- McLaren's Lewis Hamilton heads practice ahead of Sunday's Abu Dhabi Grand Prix
- World champion Sebastian Vettel spins out and only finishes sixth on Friday
- Hamilton's teammate Jenson Button sets the second fastest time at Yas Marina
- Sunday's race is the penultimate grand prix of the 2011 season
Double world champion Sebastian Vettel suffered a disrupted second practice session ahead of Sunday's Abu Dhabi Grand Prix, with McLaren's Lewis Hamilton setting the pace on Friday.
Red Bull driver Vettel was back at the track where he claimed the first of his two world championships 12 months ago -- the youngest driver to achieve the feat -- but the German spun out on the first corner of the Yas Marina Circuit.
Vettel, who has won 11 of 17 races in 2011, recovered to rejoin practice with 10 minutes remaining, but finished in sixth position on a track where he has won for the past two years. He ended the day half a second behind Hamilton's leading time of one minute 39.586 secs.
Hamilton, world champion in 2008 but only fifth overall after a disappointing season, led second-placed teammate Jenson Button ahead of Saturday's qualifying.
"I lost the car on the entrance to turn one," Vettel, who clinched the 2011 championship with third place in Japan last month, told the sport's official website.
"I think I was too wide and too far on to the kerb, so I lost the rear and couldn't catch the car anymore. I was lucky to get out again at the end of P2; there wasn't much damage apart from the front wing."
British racer Hamilton was pleased with his form and was confident ahead of this season's penultimate race.
"It was a really positive day for me," the 26-year-old said. "The track just got better and better today, so I slowly chipped away at the set-up.
"The tires are behaving well -- at the last race I had degradation and didn't have the pace, so it feels much better this weekend. That's a real positive for me.
"When you come through a Friday without any problems, it definitely makes you feel confident for the rest of the weekend."
Button, the 2009 world champion and running second this year, admitted to experimenting during his practice run on a track where passing has traditionally been difficult.
"I was playing around with overtaking on my long run," the 31-year-old said. "But I still reckon it'll be difficult to overtake people in the DRS zones.
"So I think it's going to be a bit of a struggle to make moves stick in the race -- which means it's going to be important to qualify up at the front. It's tricky around here, but we made some good progress here this afternoon and evening."
Ferrari's Fernando Alonso also slid off having spent a short period leading the field. The double world champion eventually came home third ahead of Brazilian teammate Felipe Massa.
Vettel's fellow Red Bull driver Mark Webber was fifth fastest, with seven-time world champion Michael Schumacher seventh for Mercedes.
The 2011 campaign will finish at the Brazilian Grand Prix in Sao Paulo on November 27.