Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:10:p8
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 10 (pt 8/32)
Character Range: 1291018–1294073

For Class 1 vehicles, it shall be measured at the same wind speed of ≤ 150 km/h.
              3.2.3.2.2.3.2. Alternative method for determination of aerodynamic influence of optional equipment
              At the request of the manufacturer and with approval of the responsible authority, an alternative method (e.g. CFD simulation (Level 1A only), wind tunnel not fulfilling the criteria in Annex B4) may be used to determine Δ(CD×Af) if the following criteria are fulfilled:
                  (a)  The alternative method shall fulfil an accuracy for Δ(CD×Af) of ±0.015 m².
                  For Level 1A only - In the case that CFD simulation is used, the accuracy of the CFD method shall be validated by at least two Δ(CD×Af) per types of optional equipment from a common baseline vehicle body and at least a total of eight Δ(CD×Af) as shown in the example in Figure A7/1a;
                  (b)  The alternative method shall only be used for types of aerodynamic-influencing optional equipment (e.g. wheels, cooling air control systems, spoilers etc.) for which equivalency has been demonstrated;
                  (c)  Evidence of equivalency outlined in (a) and (b) shall be shown to the responsible authority in advance of the type approval for the road load family. For any alternative method, validation shall be based on wind tunnel measurements fulfilling the criteria of this Regulation;
                  (d)  If the Δ(CD × Af) of a particular item of optional equipment is more than double the Δ(CD × Af) of the optional equipment for which the evidence was provided, aerodynamic drag shall not be determined by the alternative method; and
                  (e)  Revalidation is necessary every four years in the case that a measurement method is used. In the case that a mathematical method is used, any change made to a simulation model or to the software likely to invalidate the validation report also requires revalidation.

    Figure A7/1a
       Example of application of the alternative method for determination of aerodynamic influence of optional equipment

              3.2.3.2.2.3.2.1. The manufacturer shall declare the scope of applicable vehicles for the alternative method to the responsible authority and the declared scope shall be documented in relevant test reports when evidence of equivalency is shown to the responsible authority. The responsible authority may request the confirmation of equivalency for the alternative method by selecting the vehicle from the scope declared by the manufacturer after equivalency was demonstrated. The result shall fulfil an accuracy for Δ(CD×Af) of ±0.015 m². This procedure shall be based on wind tunnel measurements fulfilling the criteria of this Regulation. If this procedure is not satisfied, the approval of the alternative method is regarded as invalidated.
              3.2.3.2.2.3.3. Application of aerodynamic influence on the individual vehicle
              is the difference in the product of the aerodynamic drag coefficient multiplied by frontal area between an