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Lotus E21 - passive double DRS 13 March 2013

Active double drag reduction systems (DDRS) are banned for 2013. Lotus and Mercedes were the only teams to trial passive versions in the latter part of the 2012 season (insets) and both have continued experimenting during the winter tests (with Sauber and Red Bull following their lead). The main drawing shows Lotus's latest interpretation. Airflow is sucked in via the airbox above the driver's head and at lower speeds simply exits via the rear of the car (lower blue arrows). However, when a certain speed is reached, the force of the airflow becomes such that it activates a passive fluid switch and the airflow is instead directed up a vertical duct (red arrow) and blown onto the rear wing (upper blue arrows). This helps separate airflow from the wing and stalls it, cutting downforce and drag. When the car's speed again drops below a certain level, the switch is deactivated. The tricky part is getting the switch to activate and deactivate at the same speed. Unlike active DDRS, the driver has no control over the system, and if it proves unpredictable he could find himself robbed of valuable downforce at inappropriate moments - at the start of a braking phase for example. Until teams get a proper handle on this behaviour - a long and delicate process, if testing is anything to go by - no one is likely to race a passive DDRS, at least in the initial rounds of 2013.