It was not illegal , it was not banned . The "fan car" concept was withdrawn by Brabham after one race even though the FIA had ruled it could be used for the remainder of that season. Murray, Brabham's chief designer, later said that the car was withdrawn by Brabham due to concerns from Bernie Ecclestone, the team owner. Ecclestone became chief executive of the Formula One Constructors' Association (FOCA) in the same year that the Brabham BT46 appeared, and he was concerned that the upset from other teams over the fan car could collapse FOCA. Murray said in 2008 that Ecclestone "was working on getting his foothold in the Formula One Constructors’ Association and launching himself towards what he's doing now", with the words "what he's doing now" referring to Ecclestone's position as chief executive of the Formula One Group, which he held from 1987 until 2017.[3]
Thanks for an acurate description of what the true story was of the fan car. I saw a documentary once about cheating in Formula 1 and some of the things that they got up to do take some believing. LIike putting sand in chassis tubes to bring weight up to scrutineering spec.and then removing it for the race. Or a mechanic near the finish line for qualifying and breaking the light beam with his hand just before the car in his team crosses the line.