It is possible to control a helicopter with a 4-channel airplane radio. You can master hovering and move into elementary forward flight this way. For anything beyond that, you will need a helicopter radio. If you do try to use a 4-channel airplane radio, build a Y-connector, and control two separate servos (collective and throttle) off the throttle channel. Then adjust control arms to get a form of mechanical throttle and pitch curve adjustment. It's not too hard to set a heli up so that it will hover tolerably well at mid-stick this way, and you can contrive to increase lift above mid-stick and lose lift below mid-stick.
Flying

What's the deal on auto-rotation?
If a heli's engine quits in flight or you simulate this by going to throttle hold mode, it is still possible to glide the helicopter down safely. As the helicopter descends, the wind flows up through the rotor disk from below. At a low or negative collective pitch setting, the wind flowing up through the rotor disk keeps the blades spinning. Heli blades usually have lead weights epoxied into the tips, so as the blades spin they build up a fair amount of rotational inertia. When you are near the ground and ready to land, you add in collective to increase lift, and the inertia maintains head speed sufficient to execute a controlled landing. In theory. ;-) Auto-rotative glides and landings are beautiful to watch. A helicopter can sustain as much as a 4:1 glide ratio in auto-rotation.

What about aerobatics?
Helis can do awesome aerobatics: loops, rolls, pirouettes, you name it. My personal favorite is inverted flight. If looks 'way cool to see a helicopter hovering inverted right above the grass. I've seen guys do aerobatic routines flying the whole thing BACKWARD. With a helicopter you have unbelievable versatility.

How high do they fly? How fast do they go?
Helicopters can go so high they are out of sight. Being able see the thing in order to control it is the only limit on how high they can fly. R/C helis can go 60-80 MPH or more.

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