V8 Supercars star James Courtney could miss this weekend’s round at Sydney Motorsport Park after being injured in a freak off-track accident on Friday.

The Holden Racing Team driver was struck in the chest by debris blown over by a low-flying Navy helicopter during a military demonstration before the day’s second practice session.

The 2010 series champion had lifted his arms to try protect his face from the piece of hoarding outside the team’s garage, but instead was hit in the ribs.

Courtney was taken to the medical centre for checks, before being transported to Westmead Hospital for further assessment.

The 35-year-old tweeted a photo of himself in the back of the ambulance wearing an oxygen mask and wires attached to his chest.

“Didn’t think this was going to happen today … Doc has me flying,” he posted.

HRT boss Adrian Burgess said Courtney had been hit “quite hard”.

“His ribs are fine but we’re not sure about the condition of his lungs,” he said.

“He’s stable – he’s fine.

“He’s not going to die on us, but there’s a bit of damage there and we need to make sure we’re doing the right thing by him.

“He’s gone off to hospital for some proper tests.”

The Royal Australian Navy and V8 Supercars have launched investigations into the incident.

Co-driver Jack Perkins took Courtney’s place in the No.22 Commodore for the day’s final session, and could do so the rest of the weekend.

Missing the round’s three sprint races – the last before the endurance series – could put a huge dent in his hopes of a second title.

Courtney sits fifth on the championship standings, 371 points behind Ford’s leader Mark Winterbottom.

The Sydney-born driver has had one victory and four other podiums so far this season.

Further comment has been sought from HRT and Defence.