By Abhishek Takle
Belgium, (Reuters) - Nico Rosberg comfortably topped the timesheets at the end of Friday’s opening practice session for the Belgian Formula One Grand Prix.
The German set a pace of one minute 48.348 seconds, 0.730 seconds ahead of Mercedes team mate Lewis Hamilton, on a glorious sunny day at the Spa-Francorchamps circuit.
Rosberg was one of four drivers to briefly test the "halo" head protection device during the session, even setting his benchmark time with it fitted to his car.
Teams are trying out the concept ahead of the delayed introduction of some form of cockpit protection in time for the 2018 season.
Toro Rosso’s Carlos Sainz, Force India’s Nico Hulkenberg and Red Bull’s Daniel Ricciardo were the other drivers to test it out.
Ferrari’s Kimi Raikkonen, a four-times winner at Spa, set the third fastest time, 0.799 seconds adrift of Rosberg’s best.
Sergio Perez was fourth in the Force India ahead of the second Ferrari of Sebastian Vettel. Daniel Ricciardo, who won the race in 2014, was sixth ahead of team mate Max Verstappen, for whom Sunday’s race is the closest the Dutchman has to a home event.
French teenager Esteban Ocon, making his Grand Prix debut this weekend with backmarkers Manor in place of cash-strapped Indonesian Rio Haryanto, ended the session 16th. He was quicker than fellow Mercedes-backed team mate Pascal Wehrlein in 19th.
Fernando Alonso completed only three laps in his McLaren and did not set a time, with his team deciding to change his engine after discovering a water leak.
A number of drivers also tested a stronger prototype Pirelli tyre designed to better deal with running over kerbs.
Hamilton leads Rosberg by 19 points in the standings and heads into Sunday’s race aiming to become only the third driver ever to score 50 career wins.
But the reigning triple champion is set to take a penalty that will force him to start near the back of the grid for exceeding his permitted allocation of engine components.
The Briton ran a fresh power unit in practice which included a sixth turbocharger and Motor Generator Unit (Heat) hybrid component.
That is one more than the five for the entire season permitted by rules and incurs a 15-place grid drop.
(Editing by Ed Osmond)