Moving Aerodynamic Devices - A Brief History


Exulted Lord High Moderator of the Apex
Staff Member
Premium Contributor
When is a moving aerodynamic device not a moving aerodynamic device? F1 is famous for many things and one of them is certainly an ability to muddy its own waters with some of the most inconsistent interpretations of its own regulations. Sometimes the sports own governing body sets out one set of rules only to then contradict them a few months later. In the wake of yet another F1 design falling foul of the moving aerodynamic rule I thought I would take a look at where else this has been used in F1 and how inconsistent its application has been.

The rule in question is:

3.15 Aerodynamic influence :

With the exception of the driver adjustable bodywork described in Article 3.18 (in addition to minimal parts solely associated with its actuation) and the ducts described in Article 11.4, any specific part of the car influencing its aerodynamic performance :

- must comply with the rules relating to bodywork ;

- must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom) ;

- must remain immobile in relation to the sprung part of the car.

Any device or construction that is designed to bridge the gap between the sprung part of the car and the ground is prohibited under all circumstances.

No part having an aerodynamic influence and no part of the bodywork, with the exception of the skid block in 3.13 above, may under any circumstances be located below the reference plane.

With the exception of the parts necessary for the adjustment described in Article 3.18, any car system, device or procedure which uses, or is suspected of using, driver movement as a means of altering the aerodynamic characteristics of the car is prohibited.

The origins of this rule lay back in the late 60’s when wings were attached on large uprights and directly to the suspension. Some teams designed units that could be feathered at speed along long straights and by a simple attachment to the brake pedal be dipped going into corners, much in the same way as the modern DRS system works. This was at the time deemed dangerous and indeed it was. The aerodynamic loadings on these structures was never fully understood or tested to the Nth degree and this lead to many crashes as a result of wing failures.

In 1977 Lotus introduced the Type 78 which became the first F1 car to exploit underbody airflow (known as the ground effect) to produce extra down force. During the development of the previous seasons Type 77 it was observed by the Lotus design team that ground effect results improved dramatically if you could seal the gap between the sides of the car and the ground to produce a venture tunnel effect. The type 77 was originally fitted with nylon brushes to achieve this however slow motion filming revealed that these brushes were sucked up and away from the track by the force of the venture and also the wear rate was extremely high.

The 78 design incorporated flexible skirts with ceramic rubbing strips to protect the edges of the skirt and this overcame the problem to some extent. The follow up to the type 78, the Type 79 used an even more advanced system known as the “box in a box” type of skirt or more popularly known as “the sliding skirt”. This design even more so than its earlier versions was without doubt a moving aerodynamic device however it was never banned under that rule.

When other designers began to understand what Lotus had done they quickly came up with their own versions of the system and this is where the infamous Brabham BT46B fan car was introduced. This car employed skirts and a fan attached to the engine that literally sucked the air out from under the car and sucked it to the track. The car was protested by several teams after its debut 1-2 performance at the Swedish GP and the Brabham team agreed to withdraw it. Again, the fan was clearly a moving aerodynamic device however the concept of the fan was never actually banned and the result of the Swedish GP was allowed to stand.

Much has been written about the FISA / FOCA “war” of the early 80’s and a great deal of the debate centred initially on the side skirts and their continued use in F1. It was at this stage that the next contender in the moving aero battle appeared on the scene. Seeing that the rules on side skirts, which by now were fixed, had cause the cars to become almost un-driveable due to the almost zero suspension movement required to keep the skirts in contact with the ground, Colin Chapman introduced his controversial Type 88 or Twin Chassis design. The purpose of the car was to have all the aerodynamic parts on the one body which could be stiffly sprung and attached to the second chassis which would carry the driver, the engine and the main suspension which could then be softly sprung with regular suspension travels. At speed the first chassis would sit down on it’s springs and transfer loads to the second chassis while maintaining the skirts contact to the ground, the rate that the springs would rise between the two chassis would ensure that it would rise at a slower rate than it compressed maintaining the cars ability to ride over bumps like a normal vehicle and at the same time achieve maximum aero loading. The vehicle was instantly protested and FISA issued a “rule clarification” which is still evident in rule 3.15 above as the part in brackets about freedom of movement. Despite Chapman’s best efforts the Type 88 never turned a wheel in anger at an F1 track aside from a brief outing in practice for the US GP at long beach. The final twist in the Type 88 story is that it was never deemed illegal by the scrutineers at any of the race meetings that it attended and even won a court case in the USA to prove its legality. (FISA side stepped the court case victory for Lotus claiming that it only applied to GP on US soil). Chapman was even more aggrieved at the ruling because at the same time, several teams led by Brabham, in order to meet the FIA’s un-measurable 6cm ground clearance rule, were using hydraulic jacking systems that ensured the car was legal within the pits but allowed the car to be lowered so that the skirts made contact with the track surface once out on the road and out of the reach of the race stewards. Again this was another moving device that affected the aerodynamics of the car.

With the introduction of flat bottomed cars, the aerodynamic performance of the car was now incredibly sensitive to its pitch and roll. Again, Colin Chapman at Lotus had seen a way to control this by the introduction of an active suspension system. It was at while the team was testing this very system in December 1982 that Chapman passed away. Though used on a couple of occasions on Nigel Mansell’s Lotus during the 1983 season, the system was deemed far too heavy and far too primitive to be used and was shelved for further development. It was re-introduced during the 1987 season where Aytron Senna immediately saw its merits and used it to great effect in Monaco and Detroit. It was then left to other teams such as Williams and Mclaren to develop it to great effect over the coming years until its eventual ban. Active suspension it could be argued, was introduced for the purpose of maximising the aerodynamic performance of a car by producing a constant platform (i.e not one susceptible to large changes in pitch and roll due to the road surface) and yet it was never banned as a moving aerodynamic device.

Things then went quiet on the aerodynamic devices front for many years until the controversy surround the Renault mass damper system. Renault had led the development of the tuned mass damper system that featured moving weights in the nose of the car that reduced the effect of vibration and to some extent pitch at the front of the car. By mid way through the 2006 season there were 7 teams using devices similar to Renaults. It was claimed at the time that it was Mclaren that had protested the device however it was deemed legal to use by the stewards at the German GP. In one of F1’s stranger moments the FIA protested its own stewards that the device should be ruled illegal and Renault agreed not to run the system in Germany to avoid a retrospective punishment. At a subsequent appeal hearing the FIA appeal court ruled that the mass damper was indeed in contravention of rule 3.15 and was deemed a moveable aero device. The effect of the banning of this device on the Renault team was the most telling. Prior to the ban at the German GP, Fernando Alonso had won 6 races and scored 3 seconds, in the final 7 races he only won once more.

In yet another about face in the rules, from 2009 onwards, teams were allowed to use driver adjustable body work without breaching the ban on moving aero devices. These were little flaps on the front wing that could be adjusted by no more than 6 degrees and no more than twice a lap.

For 2010 Mclaren introduced the F-Duct which used the driver as part of the aerodynamic process. By covering a hole in the cars cockpit with the drivers hand (or in some designs the knee) air was circumvented through the car and over the rear wing to stall the wing at high speeds and therefore reduce drag in order to create a higher straight line speed. Initially the design was protested by Red Bull as being a moving Aero device however once the design was passed as legal most teams soon adopted some form of F-Duct on their own cars in order to achieve the same effect. The use of the driver as an aerodynamic aid was finally banned in the run up to the 2010 season and is now enshrined in the final paragraph of rule 3.15.

And so finally we end up in 2011 with the introduction of the DRS. The system designed to feather the wing when a driver is within one second of the car in front and only at a specific point on the track (or not at all in the case of Monaco) harks back to the early days of Wings. It’s somewhat ironic that the wing for which rule 3.15 was created is now back in F1 as a legal device. With that it should be the end of the story however once again rule 3.15 rears its ugly head and this time its not suspension related, skirt related or even driver related but to do with the exhaust. The saga of the Exhaust Blown Diffuser has been well documented in other threads so I won’t go into it again here but having seen just how inconsistent the rules on moving aero aids can be, what are the odds that we will be seeing the return of the EBD in time of the start of the 2040 Formula One Season?

(P.S. I’m sorry I didn’t intend for this rant to be that long but once I got going….. :) )


Too old to watch the Asian races live.
Sliding skirts and fan-generated downforce first (to my knowledge) appeared on the Chaparral 2J in 1970. When Brabham resurrected the principle for the 46B, they made the fan essential to move air through the radiators, thereby being able to claim that its primary function was cooling and any downforce generation was mere happenstance!


Exulted Lord High Moderator of the Apex
Staff Member
Premium Contributor
Sliding skirts and fan-generated downforce first (to my knowledge) appeared on the Chaparral 2J in 1970. When Brabham resurrected the principle for the 46B, they made the fan essential to move air through the radiators, thereby being able to claim that its primary function was cooling and any downforce generation was mere happenstance!

Absolutely, and Tony Rudd did most of the development on the "Wing Car" while he was at BRM in 1969. BRM didn't pursue it and Rudd left and took all he knew with him to Lotus.
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