The ornamental design for a helicopter, as shown and described.
FIG. 1 is a right side elevational view of a helicopter showing my new
design with the forward rotor blade broken away in the center for
convenience of illustration it being understood that said forward rotor
blade is of the same length as the rear upper rotor blade;
FIG. 2 is a top plan view thereof;
FIG. 3 is an enlarged front elevational view thereof with the two upper
rotor blades broken away in the center for convenience of illustration;
and
FIG. 4 is an enlarged rear elevational view thereof with the upper rotor
blades omitted and the support structure for said blades broken away for
convenience of illustration.
The side opposite to that shown in the drawing is a mirror image thereof
except for the tail vane and tail rotor.