HELICOPTER (Version 1)
This variation uses a "classifier three handshape." (CL:3)
Stick the palm of your right "five hand" on top of the tip of
the thumb of your left CL:3 hand.
Flutter the right hand from the wrist, (the fingers do not individually move
up and down but rather the whole hand flutters) representing the whirling
blades of the helicopter.
HELICOPTER (Version 2)
Another popular way to sign "helicopter" is to flutter a "5 hand" on top of
an index finger: