Fire crews were called to Breighton Aerodome, in the village of Breighton, around 10 miles east of Selby, shortly after 6pm.
The helicopter is said to have come down at the side of a runway, with five people hurt.
Humberside Police said their injuries, although serious, are not thought to be life-threatening.
Two people were transported to hospital by air ambulance, with one going to Leeds General Infirmary and the other to Hull Royal Infirmary.
The other three casualties were taken to hospital by road ambulance.
“Numerous” emergency services are in attendance at the scene.
A spokesman for Humberside Police said: “The Air Accident Investigation Branch will be leading the investigation to establish what caused the crash.”
The Breighton Aerodome website says Breighton Airfield is a former Second World War heavy bomber base.
Today, says the website, it is home to the classic aircraft collection of the Real Aeroplane Company and the Real Aeroplane Club, an active flying club.