McWilliams in action on his previous spell in MotoGP in 2004

The Ilmor rider returned to the track on Tuesday for the first time since breaking his left femur and collarbone and damaging his hand in November.

"There was a sudden surge of power at the hairpin and it kicked me in the air," he told Motorcycle News.

"For a minute I thought I'd broken the leg again. I'm surprised people couldn't hear me scream."

The 42-year-old was seen walking round the paddock on crutches after the incident, but plans to return to the track for the final day of testing on Thursday.

The 2007 MotoGP championship gets under way at the Losail circuit on 10 March.