After having a rather in depth discussion about the legality of the flexible wings, the pitfalls of proving if they are legal or illegal, and the definition of the reference plane with Galahad, I have been prompted to write the following article. Hopefully, by the end of it we can try and get a common consensus on what exactly the reference plane is, and how it is related to the flexibility of the front wing. I hasten to add, that the following is purely my interpretation, and as such may well be incorrect, so please do not hesitate to put your point across if you disagree with me. I'll start by saying that the reference plane is not a fixed distance in relation to the car and the floor. The reference plane is constantly changing be it through the change of ride height of the car, the change due to suspension effects, or even the ground, which obviously is never perfectly flat. So where to begin? I guess the first place will be a schematic or two from the FIA Technical Regulations For more detailed drawings please click here (BIG pdf file) To start to define the reference plane, first we must define a plane. In mathematics, a plane is any flat, two-dimensional surface. A plane is the two dimensional analogue of a point (zero-dimensions), a line (one-dimension) and a space (three-dimensions). Therefore the reference plane, in the case of F1, is an imaginary plane, of infinitesimal thickness, that all other measurements defined in the technical regulations are based on. As the reference plane is undefinable in relation to the ground, it is essentially imaginary. Instead all other measurements are based in relation to this imaginary plane. The easiest way to think about it, is that it is the lowest area of the car, the area closest to the ground of the sprung area of the car (the chassis). As defined in the technical regulations, the skid block is attached to the reference plane, and as such is the only part of the chassis that is allowed to lie below the reference plane: "When the skid block is new, ten of the fasteners may be flush with its lower surface but the remainder may be no more than 8mm below the reference plane." Therefore we have all the design constraints/measurements for the design of the car based on the reference plane (in the vertical direction) and the centre lines of the wheels, a more understandable concept (in the lateral directions), all based around the car centre line. In effect the exact dimensions of the reference plane, are the dimensions of the skid block and extends from 33cm rear of the front tyres all the way back to the rear tyres, and must be between 30cm and 50cm wide. From 1994, with the FIA becoming increasingly concerned with the faster speeds of cars, a further plane was defined, the 'step plane'. Lying 5cm above the reference plane, this step plane runs from a line level with the front of the plank to one 33cm in front of the rear wheels, and is the level at which any bodywork viewed from the underside which is not on the reference plane must stop. This takes in the three main areas of bargeboards, sidepods, and diffuser. In effect banning teams from building bodywork closer to the ground to gain a significant aerodynamic advantage (skirts anyone?). So how does this explain the illegality of the new flexible wings? Well the allowed dimensions for the front bodywork (i.e. the wings) is defined in the various parts of article 3. Article 3.7.1: All bodywork situated forward of a point lying 330mm behind the front wheel centre line, and more than 250mm from the car centre line, must be no less than 75mm and no more than 275mm above the reference plane.In effect, the wings have to lie within 75 mm and 275 mm above the reference plane. Many people (media) have been quoting the regulations as saying that the wings can lie no more than 85 mm from the ground. I believe this has been worked out as an approximation of the average ride height of the car plus the 75 mm, although I am not sure on this point. The wings are further defined (and in my opinion it is the following regulation that really defines the flexible wings as being illegal) in article 3.15 Article 3.15: Aerodynamic influence : With the exception of the cover described in Article 6.5.2 (when used in the pit lane), the driver adjustable bodywork described in Article 3.18 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.Understanding that the teams are very clever, and that current testing methods may be insufficient to enforce the regulations. The FIA also cover their own backs by the following declaration in article 3.17.8 Article 3.17.8: In order to ensure that the requirements of Article 3.15 are respected, the FIA reserves the right to introduce further load/deflection tests on any part of the bodywork which appears to be (or is suspected of), moving whilst the car is in motion.The difficulty, as Galahad and I have discussed in detail, is proving that any regulations have been broken, when the car is in motion. A very difficult prospect at best, with video evidence normally being seen as circumstantial, in ideal conditions. I'd appreciate any thoughts you might have on the matter.