It seems a manufacturing error lead to Saubers disqualification from the Australian GP. New rules this year set a minimum radius for the rear wing elements, these were introduced to prevent slots being added to the wings to allow blown slots and F-duct stalling slots. However in post race scrutineering the Sauber fell foul of the new test, which is to uphold the revised rules; 3.10.1 and 3.10.2. The rear wing flap on both races cars was tested and its upper surface (with the logo “Sauber F1 Team”) was found to be made with too tight a radius.
The new test involves checking a minimum 100mm radius is applied to all areas of the wing on contact with the external airstream. As exclusively revealed by Gocar.Gr, it appears the upper face of the rear wing flap was too curved by some 5mm. Sauber have three versions of the flap available and two were brought to Melbourne. It seems the version raced was not fully checked at the factory and therefore the error was not picked up, whereas the other (un-raced) specification flap was checked and deemed legal. Not every car and every component gets fully checked by the FIA scrutineers. The cars will go through different tests at different points in the weekend. It seems the Sauber flap in question was not tested until after the race.
Teams are trying to make their flaps relatively small in order to make the DRS adjustable rear wing system more effective. As a smaller flap loses more angle of attack when it pivots from its trailing edge to the maximum 50mm slot gap at its leading edge. This means the wing loses more drag as the DRS is activated, for more straight-line speed. It appears that Sauber have gone to a very tight radius flap, right on the edge of the regulations, but the manufacturing problems sent the minimum curvature over the limit of the regulations.
Sauber felt this problem did not produce a performance advantage and will appeal the decision.