Hi George there are 3 type of helis , coaxle these have 2 sets of blades one goes CW and one CCW , tail motor pushes and pulls heli( wont fly in any wind)
Then there are Fixed pitch these have a main rotor set at 45 deg with a fly bar to balance the rotor, control is with throttle to adjust head speed to to gain height and 2 cyclic servos the swash is fixed where a pitch servo would be ( will fly in very light wind)
Then there are the real heli the CP ( collective pitch ) this has a variable pitch main and tail blades , 3 servos on the swash to control elev,aile,pitch
then a high speed tail servo
There are different ways to fly scale with has a fixed head speed of about 1900 on a 500 class the control is all done by cyclic and pitch and has pitch range of -3,0,5,8,10
Then there is 3D still has fixed head speed but this time its about 2300 and has pitch range of -12 to +12 zero is at mid stick this is were you hover the right way up or inverted , When your inverted the to climb you pull throttle collective down all controls are backwards
Then the last is sport flying the same fixed throttle at about 2000 to 2300 but pitch range is -8 to +12 sport is loops rolls not full 3D
In quads 3D is called hotdog ,but the china flood of quads use the word 3D as it can fly upside down ,A variable pitch quad should be able to do what a cp heli can as you have a cp heli on each corner , If you want to Know how the full workings of a cp in video form let me know its amazing how the thing works
watch this the 800 class is over 6 feet nose to tail blades
This goblin holds a speed record 155 mph