A goat in South Australia almost brought to a rescue operation to halt by ramming a chopper and causing it to be grounded.

The helicopter landed near Onkaparinga Hills in Adelaide's north Monday afternoon where it was due to transport a car crash victim to hospital.

When the chopper landed in a paddock near the crash site a group of curious goats immediately surrounded it and one particularly territorial animal rammed the helicopter with its horns.

The blow smashed a perspex window located at the pilot's feet and forced the chopper to be grounded for three hours pending an engineering inspection.

After an inspection the helicopter was deemed safe to return to base at the Adelaide Airpot but remains grounded for a full assessment of the damage caused by the goat.

The patient was transported to Flinders Medical Centre by ambulance and is in a stable condition with leg injuries.

The helicopter is one of three used in South Australia for medical emergencies and police work.