Division 6.4.2 Wind tunnel measurement
The vehicle shall be in the condition described in paragraph 6.3. of this Sub-Annex.
F1The vehicle shall be placed parallel to the longitudinal centre line of the tunnel with a maximum tolerance of ± 10 mm.
The vehicle shall be placed with a yaw angle of 0° within a tolerance of ± 0,1°.
Aerodynamic drag shall be measured for at least for 60 seconds and at a minimum frequency of 5 Hz. Alternatively, the drag may be measured at a minimum frequency of 1 Hz and with at least 300 subsequent samples. The result shall be the arithmetic average of the drag.
In the case that the vehicle has movable aerodynamic body parts, paragraph 4.2.1.5. of this Sub-Annex shall apply. Where movable parts are velocity-dependent, every applicable position shall be measured in the wind tunnel and evidence shall be provided to the approval authority indicating the relationship between reference speed, movable part position, and the corresponding (CD × Af).