Graeme Schoneville recalled hearing a loud bang when his car hit a rock as he competed at the Snowman Rally in Inverness, in the Highlands, more than four years ago.
He said he was then aware of a “commotion” around the vehicle as it became apparent “somebody was potentially under the car”.
Joy Robson, 51, died of multiple injuries sustained at the event in February 2013.
A joint fatal accident inquiry is examining the circumstances surrounding her death and the deaths of three other motor sport fans at a separate event in Scotland - the Jim Clark Rally near Coldstream in the Scottish Borders - the following year.
Mr Schoneville, 31, from Lanarkshire, told the first day of evidence at Edinburgh Sheriff Court of the moment the incident unfolded, around seven miles into a nine-mile stage.
He said: “We came to a corner and the road surface changed and the car began to slide, which was okay, we’d experienced that plenty of times.
“As I tried to correct the slide, the car then swung in the other direction and impacted a rock.”
He added that all he can then remember “was a loud bang” at the back left hand side of the Honda Civic he and his co-driver were in.
“It just went black inside, the car just somersaulted in the air,” he said.
“I can remember it rolling: sky, then dark, sky.”
The witness told the inquiry the car landed on its wheels among some small trees.
He told the court: “Immediately after the crash, the car landing, (we were) aware of a lot of people round about the car and we could obviously see a commotion and we knew that somebody was potentially under the car.
“That’s why we exited the car as quickly as possible.”
The people surrounding the vehicle were lifting the car, he said.
Advocate depute Andrew Brown QC, for the Crown, asked him: “Presumably you were very concerned?”
“Yes,” he replied.
He became aware later that day that a woman had died and a child had been injured in the accident, the inquiry heard.
Mr Schoneville, who began rallying in 2006, told how he has effectively not returned to the pursuit since the incident.
“I tried to, it never felt the same,” he said.
He and his navigator were not injured in the incident.
The inquiry has heard there were no mechanical defects with the car and the gravel on the ground was wet at the time of the crash.
Mr Schoneville said the Snowman Rally has always been popular with members of the public.
Asked about spectators standing close to the road in places, the witness said: “Obviously, with hindsight, it’s not safe.”
He also said: “The rule of thumb is that you should never stand on the outside of a corner.”