A helicopter working to ferry people to and from the Victoria Derby races in Melbourne has crashed at the Collingwood Football Club's training oval.

Police said a 45-year-old pilot from Mornington is lucky to be alive after flipping the chopper on take off on Saturday.

Acting senior sergeant John Alexovski said a bystander dragged her out of the chopper after it flipped, adding that she was "very fortunate".

"It could have easily been a fatality," he said.

Acting senior sergeant Alexovski said the pilot is suffering from shock, has minor injuries to her hands and is recovering in the Alfred Hospital.

He said it was lucky no one else was around when the chopper came down.

A rotor came off the helicopter during the accident, flew through a nearby marquee and damaged a nearby car, police said.

Fire crews have sprayed the helicopter with fire retardant and police have begun an investigation into the crash.