SPA-FRANCORCHAMPS, Belgium (AFP) - Nico Rosberg admitted he was lucky to walk away unhurt after a spectacular high-speed tyre blow-out during Friday afternoon's second free practice session for this weekend's Belgian Grand Prix.
The 30-year-old German lost control of his Mercedes when the right rear Pirelli tyre disintegrated at around 320kmh at the Blanchimont corner.
The session was red flagged and suspended while the car and debris were cleared from the spectacular and majestic, but challenging, circuit in the Ardennes forests.
Television replays showed clearly that the right rear tyre had suffered severe delamination before it exploded, sending Rosberg into a full spin in which he was fortunate not to hit the barriers.
"That was not a nice experience," said Rosberg, whose wife Vivian is expecting their first child at any time.
Keeping his trademark cool despite the accident Rosberg, who topped the timesheets, added: "A 360 degree spin at 320kmh, or 200mph, is not something you expect at all.
"Luckily, I did not hit the wall...
"Unfortunately, it wasn't down to my skill. It was just luck that I stayed out of the wall.
"I didn't feel anything before, there was no warning. There will be a big analysis. I was feeling quick before then, comfortable."
Mercedes technical boss Paddy Lowe said he had “never seen anything like it”.
“There’s different bits of video showing some sort of unravelling up to a minute before the actual catastrophic failure,” he said.
“The big question will be what’s initiated that and I don’t know, I’ve never seen anything like that before. We simply don’t know, we’ll have to wait.
“We’ll obviously take the tyre away and make sure the car wasn’t a contributor to it in some way.”
On resumption after a brief suspension, Swede Marcus Ericsson lost control of his Sauber car and crashed heavily at the downhill Pouhon corner, a collision that produced the red flags again for a third time in the day.
Venezuelan Pastor Maldonado had set the pattern during opening practice in the morning when he hit the barriers at Malmedy. He also, like Ericsson, was unhurt.
Rosberg's accident resulted in his Mercedes team-mate Lewis Hamilton staying in his car in the pits while the team analysed the cause of Rosberg's tyre failure.
In both of the afternoon accidents, the drivers were saved from more serious damage and possible injuries by the big run-off areas built into the circuit.
Hamilton was unable to improve his time and finished the session second fastest behind Rosberg, as he had been in the morning, when both the Red Bull and Ferrari teams produced improved speed to threaten the champion team's supremacy.
Asked about Rosberg's accident, Hamilton said: "It is not something you have to think about. You just go out and drive and hope for the best.
"There was no evidence of problems with my car and, fortunately, Nico was not hurt. The car was feeling good. Nico was quick but otherwise I really enjoyed the day. I'll try and find the time and keep pushing.
"Red Bull are looking closer this weekend than they have for a while, so they should be close."
The incidents highlighted again the dangers that remain prevalent at one of the classic "traditional" long and high-speed F1 tracks where last year Hamilton and Rosberg's tense intra-team rivalry turned acrimonious and resulted in a collision during the race.
Rosberg's tyre failure also reminded all observers of the similar spectacular tyre explosions during the 2013 British Grand Prix weekend.
Hamilton finally did one more lap on the medium tyres before the end of the session when he finished three-tenths adrift of Rosberg's best lap in one minute and 49.385 seconds.
Australian Daniel Ricciardo was third quickest, seven-tenths behind, ahead of his Red Bull team-mate Daniil Kvyat, who was a full second adrift of the fastest time.
Kimi Raikkonen, who signed a new contract with Ferrari for 2016 on Wednesday, was fifth quickest ahead of German Nico Hulkenberg in a Force India, Frenchman Romain Grosjean of Lotus and Ericsson.
Felipe Masr was ninth in the second Sauber ahead of four-time champion German Sebastian Vettel in the second Ferrari.
The struggling McLaren team endured another torrid day. Jenson Button, the 2009 champion, was down in 17th and Fernando Alonso one place behind him in 18th, ahead only of the Manor Marussia team.
The McLarens, with new power units and associated other parts fitted, were handed grid penalties of 30 places for Alonso and 25 for Button, resulting in both men starting Sunday's race from the back of the grid.