The Diffuser Three


FIA Court of Appeal Decision ICA 5-7 (2009), (Full Text):

Before we progress onto the loftier and indeed more controversial matter of the FOTA 8, it is worth spending a few minutes to discuss the somewhat inauspicious start to the F1 season and the Diffuser 3 row.

So what is a diffuser and why did this row erupt?

Put simply, the diffuser is the rear part of the floor of the car between the rear wheels and under the rear wing. It gathers all the high speed air rushing under the car and redirects this pressure to maximise downforce and grip. It is therefore crucial to the car’s aerodynamics, and small changes can have a big impact on the performance of the car. (Some good pics of diffusers can be found at:

Under Article 3 of the 2009 Formula One Technical Regulations, the main part of the diffuser was limited to a width of 1000mm, a length of 350mm and a height of 175mm, with no difference in height between the main central section and the side channels. This was designed to force teams into installing much smaller diffusers which would then reduce downforce by as much as 50%, and thereby increase overtaking.

While McLaren, Ferrari, Renault, Red Bull Racing and BMW-Sauber made literal interpretations of these rules, Brawn, Williams and Toyota (the Diffuser 3) all exploited a loophole in the regulations by shaping the rear crash structure in the rear bodywork of the car to act as an additional channel(s) to lengthen and heighten the diffuser’s central section (thereby replicating the small winglets allowed in previous seasons). By creating holes between this section and the diffuser, it was possible to create double or triple diffusers, substantially lengthening the diffuser exit area and increasing the car’s downforce. This resulted in as much as a 5/10 second decrease in lap times!

The issue was further complicated by the revelation that Ross Brawn (principal of Brawn GP) was also the technical delegate to the Formula One Team’s Association (FOTA) and therefore potentially had a conflict of interest relating to the discovery of these loopholes relating to diffuser design (although this issue was later dropped and did not form part of the official protests).

Unsuprisingly, the teams without the new diffuser design complained, and with no time to refer the matter to the FIA Court of Appeal, the decision was left to the three stewards at the Melbourne Grand Prix (Radovan Novak, Steve Chopping & Olafur Gudmundsson). After a six-hour hearing, the stewards upheld the diffuser design as being legal.

An appeal was inevitable whichever side lost, and after the stewards revisited their decision at the second race of the season in Kuala Lumpur, the stage as set for a final appeal to the FIA Court of Appeal in Paris on April 14th.

The main findings of the Court of Appeal were:

  • [24] – While it was preferable for stewards to state the reasons for their decisions, these could be inferred from the appeal literature. (This plea was effectively dealt with on a technicality as none of the parties had actually submitted the ‘Guidelines for Stewards’ document for the court to refer to)
  • [31] – There was no obligation under article 2.4 that any of the ‘Diffuser 3’ had to seek clarification from the FIA before implementing their diffuser design, even where the design was new. However, even where the teams had previously communicated with the FIA technical department, this did not constitute a binding precedent on design interpretation [85]
  • The third plea by the teams was not so much a specific breach of the letter of the law but rather referred to the ‘Diffuser 3’ breaking the spirit of the rules. In particular, the court heard how the stated aim of the 2009 Technical Regs was to reduce downforce and minimise the wake of the car on following vehicles. By circumventing the diffuser rules, the new diffuser design breached the guidelines set by the Overtaking Working Group (OWG). The court rejected this plea at [39] by holding that the OWG was only an advisory rather than rule-making body and that the preamble being relied upon did not form part of the technical regs but rather could be used by the FIA for justifying making a change to them if the required downforce reduction was not produced by the 2009 rules.
  • At paragraphs [52]-[78], the court held (taking a legalistic approach to the vocabulary) that the new diffusers did not breach any of the specific technical requirements
  • Finally, the Court rejected as irrelevant the view that teams without the new diffuser design would have to expend large amounts of money and resources in direct contravention of the FIA’s stated policy to cut costs [89].
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About Kris

Associate Professor in Sports Law, Staffordshire University; British Gymnastics Senior Coach

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