The FIA has revealed it initially planned to only check Lewis Hamilton’s and Charles Leclerc’s car planks after the United States Grand Prix, before “concern” prompted it to examine others.

Hamilton and Leclerc were excluded from the result of last weekend’s race in Austin after scrutineering checks discovered that their underfloor planks had worn away by more than the 1mm that is allowed in the rulebook.

While there was no dispute that both cars were outside of the regulations, the subsequent emergence that the FIA only checked four cars in total prompted some intrigue about whether or not more competitors should have been looked at.

Hamilton suggested ahead of the Mexico GP that he had been told by sources that “a lot” of other cars were subsequently found to be illegal, but were kept in the result because they were not checked by the FIA.

More details of exactly how events unfolded have now emerged, with the FIA’s technical director Tim Goss revealing that the original intention was to only look at Hamilton and Leclerc’s planks.

The choice of these two cars is understood to have been motivated by the way that the FIA has access to car performance data that indicates when cars are bottoming a lot, which could point to the plank being worn away.

PHOTO BY: GIORGIO PIOLA

Haas VF-22 plank

Speaking to Sky Sports F1, Goss explained how the decision came about to expand the checks to involve other cars, amid concern that some unique circumstances could have triggered a wider problem.

“We selected two cars for our post-race check and inspected those,” said Goss. “The check takes a while, and we found that they were the wrong side of the regulations. That caused us some concern.

“What we wanted to do was try to understand whether the problem was systematic and something to do with that race, [or] the conditions at that race.

“So, we decided to then select another two teams, and we selected another two cars, which happened to be [Max] Verstappen and [Lando] Norris and check those.

“After we checked those two cars, then we found those two were the right side of the limit and all [was] fine.”

While the FIA was happy to stop its checks after examining cars from four teams, the 50% fail rate still led many to suggest that the governing body should have checked the entire grid before promoting drivers up the order.

But Goss has explained why such a scenario was not possible, as he shed some light on the timeframe and complications that come from checking plank thickness.

“It is beyond just sticking a ruler or depth gauge into a hole and measuring a skid thickness,” he said.

PHOTO BY: GIORGIO PIOLA

Mercedes W14 plank detail

“We actually have to disassemble part of the car. The check takes probably about half an hour to do.

“If we had two crews doing that [checking all the cars], then what we’re looking at is five hours of work to check all the cars – after which you’d be reporting cars to the stewards.

“Maybe the race result [then] comes out some six, seven, eight hours after the race is finished. I don’t think that’s acceptable for the sport.”

Williams head of vehicle performance Dave Robson agreed that the FIA had to take practical considerations into account when it came to checking compliance with the rules.

“I think the way the regulation is policed at the moment, testing all cars at the end of every race, it’s just not practical,” he said.

“I think it would take so long that I think everyone would get frustrated by that. I think the spot checks and the severity of the penalty is enough that I think, most of the time, most or all of the cars will be legal. So, I think it’s fine as it is.”