Depends on the purpose and make of the helicopter.
You go to the airport by the military base to find a helicopter.
For a fairly new helicopter, around 120 knots. Around 150 mph, except for fast military helicopters.
the original AH-1 Cobra flew at 170 mph
184 mph
The Chinook can fly at about 195 mph.
A fast aeroplane will be faster than any helicopter, but a fast helicopter can be faster than a slow aeroplane.
183 mph or 159 knots
It is a military heavy cargo helicopter
it depends how fast its going
A military helicopter
Some helicopter main rotor blades spin at roughly 185 rpm and extend out up to 20 ft so your question is subjective to the helicopter you are speaking of.