that is going to occur. It's a vicious cycle! And, for the most part, unnecessary.
So...monkeying around with the collective in a hover will only get worse and worse and worse, until the instructor takes over and gets the seemingly uncontrollable ship to settle down again. The key, I guess, is to not get so obsessed about it. Every helicopter jinks and wiggles around a little in a hover, and even "high-timers" like Walt Hawn don't hover perfectly all the time (Lord knows I surely don't!). The best of us have learned one simple rule for hovering: DON'T MOVE THE CONTROLS! And by that I mean, don't *think* about moving them - just try to get your hands to act without a direct order from your brain. By the time the throught is processed into a control movement, it's too late.
Got that? I guarantee that the next time you're trying to hover, you'll think about my technique above and say to yourself, "What the HELL was that guy talking about?! This is IMPOSSIBLE!" Ahh, but have faith, Grasshopper, it will come. In time. But it will come. And one day you too will be hovering with Shaolin priest-like ability.