Ambulance Victoria has suspended the use of helicopter winches as it investigates how a patient fell to his death during a rescue operation.

The 68-year-old man was bushwalking with a group at Macs Cove, near Mansfield in Victoria's north-east, when he broke his ankle about 10:30am AEST yesterday.

The ambulance helicopter was sent in to rescue the man about midday because of the terrain.

However, Ambulance Victoria chief executive Greg Sassella says at about 12.30pm he fell approximately 30 metres to his death while he was being winched into the helicopter with a paramedic.

"I understand he was at the door of the helicopter and they were attempting to get him into the helicopter," he said.

"This is devastating for the crew, they spend their whole lives putting themselves at risk for patients and in this instance something's gone astray."

The man is understood to have weighed more than 100 kilograms.

Mr Sassella says Ambulance Victoria has suspended all winch rescues while the equipment is tested and an investigation is completed.

"What we do know is the crews risk themselves to help the patient, they do everything they can for the patient and in this instance something has happened and the patient's deceased but helicopter operations are high risk," he said.

"We have a very good record here in Victoria but that's because we do learn and understand what goes wrong when it goes wrong."

Ambulance union secretary Steve McGhie says the man would have been brought up in a sling-like apparatus.

"They actually sit in it, is my understanding, or it goes under their arms, and the paramedic's also harnessed in and both the paramedic and the patient are winched up from the ground," he said.

"I don't know how the gentleman's come adrift from the sling, but it's a really tragic situation."

Mr Sassella says the winch equipment will be thoroughly tested.

"The winch operations will be suspended until the companies that provide the helicopters are satisfied and CASA is satisfied that we understand what happened and that there's no potential for this to happen again on other helicopters," he said.

"The standards we set for our helicopter operations here is extremely high and that includes the helicopters themselves.

"It includes the qualifications of the pilot, the qualifications of the crewmen and the qualifications of the paramedics."

Police, the Civil Aviation Safety Authority and Work Safe Victoria are also investigating.

Counselling has been offered to the paramedic and the flight crew involved.