* Hamilton fastest in Spa practice
* Formula One leader Rosberg second on timesheets
* Maldonado crashes (Adds quotes)
By Alan Baldwin
SPA-FRANCORCHAMPS, Belgium, Aug 22 (Reuters) - Mercedes dominated practice for the Belgian Grand Prix on Friday with Lewis Hamilton ending the day top of the timesheets and six tenths of a second faster than championship-leading team mate Nico Rosberg.
After Rosberg had set the pace in the morning with a lap just 0.097 seconds faster than the Briton's best, Hamilton turned the tables after lunch with a substantially quicker effort.
The time of one minute 49.189 on soft tyres was 0.604 better than Rosberg's on a cloudy but bright day at the longest track on the calendar, where the weather can combine the seasons in the space of an afternoon.
Rosberg had topped the first session timesheets in 1:51.577 as the two title rivals - separated by just 11 points after 11 of 19 races - renewed their duel after the August break and completed more than two race distances.
The afternoon running was interrupted when Venezuelan Pastor Maldonado crashed his Lotus into the barriers on the way to Pouhon.
Maldonado made a quick trip to the medical centre but was given the all-clear.
There was a further stoppage in the first half hour when Mexican Esteban Gutierrez's Sauber spun and was stranded on the track at Blanchimont.
"It's great to be back in the car and it was feeling good out there today," said Hamilton, who had buckets of ice tipped over him after he stepped out of the car as part of a social media charity challenge.
"The forecast is wet for tomorrow, so it was important to maximise track time as this may be our last dry running before the race," he added.
Ferrari's Fernando Alonso was third fastest in both sessions with McLaren's Jenson Button fourth in the morning and fifth in the afternoon.
The Mercedes-powered teams were predicted to dominate and had seven cars in the top 10 in the opening session.
But Ferrari's showing, with four times Spa winner Kimi Raikkonen fifth fastest in the morning despite a spin at La Source, indicated they would not have it all their own way.
"At this track and at Monza, engine performance counts for a lot. We know there is no magic solution but we will nevertheless try to optimise everything," Alonso said.
Williams had a low-key start, with Finland's Valtteri Bottas 10th on the timesheets and Brazilian Felipe Massa 15th, but picked up with Massa fourth in the afternoon.
Red Bull's Daniel Ricciardo, winner of the previous race in Hungary, was ninth and eighth in the two sessions while his quadruple world champion team mate Sebastian Vettel sat out the second session due to an electrical problem that forced an engine change.
At the bottom end of the field, Germany's Andre Lotterer limbered up for his F1 debut with Caterham as a replacement for Japan's Kamui Kobayashi by lapping faster than Swedish rookie team mate Marcus Ericsson in the morning.
"Having Andre in the car is definitely helping us, he has done an extraordinary job on his first day driving for us," commented team principal Christijan Albers.
American Alexander Rossi replaced Max Chilton for the session at Marussia but his hopes of completing the weekend and racing for the first time evaporated when the Briton was reinstated following contractual wrangles. (Editing by Ed Osmond)