V8 SUPERCARS star James Courtney was rushed to hospital with serious chest injuries on Friday after a freak accident involving the downdraft of a low flying Navy helicopter.

The 35-year-old Holden driver was floored by a flying piece of metal dislodged as the chopper flew over the pitlane at Eastern Creek.

He was left struggling to breathe properly for several terrifying minutes and was rushed to Westmead Hospital with a pneumothorax, which is small pocket of air in the chest, and two broken ribs.

The injuries will require him to spend days in hospital, ruling him out of this weekend’s three races and shattering his championship dream.

An urgent Navy and V8 Supercars investigation was last night under way into the flyover which was part of the track entertainment.

“He was in trouble. He couldn’t breathe,” Holden Racing Team boss Adrian Burgess said.

“James puts on a brave face. We have to force him to do the right thing and send him to hospital. I know him better than most people and I could see he was in a lot of pain.”

The incident was slammed by a number of V8 Supercar team bosses, who said they had never seen anything remotely similar in previous demonstrations.

“Madness, just madness,” the head of Triple Eight Racing, Roland Dane, said.

“The whole place was shaking like an earthquake. We had all our stuff blowing out of the back of the garage. One bloke in a wheelchair was very lucky he wasn’t hit.”

Didn't think this was going to happen today.... Doc has me flying 👊🏽👊🏽👊🏽👊🏽 pic.twitter.com/WYYWmMWYtW — James Courtney (@jcourtney) August 21, 2015

The Navy confirmed last night it was conducting an investigation but declined to confirm how low the helicopter was flying.

“An incident occurred at Sydney Motorsport Park today while a Royal Australian Navy helicopter was conducting an authorised and routine display as part of the V8 Supercars series,” the spokeswoman said.

“Navy and V8 Supercars have commenced investigations into the incident.”

Courtney tweeted a picture of himself in the ambulance with the caption: “Didn’t think this was going to happen today ... Doc has me flying.’’

His wife Carys was by his side in hospital.

She has rushed to his side before, including after watching his horror crash at Phillip Island in 2013 in which he broke his leg and his wife momentarily thought he could be dead.

Courtney will be replaced by Jack Perkins.

V8 boss James Warburton said The Daily Telegraph shortly after the shock incident that the investigation would begin immediately.

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“He got hit pretty hard in the chest and we just have to wait now and see what the doctors say,’’ Warburton said.

“There are two parts to the investigation: a V8 Supercars investigation because we are the

promoter and also a full military investigation because it was their aircraft.’’

Courtney is currently fifth in the V8 championship and trailing series leader Mark Winterbottom by 371 points.

Missing this weekend’s round of racing would almost certainly ruin his shot at the title.