Mercedes hunts down software bug that cost it victory

Mercedes says that it has identified the costly software error that led to an astounding reversal of fortunes during last weekend's Australian Grand Prix.

Lewis Hamilton had been firmly in control of the race until a virtual safety car was declared. Marshalls needed to attend to a Haas which had parked beside the track with an improperly attached wheel.

Hamilton had already made his single scheduled pit stop and remained out on track. Several other cars including Ferrari's Sebastian Vettel took the opportunity to make their pit stops. The VSC is intended to neutralise the race, but on this occasion Vettel was able to jump into the lead ahead of Hamilton.

Hamilton spoke afterwards of his 'disbelief' when he saw Vettel emerge from pit lane ahead of him. Team boss Toto Wolff later explained that it had been down to a 'software glitch'.

A major post mortem into what went wrong was immediately launched at Brackley. It identified a problem with the way the team calculated the speed Hamilton needed to lap under the VSC to keep the lead.

“The issue isn’t really with the race strategy software that we use,” trackside racing engineer Andrew Shovlin explained. “It was an offline tool that we create these delta lap times with.

"We found a bug in that tool that meant that it gave us the wrong number," he told the latest episode of Mercedes' Pure Pitwall race debrief.

“The number that we were calculating was around 15 seconds. In reality the number was slightly short of 13 seconds, so that was what created our delta.

• Wolff puts Melbourne Mercedes defeat on 'software glitch'

“That is why we thought we were safe. We thought we had a bit of margin and then you saw the result."

“It is never quite an exact science," Shovlin added. "You don’t know how fast a car is going to be able to come through that pit entry.”

Vettel was able to make up time in the pit lane, where the VSC speed restrictions don't apply.

Hamilton attempted to retake the lead at the restart but was rebuffed. He was unable to find his way around the Ferrari for the rest of the race and ended up finishing as runner-up.

"We were in second place and it is very difficult to overtake and we couldn’t get through," said Shovlin.

He said the team would learn from this and improve its procedures to make sure it didn't happen again.

"With any of these things, we look at what went wrong, work out how to solve it and then put the processes in place to make sure we don’t have a repeat.

"We are going to make sure we have more margin," he added. "We want to be able to cover for Vettel doing an amazingly good in-lap to the pits, or having an incredibly fast stop."

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