A rotor.
Q: Why is a helicopter called a "Chopper"? A: I think the names comes from the sound of the blades make: whop-whop or chop-chop. FYI, the helicopters that have the loud popping of the blades are usually a 2-blade of the Bell Helicopter design. The multi-blade helicopters do not have a sound as distinctive as the Bell helicopters. The sound comes from the blade striking the vortex generated by the blade ahead of it.
rotor
The main lifting blades make up the rotor
The rotor blade is the airfoil on helicopters.
Yes, many small helicopters have 3 blades
The rotor blades when spinning creates what is called the rotor disk, the disk is tilted in the direction that the pilot wishes to go.
A group of helicopters.
I think you're talking about Peahats.
Then the helicopter will crash.
It is the major part of the rotor. Helicopters can have 3 up to 8 blades on a rotor.
Robert B. Taylor has written: 'Helicopter rotor blade design for minimum vibration' -- subject(s): Rotors (Helicopters), Stability of helicopters
it is called heliphololigy