Fan car

An engine-driven fan at the rear of the car, declared as a cooling device, which also evacuated the underbody and generated suction downforce independent of road speed.

The movable aerodynamic device ban did not contemplate a device whose primary declared purpose was cooling. Gordon Murray's defence was that cooling was the principal function and downforce an incidental effect.

Enormous. Niki Lauda won the Swedish GP at Anderstorp by a reported margin of over half a minute from Riccardo Patrese.

The Commission Sportive Internationale declared that fan cars would not be allowed. The ban was prospective, not retroactive — the Anderstorp win stood because the car was not illegal when it raced, and the cars were converted back to BT46 specification.

Raced once, won once. A 100% win rate is the entire competitive record of the concept.

The canonical precedent for "legal when it raced, banned afterwards" — the pattern later repeated for the F-duct and, arguably, for mini-DRS.