By Jonathan Legard
BBC F1 commentator
Virgin have discovered that their car's fuel tank is too small
The new Virgin team are being forced to make major modifications to their car after discovering that its fuel tank is too small to get to the end of races.
Virgin, who entered Formula 1 this season, have asked governing body the FIA for permission to submit a new chassis for inspection.
The modified car will not be ready until the fifth race of the season, the Spanish Grand Prix on 9 May.
Technical boss Nick Wirth admitted the car's tank capacity was "marginal".
A senior F1 insider described the changes needed as a "significant modification" which would require the car to go through a series of mandatory crash tests again.
It has become clear that our fuel tank capacity is marginal and if not addressed there is the possibility that fuel pick-up could become an issue in certain circumstances
Virgin technical director
The FIA has circulated a note to the other 12 teams informing that Virgin have been given permission to change their fuel tank specification for reliability reasons - ie, if they were not allowed to do so, they would not be able to finish the races.
The team have been struggling with reliability so far in their debut season - both cars retired from the season-opening Bahrain Grand Prix by the 16th lap.
BBC Sport understands Virgin's fuel tank is about 13 litres too small to last a race distance and that the car could not reach the end of any of the next three races in Australia, Malaysia and China at full speed.
The team will have to make the chassis longer to fit in a bigger tank that can hold the required fuel loads - which are about 210 litres or 160kg of fuel.
F1 cars have carbon-fibre chassis which take months to make. Virgin will almost certainly be forced to cut off the back of their existing chassis and bond on a larger section at the rear.
Wirth said: "We recently applied to the FIA for permission to change the size of the fuel tank on the grounds of reliability and we are pleased that the FIA has granted us this permission.
"It has become clear during pre-season testing and our debut race in Bahrain that our fuel tank capacity is marginal and if not addressed there is the possibility that fuel pick-up could become an issue in certain circumstances.
"At the time that the design of the tank was locked down in June 2009, its capacity was determined by a number of factors, some of which have since changed and the tank capacity now needs to be increased accordingly.
"We thank the FIA for permitting this change, which we expect to introduce in the early part of the European season."