BAKU, Azerbaijan (AP) — Formula One's pit-to-driver radio restrictions played a decisive role in Sunday's European Grand Prix as Nico Rosberg got assistance in solving an engine-setting glitch and sailed away to an easy victory, while his Mercedes teammate and title rival Lewis Hamilton was frustrated at getting no help in fixing an identical problem and finished a distant fifth.
Rosberg's win at the Baku street circuit pushed his lead over Hamilton in the drivers' championship from nine points to 24.
Ferrari's Sebastian Vettel finished second, 16.6 seconds adrift of Rosberg, while Force India's Sergio Perez passed Ferrari's Kimi Raikkonen on the penultimate lap to take third.
Hamilton, who started the race tenth after crashing out in Saturday's qualifying, was up to an effective fifth after just 10 laps and on a charge toward a potential fight with Rosberg when his engine picked up a 'de-rating', an inability to access the stored hybrid power.
Rosberg had switched to the same engine setting as Hamilton during the race, and suffered the same problem, but was quickly told by the team that the mode was problematic and he should switch back to the original setting.
Hamilton, however, had started the engine on that mode, so the team was at first unable to work out what was causing the performance dip. Even once the issue was diagnosed, and as Hamilton was begging over the radio for the team to tell him how to fix the problem, the team was not allowed to tell him.
Under the sport's new rules designed to put more onus on driver skills, teams are banned from communicating information to drivers about how to change engine modes.
"I had no idea, there were like 16 different engine positions and in those engine positions, like 20 positions, so I had no idea what problem I had, just low power," Hamilton said.
The problem resolved itself late in the race, and Hamilton immediately set the fastest lap, but by that time there was not enough time left to catch the cars in front, leaving the Briton to mull over the logic behind the radio restrictions.
"I don't see the benefit," Hamilton said. "The FIA have made Formula One so technical. There were probably 100 different switch positions it could have been, at least 100, 200. There was no way for me to know, no matter how much I study that."
Rosberg confirmed after the race he had the same problem, and calmly said: "It was just a matter of getting out of it with the right combination of switches."
The main surprise of the race was the absence of accidents and safety-car periods. Practice and qualifying had been littered with incidences of cars hitting walls and running down escape roads, and the support GP2 races were accident-strewn, with multiple safety-car interventions and restarts.
"We are all much more experienced (than GP2 drivers) and are able to avoid accidents much better," Rosberg said. "We also all watched the GP2 and it was mayhem, and we picked up some things from that."
After winning the first four races of the season, Rosberg had watched with alarm as Hamilton won the past two to cut his lead to single figures, but the win in Azerbaijan gives him some breathing room coming into the European heart of the season.
"Everything went to plan for me so it was really awesome," Rosberg said. "The weekend went perfectly."
Williams' Valtteri Bottas was sixth, ahead of the Red Bull's Daniel Ricciardo and Max Verstappen, who both struggled on the soft tires in the first half of the race, and were forced into making two pit stops while those ahead needed just one.
Force India's Nico Hulkenberg and Williams' Felipe Massa completed the top ten.